Determination of ceftiofur metabolite desfuroylceftiofur cysteine disulfide in bovine tissues using liquid chromatography-tandem mass spectrometry as a surrogate marker residue for ceftiofur.

Ceftiofur is a widely used cephalosporin β-lactam antibiotic with frequently reported residue violations. This paper reports a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determining a ceftiofur metabolite, desfuroylceftiofur cysteine disulfide (DCCD), in bovine kidney, liver, and muscle tissues. Incurred tissue samples were obtained from dosed animals and analyzed to evaluate the utility of the method. For kidney, the target tissue, the method utilized a simple extraction with phosphate buffer followed by solid phase extraction (SPE) cleanup. For liver and muscle, acetonitrile and hexane were used to remove most proteins and fat from the initial buffer extract before the SPE cleanup. Method accuracy was between 97 and 107%, and the coefficient of variation was between 3.4 and 11.0% for all three types of tissues. The relationship between the new and regulatory methods for bovine kidney was established. It was concluded that DCCD is a suitable surrogate marker residue for ceftiofur in bovine kidney.