Multi-Residue Determination of Sulfonamides, Dapsone, Ormethoprim, and Trimethoprim in Fish and Shrimp Using Dispersive Solid Phase Extraction with LC–MS/MS

This study reports an analytical method to simultaneously determine the residues of sulfonamides, dapsone, ormethoprim, and trimethoprim in fish and shrimp. The samples were extracted with acetonitrile, magnesium sulfate, and sodium acetate, followed by dispersive solid-phase extraction (C18) for cleanup. The target analytes were confirmed and quantified by liquid chromatography–tandem mass spectrometry. The developed method was validated according to the Codex guidelines (CAC/GL 71-2009). As a result, linearity was expressed between 0.25 and 200 μg kg−1 with a correlation coefficient > 0.98. The limits of quantitation were 0.01–2.8 μg kg−1 and the accuracy (expressed as average recovery) was 76.1–115%. The precision (expressed as the coefficient of variation) was <20%. The decision limits of sulfonamides, dapsone, ormethoprim, and trimethoprim were 94.2–114, 1.3–1.5, 105–111, and 53.3–54 μg kg−1 and detection capabilities of 102–129, 1.4–1.6, 109–120, and 55.6–58.2 μg kg−1, respectively. The proposed method was applied to the analysis of real samples (n = 54) obtained from domestic markets in Korea, resulting in a detection rate of 13% (seven samples). This method is applicable for the efficient determination of sulfonamides, dapsone, ormethoprim, and trimethoprim residues in fish and shrimp according to Korean MRL.