CAPILLARY GAS-CHROMATOGRAPHIC DETERMINATION OF PERMETHRIN INSECTICIDEBY TRANSESTERIFICATION

A sensitive method was developed to determine permethrin extracted fro m phosphate buffer and cattle plasma by potassium cyanide catalyzed tr ansesterification of this insecticide with refluxing ethanol and detec tion of the resulting ethyl esters by capillary gas chromatography wit h an electron capture detector. With a reflux time of 2 h and with 3-p henoxybenzyl 2-chlorobenzoate as an internal standard, linear calibrat ion curves from buffer (5-250 ng) and plasma (5-100 ng) were obtained. Precision and accuracy of the method were less than or equal to 15%. The limit of detection was approximately 2.5 ng/ml (cis) and 1 ng/ml ( trans) from buffer. In cattle sprayed along the back at 2 mg/kg, the c oncentration of cis- and trans-permethrin in plasma was below the dete ction limit (5 ng/ml).