Abstract: An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the determination of 3-methyl-quinoxaline-2-carboxylic acid (MQCA) in animal tissues and aquatic products. The analyte was extracted with 0.2 mol/L hydrochloric acid. The extract was cleaned up on a Bond Elut C18 cartridge. Then the eluate was collected and evaporated to dryness under nitrogen gas at 35 ℃. The residue was redissolved in acetonitrile containing 0.1% (v/v) formic acid. The identification was performed by multiple reaction monitoring in positive electrospray ionization. The quantification was done by external standard method. The calibration curves showed good linearity within the range of 2~500 μg/L with the correlation coefficients (r2) greater than 0.990. The limits of detection (LODs) of MQCA in pork, swine liver, pig kidney, fish, prawn, and crab were 0.90, 1.51, 0.94, 1.04, 1.62 and 1.80 μg/kg, respectively; and the limits of quantification (LOQs) were 3.00, 5.02, 3.13, 3.46, 5.40 and 6.00 μg/kg, correspondingly. The recoveries of MQCA in animal tissues and aquatic products were 73.6%~89.0% at the spiked levels of 3~100 μg/kg. The intra-day relative standard deviations (RSDs, n=5) were less than 15%, and inter-day RSDs (n=3) were less than 20%. The results demonstrated that the sensitivity, accuracy, and precision were fit for the requirements of veterinary drug residue analysis.

Key words: 3-methyl-quinoxaline-2-carboxylic acid, aquatic products, olaquindox, residue, animal tissues, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)