Multiclass determination of 27 antibiotics in honey

A multiclass approach for the screening and confirmation of antimicrobial substances in honey has been developed and validated according to Commission Decision 2002/657/EC. A total of 27 basic drugs belonging to sulfonamide, nitroimidazole and quinolone families were determined. Sample preparation consisted in an acidic hydrolysis of honey followed by a double purification step (defatting and strong cation exchange solid-phase extraction). Instrumental determination was performed by liquid chromatography tandem mass spectrometry (LC-MS/MS) operating in positive electrospray ionization mode. Chromatographic separation was performed on a Poroshell 120 EC-C18 column (100 × 3.0 mm, 2.7 μm) using a gradient with acetonitrile and water both containing 0.1% of formic acid. The method was validated in the range 0.1-10 μg kg−1 evaluating selectivity, linearity, precision, trueness, matrix effect, decision limits and detection capabilities. Satisfactory performances were obtained for all the analytes, although important differences were observed in function of the honey type.The procedure was applied to the analysis of 74 honey samples of different botanical origins and geographical provenience collected from the Italian market. In nine honeys (12%) trace levels of sulfonamides were confirmed. The found levels (lower than 2 μg kg−1) do not raise concerns with respect to the public health.