Multiclass analysis of 25 veterinary drugs in milk by ultra-high performance liquid chromatography-tandem mass spectrometry.

The aim of this work was to develop a simple and rapid analytical method for the simultaneous determination of a wide range of drug residues in milk by UHPLC-MS/MS. A total of 25 typical veterinary drugs investigated belong to six families including β-lactams, quinolones, β-agonists, phenicols, glucocorticoids and nitrofurans. The samples were extracted by acetonitrile and defatted with n-hexane twice. Electrospray ionization and positive/negative polarity switching were utilized for the analysis of 25 veterinary drugs in a single chromatographic run. The linearity, recovery, precision and matrix effects of the method were fully validated. The intra- and inter-precision were in the range of 1.7-11.1% and 2.5-10.4%, respectively. The average recoveries ranged from 65.9% to 123.5% with RSD less than 10.8% at three concentration levels. The proposed method was demonstrated to be simple, economical and reliable for the fast monitoring of these drug residues in milk samples.