Simultaneous Determination of Residues of Chloramphenicol and Florfenicol in Animal Feed by Liquid Chromatography Tandem Mass Spectrometry

A LC/MS/MS method was developed for determining florfenicol and chloramphenicol in animal feed. The analytes were extracted with ethyl acetate, and the extracts were evaporated to dryness. The residue was dissolved in acetone-hexane mixture and passed through a silica cartridge and a SPE cartridge. The collected eluant was evaporated and the residue was dissolved in acetonitrile-water mixture for injecting LC/MS/MS. The LC separation was performed on a Shim-pack XR-ODS II column with a gradient mobile phase system of ammonium formate-acetonitrile. The recoveries of florfenicol and chloramphenicol were 94.7–114%. The limits of detection were 0.5 ng/g for both compounds.