Abstract:

A method for the determination of organic phosphorus pesticide residues is described. It covers 25 residues in scallion including dichlorvos, ethoprophos, phorate, diazinon, disulfoton, dimethoate, pirimiphos-methyl, chlorpyrifos, malathion, fenitrothion, parathion, chlorfenvinphos, ethion, EPN, dyfonate, chlorpyrifos-methyl, parathion-methyl, fenthion, quinalphos, gardona, methidathion, carbophenothion, phosmet, phosalone, and coumaphos. After the scallion samples were heated for 30 s in microwave oven, the residues were extracted with acetonitrile, and then the organic phase was salted out from the matrix. As a result, most of the interfering impurities were abolished in the heating process. In this study, these pesticides were categorized into two groups for analysis. The gas chromatographic analysis was performed on a capillary column (DB-1701, 30 m×0.25 mm×0.25 μm) and determined with a flame photometric detector. Linear correlation coefficients of the 25 organic phosphorus pesticides were not lower than 0.9910 and the linear ranges for most of the compounds were between 0.1 to 5.0 mg/L. The detection limits were between 0.025 and 0.200 mg/L. In recovery study, average recoveries ranged from 85.2% to 119.6% at the fortification levels of 0.05, 0.2 and 0.5 mg/kg and the relative standard deviations were in the range of 2.1% and 14.8%. The method is a simple, rapid and highly efficient one to determine organic phosphorus pesticide residues in scallion.

Key words: gas chromatography （GC）, microwave clean-up, organic phosphorus pesticide residues, scallion