SPE–UPLC–UV Method for the Determination of Toltrazuril and its Two Metabolite Residues in Chicken and Porcine Tissues

Ultra high performance liquid chromatography with UV detection was developed and validated for the simultaneous determination of residues of toltrazuril and its two metabolites, namely, toltrazuril sulphone and toltrazuril sulphoxide, in edible tissues (chicken and porcine muscle, liver and kidney). Acetonitrile was used to extract analytes from tissues, which were then cleaned using primary secondary amine and Oasis™ MAX solid phase extraction cartridges. Chromatographic separation was performed on a C18 column with gradient elution. The analytes were determined using a UV detector. The regression coefficients of matrix-matched calibration curves showed linearity of >0.99. Calibration ranged from 25 to 1,000 μg kg−1 for toltrazuril and toltrazuril sulphone, and 37.5–1,500 μg kg−1 for toltrazuril sulphoxide. The accuracy was between 80 and 110 %, and the inter and intraday RSDs were lower than 15.2 and 18.3 %, respectively. The limits of detection for toltrazuril, toltrazuril sulphone and toltrazuril sulphoxide were between 10 and 37.5 μg kg−1 in all the tissues. The developed method was successfully applied to detect toltrazuril, toltrazuril sulphone and toltrazuril sulphoxide in tissues of medicated chicken.