Determination of fenbendazole and oxfendazole in liver and muscle using liquid chromatography–mass spectrometry

Abstract

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 were homogenized with water, sonicated with methanol and centrifuged. The supernatants were washed with light petroleum and extracted with diethyl ether–ethyl acetate. The extracts were evaporated to dryness, dissolved in mobile phase and injected into the LC–MS system. Fenbendazole and oxfendazole were measured separately using two different mobile phases. Single-ion monitoring of the positive ion at m/z 300 was used for fenbendazole and of m/z 316 for oxfendazole. The detection limits for the assay were 0.05 µg g^–1 for fenbendazole and 0.1 µg g^–1 for oxfendazole. The mean recoveries were 91% for fenbendazole and 86% for oxfendazole. The assay has been used for statutory testing purposes and for measuring the levels of fenbendazole and oxfendazole in liver and muscle from sheep after dosing with a commercial anthelmintic containing fenbendazole.