Multiresidue automated turbulent flow online LC-MS/MS method for the determination of antibiotics in milk.

A fast and reliable multiresidue method is reported for the identification and quantification of 36 different compounds from seven different classes of antibiotics (aminoglycosides, sulfonamides, macrolides, quinolones, tetracyclines, lincosamides and trimethoprim) in milk. Automated online sample cleanup was applied using turbulent flow chromatography (Transcend TLX system), directly coupled to a mass spectrometer (MS/MS) for sensitive and specific detection. The method involved a simple extraction/protein precipitation using acetonitrile, followed by centrifugation and filtration. After this preliminary step, the extract was injected into the TLX-ESI-MS/MS using optimised turbulent flow and liquid chromatography (LC) conditions. Single-laboratory validation of the method was carried out according to the Directive 2002/657/EC, clearly demonstrating the suitability of this method for quantitative determination of this wide range of antibiotics in milk. A small survey, which covered milk samples of different origin and varied fat content, demonstrated the robustness of this method and its suitability for enforcement purposes.