Determination of a liquid chromatography–tandem mass spectrometry method for the determination of sulfonamides, trimethoprim and dapsone in honey and validation according to Commission Decision 2002/657/EC for banned compounds

This work reports a sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for identification and quantification of seven sulfonamides, trimethoprim and dapsone in honey. The method is based on a solid-phase extraction (SPE) step of the target analytes with Oasis HLB cartridges after acidic hydrolysis of the honey sample to liberate the sugar-bound sulfonamides. Analysis was performed using liquid chromatography–tandem mass spectrometry (LC–MS/MS) in the positive electro-spray ionization (ESI) mode with two different isotopically labeled internal standards with the view to improve the quantitative performance of the method. The method validation has been performed according to the Commission Decision 2002/657/EC; the average recoveries, measured at three concentration levels (1.5, 2.5 and 5.0 μg kg−1), have been estimated in the range 70 to 106% while the respective % relative standard deviations of the within-laboratory reproducibility ranged from 6 to 18%. Mean values of the expanded uncertainties calculated were in the range 22–41% at the 99% confidence level. Decision limit (CCα) and detection capability (CCβ) values were in the ranges 0.4–0.9 and 0.7–1.4 μg kg−1, respectively. Matrix effects have been investigated demonstrating a moderate signal suppression/enhancement for most of the target compounds. The method described has been successfully applied to the analysis of honey samples; sulfamethoxazole, sulfathiazole and trimethoprim were detected in some cases.