Analysis of sulfonamides, trimethoprim, fluoroquinolones, quinolones, triphenylmethane dyes and methyltestosterone in fish and shrimp using liquid chromatography–mass spectrometry

• Simple, rapid multi-class veterinary drug LC–MS/MS residue method.
• Includes the analysis of triphenylmethane dyes at 1 ng/g levels.
• Applicable to eight different types of fish and shrimp.
• Can be used as a screening method or quantitative method.

A liquid chromatography–tandem mass spectrometry (LC–MS/MS) screening method is described for the detection and identification of 26 veterinary drugs in fish and other aquaculture products. The analytes include: 13 sulfonamides, trimethoprim, 3 fluoroquinolones, 3 quinolones, 3 triphenylmethane dyes, 2 leuco dye metabolites, and 1 hormone. In this method, tissue is mixed with EDTA-McIlvaine buffer, double-extracted with acetonitrile, p-toluenesulfonic (p-TSA) acid and N,N,N′,N′-tetramethyl-p-phenylenediamine dihydrochloride (TMPD), and analyzed using LC–MS/MS. Inclusion of p-TSA and TMPD in the extraction procedure was critical for simultaneous analysis of dyes with the other groups of veterinary drugs. The proposed procedure was validated as both a quantitative analysis method and as a semi-quantitative screening method for multiple fish and shrimp matrices. The method was applied to eight types of fish (catfish, eel, pangasius, sablefish, tilapia, swai, salmon, and trout) and shrimp at the appropriate level of concern: 10 ng/g for sulfonamides, trimethoprim, and quinolones, 5 ng/g for fluoroquinolones, 1 ng/g for dyes and their metabolites, and 0.4 ng/g for methyltestosterone.