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Simple, competitive enzyme-linked Immunosorbent assays (ELISAs) have been developed for the quantitation of each of 3 major organophosphate Insecticides: fenltrothlon (FN), chlorpyrifos-methyi (CPM), and plrlmlphos-methyl (PIRM). Performance of these assays on wheat grain and (for FN and CPM) on milling fractions such as flour, wheat germ, and bran has been assessed. Each assay is specific for the particular compound, i.e., no significant cross-reaction with the other 2 pesticides is observed. Only limited reactions were noted with major metabolites or analogs of these pesticides. Assay limits of detection of 0.3 ng FN, 0.2 ng CPM, and 0.02 ng PIRM, corresponding to limits of detection in whole grain of 0.08 ppm FN, 0.2 ppm CPM, and 0.03 ppm PIRM. Each compound In grain and milling fractions could be extracted quantitatively by simple shaking in neat methanol. Multiresidue analysis of the 3 insecticides was performed by simultaneously adding the cereal extract (diluted in phosphate buffer) to separate duplicate microwells coated with antibodies to FN, CPM, and PIRM and adding appropriate pesticide-horseradish peroxidase conjugates. High correlations between gas chromatography and the ELISA methods were obtained for Insecticide levels In whole wheat and In milling fractions. In general, the ELISA assays had precision similar to those of instrumental pesticide analyses.

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