Residue analysis of chlorpyrifos and its oxygen analogue in field-treated wheat plants.

Abstract

Methods were developed for analyzing chlorpyrifos and its oxygen analogue in wheat plants and kernels. The recoveries from fortified plant samples ranged from 85 to 95% for chlorpyrifos and from 58 to 93% for the oxygen analogue ( O, O -diethyl, O -3,5,6-trichloro-2-pyridylphosphate). Wheat plants at the early-tillering stage were field treated with chlorpyrifos emulsifiable concentrate at 0.56 and 1.12 kg AI/ha. Residues decreased steadily throughout the growth period. Straw harvested 63 days after treatment contained 0.003 ppm or less chlorpyrifos, and the oxygen analogue was not detectable (<0.005 ppm). Residues were not detectable in the wheat kernels. The dilution of the residues by plant growth was calculated, and the actual disappearance of chlorpyrifos was estimated.