Simultaneous determination of cis-permethrin and trans-permethrin in rat plasma and brain tissue using gas chromatography-negative chemical ionization mass spectrometry

•A GC-NCI-MS method for the simultaneous determination of cis- and trans-permethrin from small volume biological samples.•Liquid-liquid extraction was applied as a simple sample preparation method.•Sensitivity of method (LLOQ = 0.2 ng/mL) makes it suitable for quantitating trace levels of cis-permethrin and trans-permethrin in biological samples.

A sensitive method for the simultaneous determination of cis-permethrin (cis-PERM) and trans-permethrin (trans-PERM) in small volumes (100 μL) of rat plasma and brain homogenate was developed, using a liquid-liquid extraction for sample preparation and gas chromatography-negative chemical ionization mass spectrometry (GCNCI-MS) for detection. Quantitation of trace levels of the insecticide in small volumes of biological samples is essential to support toxicokinetic studies in small animals. There are currently no validated methods in the literature for determining cis-PERM and trans- PERM in volumes as low as 100 μL of rat plasma or brain homogenate. The method provided a linear range of 0.2-150.0 ng/mL for analytes in both matrices. The intra- and inter-batch precision (as% relative standard deviation, RSD) and accuracy (as relative error, RE) of the method were better than 20% at the limit of quantitation and better than 15% across the remaining linear range. The validated method was applied in a toxicokinetic study in adult rats with oral dosing of 10 mg/kg (cis-PERM) and 100 mg/kg (trans-PERM) in corn oil. cis-PERM and trans- PERM were monitored in rat plasma and brain tissue samples for 6 h following dosing, and both analytes were detected in all plasma and brain samples.