2024-03-29T11:10:58Zhttp://oai.recercat.cat/request
oai:recercat.cat:2072/2229632014-01-30T23:20:14Zhdl_2072_171809High-Resolution Mass Spectrometry applied to the identification of new metabolites and transformation products of quinolones in chicken muscle tissuesMorales-Gutiérrez, F. J.Hermo Outeiral, Ma. del PilarBarbosa Torralbo, JoséBarrón Bueno, DoloresQuinolonesMetabòlitsGallinesMúsculsAntibiòticsAvaluació del risc per la salutEspectrometria de massesQuinolone antibacterial agentsMetabolitesHensMusclesAntibioticsHealth risk assessmentMass spectrometryThe aim of this work was the identification of new metabolites and transformation products (TPs) in chicken muscle from Enrofloxacin (ENR), Ciprofloxacin (CIP), Difloxacin (DIF) and Sarafloxacin (SAR), which are antibiotics that belong to the fluoroquinolones family. The stability of ENR, CIP, DIF and SAR standard solutions versus pH degradation process (from pH 1.5 to 8.0, simulating the pH since the drug is administered until its excretion) and freeze-thawing (F/T) cycles was tested. In addition, chicken muscle samples from medicated animals with ENR were analyzed in order to identify new metabolites and TPs. The identification of the different metabolites and TPs was accomplished by comparison of mass spectral data from samples and blanks, using liquid chromatography coupled to quadrupole time-of-flight (LC-QqToF) and Multiple Mass Defect Filter (MMDF) technique as a pre-filter to remove most of the background noise and endogenous components. Confirmation and structure elucidation was performed by liquid chromatography coupled to linear ion trap quadrupole Orbitrap (LC-LTQ-Orbitrap), due to its mass accuracy and MS/MS capacity for elemental composition determination. As a result, 21 TPs from ENR, 6 TPs from CIP, 14 TPs from DIF and 12 TPs from SAR were identified due to the pH shock and F/T cycles. On the other hand, 14 metabolites were identified from the medicated chicken muscle samples. Formation of CIP and SAR, from ENR and DIF, respectively, and the formation of desethylene-quinolone were the most remarkable identified compounds.Elsevier B.V.Universitat de Barcelona2014-01-30T23:20:14Zinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/49272eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2128612014-09-17T22:32:08Zhdl_2072_171809Determination and characterization of quinolones in foodstuffs of animal origin by CE-UV, LC-UV, LC-Fl, LC-MS and LC-MS/MSBarbosa Torralbo, JoséBarrón Bueno, DoloresHermo Outeiral, Ma. del PilarNavalón, AlbertoBallesteros, ÓscarQuinolonesTeixits (Histologia)Quinolone antibacterial agentsTissuesIn this work methods for the multiresidue determination of the series of quinolones include in the European regulation in food of animal origin are de veloped and validated in line with Commission Decision 2002/657/EC in terms of linearity, decision limit, capability detection, precision and stability. Mult iresidue methods were established to allow the determination of quinolones covered by EU legislation in 2377/90/EC in muscle of chicken, turkey, pig and cow, plasma of cow and pig, liver of pig and milk of cow. First an extraction step was optimized and a SPE step was applied to clean!up and preconcentrate quinolones prior to their separation by CE or LC and determination by CE!UV, LC!UV, LC!Fl, LC!MS with different ion sources (ESI ,ApCI) and different mass analyser (Q, ToF) and LC!E SI!QqQ tandem mass spectrometry. The limits of quantification obtained are always lower than Maxim um Residue Limit (MRL) established by EU for quinolones in animal products and they can be applied to the control of quinolones in foodstuffs of animal origin . Finally the proposed methods were applied to determine quinolones in samples of turkey and pig muscle, pig plasma and milk of cow. Excellent quality parameters and reduced time of analysis were obtained when LC!ESI!MS/MS is used, although the others techniques presented too satisfactory results.Universitatea OvidiusUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/44487eng(c) Universitatea Ovidius, 2009info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2243412015-01-08T23:51:45Zhdl_2072_171809Identification of metabolites and thermal transformation products of quinolones in raw cow milk by liquid chromatography coupled to high resolution mass spectrometryJunza Martínez, AlexandraBarbosa, S.Codony Salcedo, RafaelJuvert, A.Barbosa Torralbo, JoséBarrón Bueno, DoloresAntibiòticsLletQuinolonesMetabòlitsCromatografia de líquidsEspectrometria de massesEstructura químicaAntibioticsMilkQuinolone antibacterial agentsMetabolitesLiquid chromatographyMass spectrometryChemical structureThe presence of residues of antibiotics, metabolites, and thermal transformation products (TPs), produced during thermal treatment to eliminate pathogenic microorganisms in milk, could represent a risk for people. Cow"s milk samples spiked with enrofloxacin (ENR), ciprofloxacin (CIP), difloxacin (DIF), and sarafloxacin (SAR) and milk samples from cows medicated with ENR were submitted to several thermal treatments. The milk samples were analyzed by liquid chromatography-mass spectrometry (LC-MS) to find and identify TPs and metabolites. In this work, 27 TPs of 4 quinolones and 24 metabolites of ENR were found. Some of these compounds had been reported previously, but others were characterized for the first time, including lactose-conjugated CIP, the formamidation reaction for CIP and SAR, and hydroxylation or ketone formation to produce three different isomers for all quinolones studied.American Chemical Society, Books and Journals Division]Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/50576eng(c) American Chemical Society, Books and Journals Division], 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622712016-05-31T22:44:15Zhdl_2072_171809Thermodynamic equilibrium for the dehydration of 1-butanol to di-n-butyl etherPérez-Maciá, María ÁngelesBringue Tomás, RogerIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelÈtersAlcohol butílicResines de bescanvi iònicEthersButanolIon exchange resinsThe thermodynamic equilibrium of the bimolecular dehydration of 1-butanol to di-n-butyl ether (DNBE) and water in the liquid phase was studied. Equilibrium experiments were performed at 4 MPa and in the temperature range of 413-463 K over the ion exchange resin Amberlyst-70. The thermodynamic equilibrium for the side reactions (dehydration to 1-butene, olefins isomerization, olefins hydration and branched ether formation) was also studied. The equilibrium constant for the dehydration reaction of 1-butanol to di-n-butyl ether and water was found to be independent on the operating temperature, within the limits of the experimental error ( 5.2%). The experimental equilibrium constants at 413-463 K allows to estimate the standard enthalpy change of reaction (ΔrH0(l) = -0.3 ± 2.9 kJ¿mol-1) and the standard entropy change of reaction (ΔrS0(l) = 26.8 ± 6.7 J¿mol-1¿K-1). From these values the standard formation enthalpy (ΔfH0DNBE,(l)) and the molar entropy of DNBE (S0DNBE,(l)) at 298.15 K were computed to be -370.5 ± 10.9 kJ¿mol-1 and 408.3 ± 6.8 J¿mol-1¿K-1 respectivelyElsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99061engcc-by-nc-nd (c) Elsevier B.V., 2015info:eu-repo/semantics/embargoedAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2665062016-07-27T22:37:08Zhdl_2072_171809Efecto de la solución amortiguadora de pH en la selectividad cromatográfica de compuestos ácido-baseSubirats i Vila, XavierRosés Pascual, MartíBosch, ElisabethEquilibri àcid-baseCromatografiaConcentració dels ions d'hidrogenAcid-base equilibriumChromatographyHydrogen-ion concentrationEs bien sabido que el pH de la fase móvil es una variable fundamental en la separación de sustancias ionizables en cromatografía de líquidos, ya que de él depende el grado de ionización de los analitos presentes en la mezcla problema. En el desarrollo de métodos analíticos se requiere pues, ejercer un control eficiente sobre el pH mediante la elección de un tampón adecuado. En cromatografía de líquidos en fase inversa, suelen usarse solucio- nes hidro-orgánicas tamponadas como fases móviles. Habitualmente éstas suelen prepararse añadiendo el volumen adecuado de un disolvente orgánico, típicamente acetonitrilo o metanol, sobre una solución acuosa tamponada. Sin embargo, fases móviles del mismo contenido en modificador orgánico y preparadas a partir de soluciones acuosas del mismo pH pero que contienen ácidos distintos como reguladores del pH, pueden presentar valores de pH significativamente diferentes.Sociedad Española de Cromatografía y Técnicas Afines (SECyTA)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/101329spa(c) Subirats i Vila, Xavier et al., 2009info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2672412016-10-18T22:29:54Zhdl_2072_171809Influence of EfOM on the oxidation of micropollutants by Ozone and UV/H2O2 in secondary effluentsVieira, S. P.Dantas, R. F.Esplugas Vidal, SantiagoSans Mazón, CarmeDezotti, M.Contaminació de l'aiguaEnginyeria ambientalOzonitzacióPlaguicidesContaminants orgànics de l'aiguaToxicitat dels medicamentsDepuració d'aigües residualsWater pollutionEnvironmental engineeringOzonizationPesticidesOrganic water pollutantsDrug toxicityPurification of sewageThe aim of this work was to study the influence of effluent organic matter (EfOM) on micropollutants removal by ozone and UV/H2O2. To perform the experiments, deionized water and municipal secondary effluents (SE) were artificially contaminated with atrazine (ATZ) and treated by the two proposed methods. ATZ concentration, COD and TOC were recorded along the reaction time and used to evaluate EfOM effect on the system efficiency. Results demonstrate that the presence of EfOM can significantly reduce the micropollutant removal rate due to competition of EfOM components to react with radicals and/or molecular ozone. The hydroxyl radical scavenging caused by EfOM was quantified as well as the contribution of molecular ozone and �OH radicals during the ozonation of SE. EfOM components promoted higher inhibition of ATZ oxidation by hydroxyl radicals than by molecular ozone.David PublishingUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/48288eng(c) David Publishing, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855192017-05-23T04:48:12Zhdl_2072_171809Study on the removal of biodegradable NOM from seawater using biofiltrationSimón, Francesc XavierRudé i Payró, ElisabetLlorens Llacuna, JoanBaig, SylvieAigua de marBiodegradacióBiofilmsContaminació de l'aiguaEnginyeria químicaSeawaterBiodegradationBiofilmsWater pollutionChemical engineeringDespite the low biodegradability of seawater NOM, problems associated with biofouling are common in facilities that handle seawater. In this work, a fixed-film aerobic biofilter is proposed as an effective unit for preventing biofouling in such facilities. A packed-bed biofilter with an EBCT = 6 - 11 min was employed. The results demonstrated that the DOC is reduced by 6% and the BOD7 is reduced up to 15%. The LC-OCD analysis revealed that biofiltration abates the LMW neutrals and biopolymer fractions by 33 and 17%, respectively. However, the fractionation with UF membrane showed that the biofiltration process is able to degrade the more biodegradable compounds that have molecular weights that are greater than 1 kDa and compounds with molecular weights of less than 1 kDa. After biofiltration, the biological activity measured in terms of ATP removal was reduced by 60%. Finally, a test to evaluate the biofilm formation capacity of a water sample revealed reductions of ~94% when comparing biofiltered and non-biofiltered seawater. Therefore, a fixed-film aerobic biofiltration process could be a useful treatment for the removal of biodegradable organic matter from seawater and for improving the water quality in terms of less biofilm formation capacity.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/45687eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2672822017-05-23T04:48:22Zhdl_2072_171809Recent advances in the determination of biogenic amines in food samples by (U)HPLCSentellas, SoniaNúñez Burcio, OscarSaurina, JavierQuimiometriaCromatografia de líquidsAlimentsChemometricsLiquid chromatographyFoodThe determination of biogenic amines (BAs) in food products stirs up an increasing interest because of the implications in toxicological and food quality issues. Apart from these aspects, in the last years, the relevance of BAs because of some organoleptic and descriptive concerns has been pointed out by several researchers. This overview aims at revising recent advances in the determination of BAs in food samples based on liquid chromatography. In particular, papers published in the last five years have been commented. Special attention has been paid in the great possibilities of ultra-high performance liquid chromatography and high-resolution mass spectrometry. Regarding applications, apart from the determination of BAs in a wide range of food matrices, novel lines of research focused on the characterization, classification and authentication of food products based on chemometrics have also been discussed.American Chemical Society, Books and Journals Division]Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/102800eng(c) American Chemical Society, Books and Journals Division], 2016info:eu-repo/semantics/embargoedAccess
oai:recercat.cat:2072/2701442017-05-23T04:48:23Zhdl_2072_171809HPLC-UV polyphenolic profiles in the classification of olive oils and other vegetable oils by principal component analysisFarrés-Cebrián, M.Seró, RaquelSaurina, JavierNúñez Burcio, OscarPolifenolsOli d'olivaOlis vegetalsCromatografia de líquids d'alta resolucióPolyphenolsOlive oilVegetable oilsHigh performance liquid chromatographyHPLC-UV was applied to the analysis and characterization of olive oils and other vegetable oils. A chromatographic separation on a Zorbax Eclipse XDB-C8 reversed-phase column was proposed under gradient elution, employing 0.1% formic acid aqueous solution and methanol as mobile phase, for the determination of 14 polyphenols and phenolic acids, allowing to obtain compositional profiles in less than 20 min. Acceptable sensitivity (LOD values down to 80 µg/L in the best of cases), linearity (r2 higher than 0.986), good run-to-run and day-to-day precisions (RSD values lower than 11.5%), and method trueness (relative errors lower than 6.8%) were obtained. The proposed HPLC-UV method was then applied to the analysis of 72 oil samples (47 olive oils and 27 vegetable oils including sunflower, soy, corn, and mixtures of them). Analytes were recovered by liquid-liquid extraction method employing ethanol:water 70:30 (v/v) solution and hexane as extracting and defatting solvents, respectively. HPLC-UV polyphenolic profiles using peak areas were then analysed by principal component analysis (PCA) to extract information of the most significant data contributing to the characterization and classification of olive oils against other vegetable oils, as well as among Arbequina and Picual olive oil varieties. PCA results showed a noticeable separation among olive oils and the other classes. Besides, a reasonable discrimination of olive oils as a function of fruit varieties was also encountered.MDPIUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/104811engcc-by (c) Farrés-Cebrián, M. et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2706292017-05-23T04:48:26Zhdl_2072_171809Characterization, classification and authentication of fruit-based extracts by means of HPLC-UV chromatographic fingerprints, polyphenolic profiles and chemometric methodsPardo, NaiaraVera, AlexBarbosa, SergioHidalgo-Serrano, MíriamNúñez Burcio, OscarSaurina, JavierHernández Cassou, SantiagoPuignou i Garcia, LluísCromatografia de líquids d'alta resolucióPolifenolsQuimiometriaHigh performance liquid chromatographyPolyphenolsChemometricsHPLC-UV was applied to the analysis and characterization of fruit-based and fruit-processed products. A Kinetex C18 reversed-phase column was proposed under gradient elution for the determination of 17 polyphenols. Acceptable sensitivity (LODs below 0.16 mg/L), and good linearity (r2 higher then 0.995), precision (RSD below 6.8%), and method trueness (relative errors below 11%) were obtained. Data corresponding to polyphenolic peak areas and HPLC-UV chromatographic fingerprints were then analyzed by exploratory principal component analysis (PCA) to extract information of the most significant variables contributing to characterization and classification of analyzed samples regarding the fruit of origin. HPLC-UV chromatographic data was further treated by partial least square (PLS) regression to determine the percentages of adulteration in cranberry-fruit extracts. It was found that even mixture samples containing low percentages of adulterants could be distinguished from genuine cranberry extracts. Highly satisfactory results were obtained, with overall errors in the quantification of adulterations below 4.3%.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/105523engcc-by-nc-nd (c) Elsevier B.V., 2017info:eu-repo/semantics/embargoedAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2727592017-05-23T04:48:28Zhdl_2072_171809Kinetic study of 1-butanol dehydration to di-n-butyl ether over Amberlyst 70Pérez-Maciá, María ÁngelesBringue Tomás, RogerIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelResines de bescanvi iònicÈtersCinètica enzimàticaAlcoholsCatàlisiIon exchange resinsEthersEnzyme kineticsAlcoholsCatalysisKinetics of the catalytic dehydration of 1-butanol to di-n-butyl ether (DNBE) over Amberlyst 70 was investigated. Experiments were performed in liquid phase at 4 MPa and 413 463 K. Three elementary reaction mechanisms were considered: a Langmuir‐Hinselwood‐ Hougen‐Watson (LHHW) formulation; an Eley-Rideal (ER) formulation in which DNBE remains adsorbed; an ER formulation in which water remains adsorbed. Two kinetic models explain satisfactorily the dehydration of 1-butanol to DNBE: a LHHW formalism in which the surface reaction between two adjacent adsorbed molecules of 1-butanol is the rate limiting step (RLS) and where the adsorption of water is negligible, and a mechanism in which the RLS is the desorption of water being the adsorption of DNBE negligible. In both models the strong inhibiting effect of water was successfully taken into account by means of a correction factor derived from a Freundlich adsorption isotherm. Both models present similar values of apparent activation energies (122±2 kJ/mol)American Institute of Chemical Engineers (AIChE)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/106615eng(c) American Institute of Chemical Engineers, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2815182017-05-23T04:48:30Zhdl_2072_171809Sorption of perfluoroalkyl substances in sewage sludgeMilinovic, JelenaLacorte i Bruguera, SílviaRigol Parera, AnnaVidal Espinar, MiquelLlots de depuradoraAbsorcióContaminants persistentsSewage sludgeAbsorptionPersistent pollutantsThe sorption behaviour of three perfluoroalkyl substances (PFASs) (perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonic acid (PFBS)) was studied in sewage sludge samples. Sorption isotherms were obtained by varying initial concentrations of PFOS, PFOA and PFBS. The maximum values of the sorption solid-liquid distribution coefficients (Kd,max) varied by almost two orders of magnitude among the target PFASs: 140-281 mL g−1 for PFOS, 30-54 mL g−1 for PFOA and 9-18 mL g−1 for PFBS. Freundlich and linear fittings were appropriate for describing the sorption behaviour of PFASs in the sludge samples, and the derived KF and Kd,linear parameters correlated well. The hydrophobicity of the PFASs was the key parameter that influenced their sorption in sewage sludge. Sorption parameters and log(KOW) were correlated, and for PFOS (the most hydrophobic compound), pH and Ca + Mg status of the sludge controlled the variation in the sorption parameter values. Sorption reversibility was also tested from desorption isotherms, which were also linear. Desorption parameters were systematically higher than the corresponding sorption parameters (up to sixfold higher), thus indicating a significant degree of irreversible sorption, which decreased in the sequence PFOS > PFOA > PFBSSpringer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/108082eng(c) Springer Verlag, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855202017-05-23T04:48:31Zhdl_2072_171809Dewaterability of sewage sludge by ultrasonic, thermal and chemical treatmentsRuiz-Hernando, MariaMartinez-Elorza, GuillermoLabanda, JordiLlorens Llacuna, JoanLlots de depuradoraReologiaTractament tèrmicUltrasonsSewage sludgeRheologyHeat treatmentUltrasonicsSludges resulting from wastewater treatment processes have a characteristically high water content, which complicates handling operations such as pumping, transport and disposal. To enhance the dewatering of secondary sludge, the effect of ultrasound waves, thermal treatment and chemical conditioning with NaOH have been studied. Two features of treated sludges were examined: their rheological behavior and their dewaterability. The rheological tests consisted of recording shear stress when the shear rate increases and decreases continuously and linearly with time, and when it increases and decreases in steps. Steady-state viscosity and thixotropy were obtained from the rheological tests, and both decreased significantly in all cases with increased treatment intensity. Centrifugation of ultrasonicated and thermally treated sludges allowed the total solid content to be increased by approximately 16.2% and 17.6%, respectively. These dewatered sludges had a lower viscosity and thixotropy than the untreated sludge. In contrast, alkali conditioning barely allowed the sludge to be dewatered by centrifugation, despite decreasing its viscosity and thixotropy.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46031eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2815192017-05-23T04:48:32Zhdl_2072_171809Effect of ageing on the availability of heavy metals in soils amended with compost and biochar: evaluation of changes in soil and amendment propertiesVenegas Sepúlveda, AndreaRigol Parera, AnnaVidal Espinar, MiquelMetalls pesantsContaminació dels sòlsCompostos orgànicsHeavy metalsSoil pollutionOrganic compoundsRemediation strategies using soil amendments should consider the time dependence of metal availability to identify amendments that can sustainably reduce available pollutant concentrations over time. Drying-wetting cycles were applied on amendments, soils and soil + amendment mixtures, to mimic ageing at field level and investigate its effect on extractable Cd, Cu, Ni, Pb and Zn concentrations from three contaminated soils. The amendments investigated were municipal waste organic compost and biochars. The amendments, soils and mixtures were characterised by their physicochemical properties at different ageing times. The amendments were also characterised in terms of sorption capacity for Cd and Cu. The sorption capacity and the physicochemical properties of the amendments remained constant over the period examined. When mixed with the soils, amendments, especially the compost, immediately reduced the extractable metals in the soils with low pH and acid neutralisation capacity, due to the increase in pH and buffering capacity of the mixtures. The amendments had a relatively minor impact on the metal availability concentrations for the soil with substantially high acid neutralisation capacity. The most important changes in extractable metal concentrations were observed at the beginning of the experiments, ageing having a minor effect on metal concentrations when compared with the initial effect of amendments.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/108087eng(c) Springer Verlag, 2016info:eu-repo/semantics/embargoedAccess
oai:recercat.cat:2072/2832492017-05-23T04:48:35Zhdl_2072_171809The human mitochondrial transcription factor A is a versatile G-quadruplex binding proteinLyonnais, SébastienTarrés-Soler, AleixRubio Cosials, AnnaCuppari, AnnaBrito, ReicyJaumot Soler, JoaquimGargallo Gómez, RaimundoVilaseca Casas, MartaSilva, CristinaGranzham, AntonTeulade-Fichou, Marie-PauleEritja i Casadellà, RamonSolà, MariaADN mitocondrialG-estructuresÀcids nucleicsMitochondrial DNAG-structuresNucleic acidsThe ability of the guanine-rich strand of the human mitochondrial DNA (mtDNA) to form G-quadruplex structures (G4s) has been recently highlighted, suggesting potential functions in mtDNA replication initiation and mtDNA stability. G4 structures in mtDNA raise the question of their recognition by factors associated with the mitochondrial nucleoid. The mitochondrial transcription factor A (TFAM), a highmobility group (HMG)-box protein, is the major binding protein of human mtDNA and plays a critical role in its expression and maintenance. HMG-box proteins are pleiotropic sensors of DNA structural alterations. Thus, we investigated and uncovered a surprising ability of TFAM to bind to DNA or RNA G4 with great versatility, showing an affinity similar than to double-stranded DNA. The recognition of G4s by endogenous TFAM was detected in mitochondrial extracts by pull-down experiments using a G4-DNA from the mtDNA conserved sequence block II (CSBII). Biochemical characterization shows that TFAM binding to G4 depends on both the G-quartets core and flanking single-stranded overhangs. Additionally, it shows a structure-specific binding mode that differs from B-DNA, including G4- dependent TFAM multimerization. These TFAM-G4 interactions suggest functional recognition of G4s in the mitochondria.Nature Publishing GroupUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/108899engcc-by (c) Lyonnais, Sébastien et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2834212017-05-23T04:48:36Zhdl_2072_171809Stabilization of telomeric i-motif structures by (2'S)-2'-deoxy-2'-C-methyl-cytidine residuesAviñó Andrés, AnnaDellafiore, MariaGargallo Gómez, RaimundoGonzález, CarlosIribarren, Adolfo M.Montserrat, JavierEritja i Casadellà, RamonÀcids nucleicsOligonucleòtidsG-estructuresNucleic acidsOligonucleotidesG-structuresG-quadruplex and i-motif are tetraplex structures present in telomeres and promoter regions of oncogenes. The possibility of producing nanodevices with pH-sensitive functions has triggered the interest for modified oligonucleotides with improved structural properties. We synthesized C-rich oligonucleotides carrying conformationally restricted (2'S)-2'-deoxy-2'-C-methyl-cytidine units. The effect of this modified nucleoside on the stability of intramolecular i-motifs related to vertebrate telomere was investigated by means of spectroscopic methods (UV, CD and NMR). The replacement of selected positions of the C-core by the appropriate C-modified residues induces the formation of stable intercalated tetraplexes at pHs near neutrality. The study demonstrates the possibility of enhancing the stability of i-motif by chemical modifications.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/109785eng(c) Wiley-VCH, 2017info:eu-repo/semantics/embargoedAccess
oai:recercat.cat:2072/2837232017-05-23T04:48:37Zhdl_2072_171809The surveys to the companies: a tool for the improvement of degreesCruells Cadevall, MontserratRoca, Antoni (Roca Vallmajor)Escaja Sánchez, NuriaFernández González, JavierGarrido Ponce, José AntonioGiménez Farreras, JaumeLlauradó i Tarragó, MontserratRodríguez Raurell, LauraBernad Marcos, Josep OriolEscobar Arias, Carla SaloméLópez Vinent, NúriaSagristá Gratovil, M. LluïsaNavarro Aragay, CarmeCompanyó Beltrán, RamónCompetències professionalsQualitat de l'ensenyamentControl de qualitatAvaluació de sistemes educatiusEducació superiorVocational qualificationsEducational qualityQuality controlEducational systems evaluationHigher educationIn scientific and technical degrees, the opinion of the final employers on the given subjects is really important. For this reason, the Quality Committee (CQ) of the Faculty of Chemistry of the University of Barcelona prepared a survey for chemical, engineering and pharmaceutical companies asking about the academic training required by the companies. The survey consists of nine sections including items related to laboratory operations, chemical processes, calculation methods, management systems (quality, environment and safety) or general management information. In addition, at the end of each section, a question inquires the companies about the competences shown by students in the items of the section. The results were compared with that of a similar survey carried out in 2007. The scores obtained, between 2 and 3, for all the items (score: 1, not important; 2, unimportant; 3, important; 4, very important), show that companies accept the training given to our students and the competences achieved by them. However, according to their opinion, it is possible to improve this training, especially in the subjects related to management (time, information, environment, quality, safety, etc.). Therefore, surveys are a good tool for the evaluation of the training achieved in our degrees and, consequently, for improving degrees and the teaching task, according the Quality Management System implemented in the Faculty of Chemistry.Omnia ScienceUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/109998engcc-by (c) Cruells Cadevall, Montserrat et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2838792017-05-23T04:48:38Zhdl_2072_171809Occurrence of arsenic species in algae and freshwater plants of an extreme arid region in northern Chile, the Loa River BasinPell i Lorente, AlbertMárquez, AnnaLópez Sánchez, José FermínRubio i Rovira, RoserBarbero Castro, MercedesStegen, SusanaQueirolo, FabrizioDíaz-Palma, PaulaArsènicAlguesPlantes aquàtiquesArsenicAlgaeAquatic plantsThis study reports data on arsenic speciation in two green algae species (Cladophora sp. and Chara sp.) and in five aquatic plants (Azolla sp., Myriophyllum aquaticum, Phylloscirpus cf. desserticola, Potamogeton pectinatus, Ruppia filifolia and Zannichellia palustris) from the Loa River Basin in the Atacama Desert (northern Chile). Arsenic content was measured by Mass Spectrometry coupled with Inductively Coupled Plasma (ICP-MS), after acidic digestion. Liquid Chromatography coupled to ICP-MS was used for arsenic speciation, using both anionic and cationic chromatographic exchange systems. Inorganic arsenic compounds were the main arsenic species measured in all samples. The main arsenic species in the extracts of freshwater algae and plants were arsenite and arsenate, whereas glycerol-arsenosugar (gly-sug), dimethylarsinic acid (DMA) and methylarsonic acid (MA) were present only as minor constituents. Of the samples studied, algae species accumulated more arsenic than aquatic plants. Total arsenic content ranged from 182 to 11,100 and from 20 to 248 mg As kg-1 (d.w.) in algae and freshwater plants, respectively. In comparison with As concentration in water samples, there was hyper-accumulation (>0.1% d.w.) in Cladophora sp.Elsevier LtdUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/110162eng(c) Elsevier Ltd, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2845632017-05-23T04:48:40Zhdl_2072_171809La TFC: la Tutoria de Final de CarreraMans Teixidó, Claudi, 1948-Tutoria (Ensenyament)Currículums (Ensenyament)Competències professionalsTutoring (Teaching)Curricula (Courses of study)Vocational qualificationsEl propòsit d'aquesta comunicació és presentar l'experiència de l'autor com a tutor d'alumnes de l'ensenyament d'Enginyeria Química de la Universitat de Barcelona, i presentar un instrument que el signant denomina la TFC, la Tutoria de Final de Carrera, com a eina per a ajudar l'alumne a enfocar de manera pragmàtica i realista la darrera etapa dels seus estudis de segon cicle i fer el pas cap a l'etapa posterior en les seves múltiples facetes. Els objectius de l'activitat són reduir la incertesa de l'alumne en el moment de prendre decisions decisives per al seu futur personal i professional, donar-li autoestima i confiança, subministrar-li de forma estructurada i significativa informació sobre el món laboral i de postgrau, ajudar-lo a descobrir les pròpies aptituds i limitacions, i donar-li confiança sobre les seves possibilitats. Aquest instrument consisteix en una sessió en grup, seguida d'una tutoria individualitzada amb l'objectiu de facilitar l'orientació de l'alumne en la seva decisió sobre l'orientació futura de la seva vida professional. A part del plantejament general del tema, s'explicita el desenvolupament d'un currículum basat en competències, com a exemple del progrés de l'alumne al passar per la tutoria. Els resultats són una major satisfacció i autoestima per part de l'alumne, una superior eficàcia en el procés de pas d'alumne a preprofessional, i una superior confiança en les pròpies possibilitats.Universitat de BarcelonaUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/110777catcc-by (c) Mans Teixidó, Claudi, 1948-, 2015info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2855212017-05-23T04:48:43Zhdl_2072_171809A simple model to describe the thixotropic behavior of paints.Armelin, ElaineMartí, MireiaRudé i Payró, ElisabetLabanda, JordiLlorens Llacuna, JoanAlemán, CarlosReologiaTixotropiaHistèresiTemperaturaPintura (Producte químic)RheologyThixotropyHysteresisTemperaturePaintWe propose a simple rheological model to describe the thixotropic behavior of paints, since the classical hysteresis area, which is usually used, is not enough to evaluate thixotropy. The model is based on the assumption that viscosity is a direct measure of the structural level of the paint. The model depends on two equations: the Cross-Carreau equation to describe the equilibrium viscosity and a second order kinetic equation to express the time dependence of viscosity. Two characteristic thixotropic times are differentiated: one for the net structure breakdown, which is defined as a power law function of shear rate, and an other for the net structure buildup, which is not dependent on the shear rate. The knowledge of both kinetic processes can be used to improve the quality and applicability of paints. Five representative commercial protective marine paints are tested. They are based on chlorinated rubber, acrylic, alkyd, vinyl, and epoxy resins. The temperature dependence of the rheological behavior is also studied with the temperature ranging from 5 ºC to 35 ºC. It is found that the paints exhibit both shear thinning and thixotropic behavior. The model fits satisfactorily the thixotropy of the studied paints. It is also able to predict the thixotropy dependence on temperature. Both viscosity and the degree of thixotropy increase as the temperature decreases.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46105eng(c) Elsevier B.V., 2006info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855222017-05-23T04:48:44Zhdl_2072_171809Poly(butylene terephthalate-co-5-tert-butyl isophthalate) Copolyesters: Synthesis, Characterization and PropertiesGómez, FranciscoQuintana, RobertMartínez de Ilarduya, AntxonRudé i Payró, ElisabetMuñoz-Guerra, SebastiánCopolímersPolièstersPermeabilitatPropietats tèrmiquesPropietats mecàniquesPropietats òptiquesCopolymersPolyestersPermeabilityThermal propertiesMechanical propertiesOptical propertiesA series of poly(butylene terephthalate) copolyesters containing 5-tert-butyl isophthalate units up to 50%-mole, as well as the homopolyester entirely made of these units, were prepared by polycondensation from the melt. The microstructure of the copolymers was determined by NMR to be at random for the whole range of compositions. The effect exerted by the 5-tert-butyl isophthalate units on thermal, tensile and gas transport properties was evaluated. Both Tm and crystallinity as well as the mechanical moduli were found to decrease steadily with copolymerization whereas Tg increased and the polyesters became more brittle. Permeability and solubility sligthly increased also with the content in substituted units whereas the diffusion coefficient remained practically constant. For the homopolyester poly(5-tert-butyl isophthalate), all these properties were found to deviate significantly from the general trend displayed by copolyesters suggesting that a different chain mode of packing in the amorphous phase is likely adopted in this case.WileyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/submittedVersionhttp://hdl.handle.net/2445/46110eng(c) Wiley, 2005info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2672342017-05-23T04:48:45Zhdl_2072_171809Comblike poly(a-alkyl g glutamate)s: computer simulation studies of an intermediate thermal phase.Curcó Cantarell, DavidZanuy Gomara, DavidAlemán, CarlosMuñoz-Guerra, SebastiánRudé i Payró, ElisabetPolímersMètode de MontecarloMacromolèculesModels molecularsTemperaturaPolymersMonte Carlo methodMacromoleculesMolecular modelsTemperatureMonte Carlo (MC) simulations have been used to study the structure of an intermediate thermal phase of poly(R-octadecyl ç,D-glutamate). This is a comblike poly(ç-peptide) able to adopt a biphasic structure that has been described as a layered arrangement of backbone helical rods immersed in a paraffinic pool of polymethylene side chains. Simulations were performed at two different temperatures (348 and 363 K), both of them above the melting point of the paraffinic phase, using the configurational bias MC algorithm. Results indicate that layers are constituted by a side-by-side packing of 17/5 helices. The organization of the interlayer paraffinic region is described in atomistic terms by examining the torsional angles and the end-to-end distances for the octadecyl side chains. Comparison with previously reported comblike poly(â-peptide)s revealed significant differences in the organization of the alkyl side chains.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46111eng(c) American Chemical Society , 2002info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2177232017-05-23T04:48:46Zhdl_2072_171809Solution equilibria of cytosine- and guanine-rich sequences near the promoter region of the n-myc gene that contain stable hairpins within lateral loopsBenabou, SanaeFerreira Aguilera, RubénAviñó Andrés, AnnaGonzález, CarlosLyonnais, SébastienSolà Vilarrubias, MariaEritja i Casadellà, RamonJaumot Soler, JoaquimGargallo Gómez, RaimundoADNRNAÀcids nucleicsAnàlisi multivariableCromatografiaDNARNANucleic acidsMultivariate analysisChromatographyCytosine-and guanine-rich regions of DNA are capable of forming complex structures named i-motifs and G-quadruplexes, respectively. In the present study the solution equilibria at nearly physiological conditions of a 34 -bases long cytosine-rich sequence and its complementary guanin e-rich strand corresponding to the first intron of the n-mycgene were studied. Both sequences , not yet studied, contain a 12 - base tract capable of forming stable hairpins inside the i-motif and G-quadruplex structures, respectively ...Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46204eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855232017-05-23T04:48:48Zhdl_2072_171809Polydispersity index from linear viscoelastic data: Unimodal and bimodal linear polymer meltsLlorens Llacuna, JoanRudé i Payró, ElisabetMarcos Hernández, Rosa MariaPolímersReologiaViscoelasticitatPesos molecularsMacromolèculesPolymersRheologyViscoelasticityMolecular weightsMacromoleculesThis article describes a method for determining the polydispersity index Ip2=Mz/Mw of the molecular weight distribution (MWD) of linear polymeric materials from linear viscoelastic data. The method uses the Mellin transform of the relaxation modulus of a simple molecular rheological model. One of the main features of this technique is that it enables interesting MWD information to be obtained directly from dynamic shear experiments. It is not necessary to achieve the relaxation spectrum, so the ill-posed problem is avoided. Furthermore, a determinate shape of the continuous MWD does not have to be assumed in order to obtain the polydispersity index. The technique has been developed to deal with entangled linear polymers, whatever the form of the MWD is. The rheological information required to obtain the polydispersity index is the storage G′(ω) and loss G″(ω) moduli, extending from the terminal zone to the plateau region. The method provides a good agreement between the proposed theoretical approach and the experimental polydispersity indices of several linear polymers for a wide range of average molecular weights and polydispersity indices. It is also applicable to binary blends.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46383eng(c) Elsevier B.V., 2003info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855242017-05-23T04:48:48Zhdl_2072_171809Crystallization and properties of poly(ethylene terephtalate) copolymers containing 5-tert-butyl isophtalic unitsKint, Darwin, P. R.Rudé i Payró, ElisabetLlorens Llacuna, JoanMuñoz-Guerra, SebastiánCristal·litzacióEstructura cristal·lina (Sòlids)Propietats mecàniquesPermeabilitatTereftalat de polietilèCrystallizationLayer structure (Solids)Mechanical propertiesPermeabilityPolyethylene terephthalateThe influence of incorporating 5-tert-butyl isophthalic units (tBI) in the polymer chain of poly(ethylene terephthalate) (PET) on the crystallization behavior, crystal structure, and tensile and gas transport properties of this polyester was evaluated. Random poly(ethyleneterephthalate-co-5-tert-butyl isophthalate) copolyesters (PETtBI) containing between 5 and 40 mol% of tBI units were examined. Isothermal crystallization studies were performed on amorphous glassy films at 120 8C and on molten samples at 200 8C by means of differential scanning calorimetry. Furthermore, the non-isothermal crystallization behavior of the copolyesters was investigated. It was observed that both crystallinity and crystallization rate of the PETtBI copolyesters tend to decrease largely with the comonomeric content, except for the copolymer containing 5 mol% of tBI units, which crystallized faster than PET. Fiber X-ray diffraction patterns of the semicrystalline PETtBI copolyesters proved that they adopt the same triclinic crystal structure as PET with the comonomeric units being excluded from the crystalline phase. Although PETtBI copolyesters became brittle for higher contents in tBI, the tensile modulus and strength of PET were barely affected by copolymerization. The ncorporation of tBI units slightly increased the permeability of PET, but copolymers containing up to 20 mol% of the comonomeric units were still able to present barrier properties.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/46684eng(c) Elsevier B.V., 2002info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2203762017-05-23T04:48:49Zhdl_2072_171809Study of selenocompounds from selenium-enriched culture of edible sproutsFunes Collado, VirginiaMorell García, AlbertRubio i Rovira, RoserLópez Sánchez, José FermínSeleniPlantesAminoàcidsEnzimsLlavorsQuímica dels alimentsNutricióSeleniumPlantsAmino acidsEnzymesSeedsFood chemistryNutritionSelenium is recognised as an essential micronutrient for humans and animals. One of the main sources of selenocompounds in the human diet is vegetables. Therefore, this study deals with the Se species present in different edible sprouts grown in Se-enriched media. We grew alfalfa, lentil and soy in a hydroponic system amended with soluble salts, containing the same proportion of Se, in the form of Se(VI) and Se(IV). Total Se in the sprouts was determined by acidic digestion in a microwave system and by ICP/MS. Se speciation was carried out by enzymatic extraction (Protease XIV) and measured by LC-ICP/MS. The study shows that the Se content of plants depends on the content in the growth culture, and that part of the inorganic Se was biotransformed mainly into SeMet. These results contribute to our understanding of the uptake of inorganic Se and its biotransformation by edible plants.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/47995eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2203772017-05-23T04:48:52Zhdl_2072_171809Selenium uptake by edible plants from enriched peat.Funes Collado, VirginiaMorell García, AlbertRubio i Rovira, RoserLópez Sánchez, José FermínSeleniPlantes comestiblesTorbaNutricióEnzimsAminoàcidsSeleniumEdible plantsPeatNutritionEnzymesAmino acidsAs a constituent of selenoproteins, selenium (Se) is considered an essential element for human health.The main way that Se enters the body is via the consumption of vegetables, whose concentration of thiselement depends on soil Se content. We grew cabbage, lettuce, chard and parsley, in peat enriched in Seby means of the additive Selcote Ultra®and Na2SeO3and Na2SeO4. Total Se in plants was determinedby acidic digestion and Se speciation by an enzymatic extraction. Both were measured by ICP/MS. Theconcentration ranges were between 0.1 mg Se kg−1and 30 mg Se kg−1for plants grown in Selcote Ultra®media, and between 0.4 mg Se kg−1and 1606 mg Se kg−1for those grown in peat enriched with Se sodiumsalts. We found Se (IV), Se (VI) and SeMet in all the extracts. Peat fortified with Selcote Ultra®gave slightlyhigher Se concentration than natural content values. For plants grown with selenium sodium salts, Secontent increases with the Se added and part of the inorganic Se was converted mainly to SeMet. A highSe fortification can damage or inhibit plant growth. Cabbage showed the greatest tolerance to Se.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/47996eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2208502017-05-23T04:48:54Zhdl_2072_171809A need for determination of arsenic species at low levels in cereal-based food and infant cereals. Validation of a method by LC-ICPMS.Llorente-Mirandes, ToniCalderon, JosepCentrich, F.Rubio i Rovira, RoserLópez Sánchez, José FermínArsènicCompostos inorgànicsCereals (Aliment)Alimentació infantilQuímica dels alimentsEspectrometria de masses de plasma acoblat inductivamentArsenicInorganic compoundsGrain (feed)Child nutritionFood chemistryInductively coupled plasma mass spectrometryThe present study arose from the need to determine inorganic arsenic (iAs) at low levels in cereal-based food. Validated methods with a low limit of detection (LOD) are required to analyse these kinds of food. An analytical method for the determination of iAs, methylarsonic acid (MA) and dimethylarsinic acid (DMA) in cereal-based food and infant cereals is reported. The method was optimised and validated to achieve low LODs. Ion chromatography-inductively coupled plasma mass spectrometry (LC-ICPMS) was used for arsenic speciation. The main quality parameters were established. To expand the applicability of the method, different cereal products were analysed: bread, biscuits, breakfast cereals, wheat flour, corn snacks, pasta and infant cereals. The total and inorganic arsenic content of 29 cereal-based food samples ranged between 3.7-35.6 and 3.1-26.0 microg As kg-1, respectively. The present method could be considered a valuable tool for assessing inorganic arsenic contents in cereal-based foods.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/48244eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2212802017-05-23T04:48:56Zhdl_2072_171809LC-ICP-MS analysis of arsenic compounds in dominant seaweeds from the Thermaikos Gulf (Northern Aegean Sea, Greece).Pell i Lorente, AlbertKokkinis, GiannisMalea, ParaskeaPergantis, Spiros A.Rubio i Rovira, RoserLópez Sánchez, José FermínArsènic.Algues marines.Toxicologia alimentària.Contaminació del mar.Egea (Mar)Arsenic.Marine algae.Food toxicology.Marine pollution.Aegean Sea.The content of total arsenic and arsenic compounds in the dominant seaweed species in the Thermaikos Gulf, Northern Aegean Sea was determined in samples collected in different seasons. Total arsenic was determined by acid digestion followed by ICP-MS. Arsenic speciation was analyzed by water extraction followed by LC-ICP-MS. Total arsenic concentrations in the seaweeds ranged from 1.39 to 55.0 mg kg- 1. Cystoseira species and Codium fragile showed the highest total As contents, while Ulva species (U. intestinalis, U. rigida,U. fasciata) had the lowest Arsenosugars, the most common arsenic species in seaweeds, were found in all samples, and glycerol-arsenosugar was the most common form; however, phosphate-arsenosugar and sulfate-arsenosugar were also present. Inorganic arsenic was measured in seven algae species and detected in another. Arsenate was the most abundant species in Cystoseira barbata (27.0 mg kg- 1). Arsenobetaine was measured in only one sample. Methylated arsenic species were measured at very low concentrations. The information should contribute to further understanding the presence of arsenic compounds in dominant seaweeds from the Thermaikos Gulf.Elsevier LtdUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/48483eng(c) Elsevier Ltd, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2217642017-05-23T04:48:58Zhdl_2072_171809ISO standars on test methods for water radioactivity monitoringCalmet, D.Jerome, S.Ameon, R.Bombard, A.Forte, M.Fournier, M.Herranz, M.Kwakman, P.Llauradó i Tarragó, MontserratTokonami, S.Normes ISOAiguaRadioactivitatAigua potableAccidents nuclearsISO StandardsWaterRadioactivityDrinking waterNuclear accidentsWater is vital to humans and each of us needs at least 1.5 L of safe water a day to drink. Beginning as long ago as 1958 the World Health Organization (WHO) has published guidelines to help ensure water is safe to drink. Focused from the start on monitoring radionuclides in water, and continually cooperating with WHO, the International Standardization Organization (ISO) has been publishing standards on radioactivity test methods since 1978. As reliable, comparable and"fit for purpose" results are an essential requirement for any public health decision based on radioactivity measurements, international standards of tested and validated radionuclide test methods are an important tool for production of such measurements. This paper presents the ISO standards already published that could be used as normative references by testing laboratories in charge of radioactivity monitoring of drinking water as well as those currently under drafting and the prospect of standardized fast test methods in response to a nuclear accident.ElsevierUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/48694eng(c) Elsevier, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2229642017-05-23T04:48:59Zhdl_2072_171809High-resolution mass spectrometry applied to the study of metabolome modifications in various chicken tissues after amoxicillin administrationHermo Outeiral, Ma. del PilarSaurina, JavierBarbosa Torralbo, JoséBarrón Bueno, DoloresAmoxicil·linaAnàlisi multivariableEspectrometria de massesGallinesQualitat dels alimentsAmoxicillinMultivariate analysisMass spectrometryHensFood qualityThe performance of high resolution accurate mass spectrometry (HRMS) operating in full scan MS mode was investigated for the quantitative determination of amoxicillin (AMX) as well as qualitative analysis of metabolomic profiles in tissues of medicated chickens. The metabolomic approach was exploited to compile analytical information on changes in the metabolome of muscle, kidney and liver from chickens subjected to a pharmacological program with AMX. Data consisting of m/z features taken throughout the entire chromatogram were extracted and filtered to be treated by Principal Component Analysis. As a result, it was found that medicated and non-treated animals were clearly clustered in distinct groups. Besides, the multivariate analysis revealed some relevant mass features contributing to this separation. In this context, recognizing those potential markers of each chicken class was a priority research for both metabolite identification and, obviously, evaluation of food quality and health effects associated to food consumption.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/49273eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2229652017-05-23T04:49:00Zhdl_2072_171809Metabolomic assays of amoxicillin, cephapirin and ceftiofur in chicken muscle. Application to treated chicken samples by liquid chromatography quadrupole time-of-flight mass spectrometryHermo Outeiral, Ma. del PilarGómez-Rodríguez, P.Barbosa Torralbo, JoséBarrón Bueno, DoloresAmoxicil·linaAntibiòticsGallinesMúsculsAntibiòtics betalactàmicsMetabòlitsAmoxicillinAntibioticsHensMusclesBeta lactam antibioticsMetabolitesThe aim of this study was to identity metabolites and transformation products (TPs) in chicken muscle from amoxicillin (AMX), cephapirin (PIR) and ceftiofur (TIO), which are antibiotics of the β-lactam family. Liquid chromatography coupled to quadrupole time-of-flight (QqTOF) mass spectrometry was utilized due to its high resolution, high mass accuracy and MS/MS capacity for elemental composition determination and structural elucidation. Amoxicilloic acid (AMA) and amoxicillin diketopiperazine (DKP) were found as transformation products from AMX. Desacetylcephapirin (DAC) was detected as a metabolite of PIR. Desfuroylceftiofur (DFC) and its conjugated compound with cysteine (DFC-S-Cys) were detected as a result of TIO in contact with chicken muscle tissue. The metabolites and transformation products were also monitored during the in vivo AMX treatment and slaughtering period. It was found that two days were enough to eliminate AMX and associated metabolites/transformation products after the end of administration.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/49280eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2229662017-05-23T04:49:01Zhdl_2072_171809Comparison of three analytical methods for the determination of quinolones in pig muscle samplesJiménez-Díaz, InmaculadaHermo Outeiral, Ma. del PilarBallesteros, ÓscarZafra-Gómez, AlbertoBarrón Bueno, DoloresBarbosa Torralbo, JoséNavalón, AlbertoCromatografia de líquidsFluorescènciaEspectrometria de massesQuinolonesPorcMúsculsLiquid chromatographyFluorescenceMass spectrometryQuinolone antibacterial agentsSwineMusclesThis work presents a comparison between three analytical methods developed for the simultaneous determination of eight quinolones regulated by the European Union (marbofloxacin, ciprofloxacin, danofloxacin, enrofloxacin, difloxacin, sarafloxacin, oxolinic acid and flumequine) in pig muscle, using liquid chromatography with fluorescence detection (LC-FD), liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The procedures involve an extraction of the quinolones from the tissues, a step for clean-up and preconcentration of the analytes by solid-phase extraction and a subsequent liquid chromatographic analysis. The limits of detection of the methods ranged from 0.1 to 2.1 ng g−1 using LC-FD, from 0.3 to 1.8 using LC-MS and from 0.2 to 0.3 using LC-MS/MS, while inter- and intra-day variability was under 15 % in all cases. Most of those data are notably lower than the maximum residue limits established by the European Union for quinolones in pig tissues. The methods have been applied for the determination of quinolones in six different commercial pig muscle samples purchased in different supermarkets located in the city of Granada (south-east Spain).Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/49283eng(c) Springer Verlag, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2270092017-05-23T04:49:02Zhdl_2072_171809Identification of metabolites and thermal transformation products of quinolones in raw cow milk by liquid chromatography coupled to high resolution mass spectrometry.Junza Martínez, AlexandraBarbosa, S.Codony Salcedo, RafaelJubert, A.Barbosa Torralbo, JoséBarrón Bueno, DoloresMetabòlitsQuinolonesLletCromatografia de líquidsEspectrometria de massesAntibiòticsTractament tèrmicMetabolitesQuinolone antibacterial agentsMilkLiquid chromatographyMass spectrometryAntibioticsHeat treatmentThe presence of residues of antibiotics, metabolites, and thermal transformation products (TPs), produced during thermal treatment to eliminate pathogenic microorganisms in milk, could represent a risk for people. Cow"s milk samples spiked with enrofloxacin (ENR), ciprofloxacin (CIP), difloxacin (DIF), and sarafloxacin (SAR) and milk samples from cows medicated with ENR were submitted to several thermal treatments. The milk samples were analyzed by liquid chromatography-mass spectrometry (LC-MS) to find and identify TPs and metabolites. In this work, 27 TPs of 4 quinolones and 24 metabolites of ENR were found. Some of these compounds had been reported previously, but others were characterized for the first time, including lactose-conjugated CIP, the formamidation reaction for CIP and SAR, and hydroxylation or ketone formation to produce three different isomers for all quinolones studied.American Chemical Society, Books and Journals Division]Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/52728eng(c) American Chemical Society, Books and Journals Division], 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855282017-05-23T04:49:03Zhdl_2072_171809Vortex shedding from a spinning cylinderDíaz, Francesc (Díaz González)Gavaldà, JosefinaKawall, J. G.Keffer, J. F.Giralt, FrancescMecànica de fluidsPlasma (Gasos ionitzats)TurbulènciaVelocitatEspectroscòpiaFluid mechanicsPlasma (Ionized gases)TurbulenceSpeedSpectrum analysisAn experimental investigation of a two-dimensional turbulent wake behind a spinning cylinder at Re=9000 is carried out to determine the influence of the rotation on the initial development of the flow. Spectral analysis of the velocity data measured in the near wake shows that for peripheral velocities up to the value of the free¿stream velocity, a distinct Kármán vortex activity exists within the wake, whereas for greater peripheral velocities, the Kármán activity deteriorates and disappears for values in excess of twice the free-stream velocity.American Institute of PhysicsUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/24893eng(c) American Institute of Physics, 1983info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2394412017-05-23T04:49:05Zhdl_2072_171809Simultaneous determination of gross alpha, gross beta and Ra-226 in natural water by liquid scintillation counting.Fons Castells, JordiZapata García, DanielTent Petrus, Joana Ma.Llauradó i Tarragó, MontserratRadioactivitatMostreig mediambientalEscintil·ladors líquidsContaminació de l'aiguaEspanyaRadioactivityEnvironmental samplingLiquid scintillatorsWater pollutionSpainThe determination of gross alpha, gross beta and 226Ra activity in natural waters is useful in a wide range of environmental studies. Furthermore, gross alpha and gross beta parameters are included in international legislation on the quality of drinking water [Council Directive 98/83/EC].1 In this work, a low-background liquid scintillation counter (Wallac, Quantulus 1220) was used to simultaneously determine gross alpha, gross beta and 226Ra activity in natural water samples. Sample preparation involved evaporation to remove 222Rn and its short-lived decay daughters. The evaporation process concentrated the sample ten-fold. Afterwards, a sample aliquot of 8 mL was mixed with 12 mL of Ultima Gold AB scintillation cocktail in low-diffusion vials. In this study, a theoretical mathematical model based on secular equilibrium conditions between 226Ra and its short-lived decay daughters is presented. The proposed model makes it possible to determine 226Ra activity from two measurements. These measurements also allow determining gross alpha and gross beta simultaneously. To validate the proposed model, spiked samples with different activity levels for each parameter were analysed. Additionally, to evaluate the model's applicability in natural water, eight natural water samples from different parts of Spain were analysed. The eight natural water samples were also characterised by alpha spectrometry for the naturally occurring isotopes of uranium (234U, 235U and 238U), radium (224Ra and 226Ra), 210Po and 232Th. The results for gross alpha and 226Ra activity were compared with alpha spectrometry characterization, and an acceptable concordance was obtained.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/53191eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2280122017-05-23T04:49:06Zhdl_2072_171809Occurrence of inorganic arsenic in edible Shiitake (Lentinula edodes) productsLlorente-Mirandes, ToniBarbero Castro, MercedesRubio i Rovira, RoserLópez Sánchez, José FermínArsènicBolets comestiblesToxicologia alimentàriaQuímica organometàl·licaArsenicEdible mushroomsFood toxicologyOrganometallic chemistryThe present study reports arsenic speciation analysis in edible Shiitake (Lentinula edodes) products. The study focused on the extraction, and accurate quantification of inorganic arsenic (iAs), the most toxic form of arsenic, which was selectively separated and determined using anion exchange LC-ICPMS. A wide variety of edible Shiitake products (fresh mushrooms, food supplements, canned and dehydrated) were purchased and analysed. A cultivated Shiitake grown under controlled conditions was also analysed. The extraction method showed satisfactory extraction efficiencies (>90%) and column recoveries (>85%) for all samples. Arsenic speciation revealed that iAs was the major As compound up to 1.38 mg As per kg dm (with a mean percentage of 84% of the total arsenic) and other organoarsenicals were found as minor species. Shiitake products had high proportions of iAs and therefore should not be ignored as potential contributors to dietary iAs exposure in populations with a high intake of Shiitake products.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/53383eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855302017-05-23T04:49:11Zhdl_2072_171809Scale-up model obtained from the rheological analysis of highly concentrated emulsions prepared at three scalesMay Masnou, AnnaRibó i Besolí, JordiPorras Rodríguez, MontserratMaestro Garriga, AliciaGonzález Azón, María del CarmenGutiérrez González, José María, 1953-ReologiaEmulsionsEnginyeria químicaSimilitud (Geometria)RheologyEmulsionsChemical engineeringWe examine the scale invariants in the preparation of highly concentrated w/o emulsions at different scales and in varying conditions. The emulsions are characterized using rheological parameters, owing to their highly elastic behavior. We first construct and validate empirical models to describe the rheological properties. These models yield a reasonable prediction of experimental data. We then build an empirical scale-up model, to predict the preparation and composition conditions that have to be kept constant at each scale to prepare the same emulsion. For this purpose, three preparation scales with geometric similarity are used. The parameter N¿D^α, as a function of the stirring rate N, the scale (D, impeller diameter) and the exponent α (calculated empirically from the regression of all the experiments in the three scales), is defined as the scale invariant that needs to be optimized, once the dispersed phase of the emulsion, the surfactant concentration, and the dispersed phase addition time are set. As far as we know, no other study has obtained a scale invariant factor N¿Dα for the preparation of highly concentrated emulsions prepared at three different scales, which covers all three scales, different addition times and surfactant concentrations. The power law exponent obtained seems to indicate that the scale-up criterion for this system is the power input per unit volume (P/V).Elsevier LtdUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/62743eng(c) Elsevier Ltd, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855322017-05-23T04:49:12Zhdl_2072_171809Clotting activity of polyphosphate-functionalized silica nanoparticlesKudela, DamienSmith, Stephanie A.May Masnou, AnnaBraun, Gary B.Pallaoro, AlessiaNguyen, Chi K.Chuong, Tracy T.Nownes, SaraAllen, RileyParker, Nicholas R.Rashidi, Hooman H.Morrissey, James H.Stucky, Galen D.SiliciNanopartículesSilicatsFerides i lesionsHemorràgiaSiliconNanoparticlesSilicatesWounds and injuriesHemorrhageWe present a silica nanoparticle (SNP) functionalized with polyphosphate (polyP) that accelerates the natural clotting process of the body. SNPs initiate the contact pathway of the blood-clotting system; short-chain polyP accelerates the common pathway by the rapid formation of thrombin, which enhances the overall blood-clotting system, both by accelerating fibrin generation and by facilitating the regulatory anticoagulation mechanisms essential for hemostasis. Analysis of the clotting properties of bare SNPs, bare polyP, and polyP-functionalized SNPs in plasma demonstrated that the attachment of polyP to SNPs to form polyP-SNPs creates a substantially enhanced synergistic effect that lowers clotting time and increases thrombin production at low concentrations. PolyP-SNP even retains its clotting function at ambient temperature. The polyP-SNP system has the potential to significantly improve trauma-treatment protocols and outcomes in hospital and prehospital settings.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/62752eng(c) Wiley-VCH, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855332017-05-23T04:49:12Zhdl_2072_171809Catalytic gasification of glycerol in supercritical waterMay Masnou, AnnaSalvadó i Rovira, JoanTorras, CarlesMontané i Calaf, DanielBiotecnologiaGasificació de la biomassaHidrogenProduccióRuteniCatalitzadorsBiotechnologyBiomass gasificationHydrogenProductionRutheniumCatalystsThe conversion of glycerol in supercritical water (SCW) was studied at 510-550 °C and a pressure of 350 bars using both a bed of inert and non-porous ZrO2 particles (hydrothermal experiments), and a bed of a 1% Ru/ZrO2 catalyst. Experiments were conducted with a glycerol concentration of 5 wt% in a continuous isothermal fixed-bed reactor at a residence time between 2 and 10 s. Hydrothermolysis of glycerol formed water-soluble products such as acetaldehyde, acetic acid, hydroxyacetone and acrolein, and gases like H2, CO and CO2. The catalyst enhanced the formation of acetic acid, inhibited the formation of acrolein, and promoted gasification of the glycerol decomposition products. Hydrogen and carbon oxides were the main gases produced in the catalytic experiments, with minor amounts of methane and ethylene. Complete glycerol conversion was achieved at a residence time of 8.5 s at 510 °C, and at around 5 s at 550 °C with the 1 wt% Ru/ZrO2 catalyst. The catalyst was not active enough to achieve complete gasification since high yields of primary products like acetic acid and acetaldehyde were still present. Carbon balances were between 80 and 60% in the catalytic experiments, decreasing continuously as the residence time was increased. This was attributed partially to the formation of methanol and acetaldehyde, which were not recovered and analyzed efficiently in our set-up, but also to the formation of carbon deposits. Carbon deposition was not observed on the catalyst particles but on the surface of the inert zirconia particles, especially at high residence time. This was related to the higher concentration of acetic acid and other acidic species in the catalytic experiments, which may polymerize to form tar-like carbon precursors. Because of carbon deposition, hydrogen yields were significantly lower than expected; for instance at 550 °C the hydrogen yield potential was only 50% of the stoichiometric value.University College London, Faculty of Mathematical and Physical Sciences, Department of MathematicsUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/62753eng(c) University College London, Faculty of Mathematical and Physical Sciences, Department of Mathematics, 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855352017-05-23T04:49:13Zhdl_2072_171809Rheological behavior of hydrophobically modified hydroxyethyl cellulose solutions: A linear viscoelastic modelMaestro Garriga, AliciaGonzález, C.Gutiérrez González, José María, 1953-ReologiaCel·lulosaViscoelasticitatPolímersSolucions (Química)RheologyCelluloseViscoelasticityPolymersSolution (Chemistry)The rheological behavior of hydrophobically modified hydroxyethyl cellulose HMHEC, an associative thickener, was studied and compared with that of hydrophobically modified ethoxylated urethanes HEURs and nonassociative celluloses. In contrast to HEURs, a simple Maxwell model does not fit the linear viscoelastic behavior of HMHEC. Differences are attributed to the stiffness and comb structure of HMHEC. A generalized Maxwell model with a logarithmic distribution of relaxation times is proposed, and another parameter that includes Rouse-like relaxation is added to fit behavior at high frequencies. Four parameters are needed to describe HMHEC viscoelasticity: a mean relaxation time, lM ; its corresponding standard deviation, s; a plateau modulus, GN ; and a viscosity at infinite frequency, h ` . Satisfactory fitting is obtained for all concentrations and temperatures in the range of frequencies studied. The sharp increase of GN with concentration indicates loop-to-bridge transitions. Temperature does not influence GN , since the reduction in the number density of elastically effective chains caused by Brownian motion masks the direct effect of temperature. The dependence of lM on temperature follows the Arrhenius equation, as does the relaxation time of HEURs, but it does not change with concentration, presumably because the comb structure of HMHEC prevents the formation of long superchains.The Society of RheologyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/24847eng(c) The Society of Rheology, 2002info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855372017-05-23T04:49:15Zhdl_2072_171809Phase behavior and rheological analysis of reverse liquid crystals and W/I2, W/H2 gel emulsions using an amphiphilic block copolymer.May Masnou, AnnaAramaki, KenjiGutiérrez González, José María, 1953-Col·loidesPolímersGels (Farmàcia)EmulsionsReologiaColloidsPolymersGels (Pharmacy)EmulsionsRheologyThis article reports the phase behavior determi- nation of a system forming reverse liquid crystals and the formation of novel disperse systems in the two-phase region. The studied system is formed by water, cyclohexane, and Pluronic L-121, an amphiphilic block copolymer considered of special interest due to its aggregation and structural proper- ties. This system forms reverse cubic (I2) and reverse hexagonal (H2) phases at high polymer concentrations. These reverse phases are of particular interest since in the two-phase region, stable high internal phase reverse emulsions can be formed. The characterization of the I2 and H2 phases and of the derived gel emulsions was performed with small-angle X-ray scattering (SAXS) and rheometry, and the influence of temperature and water content was studied. TheH2 phase experimented a thermal transition to an I2 phase when temperature was increased, which presented an Fd3m structure. All samples showed a strong shear thinning behavior from low shear rates. The elasticmodulus (G0) in the I2 phase was around 1 order of magnitude higher than in theH2 phase. G0 was predominantly higher than the viscousmodulus (G00). In the gel emulsions,G0 was nearly frequency-independent, indicating their gel type nature. Contrarily to water-in-oil (W/O) normal emulsions, in W/I2 and W/H2 gel emulsions, G0, the complex viscosity (|η*|), and the yield stress (τ0) decreased with increasing water content, since the highly viscous microstructure of the con- tinuous phase was responsible for the high viscosity and elastic behavior of the emulsions, instead of the volumefraction of dispersed phase and droplet size. A rheological analysis, in which the cooperative flow theory, the soft glass rheology model, and the slip plane model were analyzed and compared, was performed to obtain one single model that could describe the non-Maxwellian behavior of both reverse phases and highly concentrated emulsions and to characterize their microstructure with the rheological properties.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/62786eng(c) American Chemical Society , 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2467122017-05-23T04:49:15Zhdl_2072_171809EMQAL: Erasmus Mundus Master in Quality in Analytical LaboratoriesEsteban i Cortada, MiquelSahuquillo Estrugo, ÀngelsEstudis de màsterBeques d'investigacióLaboratorisCientíficsQualitat totalMasters degreesResearch grantsLaboratoriesScientistsTotal quality managementERASMUS (Programa)The Erasmus Mundus Master in Quality in Analytical Laboratories (EMQAL) is a two-year Joint Master Degree. The course is funded by the European Commission through the Erasmus Mundus Programme, providing a number of attractive scholarships for European and non-European students. EMQAL prepares professionals for analytical laboratories, focusing on laboratory management and quality systems, along with complementing their technical knowledge. The EMQAL aims at training students in the most relevant issues concerning quality systems and management in analytical laboratories, and to become an expert in: Quality management, Analytical methods and Data Analysis. EMQAL promotes mobility. The students will attend one academic year of lectures in one of the European universities of the EMQAL consortium, and a 12 months master thesis at other European university, with the possibility to spend three-months in one of the non-EU partners. The language of instruction and examination is English. Further information is available at www.emqal.org.Sociedad Chilena de QuímicaUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/63048engcc-by-nc (c) Sociedad Chilena de Química, 2014info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by-nc/3.0/es">http://creativecommons.org/licenses/by-nc/3.0/es</a>
oai:recercat.cat:2072/2855382017-05-23T04:49:17Zhdl_2072_171809Characterization and Control Strategies of an Integrated Chemical-Biological System for the Remediation of Toxic Pollutants in Wastewater: A case of studyBacardit Peñarroya, JordiSans Mazón, CarmeSeminago, RamonEsplugas Vidal, SantiagoAigües residualsDepuració d'aigües residualsSistemes de control biològicSewagePurification of sewageBiological control systemsIn a previous work, a hybrid system consisting of an advanced oxidation process (AOP) named Photo-Fenton (Ph-F) and a fixed bed biological treatment operating as a sequencing batch biofilm reactor (SBBR) was started-up and optimized to treat 200 mg·L-1 of 4-chlorophenol (4-CP) as a model compound. In this work, studies of reactor stability and control as well as microbial population determination by molecular biology techniques were carried out to further characterize and control the biological reactor. Results revealed that the integrated system was flexible and even able to overcome toxic shock loads. Oxygen uptake rate (OUR) in situ was shown to be a valid tool to control the SBBR operation, to detect toxic conditions to the biomass, and to assess the recovery of performance. A microbial characterization by 16S rDNA sequence analysis reveals that the biological population was varied, although about 30% of the bacteria belonged to the Wautersia genus.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/65627eng(c) American Chemical Society , 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855392017-05-23T04:49:18Zhdl_2072_171809A Comparison of the Environmental Impact of Different AOPs: Risk IndexesGiménez Farreras, JaumeBayarri Ferrer, BernardíGonzález, O.Malato, S.Peral, J.Esplugas Vidal, SantiagoAvaluació del risc ambientalAvaluació d'impacte ambientalEnvironmental risk assessmentEnvironmental impact analysisToday, environmental impact associated with pollution treatment is a matter of great concern. A method is proposed for evaluating environmental risk associated with Advanced Oxidation Processes (AOPs) applied to wastewater treatment. The method is based on the type of pollution (wastewater, solids, air or soil) and on materials and energy consumption. An Environmental Risk Index (E), constructed from numerical criteria provided, is presented for environmental comparison of processes and/or operations. The Operation Environmental Risk Index (EOi) for each of the unit operations involved in the process and the Aspects Environmental Risk Index (EAj) for process conditions were also estimated. Relative indexes were calculated to evaluate the risk of each operation (E/NOP) or aspect (E/NAS) involved in the process, and the percentage of the maximum achievable for each operation and aspect was found. A practical application of the method is presented for two AOPs: photo-Fenton and heterogeneous photocatalysis with suspended TiO2 in Solarbox. The results report the environmental risks associated with each process, so that AOPs tested and the operations involved with them can be compared.MDPIUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/65744engcc-by (c) Giménez Farreras, Jaume et al., 2014info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2855402017-05-23T04:49:20Zhdl_2072_171809Scale invariants in the preparation of reverse high internal phase ratio emulsionsMay-Masnou, AnnaPorras Rodríguez, MontserratMaestro Garriga, AliciaGonzález, CarmeGutiérrez González, José María, 1953-EmulsionsEmulsionsReverse high internal phase ratio emulsions (HIPRE) are prepared with the system water/Span80/dodecane to identify the influence of the process variables on droplet size and polydispersity, and to study the influence of the process scale-up. After discussing the most common scale invariants used in emulsification processes, we prepare emulsions at two different scales following a complete factorial experimental design. Using the empirical models obtained with the statistical analysis of the results, we determine the scale invariants for the system. Results from a previous study indicated that the scale invariant for the preparation of HIPRE could be the stirring rate. However, the results obtained in this work show that the scale invariant, based on droplet size, could change depending on the conditions of emulsification. Only when the stirring rate is high enough (> 1500 rpm), or when the surfactant-to-oil ratio is high and the total addition time low, the scale invariant is indeed the stirring rate. The elevated shear stress inside the mixer when the stirring rate is high is responsible of the small droplet size obtained on both scales. However, for other values of the process variables, the scale-invariant can be expressed as N¿D^a, where 0 < a < 0.5, and depends on other two factors: the addition flow rate of dispersed phase or addition time, and the surfactant-to-oil ratio. We propose a methodology to determine these scale invariants and to calculate the threshold values of surfactant-to-oil ratio and addition flow rate from which the stirring rate is the scale invariant (when a → 0).Elsevier LtdUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/66318eng(c) Elsevier Ltd, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2540952017-05-23T04:49:20Zhdl_2072_171809Characterisation and determination of fullerenes: a critical reviewAstefanei, AlinaNúñez Burcio, OscarGalcerán Huguet, M. TeresaFul·lerensFullerenesA prominent sector of nanotechnology is occupied by a class of carbon-based nanoparticles known as fullerenes. Fullerene particle size and shape impact in how easily these particles are transported into and throughout the environment and living tissues. Currently, there is a lack of adequate methodology for their size and shape characterisation, identification and quantitative detection in environmental and biological samples. The most commonly used methods for their size measurements (aggregation, size distribution, shape, etc.), the effect of sampling and sample treatment on these characteristics and the analytical methods proposed for their determination in complex matrices are discussed in this review. For the characterisation and analysis of fullerenes in real samples, different analytical techniques including microscopy, spectroscopy, flow field-flow fractionation, electrophoresis, light scattering, liquid chromatography and mass spectrometry have been reported. The existing limitations and knowledge gaps in the use of these techniques are discussed and the necessity to hyphenate complementary ones for the accurate characterisation, identification and quantitation of these nanoparticles is highlighted.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/66853engcc-by-nc-nd (c) Elsevier B.V., 2015info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2544132017-05-23T04:49:22Zhdl_2072_171809Field-Amplified Sample Injection-Micellar Electrokinetic Chromatography for the Determination of Benzophenones in Food SimulantsFélez, CristinaMolet, AnnaNúñez Burcio, OscarCromatografiaEnvasament d'alimentsChromatographyFood packagingA field-amplified sample injection-micellar electrokinetic chromatography (FASI-MEKC) method for the determination of 14 benzophenones (BPs) in a food simulant used in migration studies of food packaging materials was developed, allowing almost baseline separation in less than 21 min. The use of a 10 mM sodium dodecyl sulfate (SDS) solution as sample matrix was mandatory to achieve FASI enhancement of the analyzed BPs. A 21- to 784-fold sensitivity enhancement was achieved with FASI-MEKC, obtaining limits of detection down to 5.1<br>68.4 µg/L, with acceptable run-to-run precisions (RSD values lower than 22.3%) and accuracy (relative errors lower than 21.0%). Method performance was evaluated by quantifying BPs in the food simulant spiked at 500 µg/L (bellow the established specific migration limit for BP (600 µg/L) by EU legislation). For a 95% confidence level, no statistical differences were observed between found and spiked concentrations (probability at the confidence level, p value, of 0.55), showing that the proposed FASI-MEKC method is suitable for the analysis of BPs in food packaging migration studies at the levels established by EU legislation.MDPIUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/66944engcc-by (c) Félez, Cristina et al., 2015info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2855422017-05-23T04:49:25Zhdl_2072_171809Shear thinning and thixotropy of HMHEC and HEC water solutionsMaestro Garriga, AliciaGonzález García, Ma. ConcepciónGutiérrez González, José María, 1953-ReologiaViscositatRevestimentsTixotropiaRheologyViscosityCoatingsThixotropySteady state viscosity and thixotropy of hydrophobically modified hydroxyethyl cellulose HMHEC and nonassociative cellulose water solutions are studied. Although all the samples are shear thinning, only the HMHEC is thixotropic, since the migration of hydrophobes to micelles is controlled by diffusion. The Cross model fits steady state curves. The Mewis model, a phenomenological model that proposes that the rate of change of viscosity when the shear rate is suddenly changed is related to the difference between the steady state and current values of viscosity raised to an exponent, fits structure construction experiments when the exponent, n, is estimated to be around 2. The Newtonian assumption used by Mewis cannot be used here, however. This seems to be related to the fact that the thickening is due to bridged micelle formation, which is a slow process, and also to topological constraints and entanglements, which are rapid processes. The kinetic parameter was redefined to kn in order to make it independent of initial conditions. So, kn depends only on how the shear affects the structure. kn reaches a plateau at shear rates too low to produce structure destruction and decreases at higher shear rates.The Society of RheologyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/24848eng(c) The Society of Rheology, 2002info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2580582017-05-23T04:49:25Zhdl_2072_171809RNA stem-loop to G-quadruplex equilibrium controls mature miRNA production inside the cellPandey, SatyaprakashAgarwala, PrachiJayaraj, Gopal G.Gargallo Gómez, RaimundoMaiti, SouvikRNAPorfirinesRNAPorphyrinsBiological role for existence of overlapping structures in RNA is possible yet remains very less explored. G-rich tracts of RNA form G-quadruplexes while GC-rich sequences prefer stem-loop structures. Equilibrium between alternate structures within RNA may occur and influence its functionality. We tested equilibrium between G-quadruplex and stem-loop structure in RNA and its effect on biological processes using pre-miRNA as a model system. Dicer enzyme recognizes canonical stem-loop structures in pre-miRNA to produce mature miRNAs. Deviation from stem-loop leads to deregulated mature miRNA levels, providing readout of existence of alternate structure per se G-quadruplex mediated structural interference in miRNA maturation. In vitro analysis using beacon and Dicer cleavage assays indicated that mature miRNA levels depend on relative amounts of K+ and Mg2+ ions suggesting an ion-dependent structural shift. Further in cellulo studies with and without TmPyP4 (RNA G-quadruplex destabilizer) demonstrated that miRNA biogenesis is modulated by G-quadruplex-stem-loop equilibrium in a subset of pre-miRNAs. Our combined analysis thus provides evidence for formation of non-canonical G-quadruplexes in competition with canonical stem-loop structure inside the cell and its effect on miRNA maturation in a comprehensive manner.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/69282eng(c) American Chemical Society , 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2685172017-05-23T04:49:31Zhdl_2072_171809Thermodynamic analysis of the experimental equilibria for the liquid-phase etherification of isobutene with C1 to C4 linear primary alcoholsBadia i Córcoles, Jordi HugFité Piquer, CarlesBringue Tomás, RogerRamírez Rangel, ElianaCunill García, FidelÈtersAlcoholsEquilibri químicTermodinàmicaEthersAlcoholsChemical equilibriumThermodynamicsThe chemical equilibrium of the liquid-phase syntheses of 2-methoxy-2-methylpropane (MTBE), 2-ethoxy-2-methylpropane (ETBE), 2-methyl-2-propoxypropane (PTBE), and 1-tert-butoxybutane (BTBE) by reaction of isobutene with methanol, ethanol, 1-propanol, and 1-butanol, respectively, has been studied. Four different ion exchange resins as the catalysts, and two different reactor systems, namely, a batch reactor and a setup of tubular reactors, were used. Temperature and pressure were in the range 313-383 K and 1.5-2.0 MPa, respectively. MTBE and ETBE synthesis reactions experiments were carried out mainly to validate the reliability of the reaction systems. Experiments in PTBE and BTBE etherifications allowed estimating thermodynamic properties for those reactions and involved species, namely, molar standard enthalpy and entropy changes of reaction and molar enthalpy change of formation of the four ethers. A comparison of estimated reaction thermodynamic values among the homologous series of linear alcohols, and with results quoted in the literature, when available, has been made.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/96442eng(c) American Chemical Society , 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855442017-05-23T04:49:32Zhdl_2072_171809Hierarchical meso-mesoporous and macro-mesoporous silica templated by mixtures of polyoxyethylene fluoroalkyl ether and triblock copolymerMay-Masnou, AnnaStébé, Marie JoséBlin, Jean LucAgents tensioactiusMaterials porososSiliciEmulsionsSurface active agentsPorous materialsSiliconEmulsionsWe report here the synthesis of different kinds of hierarchical porous silica materials by using mixtures of an amphiphilic block copolymer (Pluronic P123) and a nonionic fluorinated surfactant. In particular, we have taken advantage of the difference in polarities between the two compounds to design dual-mesoporous materials through the cooperative templating mechanism (CTM). We have undertaken a complete study of this system by varying the composition of the mixed micelles and the synthesis conditions. We have shown that both the dual-mesoporosity and the mesopore ordering are favored when materials are prepared with fluorine-rich and P123-rich micelles. However, when the P123-rich micelles predominate, the mesostructure is less organized and the dual-porosity depends on the P123 content. In addition, concentrated emulsions were formed by incorporating perfluorodecalin (PFD) in the surfactant mixture, and hierarchical macro-mesoporous materials were prepared by combining the CTM and the emulsion templating mechanism.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/97404eng(c) Wiley-VCH, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2612852017-05-23T04:49:35Zhdl_2072_171809Análisis of Benzalkonium chloride by capillary electrophoresis-electrospray-Tandem mass spectrometryPara, B. V. (Bianca Veronica)Núñez Burcio, OscarMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaElectroforesi capil·larCapillary electrophoresisConditions for the separation and determination of benzalkonium chloride (BAC) homologues by CE with UV-detection and CE coupled to MS (IT) using electrospray as ionization source were established. The separation was performed using fused-silica capillaries of 50 μm id and 100 mM acetic acid-ammonium acetate buffer solution at pH 4.5 with 80% of ACN as carrier electrolyte. CE-MS coupling parameters were optimized and methanol-10 mM acetic acid (90:10 v/v) was selected as sheath liquid. Detection limits, based on an S/N of 3:1, were calculated, and values between 0.8 and 1.3 mg/L with CE-ESI/MS and around 0.5 mg/L with CE-ESI-MS/MS, using hydrodynamic injection (15 s, 3.5 kPa), were obtained. Good run-to-run and day-to-day precisions on concentration were achieved with RSDs lower than 8%. Quantitative analysis was carried out by the internal standard method and the calibration curves showed good linearities (r2>0.98). The CE-ESI-MS/MS method was successfully applied to the analysis of BAC in different ophthalmic solutions, allowing the direct determination, identification and confirmation of the BAC homologues presented in these samples.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98051eng(c) Wiley-VCH, 2006info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613322017-05-23T04:49:36Zhdl_2072_171809Analysis of UV ink photoinitiators in packaged food by fast liquid chromatography at subambient temperature coupled to tandem mass spectrometryGallart Ayala, HèctorNúñez Burcio, OscarMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaEnvasament d'alimentsEspectrometria de massesCromatografia de líquidsFood packagingMass spectrometryLiquid chromatographyA fast method of liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed for the analysis of eleven UV ink photoinitiators in packaged food. Chromatographic separation was achieved in a pentafluorophenylpropyl (PFPP) column at 5ºC and acetonitrile:25 mM formic acid-ammonium formate (pH 2.7) in gradient elution. To reduce sample treatment, a QuEChERS (quick, easy, cheap, effective, rugged and safe) method for the extraction and clean-up of UV photoinitiators in packaged foods was evaluated. Triple quadrupole working in H-SRM on Q1 mode was used for both quantitation and confirmation purposes and the most intense and selective transitions were chosen. Quality parameters of the developed QuEChERS LC-MS/MS method were established and applied for the analysis of photoinitiators in food packaged at ng kg-1 levels.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98160eng(c) Elsevier B.V., 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613572017-05-23T04:49:37Zhdl_2072_171809Field-amplified sample injection-micellar electrokinetic capillary chromatography for the analysis of bisphenol A, bisphenol F, and their diglycidyl ethers and derivatives in canned soft drinksGallart Ayala, HèctorNúñez Burcio, OscarMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaBegudes carbòniquesQuímica dels alimentsFenolsCromatografiaEnvasament d'alimentsCarbonated beveragesFood compositionPhenolsChromatographyFood packagingConditions were established for the separation and analysis of Bisphenol A (BPA), Bisphenol F (BPF), and their diglycidyl ethers, by micellar electrokinetic capillary chromatography (MECC). Good resolution was obtained for all compounds, although in order to achieve the separation of ortho-ortho, ortho-para, and para-para isomers of Bisphenol F diglycidyl ether (BFDGE), BFDGE¿2H2O and BFDGE¿2HCl, it was necessary to use a 25 µm I.D. fused-silica capillary. To increase sensitivity, a field amplified sample injection (FASI)-MECC method was developed using 10 mM sodium dodecyl sulfate (SDS) solution as injection matrix and a 75 µm I.D. fused-silica capillary. Instrumental quality parameters such as limits of detection (0.999), and run-to-run and day-to-day precisions (relative standard deviations (RSD) values lower than 12.5%) were determined. Finally, the suitability of the FASI-MECC method for the analysis of BPA, BPF and their diglycidyl ethers in canned soft-drinks was evaluated. Quantitation was performed by matrix-matched calibration using a plastic-bottled isotonic drink as matrix. The results showed that FASI-MECC is an economic method for the screening and quantitation of these kinds of compounds in soft-drink beverages, with no loss of reproducibility, and effective at concentrations lower than the specific migration level (SML) values established by the European Union.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98193eng(c) Wiley-VCH, 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613582017-05-23T04:49:38Zhdl_2072_171809In-line preconcentration capillary zone electrophoresis for the analysis of haloacetic acids in waterBernad Marcos, Josep OriolDamascelli, AnnaNúñez Burcio, OscarGalcerán Huguet, M. TeresaAcetatsAigua potableElectroforesi capil·larContaminantsAcetatesDrinking waterCapillary electrophoresisPollutantsTwo in-line enrichment procedures (large volume sample stacking (LVSS) and field amplified sample injection (FASI)) have been evaluated for the capillary zone electrophoresis (CZE) analysis of haloacetic acids (HAAs) in drinking water. For LVSS, separation on normal polarity by using 20 mM acetic acid-ammonium acetate (pH 5.5) containing 20% acetonitrile as BGE was required. For FASI, the optimum conditions were 25 s hydrodynamic injection (3.5 kPa) of a water plug followed by 25 s electrokinetic injection (-10 kV) of the sample, and 200 mM formic acid-ammonium formate buffer at pH 3.0 as BGE. For both FASI and LVSS methods, linear calibration curves (r2>0.992), limit of detection (LOD) on standards prepared in Milli-Q water (49.1-200 µg/L for LVSS and 4.2-48 µg/L for FASI), and both run-to-run and day-to-day precisions (RSD values up to 15.8% for concentration) were established. Due to the higher sensitive enhancement (up to 310-fold) achieved with FASI-CZE this method was selected for the analysis of HAAs in drinking water. However, for an optimal FASI application sample salinity was removed by solid phase extraction (SPE) using Oasis WAX cartridges. With SPE-FASI-CZE, method detection limits in the range 0.05-0.8 µg/L were obtained, with recoveries, in general, higher than 90% (around 65% for monochloroacetic and monobromoacetic acids). The applicability of the SPE-FASI-CZE method was evaluated by analyzing a drinking tap water from Barcelona where seven HAAs were found at concentration levels between 3-13 µg/L.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98197eng(c) Wiley-VCH, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855452017-05-23T04:49:39Zhdl_2072_171809Effects of inorganic nitrogen (NH4Cl) and biodegradable organic carbon (CH3COONa) additions on a pilot-scale seawater biofilterSimón, Francesc XavierRudé i Payró, ElisabetBerdalet i Andrés, ElisaLlorens Llacuna, JoanBaig, SylvieAigua de marBiodegradacióDepuració de l'aiguaEcologia marinaNitrogenSeawaterBiodegradationWater purificationMarine ecologyNitrogenBiofilters degrade only a small fraction of the natural organic matter (NOM) contained in seawater which is the leading cause of biofouling in downstream processes. This work studies the effects of chemical additions on NOM biodegradation by biofilters. In this work, biofiltration of seawater with an empty bed contact time (EBCT) of 6 min and a hydraulic loading rate of 10 m h-1 reduces the biological oxygen demand (BOD7) by 8%, the dissolved organic carbon (DOC) by 6% and the UV absorbance at 254 nm (A254) by 7%. Different amounts of ammonium chloride are added to the seawater (up to twice the total dissolved nitrogen in untreated seawater) to study its possible effect on the removal of NOM by a pilot-scale biofilter. Seawater is amended with different amounts of easily biodegradable dissolved organic carbon (BDOC) supplied as sodium acetate (up to twice the DOC) for the same purpose. The results of this work reveal that the ammonium chloride additions do not significantly affect NOM removal and the sodium acetate is completely consumed by the biofiltration process. For both types of chemical additions, the BOD7, DOC and A254 in the outlet stream of the biofilter are similar to the values for the untreated control. These results indicate that this biofilter easily removes the BDOC from the seawater when the EBCT is not above 6 min. Furthermore, nitrogen does not limit the NOM biodegradation in seawater under these experimental conditions.Elsevier LtdUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/34462eng(c) Elsevier Ltd, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613592017-05-23T04:49:39Zhdl_2072_171809Preventing false negatives with high-resolution mass spectrometry: the benzophenone caseGallart Ayala, HèctorNúñez Burcio, OscarMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaMartins, Cláudia P. B.Espectrometria de massesCromatografiaEnvasament d'alimentsQuímica dels alimentsMass spectrometryChromatographyFood packagingFood compositionBenzophenone (BP) is one of the many contaminants reported as present in foodstuff due to its migration from food packaging materials. Liquid chromatography tandem mass spectrometry (LC-MS/MS) is acknowledged in the literature as the method of choice for this analysis. However, cases have been reported where the use of this methodology was not enough to unambiguously confirm the presence of a contaminant. In previous work performed by the authors, the unequivocal identification of BP in packaged foods was not possible even when monitoring two m/z transitions, since ion ratio errors higher than 20% were obtained. In order to overcome this analytical problem a fast, sensitive and selective liquid chromatography-high resolution-mass spectrometry (LC-HRMS) methodology has been developed and applied to the analysis of BP in packaged foods. A direct comparison between liquid chromatography high resolution mass spectrometry (LC-HRMS) and LC-MS/MS data indicated better selectivity when working with LC-HRMS at a resolving power of 50,000 FWHM than when monitoring two m/z transitions by LC-MS/MS. The resolving power used enabled the detection and identification of Harman as the compound impeding the confirmation of BP by LC-MS/MS. Similar quantitative results were obtained by an Orbitrap mass analyser (Exactive ¿) and a triple quadrupole mass analyser (TSQ Quantum Ultra AM ¿).WileyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98200eng(c) Wiley, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613602017-05-23T04:49:40Zhdl_2072_171809Non-aqueous capillary electrophoresis separation of fullerenes and C60 fullerene derivativesAstefanei, AlinaNúñez Burcio, OscarGalcerán Huguet, M. TeresaFul·lerensElectroforesi capil·larFullerenesCapillary electrophoresisAs the interest in the use of fullerene compounds in biomedical and cosmetic applications increases, so too does the need to develop methods for their determination and quantitation in such complex matrices. In this work we studied the behavior of C60 and C70 fullerenes in non-aqueous capillary electrophoresis, as well as two C60 fullerene derivatives not previously reported by any electrophoretic method, N-methyl-fulleropyrrolidine (C60 pyrr) and (1,2-methanofullerene C60)-61-carboxylic acid (C60-COOH). . The separation was performed using fused-silica capillaries with an I.D. of 50 µm and tetraalkylammonium salts, namely tetra-n-decylammonium bromide (TDAB, 200 mM) and tetraethylammonium bromide (TEAB, 40 mM), in a solvent mixture containing 6% methanol and 10% acetic acid in acetonitrile:chlorobenzene (1:1 v/v) as the background electrolyte (BGE). Detection limits, based on a signal-to-noise ratio of 3:1, were calculated and values between 1 and 3.7 mg/L were obtained. Good run-to-run and day-to-day precisions on concentration were achieved with RDSs lower than 15%. For the first time, an electrophoretic technique (NACE) has been applied for the analysis of C60 fullerene in a commercial cosmetic cream. A standard addition method was used for quantitation and the result was compared with that obtained by analyzing the same cream by LC-MS.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98201eng(c) Springer Verlag, 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613622017-05-23T04:49:42Zhdl_2072_171809Atmospheric pressure photoionization mass spectrometry of fullerenesNúñez Burcio, OscarGallart Ayala, HèctorMartins, Cláudia P. B.Moyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaFul·lerensEspectrometria de massesPressió atmosfèricaMaterials nanoestructuratsFullerenesMass spectrometryAtmospheric pressureNanostructured materialsAtmospheric pressure photoionization (APPI) was evaluated for the analysis of fullerenes. An important response improvement was found when using toluene mediated APPI in negative mode if compared with other API sources (electrospray and atmospheric pressure chemical ionization). Fullerene APPI negative mass spectra were dominated by the isotopic cluster of the molecular ion, although isotopic patterns for M+1, M+2 and M+3 ions showed higher than expected relative abundances. These discrepancies are explained by the presence of two isobaric ions, one due to 13C and the other to the addition of hydrogen to a double bond of the fullerene structure. Triple quadrupole tandem mass spectrometry and ultra-high resolution mass spectrometry and accurate mass measurements were used to confirm these assignments. Additionally, cluster ions M+16 and M+32 were characterized following the same strategy. Ions due to the addition of oxygen and alkyl additions were attributed to the presence of methanol in the mobile phase. For the fast chromatographic separation of fullerenes (less than 3.5 min) a sub-2 µm C18 column and isocratic elution (toluene:methanol 45:55 v/v) was used. Highly selective-selected ion monitoring (H-SIM) mode (mass resolving power >12,500 FWHM) was proposed monitoring the two most intense isotope ions in the [M]-¿ cluster. Method limits of quantitation down to 10 pg L-1 for C60 and C70 fullerenes and between 0.75-5.0 ng L-1 for larger fullerenes were obtained. Finally, the UHPLC-APPI-MS method was used to analyze fullerenes in river and pond water samples.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98204eng(c) American Chemical Society , 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613982017-05-23T04:49:45Zhdl_2072_171809New trends in fast liquid chromatography for food and environmental analysisNúñez Burcio, OscarGallart Ayala, HèctorMartins, Cláudia P. B.Lucci, PaoloCromatografia de líquidsQuímica dels alimentsContaminació de l'aiguaLiquid chromatographyFood compositionWater pollutionThere is an increasing need for applications in food and environmental areas able to cope with a large number of analytes in very complex matrices. The new analytical procedures demand sensitivity, robustness and high resolution within an acceptable analysis time. The purpose of this review is to describe new trends based on fast liquid chromatography applied to the food and environmental analysis. It includes different column technologies, such as monolithic, sub-2 m, porous shell, as well as different stationary phases such as reversed phase (C8 and C18), hydrophilic interaction liquid chromatography (HILIC) and fluorinated columns. Additionally, recent sample extraction and clean-up methodologies applied to reduce sample manipulation and total analysis time in food and environmental analysis - QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe), on line solid phase extraction coupled to ultrahigh pressure liquid chromatography (on line SPE-UHPLC), turbulent flow chromatography (TFC) and molecularly imprinted polymers (MIPs), were also addressed. The advantages and drawbacks of these methodologies applied to the fast and sensitive analyses of food and environmental samples are going to be discussed.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98259eng(c) Elsevier B.V., 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2613992017-05-23T04:49:46Zhdl_2072_171809Strategies for the multi-residue analysis of 100 pesticides by liquid chromatography-triple quadrupole mass spectrometryNúñez Burcio, OscarGallart Ayala, HèctorFerrer, ImmaMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaPlaguicidesQuímica dels alimentsCromatografia de líquidsPesticidesFood compositionLiquid chromatographyAnalytical strategies for screening, quantitation and confirmation of a group of 100 pesticides in fruit and vegetable samples by LC-MS and LC-MS/MS were developed. The pesticides studied belong to different chemical families of herbicides, insecticides and fungicides. A selection of some degradation products was also included. Chromatographic separation was performed using a Zorbax Eclipse XDB-C8 column (150 mm × 4.6 mm and 5 µm particle size), and gradient elution with acetonitrile-water (both with 0.1% formic acid) as mobile phase. LC-MS/MS using highly-selective selected reaction monitoring (H-SRM) acquisition mode monitoring two transitions for each compound showed to be the most sensitive methodology. Quantitation was carried out using matrix-matched standard calibration and good linearity of response was demonstrated (r > 0.998). Limits of detection (by acquiring two transitions and with the ion-ratio requirements) ranged between 0.01 and 20 µg/kg were obtained. So, in general, the sensitivity achieved meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. Pesticide confirmation was carried out following European Union guidelines. In order to prevent false-positives, further confirmatory strategies were proposed. LC-MS in highly-selective selected ion monitoring (H-SIM) mode with accurate mass measurement was used to obtain an orthogonal criterion (exact mass) for confirmation. Accurate mass measurements were always bellow 0.9 mDa for almost all pesticides studied (similar to those described with TOF instruments). A user reversed energy ramp (RER) product ion scan spectra library was generated by means of a data dependent analysis for routine library searching of pesticides. The combination of LC-MS/MS in H-SRM mode and the generation of the RER product ion scan spectra and library search were then used to achieve further confirmation on pesticide analysis. The LC-MS and LC-MS/MS strategies developed were successfully applied for the analysis and confirmation of pesticides in different types of fruit and vegetables samples, and examples of the screening, quantitation and confirmation of pesticides in these samples are shown in this work.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98263eng(c) Elsevier B.V., 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2614002017-05-23T04:49:47Zhdl_2072_171809Recent advances in LC-MS analysis of food packaging contaminantsGallart Ayala, HèctorNúñez Burcio, OscarLucci, PaoloEnvasament d'alimentsContaminació dels alimentsCromatografia de líquidsEspectrometria de massesFood packagingFood contaminationLiquid chromatographyMass spectrometryThe supply of safe and high-quality foodstuffs relies on the efficient protection of food from deterioration. However, all food-packaging materials can release small amounts of their chemical constituents when they touch food, and any substance that migrates from the packaging into the food is of concern if it could pose health problems to the consumer. The purpose of this review is to describe recent advances in the liquid chromatography-mass spectrometry (LC-MS) analysis of food-packaging contaminants since 2009, focusing on some relevant families of compounds (e.g., bisphenol A, bisphenol A diglycidyl ethers and related compounds, UV-ink photoinitiators, perfluorinated compounds, and phthalates).Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98270eng(c) Elsevier B.V., 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2614012017-05-23T04:49:49Zhdl_2072_171809Aggregation behaviour of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow-field flow fractionation studyAstefanei, AlinaNúñez Burcio, OscarGalcerán Huguet, M. TeresaKok, Wim ThSchoenmakers, P.J.Ful·lerensElectroforesi capil·larFullerenesCapillary electrophoresisIn this work the electrophoretic behaviour of hydrophobic fullerenes (C60, C70 and C60-pyrr) and water soluble fullerenes (C60(OH)24, C120(OH)30, C60-pyrr tris acid and C60CHCOOH) in micellar electrokinetic capillary chromatography (MECC) was evaluated. The aggregation behavior of the water soluble compounds in MECC at different buffer and SDS concentrations and pH values of the background electrolyte (BGE) was studied by monitoring the changes observed in the electrophoretic pattern of the peaks. Broad and distorted peaks that can be attributed to fullerene aggregation were obtained in MECC which became narrower and more symmetric by working at low buffer and SDS concentrations (below the critical micelle concentration, capillary zone electrophoresis (CZE) conditions). For the characterization of the suspected aggregates formed (size and shape), asymmetrical flow field-flow fractionation (AF4) and transmission electron microscopy (TEM) were used. The results showed that the increase in the buffer concentration promoted the aggregation of the particles while the presence of SDS micelles revealed multiple peaks corresponding to particles of different aggregation degree. Furthermore, MECC has been applied for the first time for the analysis of C60 in two different cosmetic products (i.e., anti-aging serum and facial mask).Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98275eng(c) Springer Verlag, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2614022017-05-23T04:49:50Zhdl_2072_171809Field amplified sample injection-capillary zone electrophoresis for the analysis of amprolium in eggsMartínez-Villalba, AnnaNúñez Burcio, OscarMoyano Morcillo, EncarnaciónGalcerán Huguet, M. TeresaQuímica dels alimentsElectroforesi capil·larFood compositionCapillary electrophoresisVeterinary medicines are widely administered to farm animals since they keep animals healthy at overcrowded conditions. Nevertheless the continuous administration of medicines to farm animals can frequently lead to the presence of residues of veterinary drugs in consumption products. Amprolium is a quaternary ammonium compound used in the treatment of coccidiosis. In this paper a method based on capillary zone electrophoresis (CZE) to analyze residues of amprolium in eggs was developed and validated for the first time. Parameters such as electrolyte type, concentration and pH were optimized. In order to improve sensitivity, field amplified sample injection (FASI) was used for in-line preconcentration after a quick and simple sample treatment based on SPE (Envi-Carb). During method validation studies using egg samples a matrix interference was found at the migration time of amprolium. This compound was identified as thiamine and confirmed by MSn experiments using capillary electrophoresis coupled to mass spectrometry (CE-MS) with an ion-trap mass analyzer. CZE conditions were re-optimized to separate thiamine from amprolium allowing the quantification of amprolium in eggs at concentrations down to 75 µg Kg-1, which are far below the MRL legislated values.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98278eng(c) Wiley-VCH, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2615702017-05-23T04:49:52Zhdl_2072_171809Investigating Aspergillus nidulans secretome during colonisation of cork cell wallsMartins, IsabelGarcia, HelgaVarela, AdéliaNúñez Burcio, OscarPlanchon, SébastienGalcerán Huguet, M. TeresaRenaut, JennyRebelo, Luís P. N.Pereira, Cristina SilviaSuroRouresFongsCorkOakFungiCork, the outer bark of Quercus suber, shows a unique compositional structure, a set of remarkable properties, including high recalcitrance. Cork colonisation by Ascomycota remains largely overlooked. Herein, Aspergillus nidulans secretome on cork was analysed (2DE). Proteomic data were further complemented by microscopic (SEM) and spectroscopic (ATRFTIR) evaluation of the colonised substrate and by targeted analysis of lignin degradation compounds (UPLC-HRMS). Data showed that the fungus formed an intricate network of hyphae around the cork cell walls, which enabled polysaccharides and lignin superficial degradation, but probably not of suberin. The degradation of polysaccharides was suggested by the identification of few polysaccharide degrading enzymes (β-glucosidases and endo-1,5--L-arabinosidase). Lignin degradation, which likely evolved throughout a Fenton-like mechanism relying on the activity of alcohol oxidases, was supported by the identification of small aromatic compounds (e.g. cinnamic acid and veratrylaldehyde) and of several putative high molecular weight lignin degradation products. In addition, cork recalcitrance was corroborated by the identification of several protein species which are associated with autolysis. Finally, stringent comparative proteomics revealed that A. nidulans colonisation of cork and wood share a common set of enzymatic mechanisms. However the higher polysaccharide accessibility in cork might explain the increase of β-glucosidase in cork secretomeElsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98390eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2615712017-05-23T04:49:53Zhdl_2072_171809Effects of the fruit ripening stage on antioxidant capacity, total phenolics, and polyphenolic composition of crude palm oil from interspecific hybrid Elaeis oleifera × Elaeis guineensisRodríguez, Juanita C.Gómez, DanielaPacetti, DeborahNúñez Burcio, OscarGagliardi, RiccardoFrega, Natale G.Ojeda, Myriam L.Loizzo, Monica R.Tundis, RosaLucci, PaoloPolifenolsOlis vegetalsOli de palmaPolyphenolsVegetable oilsPalm oilIn the present study, we assessed for the first time the changes in the antioxidant capacity, total phenolic content, and polyphenolic composition of interspecific hybrid palm oil extracted from Elaeis oleifera x Elaeis guineensis (O×G, Coari × La Mé cultivar) during the fruit ripening process 18, 20, 22, and 24 weeks after anthesis. A progressive decrease (p<0.05) of phenolic content occurred during fruit development together with marked changes in polyphenol profiles. Significant negative correlations were established between antioxidant activity measured by TEAC (R = -0.954, p<0.05) and ORAC (R = -0.745, p<0.05) and fruits ripening stage while positive correlation between total phenolic content was found using either the TEAC assay or the ORAC assay. Highest DPPH radicals scavenging activity was also obtained with oils extracted at 18 WAA. These results highlight that O×G fruits of early ripeness represent a better source of phenolic compounds and may provide extracts with higher antioxidant activities when hybrid palm oil is aimed to be used as functional ingredient for the development of food or food products with antioxidant properties.American Chemical Society, Books and Journals Division]Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98392eng(c) American Chemical Society, Books and Journals Division], 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2615982017-05-23T04:49:54Zhdl_2072_171809Solid-phase extraction using molecularly imprinted polymer for selective extraction of natural and syntetic estrogens from aqueous samplesLucci, PaoloNúñez Burcio, OscarGalcerán Huguet, M. TeresaEstrògensCromatografia de líquids d'alta resolucióEspectrometria de massesEstrogenHigh performance liquid chromatographyMass spectrometryA method is proposed for the clean-up and preconcentration of natural and synthetic estrogens from aqueous samples employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE). The selectivity of the MIP was checked toward several selected natural and synthetic estrogens such as estrone (E1), 17β-estradiol (β-E2), 17α-estradiol (α-E2), estriol (E3), 17α-ethinylestradiol (EE2), dienestrol (DIES) and diethylstilbestrol (DES). Ultrahigh pressure liquid chromatography (UHPLC) coupled to a TSQ triple quadrupole mass spectrometry (QqQ) was used for analysis of target analytes. The chromatographic separation of the selected compounds was performed in less than 2 min under isocratic conditions. The method was applied to the analysis of estrogens in spiked river and tap water samples. High recoveries (>82%) for estrone, 17β-estradiol, 17α-estradiol, estriol and 17α-ethinylestradiol were obtained. Lower but still satisfactory recoveries (>48%) were achieved for dienestrol and diethylstilbestrol. The method was validated and found to be linear in the range 50-500 ng L-1 with correlation coefficients (R2) greater than 0.995 and repeatability relative standard deviation (RSD) below 8% in all cases. For analysis of 100-ml sample, the method detection limits (LOD) ranged from 4.5 to 9.8 ng L-1 and the limit of quantitation (LOQ) from 14.9 to 32.6 ng L-1. To demonstrate the potential of the MIP obtained, a comparison with commercially available C18 SPE was performed. Molecularly imprinted SPE showed higher recoveries than commercially available C18 SPE for most of the compounds. These results showed the suitability of the MIP-SPE method for the selective extraction of a class of structurally related compounds such as natural and synthetic estrogens.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98420eng(c) Elsevier B.V., 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2616002017-05-23T04:49:56Zhdl_2072_1718095-Hydroxymethylfurfural content in foodstuffs determined by micellar electrokinetic chromatographyTeixidó, ErikaNúñez Burcio, OscarSantos Vicente, Francisco JavierGalcerán Huguet, M. TeresaQuímica dels alimentsCromatografiaFood compositionChromatographyMicellar electrokinetic chromatography (MEKC) has been applied for the determination of 5-hydroxymethylfurfural in several foodstuffs. A 75 mM phosphate buffer solution at pH 8.0 containing 100 mM sodium dodecylsulfate was used as background electrolyte (BGE), and the separation was performed by applying +25 kV in a 50 µm I.D. uncoated fused-silica capillary. Good linearity over the range 2.5-250 mg kg-1 (r2 ≥ 0.999) and run-to-run and day-to-day precisions at low and medium concentration levels were obtained. Sample limit of detection (0.7 mg kg-1) and limit of quantification (2.5 mg kg-1) were established by preparing the standards in blank matrix. The procedure was validated by comparing the results with those obtained with liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Levels of HMF in 45 different foodstuffs such as breakfast cereals, toasts, honey, orange juice, apple juice, jam, coffee, chocolate and biscuits were determined.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98432eng(c) Elsevier B.V., 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2616012017-05-23T04:49:57Zhdl_2072_171809State-of-the-art in fast liquid chromatography-mass spectrometry for bioanalytical applicationsNúñez Burcio, OscarGallart Ayala, HèctorMartins, Cláudia P. B.Lucci, PaoloBusquets, RosaCromatografiaMarcadors bioquímicsEspectrometria de massesChromatographyBiochemical markersMass spectrometryThere is an increasing need of new bio-analytical methodologies with enough sensitivity, robustness and resolution to cope with the analysis of a large number of analytes in complex matrices in short analysis time. For this purpose, all steps included in any bio-analytical method (sampling, extraction, clean-up, chromatographic analysis and detection) must be taken into account to achieve good and reliable results with cost-effective methodologies. The purpose of this review is to describe the state-of-the-art of the most employed technologies in the period 2009-2012 to achieve fast analysis with liquid chromatography coupled to mass spectrometry (LC-MS) methodologies for bio-analytical applications. Current trends in fast liquid chromatography involve the use of several column technologies and this review will focus on the two most frequently applied: sub-2 µm particle size packed columns to achieve ultra high pressure liquid chromatography (UHPLC) separations and porous-shell particle packed columns to attain high efficiency separations with reduced column back-pressures. Additionally, recent automated sample extraction and clean-up methodologies to reduce sample manipulation, variability and total analysis time in bio-analytical applications such as on-line solid phase extraction coupled to HPLC or UHPLC methods, or the use of other approaches such as molecularly imprinted polymers, restricted access materials, and turbulent flow chromatography will also be addressed. The use of mass spectrometry and high or even ultra-high resolution mass spectrometry to reduce sample manipulation and to solve ion suppression or ion enhancement and matrix effects will also be presented. The advantages and drawbacks of all these methodologies for fast and sensitive analysis of biological samples are going to be discussed by means of relevant applications.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98436eng(c) Elsevier B.V., 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2616022017-05-23T04:49:58Zhdl_2072_171809On-line solid-phase extraction for liquid chromatography-mass spectrometry analysis of pesticidesLucci, PaoloNúñez Burcio, OscarPlaguicidesEspectrometria de massesQuímica dels alimentsCromatografia de líquidsAnàlisi de l'aiguaPesticidesMass spectrometryFood compositionLiquid chromatographyWater analysisPublic concern about pesticides in food and water has increased dramatically in the last two decades. In order to guarantee consumers' health and safety, analytical methods that could provide fast and reliable answers without compromising accuracy and precision are required. Sample treatment is probably the most tedious and time-consuming step in many analytical procedures and, despite the significant advances in chromatographic separations and mass spectrometry techniques, sample treatment is still one of the most important parts of the analytical process for achieving good analytical results. Therefore, over the last years, considerable efforts have been made to simplify the stage and to develop fast, accurate and robust methods which allow the determination of a wide range of pesticides without compromising the integrity of the extraction process. This review article intends to give a short overview of recently developed on-line solid-phase extraction, pre-concentration and clean-up procedures for the determination of pesticides in complex matrices by liquid chromatography-mass spectrometry techniques.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98441eng(c) Wiley-VCH, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2621252017-05-23T04:49:59Zhdl_2072_171809Viral uncoating is directional: exit of the genomic RNA in a common cold virus starts with the poly-(A) tail at the 3′-endHarutyunyan, ShushanKumar, MohitSedivy, ArthurSubirats i Vila, XavierKowalski, HeinrichKöhler, GottfriedBlaas, DieterReovirusRNAHibridacióReovirusesRNAHybridizationUpon infection, many RNA viruses reorganize their capsid for release of the genome into the host cell cytosol for replication. Often, this process is triggered by receptor binding and/or by the acidic environment in endosomes. In the genus Enterovirus, which includes more than 150 human rhinovirus (HRV) serotypes causing the common cold, there is persuasive evidence that the viral RNA exits single-stranded through channels formed in the protein shell. We have determined the time-dependent emergence of the RNA ends from HRV2 on incubation of virions at 56°C using hybridization with specific oligonucleotides and detection by fluorescence correlation spectroscopy. We report that psoralen UV crosslinking prevents complete RNA release, allowing for identification of the sequences remaining inside the capsid. We also present the structure of uncoating intermediates in which parts of the RNA are condensed and take the form of a rod that is directed roughly towards a two-fold icosahedral axis, the presumed RNA exit point. Taken together, in contrast to schemes frequently depicted in textbooks and reviews, our findings demonstrate that exit of the RNA starts from the 3′-end. This suggests that packaging also occurs in an ordered manner resulting in the 3′-poly-(A) tail becoming located close to a position of pore formation during conversion of the virion into a subviral particle. This directional genome release may be common to many icosahedral non-enveloped single-stranded RNA virusesPublic Library of Science (PLoS)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/98786engcc-by (c) Harutyunyan, Shushan et al., 2013info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2622312017-05-23T04:50:01Zhdl_2072_171809Solid-phase extraction and field-amplified sample injection-capillary zone electrophoresis for the analysis of benzophenone UV-filters in environmental water samplesPurrà, MiquelCinca, RoserLegaz, JessicaNúñez Burcio, OscarAnàlisi de l'aiguaElectroforesi capil·larWater analysisCapillary electrophoresisA field amplified sample injection-capillary zone electrophoresis (FASI-CZE) method for the analysis of benzophenone (BP) UV-filters in environmental water samples was developed, allowing the separation of all compounds in less than 8 minutes. A 9- to 25-fold sensitive enhancement was obtained with FASI-CZE, achieving limits of detection down to 21-59 µg/L for most of the analyzed BPs, with acceptable run-to-run and day-to-day precisions (relative standard deviations lower than 17%). In order to remove water sample salinity and to enhance FASI sensitivity, an off-line solid-phase extraction (SPE) procedure using a Strata X polymeric reversed-phase sorbent was proposed, obtaining recoveries up to 72-90% for most of benzophenones. With the combination of off-line SPE and FASI-CZE, limits of detection in the range 0.06-0.6 µg/L in a river water matrix, representing a 2400- to 6500-fold enhancement, were obtained. Method performance was evaluated by quantifying a blank river water sample spiked at 1 µg/L. For a 95% confidence level, no statistical differences were observed between found concentrations and spiked concentrations (probability at the confidence level, p value, of 0.60), showing that the proposed off-line SPE-FASI-CZE method is suitable for the analysis of benzophenone UV-filters in environmental water samples at low µg/L levels. The method was successfully applied to the analysis of BPs in river water samples collected before and after industrialized and urban areas, and in some drinking water samples.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99019eng(c) Springer Verlag, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622322017-05-23T04:50:02Zhdl_2072_171809Analysis of C60-fullerene fullerene derivatives and pristine fullerenes in environmental samples by ultrahigh performance liquid chromatography-atmospheric pressure photoionization-mass spectrometryAstefanei, AlinaNúñez Burcio, OscarGalcerán Huguet, M. TeresaFul·lerensEspectrometria de massesCromatografia de líquids d'alta resolucióMostreig mediambientalFullerenesMass spectrometryHigh performance liquid chromatographyEnvironmental samplingIn this work, a method is proposed for the simultaneous analysis of several pristine fullerenes (C60, C70, C76, C78, and C84) and three C60-fullerene derivatives (N-methyl fulleropyrrolidine, [6,6]-Phenyl C61 butyric acid methyl ester and [6,6]-Phenyl C61 butyric acid buthyl ester) in environmental samples. The method involves the use of ultrahigh performance liquid chromatography coupled to atmospheric pressure photoionization mass spectrometry (UHPLC-APPI-MS) and allowed the chromatographic separation in less than 4.5 minutes. The product ions from tandem mass spectrometry studies of fullerene derivatives, were characterized and the most abundant one (m/z 720), corresponding to [C60]-¿, was selected for quantitation. Selected reaction monitoring (SRM at 0.7 m/z FWHM) by acquiring two transitions using both isotopic cluster ions [M]-¿ and [M+1]-¿ as precursor ions was proposed for quantitation and confirmation purposes. For pristine fullerenes, highly-selective selected ion monitoring (H-SIM) acquisition mode by monitoring the isotopic cluster ions [M]-¿ and [M+1]-¿ was used. Pressurized solvent extraction conditions were optimized in order to improve recoveries of the studied fullerene compounds from sediment samples. Values up to 87-92% for C60-fullerene derivatives and lower but still acceptable, 70-80%, for pristine fullerenes were obtained. Method limits of quantitation (MLOQs) ranging from 1.5 pg L-1to 5.5 ng L-1 in water samples and from 0.1 ng Kg-1 to 523 ng Kg-1 in sediments were obtained with good precision (relative standard deviations always lower than 13%). The applicability of the developed method was evaluated by analyzing several environmental samples such as sediments and pond water and the detected levels for C60-fullerene derivatives were of 0.1-2.7 ng Kg-1and 1.5-8.5 pg L-1, respectively. C60 and C70 were the only pristine fullerenes detected in the analyzed samples (0.1-7.2 ng Kg-1 in sediments and 9-330 pg L-1 in water pond samples).Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99043eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622722017-05-23T04:50:03Zhdl_2072_171809Alkylation of toluene with 1-hexene over macroreticular ion-exchange resinsCadenas, MadelinBringue Tomás, RogerFité Piquer, CarlesIborra Urios, MontserratRamírez, ElianaCunill García, FidelResines de bescanvi iònicCatàlisiIon exchange resinsCatalysisThe macroreticular acidic ion-exchange resins Amberlyst 35, Amberlyst 46 and Purolite CT 275 were investigated as catalysts for the alkylation of toluene with 1-hexene and simultaneous dimerization and isomerization of the olefin at 373 K. After six hours of reaction, 1-hexene conversion was complete. At low toluene concentration double-bound isomerization of 1-hexene was the main reaction. As toluene concentration increased, double-bond isomerization decreased and toluene alkylation and olefin dimerization reactions increased. By using Purolite CT 275 resin and for an almost equimolar toluene to 1-hexene ratio, the selectivity to dimers was 22%, that of mono- and di-alkylated compounds were 42% and 3.5%, respectively, while that of double-bound isomerization was 32.5%. These reactions catalyzed by macroreticular ion-exchange resins of high acid capacity and degree of crosslinking can be useful to boost naphtha streams in the refining industry by reducing volatile compounds and aromatics of low boiling point.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99064eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622732017-05-23T04:50:12Zhdl_2072_171809Kinetics of 1-hexanol etherification on Amberlyst 70Bringue Tomás, RogerRamírez Rangel, ElianaIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelResines de bescanvi iònicÈtersCinètica enzimàticaAlcoholsCatàlisiIon exchange resinsEthersEnzyme kineticsAlcoholsCatalysisThe kinetics of the liquid-phase etherification of 1-hexanol to di-n-ethyl ether and water on the ion-exchange resin Amberlyst 70 in the temperature range 423-463 K is studied. The strong inhibition effect of water is considered following two approaches. First, a model stemming from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and hexanol. Secondly, a modified Eley-Rideal (ER) model that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of hexanol to the active centers. Both models fitted data quite well, although the best fitting results were obtained with the modified ER model. The activation energy was 125 ± 3 kJ/mol for the LHHW model and 121 ± 3 kJ/mol for the modified ER oneElsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99068eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622742017-05-23T04:50:13Zhdl_2072_171809Thermodynamic equilibrium for the dehydration of 1-butanol to di-n-butyl etherPérez-Maciá, María ÁngelesBringue Tomás, RogerIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelÈtersAlcohol butílicResines de bescanvi iònicEthersButanolIon exchange resinsThe thermodynamic equilibrium of the bimolecular dehydration of 1-butanol to di-n-butyl ether (DNBE) and water in the liquid phase was studied. Equilibrium experiments were performed at 4 MPa and in the temperature range of 413-463 K over the ion exchange resin Amberlyst-70. The thermodynamic equilibrium for the side reactions (dehydration to 1-butene, olefins isomerization, olefins hydration and branched ether formation) was also studied. The equilibrium constant for the dehydration reaction of 1-butanol to di-n-butyl ether and water was found to be independent on the operating temperature, within the limits of the experimental error ( 5.2%). The experimental equilibrium constants at 413-463 K allows to estimate the standard enthalpy change of reaction (ΔrH0(l) = -0.3 ± 2.9 kJ¿mol-1) and the standard entropy change of reaction (ΔrS0(l) = 26.8 ± 6.7 J¿mol-1¿K-1). From these values the standard formation enthalpy (ΔfH0DNBE,(l)) and the molar entropy of DNBE (S0DNBE,(l)) at 298.15 K were computed to be -370.5 ± 10.9 kJ¿mol-1 and 408.3 ± 6.8 J¿mol-1¿K-1 respectivelyElsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99072engcc-by-nc-nd (c) Elsevier B.V., 2015info:eu-repo/semantics/embargoedAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2622752017-05-23T04:50:13Zhdl_2072_171809Ion exchange resins as catalysts for the liquid-phase dehydration of 1-butanol to di-n-butyl etherPérez-Maciá, María ÁngelesBringue Tomás, RogerIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelÈtersResines de bescanvi iònicCatàlisiAlcohol butílicEthersIon exchange resinsCatalysisButanolThis work reports the production of di-n-butyl ether (DNBE) by means of 1-butanol dehydration in the liquid phase on acidic ion-exchange resins. Dehydration experiments were performed at 150 ºC and 40 bar on 13 styrene-codivinylbenzene ion exchangers of different morphology. By comparing 1-butanol conversions to DNBE and initial reaction rates it is concluded that oversulfonated resins are the most active catalysts for 1-butanol dehydration reaction whereas gel-type resins that swell significantly in the reaction medium as well as the macroreticular thermostable resin Amberlyst-70 are the most selective to DNBE. The highest DNBE yield was achieved on Amberlyst 36. The influence of typical 1-butanol impurities on the dehydration reaction were also investigated showing that the presence of 2-methyl-1-propanol (isobutanol) enhances the formation of branched ethers such as 1-(1-methylpropoxy) butane and 1-(2-methylpropoxy) butane, whereas the presence of ethanol and acetone yields ethyl butyl ether and, to a much lesser extent, diethyl ether.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99085eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622762017-05-23T04:50:14Zhdl_2072_171809Influence of acid ion-exchange resins morphology in swollen state on the synthesis of ethyl octyl ether from ethanol and 1-octanolBringue Tomás, RogerRamírez Rangel, ElianaIborra Urios, MontserratTejero Salvador, XavierCunill García, FidelResines de bescanvi iònicÈtersAlcoholIon exchange resinsEthersAlcoholEthyl-octyl ether (EOE) liquid phase synthesis from ethanol and 1-octanol over ion-exchange resins is feasible at 423K, though di-ethyl ether and di-n-octyl ether were also formed. The influence of the catalyst morphology on the reaction was checked by testing twenty-two acidic resins. Gel-type resins of low crosslinking degree yielded the higher amounts of EOE, whereas macroreticular ones of high crosslinking degree gave mainly di-ethyl ether. Ethanol conversion highly depends on the resin acid capacity, [H+], whereas 1-octanol conversion and selectivity to EOE depends on the specific volume of swollen polymer, Vsp, and porosity. The variation of ethanol and 1-octanol conversion, selectivity to EOE with respect to both alcohols as well as ethers TOF as a function of [H+]/Vsp suggests that a part of the active sites does not take part in the EOE synthesis reaction on highly cross-linked resins. Amberlyst 70 could be interesting in industry due to its selectivity to EOE and higher thermal stabilityAcademic PressUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99091eng(c) Academic Press, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2622702017-05-23T04:50:15Zhdl_2072_171809Study of the oligomerization of 1-octene catalyzed by macroreticular ion-exchange resinsBringue Tomás, RogerCadenas, MadelinFité Piquer, CarlesIborra Urios, MontserratCunill García, FidelResines de bescanvi iònicCinètica enzimàticaCatàlisiIon exchange resinsEnzyme kineticsCatalysisOligomerization of 1-octene is a feasible alternative to improve the properties and the quality of fuels and lubricants oils. The performance of macroreticular ion-exchange resins as catalysts for such reaction has been evaluated. The experimental setup consisted of a batch stirred-tank reactor that operated at 353-393 K and 2 MPa. 1-Octene conversion was practically complete and the selectivity to double-bond isomerization and dimers after 6 h at 373 K was up to 95% and 12%, respectively. The accessible acidity of the catalysts was the most important structural parameter for these reactions. Selectivity to dimers and branched isomers increased with increasing temperature. Cracking compounds were not detected at all. The theoretical equations derived from the proposed kinetic model fit well the experimental results.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99092eng(c) Elsevier B.V., 2012info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2855472017-05-23T04:50:15Zhdl_2072_171809Study of seawater biofiltration by measuring adenosine triphosphate (ATP) and turbiditySimón, Francesc XavierRudé i Payró, ElisabetLlorens Llacuna, JoanBaig, SylvieAigua de marBiodegradacióBiofilmsBiomassaEnginyeria químicaContaminació de l'aiguaSeawaterBiodegradationBiofilmsBiomassChemical engineeringWater pollutionIn the present study, we examined seawater biofiltration in terms of adenosine triphosphate (ATP) and turbidity. A pilot biofilter continuously fed with fresh seawater reduced both turbidity and biological activity measured by ATP. Experiments operated with an empty bed contact time (EBCT) of between 2 and 14 min resulted in cellular ATP removals of 32% to 60% and turbidity removals of 38% to 75%. Analysis of the water from backwashing the biofilter revealed that the first half of the biofilter concentrated around 80% of the active biomass and colloidal material that produces turbidity. By reducing the EBCT, the biological activity moved from the first part of the biofilter to the end. Balances of cellular ATP and turbidity between consecutive backwashings indicated that the biological activity generated in the biofilter represented more than 90% of the detached cellular ATP. In contrast, the trapped ATP was less than 10% of the overall cellular ATP detached during the backwashing process. Furthermore, the biological activity generated in the biofilter seemed to be more dependent on the elapsed time than the volume filtered. In contrast, the turbidity trapped in the biofilter was proportional to the volume filtered, although a slightly higher amount of turbidity was found in the backwashing water; this was probably due to attrition of the bed medium. Finally, no correlations were found between turbidity and ATP, indicating that the two parameters focus on different matter. This suggests that turbidity should not be used as an alternative to cellular concentration.Springer Science + Business MediaUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/45683eng(c) Springer Science + Business Media, 2013info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2624212017-05-23T04:50:16Zhdl_2072_171809Kinetics of 1-pentanol etherification without water removalBringue Tomás, RogerRamírez, ElianaFité Piquer, CarlesIborra Urios, MontserratTejero Salvador, XavierÈtersAdsorcióCatàlisiEthersAdsorptionCatalysisThe effect of water on the kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE) and water over Amberlyst 70 is revisited. To explain the strong inhibitor effect of water, two approaches were compared. First, a model stemming from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and pentanol. Second, a modified Eley-Rideal (ER) model was used that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of pentanol to the active centers. Both models fitted data quite well, although the best results were obtained with the modified ER model. The activation energy was 118.7 ± 0.2 kJ/mol for the LHHW model and 114.0 ± 0.1 kJ/mol for the modified ER one.American Chemical SocietyUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99289eng(c) American Chemical Society , 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2624222017-05-23T04:50:17Zhdl_2072_171809Ultrahigh pressure liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometry for the determination of polyphenolic profiles in the characterization and classification of cranberry-based pharmaceutical preparations and natural extracts.Parets, LídiaAlechaga Silva, ÉlidaNúñez Burcio, OscarSaurina, JavierHernández Cassou, SantiagoPuignou i Garcia, LluísCromatografia de líquidsPolifenolsLiquid chromatographyPolyphenolsUltrahigh pressure liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometry (UHPLC-APPI-MS/MS) was applied to the analysis and authentication of fruit-based products and pharmaceutical preparations. Two sub-2 µm C18 reversed-phase columns, Syncronis (100x2.1 mm, 1.7 µm) and Hypersil Gold (50x2.1 mm, 1.9 µm) were proposed under gradient elution with 0.1 % formic acid aqueous solution and methanol mobile phases for the determination of 29 polyphenols, allowing to obtain polyphenolic profiles in less than 13.5 and 23.5 min, respectively. Several atmospheric pressure ionization (API) sources (H-ESI, APCI, APPI) were compared. For dopant-assisted APPI, four organic solvents, toluene, acetone, chlorobenzene and anisole were evaluated as dopants. Both, H-ESI and acetone-assisted APPI were selected as the best ionization sources for the analysis of targeted polyphenols. Acceptable sensitivity (LOD values down to 0.5 µg kg-1 in the best of cases), linearity (r2 higher than 0.995) and good precision (RSD values lower than 15.1%) and trueness (relative errors lower than 10.2%) were obtained with both UHPLC-API-MS/MS methods. A simple extraction procedure, consisting of a sample sonication with acetone/water/hydrochloric acid (70:29.9:0.1 v/v/v) and centrifugation, was used. The proposed UHPLC-ESI-MS/MS and UHPLC-APPI-MS/MS methods with both C18 reversed-phase columns were then applied to the analysis of 32 grape-based and cranberry-based natural products and pharmaceutical preparations. Polyphenolic profiles data were then analyzed by principal component analysis (PCA) to extract information of the most significant data contributing to classification of natural extracts according to the type of fruit.Royal Society of ChemistryUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/99325engcc-by (c) Parets, Lídia et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2628622017-05-23T04:50:19Zhdl_2072_171809High throughput determination log Po/w/pKa/log Do/w of drugs by combination of UHPLC and CE methodsCabot Canyelles, Joan MarcSubirats i Vila, XavierFuguet i Jordà, ElisabetRosés Pascual, MartíDisseny de medicamentsFunció d'acidesaMedicamentsDrug designAcidity functionDrugsn 1997Valkó et al. developed a generic fast gradient HPLC method, based on the calculation of the Chromatographic Hydrophobicity Index (CHI) from the gradient retention times, in order to measure lipophilicity. We have employedthe correlations between CHI and log Po/wand adapted the rapid gradient HPLC method to UHPLC obtaining excellent resolution and repeatability in a short analysis time (<4min). log Po/wvalues can be easily obtained from these CHI measurementsbut, unfortunately, these correlations are only valid for non-ionized compounds. Consequently, in order to determine the effective log Po/wvalue at a particular pH, afast high-throughput method for pKadeterminationwas required. The IS-CE method, based on the use of internal standards (IS) and capillaryelectrophoresis(CE),is a fast and attractive alternative to other methods for pKadetermination,since itoffers multiple advantages compared to them: low amounts of test compounds and reagents are needed, high purity is not required, specific interactions between test compounds and buffers are corrected, etc. In addition, it allows the determination of a pKavalue in less than 5 minutes. Both CHI and IS-CE have beencombined in order to describe a high throughput alternative in thedetermination ofthe lipophilicity profiles of bioactive compounds.IAPC PublishingUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/99599engcc-by (c) Cabot Canyelles, Joan Marc et al., 2014info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2628632017-05-23T04:50:20Zhdl_2072_171809Prunus persica var. platycarpa (Tabacchiera Peach): bioactive compounds and antioxidant activity of pulp, peel and seed ethanolic extractsLoizzo, Monica R.Pacetti, DeborahLucci, PaoloNúñez Burcio, OscarMenichini, FrancescoFrega, Natale G.Tundis, RosaFenolsArbres fruitersAntioxidantsPhenolsFruit treesAntioxidantsA comparative analysis of ethanol extracts from peel, pulp and seed of Prunus persica var. platycarpa (Tabacchiera peach) was done. The total phenols, flavonoids and carotenoids content as well as the antioxidant properties were evaluated. Peach pulp extract was characterized by the highest total phytonutrients content and exhibited the highest antioxidant activity in all in vitro assays. Interestingly, pulp extract showed IC50 values of 2.7 and 2.2 g/mL at 30 and 60 minutes of incubation, respectively using -carotene bleaching test. A remarkable result was also obtained by using Fe-chelating assay (IC50 of 2.9 g/mL vs 1.3 g/mL for positive control BHT). Pulp extract was subjected to liquid chromatography-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS). Six main compounds, namely gallic acid, protocatechuic acid, protocatechualdehyde, chlorogenic acid, p-coumaric acid, and ferulic acid, were identified. Overall, the results suggest that Prunus persica var. platycarpa displays a good antioxidant activity and its consumption could be promotedSpringer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99604eng(c) Springer Verlag, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2628642017-05-23T04:50:21Zhdl_2072_171809Catalytic activity and accessibility of acidic ion-exchange resins in liquid-phase etherification reactionsBadia i Córcoles, Jordi HugFité Piquer, CarlesBringue Tomás, RogerIborra Urios, MontserratCunill García, FidelÈtersResines de bescanvi iònicAlcoholsCatàlisiEthersIon exchange resinsAlcoholsCatalysisAlthough macroreticular acidic ion-exchange resins have been widely used as catalysts in the industrial world for decades, their catalytic behavior is still far from being completely understood at a molecular level. Several characterization techniques coexist, which provide information about their properties. Only few of these techniques give an actual picture of their working-state features when swollen in anhydrous polar reactive media such as in etherification processes, where they are extensively used. The inverse steric exclusion chromatography technique, based on modeling the micropores structure, or gel phase, as a set of discrete volume fractions with a characteristic polymer chain density, constitutes an appropriate procedure to assess the morphology of ion-exchangers in the swollen state. Present work proposes an empirical model to correlate the properties of the volume fractions with their catalytic activity in the etherification reaction rates of isobutene by addition of C1 to C4 linear primary alcohols. Sixteen different macroreticular acidic ion-exchange catalysts, both commercial and lab-made, have been used, which differ in acid capacity, sulfonation type, cross linking degree and swollen-phase volume fractions distribution. Experimental reaction rates have been expressed as a sum of contributions of each individual volume fraction. The contribution of each polymer volume fraction corresponds to the product of the catalyst acidity, the characteristic volume fraction within the gel phase of the catalyst, and a specific turnover frequency (TOF) of that fraction. Accessibility of the reacting alcohol, expressed in terms of the Ogston coefficient, has been also included in the empirical dependency equation presented in this work.Springer VerlagUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/99605eng(c) Springer Verlag, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2665052017-05-23T04:50:23Zhdl_2072_171809Microemulsion electrokinetic chromatography as a suitable tool for lipophilicity determination of acidic, neutral, and basic compoundsSubirats i Vila, XavierYuan, Hui-PingChaves, VerónicaMarzal, NúriaRosés Pascual, MartíElectroforesi capil·larCromatografia de líquidsLipofíliaCapillary electrophoresisLiquid chromatographyLipophilicityIn the present work, several MEEKC systems are studied to assess their suitability for lipophilicity determination of acidic, neutral, and basic compounds. Thus, several microemulsion compositions over a wide range of pH values (from 2.0 to 12.0), containing heptane, 1−butanol and different types and amounts of surfactant (SDS or sodium cholate: from 1.3 to 3.3%) are characterized using Abraham's solvation model. The addition of acetonitrile (up to 10%) is also studied, since it increases the resolution of the technique for the most lipophilic compounds. The system coefficients obtained are very similar to those of the 1−octanol/water, used as the reference lipophilicity index, allowing simple and linear correlations between the 1−octanol/water partition values (log Po/w) and MEEKC mass distribution ratios (log kMEEKC). Variations in the microemulsion composition (aqueous buffer, surfactant, concentration of ACN) did not significantly affect the similarity of the MEEKC systems to log Po/w partition.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/101321eng(c) Wiley-VCH, 2016info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2668632017-05-23T04:50:25Zhdl_2072_171809HPLC fingerprints for the authentication of cranberry-based products based on multivariate calibration approachesPuigventós, LídiaNúñez Burcio, OscarSaurina, JavierCromatografia de líquidsQuimiometriaPolifenolsQuímica dels alimentsLiquid chromatographyChemometricsPolyphenolsFood compositionThis work introduces the topic of the authentication of cranberry-based products and the detection and quantification of possible adulterations with other raw materials of lower quality. For such a purpose, genuine and adulterated cranberry samples were analyzed by reversed-phase HPLC with UV detection. Sample components were separated using an elution gradient based on 0.1% (v/v) formic acid aqueous solution and methanol as the components of the mobile phase. Chromatograms were recorded at 280, 370 and 520 nm. Data resulting from the injection of pure and adulterated samples, consisting of chromatographic fingerprints at each detection wavelength, were analyzed chemometrically. Preliminary studies by Principal Component Analysis showed that the sample extracts were clearly distributed depending on the extent of adulteration. Data was further treated by Partial Least Square regression to determine the percentages of grape contamination. It was found that even mixture samples containing low percentages of grape could be distinguished from genuine cranberry extracts. Besides, results obtained were highly satisfactory, with overall quantification errors lower than 5%. As a conclusion, the method proposed here resulted in an excellent approach to carry out the authentication of cranberry-based products relying on polyphenolic fingerprints.Bentham Science PublishersUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/101986eng(c) Bentham Science Publishers, 2016info:eu-repo/semantics/embargoedAccess
oai:recercat.cat:2072/1838432017-06-01T00:46:49Zhdl_2072_171809Comparative study of the LC-MS/MS and UPLC-MS/MS for the multi-residue analysis of quinolones, penicillins and cephalosporins in cow milk, and validation according to the regulation 2002/657/ECJunza Martínez, AlexandraAmatya, RameshwariBarrón Bueno, DoloresBarbosa Torralbo, JoséLletQuinolonesQuímica analíticaMilkQuinolone antibacterial agentsAnalytical chemistryThe aim of this study was to develop and validate an analytical method to simultaneously determine European Union-regulated beta-lactams (penicillins and cephalosporins) and quinolones in cow milk. The procedure involves a new solid phase extraction (SPE) to clean-up and pre-concentrate the three series of antibiotics before analysis by liquid chromatography¿tandem mass spectrometry (LC-MS/MS) and ultra-high-performance liquid chromatography¿tandem mass spectrometry (UPLC-MS/MS). LC-MS/MS and UPLC-MS/MS techniques were also compared. The method was validated according to the Directive 2002/657/EC and subsequently applied to 56 samples of raw cow milk supplied by the Laboratori Interprofessional Lleter de Catalunya (ALLIC) (Laboratori Interprofessional Lleter de Catalunya, Control Laboratory Interprofessional of Milk of Catalunya).ElsevierUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/submittedVersionhttp://hdl.handle.net/2445/24558eng(c) Elsevier, 2011info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2138912017-06-01T00:49:04Zhdl_2072_171809Residues of b-lactams and quinolones in tissues and milk samples. Confirmatory analysis by liquid chromatography-mass spectrometryJunza Martínez, AlexandraAmatya, RameshwariPérez-Burgos, RafaelGokce, GultekinGrzelak, EdytaBarrón Bueno, DoloresBarbosa Torralbo, JoséQuinolonesPenicil·linaTeixits (Histologia)LletCefalosporinesQuinolone antibacterial agentsPenicillinTissuesMilkCephalosporinesThe aim of this work is to optimize and validate methods for the multiresidue determination of series of families of antibiotics as quinolones, penicillins and cephalosporins included in European regulation in food samples using LC-MS/MS. Different extraction techniques and clean-up applied to antibiotics in meat were compared. The quality parameters were established according with EU guideline. The developed method was applied to 49 positive raw milk samples from animal medicated with different antibiotics; the 63% of the analyzed samples were found to be compliant. ___________________________________________________________________________________________Universitatea OvidiusUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/44669eng(c) Universitatea Ovidius, 2010info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2734722017-06-09T00:57:04Zhdl_2072_171809The effect of l-thymidine, acyclic thymine and 8-bromoguanine on the stability of model G-quadruplex structuresAviñó Andrés, AnnaMazzini, StefaniaFàbrega i Claveria, Ma. CarmePeñalver, PabloGargallo Gómez, RaimundoMorales, J.C.Eritja i Casadellà, RamonBiologia molecularBioquímicaOligonucleòtidsG-estructuresMolecular biologyBiochemistryOligonucleotidesG-structuresBackground Guanine-rich oligonucleotides are capable of forming tetrahelical structures known as G-quadruplexes with interesting biological properties. We have investigated the effects of site-specific substitution in the loops and in the tetrads model G-quadruplexes using thymine glycol nucleic acid (GNA) units, l-thymidine and 8-Br-2′-deoxyguanosine. Methods Modified oligonucleotides were chemically synthesized and spectroscopic techniques were used to determine the relative stability of the modified G-quadruplex. The double 8-BrdG-modified quadruplexes were further characterized by Nuclear Magnetic Resonance. Binding to thrombin of selected quadruplex was analyzed by gel electrophoresis retention assay. Results The most interesting results were found with a 8-bromoG substitution that had the larger stabilization of the quadruplex. NMR studies indicate a tight relationship between the loops and the tetrads to accommodate 8-bromoG modifications within the TBA. Conclusions The substitutions of loop positions with GNA T affect the TBA stability except for single modification in T7 position. Single l-thymidine substitutions produced destabilization of TBA. Larger changes on quadruplex stability are observed with the use of 8-bromoG finding a single substitution with the highest thermal stabilization found in thrombin binding aptamers modified at the guanine residues and having good affinity for thrombin. Double 8-BrdG modification in anti positions of different tetrads produce a conformational flip from syn to anti conformation of 8-Br-dG to favor loop-tetrad interaction and preserve the overall TBA stability.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/107055engcc-by-nc-nd (c) Elsevier B.V., 2016info:eu-repo/semantics/embargoedAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2397342017-07-18T08:02:21Zhdl_2072_171809Migration of antimony from polyethylene terephthalate used in mineral water bottles.Carneado Moreno, SergioHernández-Nataren, E.López Sánchez, José FermínSahuquillo Estrugo, ÀngelsAigües mineralsTereftalat de polietilèEnvasosQuímica analíticaSemimetallsContaminació de l'aiguaMineral watersPolyethylene terephthalateContainersAnalytical chemistrySemimetalsWater pollutionThe influence of storage time and temperature on Sb migration from PET bottles into mineral water was studied in short-term tests lasting up to 15 days and long-term studies lasting up to 220 days. Samples purchased were stored in three different coloured bottles: clear (CL), light blue (LB) and dark blue (DB). Sb migration was assayed by HG-AFS for total determination and HPLC-ICP-MS for speciation analysis. Migration studies showed that waters stored at 4 and 20 oC were not subject to Sb migration. At 40 oC there was a significant increase in Sb concentration, although the maximum limit established by the European Union (5.0 ug/L) was not exceeded, whereas at 60 oC samples were subject to considerable Sb migration after 30 days of storage. In this case, the maximum limit established by the European Union was exceeded and both Sb (V) and Sb (III) were detected.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/57563eng(c) Elsevier B.V., 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2900212017-07-18T08:02:24Zhdl_2072_171809Cellular uptake studies of antisense oligonucleotides using G-quadruplex- nanostructures. The effect of cationic residue on the biophysical and biological propertiesGrijalvo, SantiagoAlagia, AdeleGargallo Gómez, RaimundoEritja i Casadellà, RamonOligonucleòtidsG-estructuresNanoestructuresOligonucleotidesG-structuresNanostructuresOligonucleotides carrying cationic peptides have been used to improve hybridization and cellular uptake of oligonucleotides. In this study, a series of four cationic amino acid derivatives were covalently linked at the 3′-termini with the objective of modifying the Tetrahymena telomeric repeat sequence d(TGGGGT). This led to the synthesis of a small cationic G-quadruplex-forming oligonucleotide series containing lysine, ornithine, homo-arginine and arginine moieties. The preparation of the appropriate solid-supports afforded the synthesis of 3′-lysine and 3′-ornithine oligonucleotides which were converted to homo-arginine and arginine conjugates through post-synthetic modifications. Circular dichroism and thermal denaturation experiments confirmed that the presence of the four cationic residues did not affect the formation of stable parallel G-quadruplex structures. Afterwards, a phosphorothioate oligonucleotide targeting Renilla luciferase mRNA was prepared at the 5′-termini of this telomeric sequence which afforded a series of phosphorothioate oligonucleotide/[d(TG4T)]4 hybrid constructs modified with lysine, ornithine, homo-arginine and arginine units after incubation. In addition, the phosphodiester/phosphorothioate mixed backbone contributed to the degradation of the G-quadruplex moiety by exonucleases liberating the antisense sequence. Cell culture analysis of gene expression showed that the formation of self-assembled G-quadruplex nanostructures did not disrupt the antisense mechanism and therefore were able to induce luciferase gene inhibition in mammalian cells without using cationic lipids. Flow cytometry analyses confirmed that fluorescently labelled antisense G4-quadruplex nanostructures were efficiently taken up by HeLa cells. These results suggest that G-quadruplex nanostructures may be used to improve cellular uptake of therapeutic oligonucleotides. © 2016 The Royal Society of Chemistry.Royal Society of ChemistryUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/113893engcc-by (c) Grijalvo, Santiago et al., 2016info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2408422017-07-18T08:02:25Zhdl_2072_171809Method development for the simultaneous determination of methylmercury and inorganic mercury in seafoodZmozinski, Ariane V.Carneado Moreno, SergioIbáñez Palomino, CarmenSahuquillo Estrugo, ÀngelsLópez Sánchez, José FermínDa Silva, Márcia M.MercuriMariscTests de toxicitatQuímica analíticaMercurySeafoodToxicity testingAnalytical chemistryThis paper reports the method development for the simultaneous determination of methylmercury MeHgþ) and inorganic mercury (iHg) species in seafood samples. The study focused on the extraction and quantification of MeHgþ (the most toxic species) by liquid chromatography coupled to on-line UV irradiation and cold vapour atomic fluorescence spectroscopy (LC-UV-CV-AFS), using HCl 4 mol/L as the extractant agent. Accuracy of the method has been verified by analysing three certified reference materials and different spiked samples. The values found for total Hg and MeHgþ for the CRMs did not differ significantly from certified values at a 95% confidence level, and recoveries between 85% and 97% for MeHgþ, based on spikes, were achieved. The detection limits (LODs) obtained were 0.001 mg Hg/kg for total mercury, 0.0003 mg Hg/kg for MeHgþ and 0.0004 mg Hg/kg for iHg. The quantification limits (LOQs) established were 0.003 mg Hg/kg for total mercury, 0.0010 mg Hg/kg for MeHgþ and 0.0012 mg Hg/kg for iHg. Precision for each mercury species was established, being 12% in terms of RSD in all cases. Finally, the developed method was applied to 24 seafood samples from different origins and total mercury contents. The concentrations for Total Hg, MeHg and iHg ranged from 0.07 to 2.33, 0.003-2.23 and 0.006-0.085 mg Hg/kg, respectively. The established analytical method allows to obtain results for mercury speciation in less than 1 one hour including both, sample pretreatment and measuring step.University College London, Faculty of Mathematical and Physical Sciences, Department of MathematicsUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/58572eng(c) University College London, Faculty of Mathematical and Physical Sciences, Department of Mathematics, 2014info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2522312017-07-18T08:02:25Zhdl_2072_171809Mercury (II) and methylmercury determination in waters by liquid chromatography hyphenated to cold vapour atomic fluorescence spectrometry after online short-column preconcentrationCarneado Moreno, SergioPeró Gascón, RogerIbáñez Palomino, CarmenLópez Sánchez, José FermínSahuquillo Estrugo, ÀngelsMercuriCromatografia de líquidsContaminació de l'aiguaMetilmercuriMercuryLiquid chromatographyWater pollutionMethylmercuryThis paper reports a method developed for the simultaneous determination of methylmercury (MeHg+) and mercury(II) (Hg2+) species in water by liquid chromatography coupled to online UV irradiation and cold vapour atomic fluorescence spectrometry (LC-UV-CV-AFS) after online short-column preconcentration. This work focused on systematic studies of several variables to establish the maximum species recoveries, preconcentration factors and good reproducibility. The optimum results obtained were the following: 0.07 mmol L 1 2-mercaptoethanol as a complexing agent, precolumn conditioning with the mobile phase: a mixture of 80% of methanol (MeOH) and 20% of the following buffer: 0.0015 mol L 1 ammonium pyrrolidine dithiocarbamate (APDC) and 0.01 mol L 1 ammonium acetate (NH4CH3COO) at pH 5.5, 2 cm precolumn length and 2 mL min 1 sample flow. This method was applied to three water samples with different mineralisation contents. Various tests, based on spikes, were performed on each sample. A breakthrough volume of 4 mL was found. The recovery values of 72 3% and 81 5% for MeHg+ and Hg2+, respectively, were obtained regardless of the matrix composition, and the PF values were 30 and 32 for MeHg+ and Hg2+, respectively. The accuracy of the preconcentration method was verified by analysing a certified reference material. The detection limits (LDs) obtained were 15 ng L 1 for MeHg+ and 2 ng L 1 for Hg2+. The quantification limits (LQs) were 50 ng L 1 for both species. The established analytical online preconcentration method is suitable for the quantification of mercury species in a wide range of environmental waters.Royal Society of ChemistryUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/66291eng(c) Carneado, S. et al., 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2612602017-07-18T08:02:26Zhdl_2072_171809Mercury films on commercial carbon screen-printed devices for the analysis of heavy metal ions: a critical evaluationPérez Ràfols, ClaraSerrano i Plana, NúriaDíaz Cruz, José ManuelAriño Blasco, CristinaEsteban i Cortada, MiquelAnàlisi electroquímicaElectrochemical analysisThe suitability of mercury films on commercial screen-printed electrodes for the analysis of heavy metal ions is critically tested for the particular case of Pb(II)-ions. Although determination is possible by anodic stripping voltammetry with a reasonable detection limit (8.9 µg L-1), important drawbacks are noticed as a consequence of the heterogeneous deposition of mercury on the rough surface of screen-printed devices.Wiley-VCHUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/97965eng(c) Wiley-VCH, 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2614052017-07-18T08:02:27Zhdl_2072_171809Characterization of aggregates of surface modified fullerenes by asymmetrical flow field-flow fractionation with multi-angle light scattering detectionAstefanei, AlinaKok, Wim Th.Bäuerlein, PatrickNúñez Burcio, OscarGalcerán Huguet, M. TeresaDe Voogt, PimSchoenmakers, P.J.Ful·lerensNanopartículesFullerenesNanoparticlesFullerenes are carbon nanoparticles with widespread biomedical, commercial and industrial applications. Attributes such as their tendency to aggregate and aggregate size and shape impact their ability to be transported into and through the environment and living tissues. Knowledge of these properties is therefore valuable for their human and environmental risk assessment as well as to control their synthesis and manufacture. In this work, asymmetrical flow-field flow fractionation (AF4) coupled to multi-angle light scattering (MALS) was used for the first time to study the size distribution of surface modified fullerenes with both polyhydroxyl and carboxyl functional groups in aqueous solutions having different pH (6.5-11) and ionic strength values (0-200 mM) of environmental relevance. Fractionation key parameters such as flow rates, flow programming, and membrane material were optimized for the selected fullerenes. The aggregation of the compounds studied appeared to be indifferent to changes in solution pH, but was affected by changes in the ionic strength. Polyhydroxy-fullerenes were found to be present mostly as 4 nm aggregates in water without added salt, but showed more aggregation at high ionic strength, with an up to 10-fold increase in their mean hydrodynamic radii (200 mM), due to a decrease in the electrostatic repulsion between the nanoparticles. Carboxy-fullerenes showed a much stronger aggregation degree in water (50 100 nm). Their average size and recoveries decreased with the increase in the salt concentration. This behavior can be due to enhanced adsorption of the large particles to the membrane at high ionic strength, because of their higher hydrophobicity and much larger particle sizes compared to polyhydroxy-fullerenes. The method performance was evaluated by calculating the run-to-run precision of the retention time (hydrodynamic radii), and the obtained RSD values were lower than 1 %. MALS measurements showed aggregate sizes that were in good agreement with the AF4 data. A comparison of the scattering radii from the MALS with the hydrodynamic radii obtained from the retention times in AF4 indicated that the aggregate shapes are far from spherical. TEM images of the fullerenes in the dry state also showed branched and irregular clusters.Elsevier B.V.Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/acceptedVersionhttp://hdl.handle.net/2445/98258engcc-by-nc-nd (c) Elsevier B.V., 2015info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by-nc-nd/3.0/es">http://creativecommons.org/licenses/by-nc-nd/3.0/es</a>
oai:recercat.cat:2072/2900222017-07-18T08:02:28Zhdl_2072_171809Implementing the flipped classroom methodology to the subject 'applied computing' of two engineering degrees at the University of BarcelonaIborra Urios, MontserratRamírez Rangel, ElianaBadia i Córcoles, Jordi HugBringue Tomás, RogerTejero Salvador, XavierClasse inversaAprenentatge actiuInnovacions educativesEnsenyament de la químicaFlipped classroomActive learningEducational innovationsChemistry educationThis work is focused on the implementation, development, documentation, analysis, and assessment of the flipped classroom methodology, by means of the just-in-time teaching strategy, for a pilot group (1 out of 6) in the subject 'Applied Computing' of both the Chemical and Materials Engineering Undergraduate Degrees of the University of Barcelona. Results show that this technique promotes self-learning, autonomy, time management as well as an increase in the effectiveness of classroom hours.Omnia ScienceUniversitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/112322engcc-by (c) Iborra Urios, Montserrat et al., 2017info:eu-repo/semantics/openAccess<a href="http://creativecommons.org/licenses/by/3.0/es">http://creativecommons.org/licenses/by/3.0/es</a>
oai:recercat.cat:2072/2907282017-07-19T22:36:17Zhdl_2072_171809Estrategias de aprendizaje colaborativo en asignaturas experimentalesDago Busquets, ÀngelaFuguet i Jordà, ElisabetNúñez Burcio, OscarSerrano i Plana, NúriaSubirats i Vila, XavierEnsenyament de la químicaDidàctica de la ciènciaAprenentatge cooperatiuAprenentatge actiuChemistry educationScience teaching methodsTeam learning approach in educationActive learningLa presente comunicación se enmarca en el contexto del Espacio Europeo de Educación Superior, dirigido a diseñar, practicar y reflexionar sobre una enseñanza centrada en el aprendizaje de los estudiantes. Esta forma de aprendizaje ha sido abordada por diversos investigadores en el ámbito docente universitario estableciéndose una importante relación con el área de conocimiento. Así, tradicionalmente, los profesores de ciencias catalogadas como "puras" tienden a una perspectiva de enseñanza centrada en el conocimiento y la transmisión del mismo, mientras que los profesores de ciencias catalogadas como "mixtas" se centran más en el aprendizaje del estudiante. Sin dejar de tener en cuenta que el área de conocimiento influye en nuestra actividad docente, estas tendencias impermeables deben ser superadas, pues hay que comprender que la transmisión de conocimiento se vehicula a través del aprendizaje del estudiante. Además, es necesario que la enseñanza se centre en un aprendizaje participativo, significativo, reflexivo y crítico. Esto no implica que el docente quede relegado a un segundo plano, sino que el docente, especialista en un área de conocimiento, ha de generar un ambiente propicio que promueva el aprendizaje de sus estudiantes.Sociedad Española de Química Analítica (SEQA)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/114103spa(c) Dago Busquets, Àngela et al., 2015info:eu-repo/semantics/openAccess
oai:recercat.cat:2072/2907292017-07-19T22:36:18Zhdl_2072_171809GIR: Grupo de ElectroanálisisEsteban i Cortada, MiquelAriño Blasco, CristinaDíaz Cruz, José ManuelSerrano i Plana, NúriaDago Busquets, ÀngelaPérez, ClaraAnàlisi electroquímicaQuimiometriaVoltametriaElectrochemical analysisChemometricsVoltammetryDesde mediados de los años 90 el grupo inició una gran actividad en la aplicación de métodos quimiométricos para el estudio de complejación de metales mediante diversas técnicas electroanalíticas (voltamperometría), campo que estaba prácticamente inexplorado en aquellos momentos. Se adaptó en primer lugar, el método MCR-ALS (multivariate Curve Resolution by Alternating Least Squares)empleado con datos espectroscópicos, pero nunca, hasta entonces, aplicado a datos electroquímicos. El método fue mejorado mediante la incorporación de nuevas restricciones basadas en las características de las señales electroquímicas. Posteriormente, y debido a las limitaciones de MCR-ALS para el caso de datos(I vs. conc.)no bilineales, se han propuesto nuevos métodos, y desarrollado algoritmos, para este tipo de datos. Así mismo, se ha aplicado, también por primera vez, MCR-ALS al tratamiento simultáneo de datos electroquímicos y espectroscópicos.Sociedad Española de Química Analítica (SEQA)Universitat de Barcelonainfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/2445/114104spa(c) Esteban i Cortada, Miquel et al., 2015info:eu-repo/semantics/openAccess
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