Determination of fenbendazole and its metabolites in trout by a high-performance liquid chromatographic method

A high-performance liquid chromatographic (HPLC) method based on solid phas e extraction was developed for the simultaneous determination of fenbendazo le (FBZ), fenbendazole sulfoxide (FBZ-SO) and fenbendazole sulfone (FBZ-SO2 ) in trout muscle and skin tissues. The compounds were extracted with aceto nitrile and the extract was concentrated and cleaned up by solid phase extr action on Cls and CN cartridges. The extract was analysed by reversed-phase gradient HPLC on a Cis column followed by ultraviolet detection at 290 nm. The method's detection limits were 4.0 mu g kg(-1) for FBZ, 4.5 mu g kg(-1 ) for FBZ-SO and 3.8 mu g kg(-1) for FBZ-SO2. The mean recovery in muscle w as 88% for FBZ, 94% for FBZ-SO and 92% for FBZ-SO2 at a level of 5-150 mu g kg(-1). The corresponding mean recoveries in skin tissue were 88, 81 and 8 6% at a level of 10-100 mu g kg(-1). The mean relative repeatability standa rd deviation was 9.2% at a level of 5 mu g kg(-1), 5.9% at a level of 10-10 0 mu g kg(-1) and 2.3% at a level of 150 mu g kg(-1). The method was applie d to trout given feed containing FBZ in an aquaculture pilot plant. The thr ee compounds FBZ, FBZ-SO and FBZ-SO2 were all detected in muscle and skin t issues shortly after administration. The concentrations were generally high est in skin tissue.