A Specific Bioassay Method for Determining Bidrin® Insecticide Residues

Abstract A specific bioassay method based on the application of physico-chemical and biological techniques has been developed for the determination of Bidrin® (3-hydroxy-iV,Ardimethyl-cis-crotonamide dimethyl phosphate) residues. The experimental design, procedure, and evaluation of bioassay results are essentially the same as in a residue-film bioassay. Interferences of most insecticides tested were less than 0.1% ; however, water-miscible insecticides, such as dimethoate and phosphamidon, gave relatively high interferences (1–6%). Mixtures containing 100-150 ppm of "less toxic" insecticides gave interferences of 0.6 to < 0.03% of apparent Bidrin. When several crops were fortified with 0.1–22 ppm of Bidrin, either before or after extraction, recoveries were satisfactory. About 0.05 ppm of Bidrin can be detected. The reproducibility of this method is comparable to that of a residue-film bioassay. The overall coefficient of variation is 8.8%. A comparison of results for several Bidrin-treated materials, obtained by a cholinesterase-inhibition method and the specific bioassay method, shows good agreement.