Determination of Carbadox, Cyadox, Mequindox, and Quinocetone Metabolites in Livestock Products by HPLC–MS/MS

A procedure for the simultaneous determination of the main metabolites of carbadox, cyadox, mequindox, and quinocetone in livestock products by high-performance liquid chromatography–tandem mass spectrometry is developed and validated. Sample preparation is performed by two methods: for fat matrices, extraction with a mixture of acetonitrile, methanol, and ethyl acetate is used, followed by purification with hexane; for other matrices, extraction with acetonitrile followed by solid-phase extraction on cartridges with a polystyrene–divinylbenzene sorbent. The procedure enables the determination of metabolites in the concentration range 0.5–200 μg/kg, depending on the compound and matrix type. Validation experiments are conducted on samples of muscle tissue from poultry, pork, beef, offal, fish, eggs, adipose tissue, and dairy products. The suitability of the procedure for determining residual amounts of metabolites in a wide range of livestock product matrices is confirmed. The expanded uncertainty of the measurement results is in the range 16–39%. The developed procedure is highly specific and can be used as a reference procedure.