Abstract:

A new approach for the simultaneous determination of residues of three classes of antibiotics, i.e., penicillins,
sulfoamides and tetracyclines, in milk by ultra performance liquid chromatographytandem mass spectrometry (UPLC-MSMS)
was established. Samples were extracted with acetonitrile-water (3:1, V/V), cleaned up using an HLB SPE cartridge and
blown to dryness under nitrogen and the residues were then dissolved in 1.0 mL of mobile phase. A total of 15 analytes were
separated on ZORBAX Ecliplus C18 column with a mobile phase composed of acetonitrile and 5 mmol/L formic ammonium
acetate solution containing 0.2% formic acid with gradient elution, detected by ESI-MS/MS and quantified by the external
standard method. The correlation coefficients of the linear calibration curves were over 0.999 in the corresponding
concentration range. The average recoveries of the 15 analytes ranged from 75.1% to 103.7%, with relative standard
deviations (RSDs) at three spiked concentrations of 1.4%–7.3%. The limit of detection (LOD, RSN≥3) and quantification
(LOQ, RSN ≥ 10) were 0.2–4.0 and 1.0–4.0 μg/kg, respectively. The new method is simple, fast, sensitive and reliable, and it
is suitable for the determination of antibiotic residues in milk.

Key words: ultra high pressure liquid chromatography-tandem mass spectrometry, antibiotics, milk, residues