Two-procedure approach for multiclass determination of 64 antibiotics in honey using liquid chromatography coupled to time-of-flight mass spectrometry

A “two-procedure approach” was developed to detect and confirm residues of 64 antibiotic substances in honey using liquid-chromatography coupled to quadrupole time-of-flight mass spectrometry. Eight antimicrobial classes were determined (amphenicols, lincosamides, macrolides, nitroimidazoles, pleuromutilins, quinolones, sulfonamides and tetracyclines) together with single drugs. The procedures were validated in the range 0.2–50 μg kg−1, obtaining recovery factors from 67 to 100% and coefficients of variation in within-lab reproducibility conditions lower than 20%. Limits of detection and quantification were in the ranges 0.1–3.3 μg kg−1 and 0.2–11 μg kg−1, respectively, satisfying the current European levels for analytical control of antibiotic residues in honey. An extensive matrix effect study was performed considering acacia, chestnut and multiflower honey types. Method performances were confirmed through participation in proficiency tests obtaining z-scores between −0.7 and +1.08. The proposed approach was applied to honey samples collected in local markets and three out of fifty-five samples tested positive. The found molecules were sulfonamides (sulfamethazine and sulfathiazole) and tetracyclines (oxytetracycline and tetracycline) at concentrations lower than 2 μg kg−1. Two out of three contaminated samples contained honey from extra-EU countries.