Determination of Residues of Alachlor and Related Herbicides in Crops by Liquid Chromatography with Electrochemical Detection

Abstract A method is described for determining residues of 3 acetamide herbicidesalachlor [2-chloro-N(2,6- diethylphenyl)-N(methoxymethyl)acetamide], acetochlor [2-chloro-N(2-ethyl-6-methylphenyl)-N (ethoxymethyl)acetamide), and butachlor [2-chloro-N(2,6-diethylphenyl)-N(butoxymethyl)- acetamide)by liquid chromatography (LC). Currently no published method determines metabolites from all 3 herbicides in crops. Strong-base hydrolysis after extraction of a test portion with water-acetonitrile results in the formation of 2,6- diethylaniline (DEA) and 2-(1-hydroxyethyl)-6-ethylaniline from alachlor metabolites, 2-ethyl-6-methylaniline and 2-(1-hydroxyethyl)-6-methylaniline from acetochlor metabolites, and DEA from butachlor. The anilines are isolated by steam distillation, partitioned with Supelclean ENVI-Chrom P solid-phase extraction columns, and methylated prior to LC analysis. The limit of quantitation of aniline moieties is about 0.01 ppm. Recoveries of 0.01- 0.40 ppm aniline moieties are generally 74-103%, with relative standard deviations of 2.2 to 14.0%.