Abstract: A method for detecting residues of nalidixic acid, tiamulin, trimethoprim, difloxacin, florfenicol and praziquantel in aquatic products by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)after liquid-liquid extraction approach was established. The samples were extracted using acetonitrile as the solvent, purified by hexane and detected by UPLC-MS/MS within 6 minutes. The linear regression coefficients corresponding to 6 spiked levels in the range of 5 to 200μg/L were between 0.9977 and 0.9999. The detection limit for each of the six substances was 1.0μg/kg, and their recoveries were in the range of 61.2% to 90.5%. The developed method is simple and sensitive and can meet the requirements for qualitative and quantitative analysis of aquatic products.

Key words: nalidixic acid, tiamulin, trimethoprim, difloxacin, florfenicol, praziquantel, ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), multiple-reaction monitoring (MRM)