| Triclabendazole (TCB) is a benzimidazole anthelmintic widely used to treat liver fluke infections in ruminants since its introduction in the early 1980s, due to its excellent activity against both adult and juvenile flukes.TCB is normally given as an oral treatment. It is rapidly removed from portal blood by the liver and cannot be detected in the plasma as it is oxidized to the sulphoxide (TCB-SO) and sulphone (TCB-SO2) metabolites, and then oxidized to the final metabolites (ketotriclabendazole, KETO). The EU, FAO/WHO, and Ministry of Agriculture of China have reported recommended maximum residue limits (MRLs) for TCB in edible ruminant tissues, and set the sum of extractable residues that may be oxidized to KETO as a marker residue. In China, TCB was approved for use in ruminants, and the MRLs in muscle, liver, kidney and fat tissues of bovines were set at 200, 300, 300 and 100μg/kg, respectively. MRLs in the same tissues in goats were all set at 100μg/kg. At present, no attempt has been made to simultaneously determine TCB, its metabolites (TCB-SO and TCB-SO2), and a marker residue (KETO) in edible ruminant tissues, such as muscle, liver, kidney and fat tissues using LC–MS/MS.The aim of the present study is to develop a rapid, selective, and low-cost LC–MS/MS method to simultaneously determine TCB, TCB-SO, TCB-SO2, and KETO with a simple preparation in edible bovine and goat tissues. The results are as the following:1. A sensitive liquid chromatography tandem mass spectrometry method for the simultaneous determination of triclabendazole, its main metabolites and a marker residue (ketotriclabendazole) in bovine and goat muscle, liver, and kidney samples is developed and validated. Analyte extraction from samples is effectively performed using liquid-liquid extraction by acetonitrile. Chromatographic separation is performed on a C18 reversed-phase column with gradient elution. The analytes are detected by tandem quadrupole mass spectrometry after positive electrospray ionization by multiple reaction monitoring. The limits of detection for analytes are found to be 0.25–2.5μg/kg in muscle tissues and 1–10μg/kg in liver and kidney tissues, respectively. The recoveries of edible bovine and goat tissues range from 84.9% to 109.5% when spiked at different levels with analytes, with relative standard deviations generally below 12.8%.2. A rapid, sensitive, and reliable multi-residue method for the simultaneous determination of triclabendazole, its main metabolites and a marker residue (ketotriclabendazole) in edible ruminant fat tissues is developed and validated. Analytes are extracted from fat tissues with acetonitrile, and crude extracts are subjected to defatting with n-hexane. Limits of detection and quantification for analytes are within 0.125–1.25 and 0.5–5μg/kg, respectively. Relative recoveries from spiked samples range from 86.1% to 114.3%, with relative standard deviations generally below 13.8%.3. The method proposed in this study is successfully applied to real sample testing, which come from supermarket and animal experiment. Moreover, the ion ratio, relative time, and identification points of real-life samples met the confirmatory requirements of the Commission Decision 2002/657/EC.In conclusion, a rapid, simple, reliable, and sensitive multi-residue method for the determination of TCB, TCB-SO2, TCB-SO, and KETO in edible bovine and goat fat tissues with LC–MS/MS was developed. This method satisfactory validated characteristics with respect to specificity, sensitivity, accuracy, precision, and stability. Thus, the proposed analytical method can be employed to detect TCB and its metabolites in edible bovine and goat fat tissues as routine analysis.
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