Procedure for Nine Organothiophosphate Pesticide Residues on Fruits and Vegetables, Using Microcoulometric Gas Chromatography

Abstract

Abstract A method, using microcoulometric gas chromatography (sulfur dioxide detector), is proposed for determining 9 organothiophosphate pesticide residues in fruits and vegetables. Extraction and cleanup principles and procedures are those used in the Mills-Onley-Gaither method for chlorinated pesticides, with modifications, particularly in the Florisil cleanup step. Recoveries of the compounds (sulfotepp, Thimet, diazinon, Di-Syston, methyl parathion, parathion, ethion, Trithion, and EI'IV) from crops fortified just prior to extraction ranged from 73 to 109%, with an overall average of 92%. Average recoveries of individual thiophosphates ranged from 82 to 99%. Recoveries were made at low (0.1— 0.2), intermediate (0.5), and high (2.0- 3.0) ppm levels. Cleanup on all crops tested was adequate for the detector used. In addition to the above compounds, malathion was quantitatively cluted from the Florisil column with an additional eluting mixture of higher polarity. Studies of the method should be continued to include both petroleum ether- and water-soluble compounds, and additional column packings will be investigated.