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 ery thromycin) in bovine muscle, liver and kidney by micro-LC-MS-MS using an at mospheric pressure ionisation source and an ionspray interface has been dev eloped. 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 9 16 for erythromycin and tylosin, respectively, were the precursor ions for collision-induced-dissociation and two diagnostic product ions for each mac rolide were identified for the unambiguous confirmation by selected reactio n 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. T he limits of quantification were 30 (muscle) or 40 (liver, kidney) mug kg(- 1), 20 (muscle) or 150 (liver, kidney) mug kg(-1), 50 (muscle, liver) or 80 (kidney) mug kg(-1), 20 (muscle, liver) or 50 (kidney) mug kg(-1) for tylo sin, tilmicosin, erytromycin and roxithromycin, respectively. (C) 2001 Else vier Science B.V. All rights reserved.