Analysis of crops and soils for residues of chlorfenvinphos insecticide and its breakdown products

Field crops treated with chlorfenvinphos insecticide have been analysed for residues of the parent compound and for possible residues of its breakdown products, 1‐(2′,4′‐dichlorophenyl)ethan‐1‐ol (II), 2,4‐dichloroacetophenone (III), 2,4‐dichlorophenacyl chloride (VIII) and conjugates of (II). Residues of (II) and (III) did not exceed 0.2 ppm in soils within six months of application of chlorfenvinphos at up to 8 lb/ac. Residues of (VIII) could not be detected in any of these soils, and the limit of detectability was 0.02‐0.04 ppm. Crops that were grown in soils treated with up to 4 kg/ha ( to 3.6 Ib/ac) of chlorfenvinphos contained detectable residues of chlorfenvinphos (<0.01‐0.95 ppm) at harvest, and the highest residues were found in radishes. However, residues of the possible breakdown products (II), (III) and (VIII) could not be detected in any of these crops, and the limit of detectability was 0.01‐0.05 ppm. When chlorfenvinphos was applied to the foliage of potatoes there was some evidence for conversion of the trans (β) isomer to the cis (a) isomer. Both isomers were degraded rapidly and the initial half‐life of chlorfenvinphos (cis + trans) was about 3 days. Residues of chlorfenvinphos and the breakdown products (II, free and conjugated), (III) and (VIII) could not be detected on potato foliage, potato tubers, or maize grain 13‐98 days after foliar application of chlorfenvinphos at up to 1 kg/ha on potatoes and up to 2 kg/ha on maize. The limits of detectability were 0.005‐0.05 ppm.