Development of fast screening methods for the analysis of veterinary drug residues in milk by liquid chromatography-triple quadrupole mass spectrometry

Two rapid multi-residue screening methods for the determination of 21 veterinary drugs in milk by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) have been developed and compared. For both methods, veterinary drugs were extracted from milk samples using a rapid extraction procedure based on the modification of the well-known QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method, and no further clean-up steps were necessary. One screening method was based on the selection of a characteristic neutral loss or product ion of the various families of compounds, whereas another one was based on the choice of a selected reaction monitoring (SRM) for each compound. These methods were compared with regards to false negatives, cut-off values and the unreliability region. The total run time for both methods was 3 min, allowing quick selection of samples that contained veterinary drugs. Non-negative samples were re-analyzed by the UHPLC-MS/MS confirmation/quantification method, which consisted in the monitoring of two SRM for each compound. The methods were validated according to international guides. The proposed analytical methods allow for the identification and confirmation of the target veterinary drugs at trace levels employing quick analysis time.