DETERMINATION OF FENBENDAZOLE AND OXFENDAZOLE IN LIVER AND MUSCLE USING LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY

A method has been developed for the determination of the anthelmintics fenbendazole and oxfendazole in liver and muscle samples using liquid chromatography-thermospray mass spectrometry (LC-MS). The samples wer e homogenized with water, sonicated with methanol and centrifuged. The supernatants were washed with light petroleum and extracted with diet hyl ether-ethyl acetate. The extracts were evaporated to dryness, diss olved in mobile phase and injected into the LC-MS system. Fenbendazole and oxfendazole were measured separately using two different mobile p hases. Single ion monitoring of the positive ion at m/z 300 was used f or fenbendazole and of m/z 316 for oxfendazole. The detection limits f or the assay were 0.05 mu g g(-1) for fenbendazole and 0.1 mu g g(-1) for oxfendazole. The mean recoveries were 91% for fenbendazole and 86% for oxfendazole. The assay has been used for statutory testing purpos es and for measuring the levels of fenbendazole and oxfendazole In liv er and muscle from sheep after dosing with a commercial anthelmintic c ontaining fenbendazole.