β-lactam antibiotics residues analysis in bovine milk by LC-ESI-MS/MS: a simple and fast liquid–liquid extraction method

Abstract

This study presents the development and validation of a simple method for the detection and quantification of six β-lactam antibiotics residues (ceftiofur, penicillin G, penicillin V, oxacillin, cloxacillin and dicloxacillin) in bovine milk using a fast liquid–liquid extraction (LLE) for sample preparation, followed by liquid chromatography-electrospray-tandem mass spectrometry (LC-MS/MS). LLE consisted of the addition of acetonitrile to the sample, followed by addition of sodium chloride, centrifugation and direct injection of an aliquot into the LC-MS/MS system. Separation was performed in a C₁₈ column, using acetonitrile and water, both with 0.1% of formic acid, as mobile phase. Method validation was performed according to the criteria of Commission Decision 2002/657/EC. Limits of detection ranged from 0.4 (penicillin G and penicillin V) to 10.0 ng ml⁻¹ (ceftiofur), and linearity was achieved. The decision limit (CCα), detection capability (CCβ), accuracy, inter- and intra-day repeatability of the method are reported.

Keywords:

• chromatography – LC/MS
• method validation
• regulations
• veterinary drug residues
• veterinary drug residues – antibiotics
• milk

Acknowledgements

The authors would like to thank the National Council for Scientific and Technological Development (CNPq) for the fellowships provided to L. Jank and P. Tarouco.