Development and validation of a multiclass confirmatory method for the determination of over 60 antibiotics in eggs using liquid-chromatography high-resolution mass spectrometry

A multiclass method for the determination of antimicrobial substances in eggs has been developed and validated, covering sixty-three antibiotics belonging to ten families. After extraction with acidified acetonitrile and EDTA, the analytes were injected into a liquid-chromatography high-resolution mass-spectrometry system operating in positive ionization mode. The procedure was successfully validated as confirmatory method evaluating selectivity, linearity, precision, recovery, decision limit, detection capability, limits of detection and quantitation. The here developed is the first method including all the antibiotics with Maximum Residue Limit (MRL) in eggs, except very polar drugs (aminoglycosides and colistins), which require specific protocols. Finally, a wide survey was carried out analyzing 100 commercial eggs samples from local markets. Only 3% contained residues of authorized substances at concentrations lower than the relevant MRLs.