Fast liquid chromatography/tandem mass spectrometry (highly selective selected reaction monitoring) for the determination of toltrazuril and its metabolites in food

In this work a fast liquid chromatography (LC)–tandem mass spectrometry (MS/MS) method was developed for the analysis of toltrazuril, a coccidiostatic drug, and its metabolites in meat food products. The applicability of atmospheric pressure chemical ionization (APCI) and heated electrospray ionization in both positive and negative modes was studied. APCI in negative mode provided the best results and the base peak originated from the loss of CF₃ (toltrazuril and toltrazuril sulfone) and CHF₃• (toltrazuril sulfoxide) was used as the precursor ion in MS/MS. A fast LC separation on a C₁₈ Fused-Core™ column was used together with the APCI-MS/MS method developed using enhanced mass resolution mode (highly selective selected reaction monitoring, H-SRM) to improve the sensitivity and selectivity for the analysis of these compounds in food samples. A simple sample treatment based on an extraction with acetonitrile and a cleanup with a C₁₈ cartridge was used. The LC-MS/MS (H-SRM) method showed good precision (relative standard deviation lower than 10%), accuracy, and linearity and allowed the determination of these compounds in food samples down to the parts per billion level (limits of detection between 0.5 and 5 μg kg^-1).