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We studied the simultaneous determination of demeton-S-methyl, oxydemeton-methyl, and their oxide demeton-S-methylsulfone, in agricultural products by liquid chromatography coupled with mass spectrometry (LC-MS). The sample homogenized with antioxidants L-ascorbic acid and butylhydroxytoluene was extracted with acetone. An aliquot of the crude extract was reextracted with ethyl acetate by using an EXtrelut column. After hexane/acetonitrile partitioning lipid-rich samples such as cereals, the extract was cleaned up on a PSA column or tandem graphitized carbon/PSA column, and determined by ESI-SIM mode LC-MS. Average recoveries (n=5) of compounds from ten kinds of samples fortified at the analyte concentration of 0.05 microg/g were from 73.8% to 102.5%, and the relative standard deviations were

Based on the data for pesticide residues in vegetables and fruits collected in Aichi prefecture (fiscal years 2001-2005), we selected groups of foods and pesticides that would allow efficient and effective inspection under the positive list system. Statistical analyses were done to examine the rates of detection of pesticides and the numbers of kinds of pesticides detected in samples of domestic vegetables, domestic fruits, imported vegetables, and imported fruits. The rate of detection of pesticides has decreased gradually in domestic vegetables. The number of different kinds of pesticides detected in each sample was significant higher in domestic fruits. Data for previous years were reassessed in terms of the present maximum residue limits (MRL), and classified as relative value to the MRL. The proportion of pesticides detected at levels that exceeded the MRLs showed a decreasing tendency. In addition, we were able to identify combinations of pesticides and agricultural commodities in which the MRLs were more likely to be exceeded.

We evaluated a multiresidue method for determination of pesticides in agricultural products by SCAN mode GC/MS coupled with three kinds of database for 253 pesticides: relative retention time, mass spectra and calibration curve (SCAN method). Twenty-six pesticides, a total of 131 pesticides were detected in samples by the SCAN method. The detection results agreed closely with those of the SIM mode GC/MS method using calibration standards (SIM method). The ratios of the SCAN method to the SIM method ranged from 0.3 to 3.1 with SD values of 0.63. It was judged that the SCAN method could be applied to the screening analysis of pesticide residues in agricultural products, provided that the sample preparation method makes it possible to effectively remove sample matrixes with minimal loss of analytes.

A sensitive and quantitative multiresidue method using NCI mode GC/MS and GC-micro ECD for determining pesticides in animal and fishery products was established. The crude sample extract obtained by acetone-hexane extraction for solid samples or acetonitrile extraction for liquid samples was cleaned up with a GPC/SPE system. The first GPC pesticide fraction containing lipids and pigments was selectively collected, and loaded directly onto a graphitized carbon/PSA 2-layered column. After the second GPC pesticide fraction was collected, the 2-layered column was eluted with acetone-hexane (3 : 7). The combined eluate was subjected to NCI-SIM/Scan mode GC/MS for semi-quantification. After fractionation by Florisil cartridge column SPE, each fraction was subjected to dual-column GC-micro ECD for quantification. Average recoveries (n=5) of pesticides, except for chlorothalonil and some others, from fortified samples ranged from 76.8% to 107.9% with RSD values of <9.7%.