Optimization and evaluation of low-pressure gas chromatography-mass spectrometry for the fast analysis of multiple pesticide residues in a food commodity
ABSTRACT A fast method of analysis for 20 representative pesticides was developed using low-pressure gas chromatography-mass spectrometry (LP-GC-MS). No special techniques for injection or detection with a common quadrupole GC-MS instrument were required to use this approach. The LP-GC-MS approach used an analytical column of 10 m x 0.53 mm I.D., 1 microm film thickness coupled with a 3 m x 0.15 mm I.D. restriction capillary at the inlet end. Thus, the conditions at the injector were similar to conventional GC methods, but sub-atmospheric pressure conditions occurred throughout the analytical column (MS provided the vacuum source). Optimal LP-GC-MS conditions were determined which achieved the fastest separation with the highest signal/noise ratio in MS detection (selected ion monitoring mode). Due to faster flow-rate, thicker film, and low pressure in the analytical column, this distinctive approach provided several benefits in the analysis of the representative pesticides versus a conventional GC-MS method, which included: (i) threefold gain in the speed of chromatographic analysis; (ii) substantially increased injection volume capacity in toluene; (iii) heightened peaks with 2 s peak widths for normal MS operation; (iv) reduced thermal degradation of thermally labile analytes, such as carbamates; and (v) due to larger sample loadability lower detection limits for compounds not limited by matrix interferences. The optimized LP-GC-MS conditions were evaluated in ruggedness testing experiments involving repetitive analyses of the 20 diverse pesticides fortified in a representative food extract (carrot), and the results were compared with the conventional GC-MS approach. The matrix interferences for the quantitation ions were worse for a few pesticides (acephate, methiocarb, dimethoate, and thiabendazole) in LP-GC-MS, but similar or better results were achieved for the 16 other analytes, and sample throughput was more than doubled with the approach.
Full-textDOI: · Available from: Katerina Mastovska, Jul 05, 2015
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ABSTRACT: A method for the fast identification of trace levels of pesticide residues in agricultural crops was developed using low pressure gas chromatography/mass spectrometry (LP-GC/MS). The final chromatographic determination took 12 min-utes per sample while conventional GC/MS required at least 30 minutes. Also, im-proved peak shapes for dichlorvos, dimethoate, chlorothalonil, pirymethanil, pirimicarb, carbaryl, myclobutanil, flusilazole tebuconazole, fenarimol and ipro-dione were obtained which generally enabled lower limits of detection. The method was successfully applied to analysis of more than 40 pesticides in 120 sam-ples of fruits, vegetables and cereals. With the aid of LP-GC/MS the number of samples analysed on the particular instrument could be at least doubled.
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ABSTRACT: Practical applications of fast gas chromatography (GC) with time-of-flight mass spectrometry (TOFMS) are presented. A narrow-bore column (0.10-mm i.d.) is used to analyze over 100 specific polychlorinated biphenyl congeners in an Aroclor mix and a sediment sample in 10.5 min. Sample preparation is minimized for the sediment to more closely match the speed advantage gained by using fast GC-TOFMS. The possibility of using a 0.53-mm-i.d. column operated under vacuum-outlet conditions for fast GC-TOFMS is established for Aroclors and a suite of environmental contaminants. Fast acquisition rates and automated peak-find and spectral deconvolution capabilities are demonstrated for TOFMS.Journal of chromatographic science 05/2002; 40(5):254-68. DOI:10.1093/chromsci/40.5.254