Expanded Coagulating Cleanup Procedures for Simultaneous Gas Chromatographic Determination of Organoposphorus Pesticides in Crops and Fruits

A simplified method is described for determining 7 organophosphorus pesticides (mevinphos, phosphamidon, fenamiphos, crufomate, carbophenothion, fenchlorphos, coumaphos) in citrus fruits, banana, soybeans and wheat. Residues were extracted with acetonitrile or acetone, and if necessary, were partitioned with n-hexane. Coextractives were coagulated with a solution containing phosphoric acid and ammonium chloride, and were separated by filtration. The filtrate was extracted with dichloromethane. The extract was concentrated and injected into a gas chromatograph equipped with a flame photometric detector and a fused silica capillary column. Recovery data were obtained by fortifying market samples at 0.1 and 0.2 ppm. Recoveries of most organophosphorus pesticides exceeded 80%. The limit of detection ranged from 0.005 to 0.05 ppm, depending on the compound.