Improvement of chemical analysis of antibiotics. XXIII. Identification of residual tetracyclines in bovine tissues by electrospray high-performance liquid chromatography-tandem mass spectrometry.

To reliably identify the residual tetracycline antibiotics (TCs), oxytetracycline (OTC), tetracycline, chlortetracycline (CTC) and doxycycline (DC), in bovine tissues, we have established a confirmation method using electrospray ionization liquid chromatography-tandem mass spectrometry (ESI LC-MS-MS) with daughter ion scan. All TCs gave [M+H-NH3]+ and [M+H-NH3-H2O]+ as the product ions, except for DC when [M+H]+ was selected as the precursor ion. The combination of C18 cartridge clean-up and the present ESI LC-MS-MS method can reliably identify TCs fortified at a concentration of 0.1 ppm in bovine tissues, including liver, kidney and muscle, and has been successfully applied to the identification of residual OTC in bovine liver and residual CTC in bovine muscle samples previously found at concentrations of 0.58 ppm and 0.38 ppm by LC, respectively.