Bioassay of residues of endrin, diazinon, carbaryl, and naled on sorghum grain

Abstract

The objective of the study was to evaluate the efficiency and suitability of biological analyses of residues of endrin, diazinon, naled, and carbaryl insecticides on sorghum grain. Two methods of biological assay were found useful in this study; a treated surface or film method of bioassay utilizing the house fly, Musca domestica L., and a photo-migration-dilution test employing the yellow fever mosquito, Aedes aegypti (L .) as the test organism. Initial studies required selection and adaptation of rearing and handling procedures to provide practical methods for obtaining adequate numbers of insects of uniform vigor and response for testing. The sensitivity of the test insects to each of the four insecticides was determined prior to examination of field treated samples. To improve reproducibility of treated surface assays, studies were conducted to compare the effects of several sample sizes, number of replications, and observation times. Best results were obtained by making counts at 48 hours, using 10 replications and a sample size of 25. Seven different extraction procedures were compared for efficiency in removal of each of the four insecticides from sorghum grain. These included tumbling, combination blend-tumbling, and soxhlet extraction with ether, hexane, chloroform, methylene chloride, dimethyl sulfoxide, isopropyl alcohol, and acetonitrile. Extractive interferences resulting from use of each of the extraction methods were determined and the efficiency of six cleanup methods were compared. The cleanup methods included petroleum ether-acetonitrile partition, nuchar adsorption, and chromatographing on alumina, polyethylene-coated alumina, and wax-coated alumina. Cleanup methods were compared for recovery of each insecticide. The practical applicability of the procedures resulting from this study were tested using field collected samples of sorghum grain treated with endrin, diazinon, naled, and carbaryl at 0, 7, 14, and 21 days before harvest.