Determination of albendazole-2-aminosulfone in bovine milk using high-performance liquid chromatography with fluorometric detection.

An analytical method for the determination of albendazole (ABZ) residues in bovine milk was developed using one of its major metabolites, albendazole-2-aminosulfone (ABZ2NH2) as the marker. The method involved acid hydrolysis of milk followed by liquid-liquid extraction and solid-liquid phase clean-up of the extract. A reversed-phase HPLC with fluorometric detection was used to quantitate the marker residue. The method exhibited a high degree of precision and good accuracy as demonstrated by a relative standard deviation (R.S.D.) < 5% for the replicate analyses and 91.8 to 104.1% recovery of the fortification level (25-200 ng/ml), respectively. The ratio of the concentrations of the marker and total residues in milk over a 36-120 h withdrawal period was found to be steady at 43.1 indicating a definite relationship between the marker and the total residues of ABZ. The analytical method was used successfully to determine total residues in milk of cattle treated with ABZ.