Determination of abamectin and doramectin in sheep faeces using HPLC with fluorescence detection

An analytical procedure for the determination of abamectin and/or doramectin in sheep faeces has been developed. Avermectins were extracted from sheep faeces with acetonitrille, clean-up using solid phase extraction (SPE) and analysed by high performance liquid chromatography (HPLC) with fluorescence detection after derivatization with N-methylimidazole. The method has a low detection limit (1.0 ng/g of moist sheep faeces), low quantification limit (2.5 ng/g of moist sheep faeces), good recovery in the range 66.4-80.8% for abamectin and 67.7-85.5% for doramectin as well as good repeatability (>85%). The method is applicable to the study of the time profile of excretion in sheep faeces and also for ecotoxicological studies of both avermectins. Copyright (C) 2003 John Wiley Sons, Ltd.