Matrix solid-phase dispersion technique for the determination of moxidectin in bovine tissues.

An HPLC method has been developed for the determination of moxidectin in bovine tissues. The extraction and clean-up procedure is based on the matrix solid-phase dispersion technique. Control and moxidectin-fortified bovine tissue samples (0.25 g) are blended with octadecyl (C18 end-capped) packing material. A column made from the C18-bovine tissue blend is washed with hexane (2 ml); when all the hexane has eluted, an Alumina-B SPE cartridge is attached below the C18-tissue column and, after washing, moxidectin is eluted with methanol (6 ml). Moxidectin is derivatized and determined by HPLC with fluorescence detection. The recovery from fortified samples was greater than 80% in the concentration range 1-100 ng g-1 of tissue. This method permits the determination of moxidectin at levels as low as 1 ng g-1 (1 ppb).