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

• This is the first report that established an analytical method for the determination of toltrazuril and its metabolites in skin + fat of chicken and pig.
• A reliable UPLC-UV method for simultaneously detecting toltrazuril and its metabolites in skin and fat of chicken and pig was developed.
• The developed method has been successfully applied to the depletion study of toltrazuril drug residues in chicken skin + fat after experimental application of toltrazuril to chicken. The recommended withdrawal period with oral administration based on our research is 24.18 days.

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 25–37.5 μg kg−1 and 50–75 μg kg−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.