A selective pressurized liquid extraction and gas chromatography coupled with triple quadrupole mass spectrometer method was developed for simultaneous determination of 52 pesticide residues in medicine and food dual-purpose herbs. The developed extraction method integrated extraction and cleanup processes for sample preparation. The sorbents, 5 g Florisil and 100 mg graphitized carbon black, were placed inside the extraction cell to remove matrix interferences. Optimized conditions of selective pressurized liquid extraction were ethyl acetate as extraction solvent, 120°C of extraction temperature, 6 min of static extraction time, 50% of flush volume extracted for two cycles. An ultra inert capillary GC-MS HP-5 UI column (20 m × 0.18 mm id, 0.18 μm) and column backflush system were used for the analysis. Multiple-reaction monitoring was employed for the quantitative analysis with electron ionization mode. All calibration curves showed good linearity (r(2) > 0.995) within the test ranges. The average recoveries of most pesticides were from 81 to 118%. The validated method was successfully applied for the determination of pesticide residues in four herbs. The results indicate that selective pressurized liquid extraction and GC-MS/MS is a sensitive and reliable analytical method for the simultaneous determination of multiple pesticide residues in herbs.
"GC × GC is considered an established separation technique and for the last decade focus has shifted away from the development of modulation technology to applying the technique to an ever increasing number of analytical challenges. Fields in which GC × GC applications are popular include petroleum and petrochemicals           ; food, flavours and fragrances              ; metabolomics             and environmental analysis       . Although GC × GC has never been more widespread, there are some applications that remain challenging for a chromatographer to perfect. "
[Show abstract][Hide abstract] ABSTRACT: This review updates our knowledge on pressurised liquid extraction, PLE (also known as accelerated solvent extraction and pressurised fluid extraction) of persistent organic pollutants such as polynuclear aromatic hydrocarbons and polychlorinated biphenyls from environmental matrices. The basic experimental set-up is presented, and parameters influencing the extraction process are discussed. PLE can be used for a broad range of applications, and clearly has the potential for replacing tedious classic extraction methods such as Soxhlet extraction.
[Show abstract][Hide abstract] ABSTRACT: Pre-column back-flushing is a matrix minimization technique in GC in which the carrier gas flow of the pre-column is reversed after the transfer of the highest boiling analyte to the analytical column. Practical details concerning this technology have rarely been published although it is widely used. This paper now-focuses on the practical implementation of pre-column back-flushing for pesticide residue analysis of complex food matrices. Fitting the analytical column into the pre-column was found to be essential for comparable analyte responses with and without back-flushing. The effectiveness of the reverse column flow technique is mainly affected by the transfer time after which back-flushing starts. The transfer time was found to depend on which kind of injected matrix is used and the state of the pre-column. For the regular adaptation of the transfer time in routine analysis, a simple test was introduced in which 13-C-labeled deltamethrin and indeno[1,2,3-c,d]pyrene were added to the prepared extract. Chromatograms, limits of quantification and relative standard deviations of up to 99 pesticides in citrus oil and liver extracts proved a clearer identification and enhanced quantification using pre-column back-flushing compared to measurements without this technology. Furthermore, reduced system maintenance could be achieved through back-flushing. This article is protected by copyright. All rights reserved.
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