Analysis of macrolide antibiotics in eggs validated according to European Commission Decision 2002/657/EC: a rapid extraction followed by liquid chromatography –tandem mass spectrometry

A direct method able to determine residues of macrolide antibiotics erythromycin, tylosin and tilmicosin in whole eggs is here presented. This method proposed is based on a one-step extraction followed by liquid chromatography-tandem mass spectrometry. Analytes were extracted with acetonitrile from 1 g of egg. No cleanup was found to be necessary. Extraction was effective, since absolute recovery of the analyte in egg at the level of 5 ng/g for tilmicosin and at the Maximum Residue Limit (MRL) for erythromycin and tylosin were 89-103%. Based on the EU Commission Decision 2002/657/EC1, the method was in-house validated in terms of ruggedness, specificity, linearity, within-laboratory reproducibility, decision limit (CCα) and detection capability (CCβ). The within-laboratory reproducibility (n= 18) at MRL level was in the 12-13% range. After validation, a short evaluation of the depletion of erythromycin in eggs was conducted after administration of this drug to laying hens