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A procedure for the determination of perfluorocarboxylic acids (i.e. PFC7–10A) in sediment by pressurized fluid extraction (PFE), derivatization, headspace solid-phase microextraction and GC–MS determination in the negative ion chemical ionisation mode was developed. The PFE extraction variables such as solvent composition, number and time per extraction cycle, and extraction temperature were optimised. In the optimum extraction conditions, recoveries exceeding 95% with a limit of detection and RSDs of 0.5–0.8 ng g−1 and 15.5–16.8%, respectively, were obtained. The developed analytical procedure was applied to harbour sediments where PFC8A and PFC10A were detected for the first time at low ppb concentrations (i.e. 8–11 ng g−1).

Extraction selectivity of whole wool wax from raw wool by using ethanol-modified carbon dioxide at constant pressure (100 bar) and temperature (60°C) was studied. A kinetic study was carried out to optimize the percentage of ethanol and the extraction time. The modified carbon dioxide was decompressed in ethanol as a collection solvent, leading to the formation of two different fractions as a function of their solubility. Qualitative and quantitative analyses of the lipid classes present in the collected fractions were performed by TLC coupled to an automated FID system (TLC-FID). Moreover, a detailed structural comparison was carried out between the aliphatic high-molecular-mass esters and the steryl ester patterns by means of subambient pressure GC-MS in both the EI and the ammonia positive Cl modes. Considerable differences in the lipid composition of the two wool wax fractions collected were observed by TLC-FID and GC-MS.

Steryl esters occurring in lanolin have been characterised by sub-ambient pressure gas chromatography coupled to mass spectrometry. Electron impact and chemical ionisation modes with different reagent gases have been evaluated in order to carry out unambiguous peak identification. Steryl esters with different sterol (i.e. cholesterol, lanosterol and dihydrolanosterol) and acid moieties either according to carbon number (i.e C10-C23) or isomeric forms (i.e. normal, iso and anteiso) have been identified. Identification of the sterol and acid moieties has been carried out by means of the mass spectral information obtained in the electron impact, chemical ionisation mode either in the positive or negative modes using methane, isobutane and ammonia as reagent gases. Isomeric identification has been achieved by chromatographic retention parameters (i.e. entire-chain length and fractional-chain length) and by the free fatty acid profile also present in lanolin.

A review of the existing methods for the separation, identification and quantification of fatty acids mainly by chromatography and mass spectrometry (MS) techniques is presented. Moreover, a method for the simultaneous determination of the following lipidic classes, which are constituents of the wool wax, namely fatty acids, fatty alcohols, 2-hydroxy fatty acids and 2-hydroxy fatty alcohols have been developed. Every compound class consist of normal-, iso - and anteiso -branched chain isomers. The separation of all molecular species, in the range of carbon atom number C 8 –C 33 was achieved on a low polar capillary gas chromatograph (GC) column. Compound identification has been made by interpretation of mass spectra of mono- and di-tandem mass spectrometry (TMS) derivatives as well as on the basis of equivalent (ECL) and fractional chain length (FCL) retention parameters. The relative abundance of every compound class has been obtained as a function of carbon atom number.

Benzothiazoles, benzotriazoles and benzosulfonamides are high-production-volume chemicals found in various environmental aqueous samples that should be considered as emerging pollutants. This study examines the suitability of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOF-MS) for the characterization of benzothiazoles, benzotriazoles and benzosulfonamides in aqueous matrices. Solid-phase extraction was optimized in order to ensure the proper preconcentration of these contaminants prior to their analysis. Column selection, in both the first and second dimensions, was optimized to ensure a good chromatographic separation of the target analytes and of the potential interfering compounds extracted from the matrix. Several column phases were tested. The combined power of two-dimensional separation was fully illustrated by identifying minor compounds and avoiding the overestimations usually made by one-dimensional systems. Finally, the suitability of GC x GC-TOF-MS to quantify the aforementioned emerging pollutants was proven by determining those pollutants in several real samples such as river water, effluent from a wastewater treatment plant, and raw sewage.

Simultaneous determination of cyanide and volatile alkylnitriles such as acetonitrile, cis- and trans-crotononitrile, allylnitrile and butyronitrile at low ppb concentration on whole blood (rat and mice) by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography (GC) with nitrogen phosphorus detection has been achieved for the first time. SPME extraction time and temperature were optimized using a star experimental design. Optimum conditions for cyanide extraction were chosen to analyze unspiked blood samples containing alkylnitriles as that analyte occurs at the lowest concentrations. For all analytes, the developed methodology yielded good quality parameters. In all cases, good reproducibility (relative standard deviation < or =12%), detection limits (

A twin GC × GC system has been designed which enables the analysis of a sample by means of two different and independent column combinations simultaneously. Both combinations are incorporated in the same oven, using the same temperature programme, and are fed using a 50:50 column-entrance-split. It is demonstrated that, employing combinations of a conventional non-polar × polar and a reversed-type polar × non-polar column set, the information content is as high, and the analytical performance is as good as when using two separate GC × GC systems. That is, there is an appreciable gain of time and a reduction of costs without any loss of quality. The general usefulness of performing, and comparing two mutually different GC × GC runs is further illustrated with FAMEs in olive oil, and pollutants in a sediment sample. © 2004 Elsevier B.V. All rights reserved.

Most lipids are a complex mixture of classes of compounds such as fatty acids, fatty alcohols, diols, sterols and hydroxy acids. In this study, the suitability of comprehensive two-dimensional gas chromatography coupled to a time-of-light mass spectrometer is studied for lipid characterization in complex samples. With lanolin, a refined wool wax, as test sample, it is demonstrated that combined methylation plus silylation is the preferred derivatization procedure to achieve (i) high-quality GC × GC separation and (ii) easily recognizable ordered structures in lipid analysis. Optimization of the GC × GC column combination, the influence of the temperature programme on the quality of the separation, and the potential and limitations of automated TOF-MS-based identification are discussed. The combined power of a 2D separation, ordered structures and MS detection is illustrated by the identification of several minor sample constituents. © 2005 Elsevier B.V. All rights reserved.

5 pages, 3 figures.-- PMID: 14753673 [PubMed].-- Available online Nov 21, 2003.-- Issue title: "ExTech 2003 - The 5th International Symposium on Advances in Extraction Technologies " (St. Pete Beach, Florida, USA, Mar 5-7, 2003)., Improvements in the methylmercury extraction from human hair by solid-phase microextraction followed by gas chromatography coupled to cold-vapour atomic fluorescence spectrometry (GC-CVAFS) have been carried out. They consisted in the optimisation of the digestion step prior to the aqueous-phase ethylation and in the GC-CVAFS interface set-up. The main digestion parameters such as acid type, concentration, temperature and time have been optimised for hair sample analysis, thereby avoiding methylmercury degradation. Moreover, the stability of the digested samples was evaluated to improve the sample throughput.

A methodology for multi-class pesticide determination at trace level in lanolin is presented. Gel permeation chromatography on a Bio-Beads SX-3 column followed by a dual GC chromatographic determination has been developed. The effluent of the analytical column (50% diphenyl-methyl- or 14% cyanopropyl-phenylpolysiloxane) was split into an electron-capture and a nitrogen-phosphorus detection system. The chromatographic system was optimised for 28 pesticides commonly used to control sheep pests and corresponding to organochlorine, organophosphorus and pyretroid classes. Identification has been carried out by gas chromatography coupled to negative chemical ionization mass spectrometry. Recoveries ranged from 72 to 94% and the detection limits from 20 to 97 ng/g depending on the pesticide class, the RSDs were below 10%. Finally, the developed analytical methodology has been successfully applied to the determination of pesticides in several lanolin samples.