The Experts below are selected from a list of 31314 Experts worldwide ranked by ideXlab platform
Carmelo Garcia Barroso - One of the best experts on this subject based on the ideXlab platform.
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optimisation of headspace solid phase microextraction for the analysis of volatile phenols in wine
Journal of Chromatography A, 2003Co-Authors: Remedios Castro Mejias, Ramon Natera Marin, M V G Moreno, Carmelo Garcia BarrosoAbstract:Headspace solid-phase microextraction has been applied to the analysis of volatile phenols in wine. Silica fibre coated with Carbowax-divinylbenzene was found to be more efficient at extracting these compounds than other fibres such as those coated with Polydimethylsiloxane, polyacrylate, carboxen-Polydimethylsiloxane, and Polydimethylsiloxane-divinylbenzene. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength and sample volume were optimised using a two-level factorial design expanded further to a central composite design, in order to evaluate several possibly influential and/or interacting factors. The headspace (HS)-SPME procedure developed shows adequate detection and quantitation limits, and linear ranges for correctly analysing these compounds in wine. The recoveries obtained were close to 100%, with repeatability values lower than 16%. The method was applied to a variety of white and red wines.
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optimisation of headspace solid phase microextraction for analysis of aromatic compounds in vinegar
Journal of Chromatography A, 2002Co-Authors: Remedios Castro Mejias, Ramon Natera Marin, M V G Moreno, Carmelo Garcia BarrosoAbstract:Abstract Headspace solid-phase microextraction has been applied to the analysis of aroma compounds in vinegar. Silica fibre coated with Carboxen–Polydimethylsiloxane was found to be more efficient at extracting these compounds than other fibres such as those coated with Polydimethylsiloxane, Carbowax–divinylbenzene, and Polydimethylsiloxane–divinylbenzene, but its repeatability was low. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength, and sample volume were optimised using a two-level factorial design expanded further to a central composite design. This chemometric tool is very appropriate in screening experiments where the aim is to investigate several possibly influential and/or interacting factors. The extraction efficiency is inversely affected by the acetic acid content—an increase in the acetic acid concentration decreases the extraction efficiency. No interference is observed with the increase in content of polyphenols.
Silvia Fustinoni - One of the best experts on this subject based on the ideXlab platform.
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determination of low level methyl tert butyl ether ethyl tert butyl ether and methyl tert amyl ether in human urine by hs spme gas chromatography mass spectrometry
Analytica Chimica Acta, 2007Co-Authors: L Scibetta, Laura Campo, Rosa Mercadante, V Foa, Silvia FustinoniAbstract:Abstract Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/Polydimethylsiloxane, Polydimethylsiloxane/divinylbenzene, and Polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the Polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30–4600 ng L−1, within- and between-run precision, as coefficient of variation,
Remedios Castro Mejias - One of the best experts on this subject based on the ideXlab platform.
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optimisation of headspace solid phase microextraction for the analysis of volatile phenols in wine
Journal of Chromatography A, 2003Co-Authors: Remedios Castro Mejias, Ramon Natera Marin, M V G Moreno, Carmelo Garcia BarrosoAbstract:Headspace solid-phase microextraction has been applied to the analysis of volatile phenols in wine. Silica fibre coated with Carbowax-divinylbenzene was found to be more efficient at extracting these compounds than other fibres such as those coated with Polydimethylsiloxane, polyacrylate, carboxen-Polydimethylsiloxane, and Polydimethylsiloxane-divinylbenzene. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength and sample volume were optimised using a two-level factorial design expanded further to a central composite design, in order to evaluate several possibly influential and/or interacting factors. The headspace (HS)-SPME procedure developed shows adequate detection and quantitation limits, and linear ranges for correctly analysing these compounds in wine. The recoveries obtained were close to 100%, with repeatability values lower than 16%. The method was applied to a variety of white and red wines.
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optimisation of headspace solid phase microextraction for analysis of aromatic compounds in vinegar
Journal of Chromatography A, 2002Co-Authors: Remedios Castro Mejias, Ramon Natera Marin, M V G Moreno, Carmelo Garcia BarrosoAbstract:Abstract Headspace solid-phase microextraction has been applied to the analysis of aroma compounds in vinegar. Silica fibre coated with Carboxen–Polydimethylsiloxane was found to be more efficient at extracting these compounds than other fibres such as those coated with Polydimethylsiloxane, Carbowax–divinylbenzene, and Polydimethylsiloxane–divinylbenzene, but its repeatability was low. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength, and sample volume were optimised using a two-level factorial design expanded further to a central composite design. This chemometric tool is very appropriate in screening experiments where the aim is to investigate several possibly influential and/or interacting factors. The extraction efficiency is inversely affected by the acetic acid content—an increase in the acetic acid concentration decreases the extraction efficiency. No interference is observed with the increase in content of polyphenols.
Helena Teixeira Godoy - One of the best experts on this subject based on the ideXlab platform.
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Optimization of headspace solid-phase microextraction conditions to determine fruity-aroma compounds produced by Neurospora sitophila
Anal. Methods, 2014Co-Authors: Daniele Souza De Carvalho, Mário Roberto Maróstica Júnior, Stanislau Bogusz Junior, Ana Paula Dionísio, Helena Teixeira Godoy, Glaucia Maria PastoreAbstract:The biotechnological production of aromatic compounds is an important alternative to the chemical synthesis of flavor ingredients in food industry. Therefore, the development of an accurate and precise analytical technique for the measurement of the biotechnological production of aromatic compounds is of significant importance. In this paper, we optimize the extraction conditions for headspace solid-phase microextraction coupled to GC-FID and GC-MS for the determination of ethyl hexanoate produced by Neurospora sitophila in a malt-extract medium. Following three SPME fibers were tested: Polydimethylsiloxane (PDMS), carboxen-Polydimethylsiloxane (CAR/PDMS) and Polydimethylsiloxane-divinylbenzene (PDMS/DVB). The PDMS/DVB was the most efficient fiber for trapping the volatile aromatic compound. The optimized SPME extraction temperature and time were 30 °C and 10 min, respectively. This method showed good linearity and the limits of detection (LOD) and limits of quantification (LOQ) of the targeted aromatic compound were 0.6 and 1.9 mg L−1, respectively. The HS-SPME methodology proved to be a simple and rapid approach to quantify ethyl hexanoate accurately and precisely for the biotechnological production process.
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optimization of the extraction conditions of the volatile compounds from chili peppers by headspace solid phase micro extraction
Journal of Chromatography A, 2011Co-Authors: Stanislau Bogusz, Arlete Marchi Tavares De Melo, Claudia Alcaraz Zini, Helena Teixeira GodoyAbstract:A method involving headspace-solid phase micro-extraction (HS-SPME), gas chromatography with flame ionization detection (GC-FID) and gas chromatography with mass spectrometry (GC-MS) was developed and optimized to investigate the volatile composition of Capsicum chili peppers. Five SPME fibers were tested for extraction: carboxen/Polydimethylsiloxane (CAR/PDMS-75μm), Polydimethylsiloxane (PDMS-100μm), divinylbenzene/Polydimethylsiloxane (DVB/PDMS-65μm), carbowax/divinylbenzene (CW/DVB-70μm), and divinylbenzene/carboxen/Polydimethylsiloxane (DVB/CAR/PDMS-50/30μm), the last of which was shown to be the most efficient fiber to trap the volatile compounds. Optimization of the extraction conditions was carried out using multivariate strategies such as factorial design and response surface methodology. Eighty three compounds were identified by GC-MS when using the optimized extraction conditions, the majority of which were esters.
Alain Pouchelon - One of the best experts on this subject based on the ideXlab platform.
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rheological studies of fumed silica Polydimethylsiloxane suspensions
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Jeannoel Paquien, Jocelyne Galy, Jeanfrancois Gerard, Alain PouchelonAbstract:In this study, dynamic mechanical measurements and transmission electron microscopy are used to examine the behavior of fumed silica/Polydimethylsiloxane (PDMS) suspensions. The work focuses on three aspects: (i) the modulation of the interactions between silica and PDMS through a controlled silylation of the silica surface; (ii) the effect of the process used to graft the silica surface; (iii) the effect of the silica volume fraction used in the dispersions. A relation between the silica grafting ratio, the aggregate size and the rheological properties has been established and the results have interpreted through a model of fractal clusters.