Residues of antibiotics and sulfonamides in honeys from Basque Country (NE Spain)

BACKGROUND: The aim of this work was to ensure that Label Basque market honey is free of veterinary residues. RESULTS: A total of 567 Basque honey samples were previously analyzed with the respective Charm 11 system - 68 samples were presumptive positive for sulfonamides (SA-s), 24 samples for tetracyclines (TC-s), and no positive samples for chloramphenicol (CAP) (<0.3 mu g kg(-1)) residues. The residues were mostly confirmed by liquid chromatography fluorescence detection (LC-FD) and tandem mass spectrometry (LC-MS/MS), according to the latest European Union criteria for the analyses of veterinary drug residues (2002/657/EC). These techniques confirmed that 19 of the 68 samples, presumptive contaminated with SA-s, contained sulfathiazole (STZ) residues at levels from 20 to 210 mu g kg(-1), and the 24 samples presumptive contaminated with TC-s, were also confirmed, showing tetracycline (TC) levels from 15 to 920 mu g kg(-1). Linearity range, decision limit (CC alpha), detection capability (CC beta), precision and reproducibility were also determined. CONCLUSION: Residues of veterinary drugs were confirmed in a very limited number of honey samples: sulfathiazole (3.40%) and tetracycline (4.22%). This work reports the advantages of the Charm 11 assay, but also its limitations, detecting SA-s in most (87.7%) of the heather (Erka vagans) honey samples. The false positives detected in this honey were assumed to be of an unknown compound that has not been confirmed as a drug residue. Until now, no studies have been performed to find out if other heather honeys of different geographical origins give similar false positives for SA-s. (C) 2008 Society of Chemical Industry