Validation of a confirmatory method for the determination of macrolides in liver and kidney animal tissues in accordance with the European Union regulation 2002/657/EC

This study proposes a simple multiresidue liquid chromatography–diode array detector (LC–DAD) method capable of determining seven macrolide antibiotics in samples of liver and kidney animals at concentrations lower than those allowed by current legislation. Samples were prepared by homogenizing the tissue with EDTA–McIlvaineʹs buffer and extracted with an Oasis HLB cartridge. The consumption of organic solvent during extraction was minimum. The analytes were detected by LC–DAD and also by liquid chromatography–mass spectrometry with electrospray ionization (LC–(ESI)MS). The method was specific, stable and robust enough for the required purposes. The DAD method was validated in accordance with the European Commission Decision 657/2002. Recovery data were also satisfactory with values higher than 67% for most macrolide antibiotics extracted from liver and kidney samples spiked at 200 μg/kg, the lowest MRL established for the macrolides studied. The relative standard deviations (RSD (%), (n = 3)) were lower than 13% and 15% for intra-day and inter-day assays. The method was applied to investigate the occurrence of the studied macrolides in 31 beef and kidney animal samples. The results obtained by LC–DAD for positive samples were compared to those obtained by LC–(ESI)MS. Therefore, the method with simpler instrumentation than a LC–(ESI)MS can be used as a control method and the results of the validation process demonstrate that this method is suitable for application in a European Union program for monitoring residues of veterinary drugs.