DETERMINATION OF THE MARKER RESIDUE OF ALBENDAZOLE IN MILK USING ION-PAIR LIQUID-CHROMATOGRAPHY AND FLUORESCENCE DETECTION

A simple, rapid, and sensitive ion-pair liquid chromatographic (LC) me thod for the determination of the sulphoxide, sulphone and 2-aminosulp hone metabolites that comprise the marker residue of albendazole in mi lk has been developed. Samples are made alkaline with sodium hydroxide solution and extracted with ethyl acetate, and the extracts are clean ed-up by partition with water. Chromatographic separation of the analy tes is performed isocratically in presence of both positive and negati ve pairing ions, while detection is carried out fluorometrically using excitation and emission wavelengths of 290 and 320 nm, respectively. The method shows accuracy and precision figures well within acceptable limits. Overall recoveries were 85.3+/-9.0%, 96.4+/-6.2% and 83.4+/-7 .5% for the sulphoxide, sulphone and 2-aminosulphone metabolites, resp ectively while precision data, based on within- and between-days varia tion, suggested overall relative standard deviation values ranging fro m 2.9% to 6.0%. The good analytical characteristics of the method coul d allow limits of detection in the low ng ml(-1) range to be realised. The method was successfully applied to determine total residues in mi lk of a dairy cow treated with albendazole and, also, to study the sta bility of the residues with storage.