DETERMINATION OF ABAMECTIN AND/OR IVERMECTIN IN CATTLE FECES AT LOW PARTS-PER-BILLION LEVELS USING HPLC WITH FLUORESCENCE DETECTION

Abamectin and ivermectin are potent antiparasitic animal health drugs that differ structurally by a double bond. Abamectin is a natural product produced by the soil microorganism Streptomyces avermitilis. Ivermectin is a unique hydrogenation product of abamectin. A sensitive HPLC-fluorescence method was developed to determine abamectin or ivermectin residues in bovine feces. The limit of quantitation is 2 ppb (ng/g) and the limit of detection is 1 ppb (wet weight basis). The range validated was from 2 ppb to 2 ppm (mu g/g) with average recoveries of 84% for both abamectin and ivermectin. Abamectin and ivermectin can be analyzed simultaneously because the fluorescent derivatives of the two compounds are chromatographically well resolved on the C-18 column used. The method was developed to support studies concerning the dissipation of incurred abamectin or ivermectin residues in cattle feces postdose and postdeposition.