Screening Procedure for Organothiophosphate Pesticide Residues on Fruits and Vegetables by Microcoulometric Gas Chromatography

Abstract

Abstract The Mills-Onley-Gaither procedure for extraction and cleanup of chlorinated pesticide residues in fruits and vegetables was adapted for use in organothiophosphate residue screening. The acetonitrile extraction-petroleum ether shakeout was employed, and up to 5 g of sample was injected into a microcoulometric gas chromatograph with no further cleanup. The microplatinum cell, which titrates only sulfur, was used. Recoveries from “spiked” fruits and vegetables (average of 2—3 determinations) were: Systox, 33%; Delnav, 68%; Diazinon, 86%; Di-Syston, 85%; methyl parathion, 82%; parathion, 88%; malathion, 71%; ethion, 107%; Trithion, 94%; EPN, 78%. Satisfactory baselines were obtained on plums, peaches, cherries, grapes, carrots, lettuce, cabbage, cauliflower, asparagus, and celery. Standard parent compounds only were studied.