Simultaneous determination of toltrazuril and its metabolites in chicken and pig skin+fat by UPLC-UV method

A reliable method for the simultaneous determination of toltrazuril and its main metabolites (toltrazuril sulphone and toltrazuril sulphoxide) in chicken and pig skin+fat was developed and validated. Analytes were extracted from skin+fat with acetonitrile. The crude extracts were subjected to liquid-liquid extraction with n-hexane, and then further cleaned using primary secondary amine and Oasis™ MAX solid phase extraction cartridges. Chromatographic separation by UPLC-UV was performed on a C18+ reversed-phase column with gradient elution. Relative recovery from the spiked samples ranged from 84.8% to 109.1%. Limits of detection and quantification for the analytes were within 25-37.5μgkg(-1) and 50-75μgkg(-1), respectively. The developed method has been successfully applied to the depletion study of toltrazuril drug residues in chicken skin+fat. The recommended withdrawal period with oral administration based on our research is 24.18 days.