Optimization for the determination of residual levomycetin (chloramphenicol) in cow milk by reversed-phase high-performance liquid chromatography

A sensitive, selective, accurate, and precise method is developed for determining residual levomycetin (chloramphenicol), in raw and pasteurized milk. It includes sample filtration, purification of sample by solid-phase extraction, purification of eluate by liquid-liquid extraction, preconcentration by evaporation under reduced pressure, and analysis by reversed-phase HPLC with UV detection at 278 nm. The mobile phase is an acetonitrile-water mixture 15: 85 with an addition of 1 vol % of isopropanol. The method detection limit is 0.45 μg/kg; the limit of quantification is 1.40 μg/kg; the repeatability limit is 6.93%.