[Simultaneous determination of multi-classes of veterinary drug residues in pork by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry].

An analytical method was established for the simultaneous determination of six classes of 33 veterinary drug residues in pork by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF MS). The QuEChERS method has been validated for the extraction. In this method, the sample was extracted by acetonitrile containing 5% (v/v) acetic acid and cleaned-up with C18 and NH2 adsorbents. The extract was measured directly by UPLC-Q-TOF MS with electrospray ionization in positive mode. The compounds were separated on a ZORBAX SB-C18 column (100 mm x 2.1 mm, 3.5 µm) with acetonitrile-0.1% formic acid containing 5 mmol/L ammonium acetate as mobile phases under gradient elution. The confirmatory analysis was carried out by determining the retention times and accurate masses of all the compounds and fragment ions upon Target MS/MS. The correlation coefficients of the 33 veterinary drugs were more than 0. 99 within their linear ranges. The limits of quantification (LOQs) were 2.5-100 µg/kg. The recoveries ranged from 67.0% to 109.0% with the relative standard deviations (RSDs, n = 6) not more than 15.1%. The method is rapid, sensitive, and suitable for the simultaneous determination of multi-classes of veterinary drugs in pork.