Simultaneous Determination of Twenty Antibiotics Residues in Dairy Using Hydrophilic Interaction Chromatography-Reversed Phase Two Dimensional Liquid Chromatography-Tandem Mass Spectrometry

A method for the simultaneous determination of residues of 7 classes (20 species) antibiotics, beta -lactams, tetracyclines, macrolides, aminoglycosides, amphenicols, quinolones and sulphonamides in dairy was established by hydrophilic interaction chromatography-reversed phase (HILIC x RP) two-dimensional liquid chromatography with tandem mass spectrometric detection. The sample of milk powder or milk was extracted by mixed matrix solid phase dispersion with C sub(18) and CN material. The analytes were eluted by acetonitrile and water, and nearly dried with rotary evaporation. Finally, the residues were dissolved with mobile phase and then analyzed. The sample pretreatment conditions, chromatographic mobile phase and mass spectrometric parameters were optimized. Twenty analytes showed good linearity with correlation coefficients of 0.9945-0.9998. The LODs of milk powder and milk samples were in the range of 0.10-2.40 mu g/kg at a S/N of 3, and LOQs were in the range of 0.33-7.92 mu g/kg at a S/N of 10. The recoveries of standard addition for milk powder and milk samples were 72.5%-97.2% and 70.1%-96. 8% at the spiked level of 25 mu g/kg, and the relative standard deviations were in the ranges of 4.2%-8.8% and 3.7% -9. 9% respectively. The proposed method has been applied to the determination of antibiotics residues in actual milk powder and milk samples.