A gas chromatographic determination of permethrin isomers on peach foliage

Abstract

A gas chromatographic (GC) method to determine cis and trans isomers of permethrin, 3‐phenoxybenzyl (‐)‐cis, trans‐3‐(2,2‐dichlorovinyl)‐2,2‐dimethyl‐cyclopropanecarboxylate, is described. Permethrin was applied at 0.21 kg(AI)/ha as a 25% WP formulation (cis/trans=40/60) to peach trees in early June and mid July. Leaf samples were collected 0,3,7,10,14 and 21 days after each application. Permethrin deposits were extracted with benzene and the extracts were analysed by GC without cleanup. A glass column packed with 5% QF‐1 on Gas Chrom Q gave good separation of the cis and trans isomers; the lowest detectable amount was 30 pg with a H electron capture detector. Initial deposits were 6–10 ppm or 0.06–0.10 μg/cm of leaf surface, and both isomers dissipated at about the same rate. About 10% and 41% of the initial deposits were present 21 days after the June and July applications, respectively.