- 1 - DETERMINATION OF ERYTHROMYCIN AND TYLOSIN RESIDUES IN HONEY BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY. Rodrigo H. M. M. Granja 1 , Alfredo M. Montes Niño 1 , Roberto A. M. Zucchetti 1 ,Rosario E. Montes Nino 1 , Raj Patel 2 , Alessandro G. Salerno 1 . 1 Microbioticos Laboratories, Av. Santa Isabel 2120, Campinas, SP, 13084-471, Brazil. 2 Centre for Chemical and Bioanalytical Sciences, School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 OEX, UK. Abstract Antibiotics are used in apiculture to protect bees against a variety of brood diseases. As a result of development of resistance to oxytetracycline, erythromycin (ERY) and tylosin (TYL) are increasingly used for the prevention and treatment of these diseases. Brazilian authorities have therefore added these to the National Regulatory Monitoring Program for the control of residues in honey. An analytical method for the determination of residues of ERY and TYL in honey has been developed. The procedure involves solid-phase extraction of diluted honey samples followed by liquid chromatography-mass spectrometry with a positive ionization electrospray in multiple reaction-monitoring mode. Two characteristic transitions were monitored for both drugs. Average analyte recoveries for ERY and TYL ranged from 99 to 109% in replicates sets of honey samples fortified with drug concentrations of 5, 10, 15 and 20 ng g -1 . The method decision limits were determined to be at 1.27 and 0.59 ng g -1 for ERY and TYL, respectively. The detection capabilities were 3.57 and 1.32 ng g -1 for ERY and TYL, respectively. Introduction Erythromycin (Fig. 1) and Tylosin (Fig. 2) are macrolide antibiotics and are active against Gram-positive and some Gram-negative bacteria. These antibiotics seem to be increasingly in substitution of tetracyclines and sulphonamides in beekeeping for the prevention and treatment of American foulbrood in honey bees. It is believed that macrolide residues in food may pose a potential risk to consumers because of allergic reaction of individuals to these antibiotics. Figure 1. Erythromycin Molecular Structure