Multiresidue method for confirmation of macrolide antibiotics in bovine muscle by liquid chromatography/mass spectrometry.

A particle beam/liquid chromatographic/mass spectrometric (PB/LC/MS) method capable of determining 5 macrolides in bovine muscle is described. Spiramycin, tylosin, tilmicosin, erythromycin, and josamycin residues in bovine muscle are confirmed by reversed-phase LC/MS incorporating gradient elution. Macrolides are extracted from tissue with chloroform, and the extract is purified with a diol solid-phase extraction cleanup. The 5 macrolides are identified by negative and positive chemical ionization with selective ion monitoring of 2 ions in each mode. The procedure confirms the presence of each macrolide at 50 micrograms/kg in spiked samples.