Abstract: A new approach for the determination of methyl-3-quinoxaline-2-carboxylic acid (MQCA) residue in fish and shrimp samples by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based on immunoaffinity column (IAC) purification was developed. MQCA was extracted from samples with 2 mol/L hydrochloric acid and adjusted with water to pH 7–8. After being cleaned up and concentrated by immunoaffinity column, the analyte was analyzed by UPLC-MS/MS with electrospray ionization in positive ion mode (ESI+) using multiple reaction monitoring (MRM) and quantitatively determined by an external standard method. The separation was performed on an ACQUITY UPLC BEH C18 column with a gradient system consisting of 0.1% formic acid (V/V) and methanol as the mobile phase. Good linearity in response was obtained in the concentration range of 1.0–50.0 ng/mL with correlation coefficients larger than 0.995. The limit of quantification (LOQ) was 1.0 μg/kg. The average recoveries of MQCA at spiked concentrations of 1.0, 5.0, and 20.0 μg/kg ranged from 74.2% to 86.5% with relative standard deviations (n = 5) less than 10%. The method is simple, fast, sensitive and reliable, and suitable for the determination of MQCA residue in fish and shrimp samples.

Key words: immunoaffinity column, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), fish and shrimp samples, methyl-3-quinoxaline-2-carboxylic acid (MQCA)