Determination of the marker residue of albendazole in cheese by ion-pair liquid chromatography and fluorescence detection.

A liquid chromatographic method is described that allows quantitative determination of the marker residue of albendazole in cheese. Samples were extracted with acetonitrile, and the extracts were defatted with hexane, evaporated to dryness, reconstituted in ethyl acetate, and purified by partitioning with phosphate buffer. Separation of the sulfoxide, sulfone, and 2-aminosulfone metabolites that constitute the marker residue of albendazole was carried out isocratically with a mobile phase containing both positively and negatively charged pairing ions; detection was performed fluorometrically, with excitation and emission wavelengths of 290 and 320 nm, respectively. Overall recoveries ranged from 73.7 to 84.9%. Precision data based on variation within and between days suggested overall values for relative standard deviation of 3.0 to 3.9%. The sensitivity of the method permitted low limits of detection, particularly for the sulfone and 2-aminosulfone metabolites.