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161.
F. Vela-Soria O. Ballesteros A. Zafra-Gómez L. Ballesteros A. Navalón 《Analytical and bioanalytical chemistry》2014,406(15):3773-3785
In the present work, a new method based on a sample treatment by dispersive liquid–liquid microextraction (DLLME) for the extraction of six bisphenols (bisphenol A, bisphenol S, and monochloro-, dichloro-, trichloro-, and tetrachlorobisphenol A), four parabens (methyl-, ethyl-, propyl-, and butylparaben), and six benzophenones (benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-6, benzophenone-8, and 4-hydroxybenzophenone) in human urine samples, followed by ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) analysis, is validated. An enzymatic treatment allows determining the total content of the target EDCs. The extraction parameters were accurately optimized using multivariate optimization strategies. Ethylparaben ring-13C6, benzophenone-d10, and bisphenol A-d16 were used as surrogates. Limits of quantification ranging from 0.1 to 0.6 ng mL?1 and interday variabilities (evaluated as relative standard deviations) from 2.0 to 13.8 % were obtained. The method was validated using matrix-matched standard calibration followed by a recovery assay with spiked samples. Recovery rates ranged from 94 to 106 %. A good linearity, for concentrations up to 300 ng mL?1 for parabens and 40 ng mL?1 for benzophenones and bisphenols, was also obtained. The method was satisfactorily applied for the determination of target compounds in human urine samples from 20 randomly selected individuals. 相似文献
162.
Inmaculada Jiménez-Díaz María Pilar Hermo Oscar Ballesteros Alberto Zafra-Gómez Dolores Barrón José Barbosa Alberto Navalón 《Chromatographia》2013,76(11-12):707-713
This 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). 相似文献
163.
Claudio De Rosa Finizia AuriemmaOdda Ruiz de Ballesteros Rocco Di GirolamoMartina Pepe Oreste TaralloAnna Malafronte 《European Polymer Journal》2013
A study of the thermodynamic stability and the related polymorphic transformations induced by thermal treatments of the mesomorphic form that crystallizes in stereodefective metallocene isotactic polypropylene (iPP) is presented. We show that the mesomorphic form of the more isotactic samples is stable at room temperature, whereas the mesomorphic form crystallizing in the more stereoirregular sample is unstable and crystallizes at room temperature in the crystalline α form. In any case, the mesomorphic form transforms during heating or by annealing at temperatures higher than 60–80 °C always in the α form, regardless of the stereoregularity, even in the case of stereoirregular samples generally crystallizing from the melt in the γ form. These data confirm the proposed model of structure of the mesomorphic form as small aggregates of chains in three-fold helical conformation packed with lateral correlations similar to the α form of iPP. 相似文献
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165.
Ballesteros I. Oliva J. M. Carrasco J. C. Ballesteros M. 《Applied biochemistry and biotechnology》1994,45(1):283-294
Applied Biochemistry and Biotechnology - In this study, fermentation tests on different initial glucose concentrations, ranging from 100 to 200 g/L, were conducted to identify the ethanol tolerance... 相似文献
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Multiparametric quantum gl(2) algebras are presented according to a classification based on their corresponding Lie bialgebra structures. From them, the non-relativistic limit leading to quantum harmonic oscillator algebras is implemented in the form of generalized Lie bialgebra contractions. 相似文献
170.
J. I. Fernández Palop J. Ballesteros M. A. Hernández R. Morales Crespo S. Borrego del Pino 《Czechoslovak Journal of Physics》2004,54(2):225-238
An extension of the previous work which only dealt with the sheath zone is used to analyze the wall-plasma interaction in electronegative plasmas. Ionization is introduced as the presheath mechanism. This extension includes the joining of the sheath and the plasma solutions. For certain plasma parameters a stratified presheath is obtained. In this case, the plasma and the sheath solutions are matched in a very simplified way, by introducing a discontinuity in the electric field. This discontinuity is equivalent to consideration of a negatively charged layer between the presheath and the sheath. The parameter space region in which this matching should be made has been delimited. The model includes the previous one in the limiting case of no ionization. 相似文献