Multi-residue method for the determination of benzimidazoles in bovine liver

A method has been developed to analyse for 12 benzimidazole drug residues in bovine liver. Liver samples were extracted with ethyl acetate, sample extracts were defatted with hexane and cleaned-up by automated SPE on C18 solid phase extraction cartridges. Aliquots of the extracts were analysed by LC with UV detection (298 nm). The method was validated in bovine liver, according to the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCα) was between MRL + 12% and MRL + 25% and the detection capability (CCβ) was between MRL + 25% and MRL + 45% for the range of benzimidazoles investigated. The results of the inter-assay study, which was performed by fortifying bovine liver samples (n = 6) in three separate assays, show the mean recovery to be between 60% and 100% for albendazole sulphoxide, albendazole sulphone, thiabendazole, oxfendazole/fenbendazole sulphoxide, hydroxy-mebendazole, fenbendazole sulphone, oxibendazole, mebendazole and flubendazole. Lower mean recovery was obtained for amino-flubendazole and albendazole (approximately 50%) and amino-albendazole sulphone (approximately 25%). The precision of the method, expressed as R.S.D. values for the within-laboratory repeatability, was generally below 25%.