Confirmatory method for macrolide residues in bovine tissues by micro-liquid chromatography–tandem mass spectrometry

A new confirmatory method for three macrolides (tylosin, tilmicosin and erythromycin) in bovine muscle, liver and kidney by micro-LC–MS–MS using an atmospheric pressure ionisation source and an ionspray interface has been developed. Roxithromycin was used as internal standard. The molecular related ions, [M+2H]2+, at m/z 435 for tilmicosin, and [M+H]+, at m/z 734 and 916 for erythromycin and tylosin, respectively, were the precursor ions for collision-induced-dissociation and two diagnostic product ions for each macrolide were identified for the unambiguous confirmation by selected reaction monitoring LC–MS–MS. Precision values (relative standard deviations) were all below 14.9%, whereas the overall accuracy (relative error) ranged from −17.7 to −9.8% for tylosin, from −17.5 to −10.7% for tilmicosin and from −19.6 to −13.7% for erythromycin, in all the investigated bovine tissues. The limits of quantification were 30 (muscle) or 40 (liver, kidney) μg kg−1, 20 (muscle) or 150 (liver, kidney) μg kg−1, 50 (muscle, liver) or 80 (kidney) μg kg−1, 20 (muscle, liver) or 50 (kidney) μg kg−1 for tylosin, tilmicosin, erytromycin and roxithromycin, respectively.