Minimizing geometric isomerization of α-cypermethrin in the residue analysis

Abstract

Isomerization of chiral pesticides in residue analysis has not drawn much attention which can cause wrong decisions on the enantioselective environmental behavior. A residue analysis method for α-cypermethrin and its three acid metabolites, cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanecarboxylic acid (cis/trans-DCVA) and 3-phenoxybenzoic acid (3-PBA), in foods such as chicken, honey, milk and pork has been established, in which the isomerization of α-cypermethrin was minimized. The target compounds were determined by GC–ECD after a derivatization reaction with 1,1,1,3,3,3-hexafluoroisopropanol. The conditions of the method were optimized by Taguchi orthogonal experiment. Under the optimized conditions, good linearity was obtained with correlation coefficients ranging from 0.9964 to 0.9998. The limits of detection were 0.001–0.005mgkg−1. The recoveries were 70.9–114.9% with relative standard deviations of 0.6–15%. In addition, ratios of isomerization ranged only from 2.3% to 7.0%. This method was applied in commercial animal food products.