Determination of ceftiofur and its desfuroylceftiofur-related metabolites in swine tissues by high-performance liquid chromatography.

An HPLC method was developed and validated for the determination of ceftiofur-related metabolites that have the potential to be microbiologically active in swine muscle, kidney, liver and fat. Its performance was evaluated against incurred-residue swine tissues. This method is based on the cleavage of the disulfide and/or thioester bonds between the metabolites and their conjugate sulfur containing moiety using dithioerythritol to yield desfuroylceftiofur, and further stabilization to desfuroylceftiofur acetamide. The limit of quantitation was 0.1 micrograms ceftiofur equivalents/g tissue. The assay is specific for ceftiofur-related metabolites when evaluated against commercially available antibiotics for swine.