Development of a high-performance liquid chromatography method to monitor the residues of benzimidazoles in bovine milk

A reversed-phase high-performance liquid chromatography with ultraviolet (UV) detection was developed that can determine 11 benzimidazole (BZDs) and 10 metabolites of albendazole, fenbendazole and mebendazole in bovine milk. Samples were extracted with acetonitrile and purified by mixed-mode cation exchange (MCX) solid phase extraction cartridges. LC separations were performed on a C18 column with gradient elution using acetonitrile and ammonium acetate solution. The UV-detection was set at 292 nm. The method is very sensitive to each analyte with limits of quantification (LOQs) of lower than 10 μg kg−1. The recoveries of the BZDs and their metabolites spiked in milk were more than 78% with between-day relative standard deviation values less than 16% at the concentration of 10, 50 and 100 μg kg−1. The method developed has been successfully applied to monitoring real samples containing BZDs, which demonstrated that it is a simple, fast and robust method, and could be used as a regulatory toll to determine the residues of BZDs in milk.