RAPID QUANTITATIVE SCREENING ASSAY OF TRACE BENZIMIDAZOLE RESIDUES INMILK BY LIQUID-CHROMATOGRAPHY

A simple, rapid, and sensitive liquid chromatographic (LC) assay for q uantitative screening of albendazole 2-aminosulfone, albendazole sulfo xide, oxibendazole, oxfendazole, albendazole sulfone, p-hydroxyfenbend azole, albendazole, mebendazole, fenbendazole sulfone, and fenbendazol e residues in milk was developed, Samples are made basic (pH 10) and e xtracted with ethyl acetate, Extracts are partitioned with water, evap orated to dryness, reconstituted with mobile phase, and analyzed isocr atically by ion-pair reversed-phase LC at 292 nm, Overall recoveries r anged from 79 to 100%. Linearity was excellent in the fortification ra nge examined (5.3-200 ng/mL), Precision data, based on within- and bet ween-days variations, suggested an overall relative standard deviation of 2.0 to 5.8%. The method was successfully used to quantitate albend azole and fenbendazole and metabolites in milk from 2 drug-treated dai ry cows.