Simultaneous determination of chlorpyrifos, permethrin, and their metabolites in rat plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method was developed for the separation and quantitation of the insecticide chlorpyrifos (O,O-diethyl-O[3,5,6-trichloro-2-pyridinyl]phosphorothioate), its metabolites chlorpyrifos-oxon (O,O-diethyl-O[3,5,6-trichloro-2-pyridinyl]phosphate) and TCP (3,5,6-trichloro-2-pyridinol), the insecticide permethrin (3-(2,2-dichloro-ethenyl)2,2-dimethylcyclopropanecarboxylic acid-(3-phenoxyphenyl)methylester), and two of its metabolites, m-phenoxybenzyl alcohol and m-phenoxybenzoic acid, in rat plasma and urine. The method is based on using C18 Sep-Pak® cartridges for solid-phase extraction and reversed-phase HPLC. The compounds were separated using a gradient of 1 to 80% acetonitrile in water (pH 3.2) at a flow rate ranging between 1 and 1.5 mL/min in a period of 17 min and gradient UV detection ranging between 210 and 280 nm. The retention times ranged from 9.3 to 14.5 min. The limits of detection ranged between 20 and 150 ng/mL, whereas the limits of quantitation were 150-200 ng/mL. The respective average percentage recoveries of chlorpyrifos, chlorpyrifos-oxon, TCP, permethrin, m-phenoxybenzyl alcohol, and m-phenoxybenzoic were 78.6 ± 6.4, 72.8 ± 6.8, 84.8 ± 8.0, 79.2 ± 8.4, 80.5 ± 7.2, and 82.3 ± 7.1 from five spiked plasma samples and 77.5 ± 8.1, 72.8 ± 8.3, 79.9 ± 6.4, 79.1 ± 8.9, 80.5 ± 7.6, and 81.4 ± 7.8 from urine samples. The relationship between peak areas and concentration was linear for concentrations between 200 and 2000 ng/mL. This method was used to analyze these chemicals and metabolites following dermal administration in rats.