The aim of this study was to develop and validate an analytical method to simultaneously determine European Union-regulated ȕ-lactams (penicillins and cephalosporins) and quinolones in cow milk. The procedure involves a new solid phase extraction (SPE) to clean-up and pre-concentrate the three series of antibiotics before analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). LC-MS/MS and UPLC-MS