Determination of the Residues of Three Sulfonamides in Fish by Graphene Foam-Based Electro-Enhanced Solid-Phase Microextraction Coupled with High Performance Liquid Chromatography

A rapid and sensitive method for the determination of sulfonamide (SA) residues in fish was developed using electro-enhanced solid-phase microextraction (EE-SPME) based on nitrogen-doped three-dimensional graphene foam (NGF) functionalized monolithic column (monolith@NGF, M@NGF) combined with high performance liquid chromatography (HPLC). To improve the enrichment efficiency of SA residues in fish, porous M@NGF was prepared on the surface of stainless-steel wires by in situ polymerization using ionic liquids as the functional monomer and NGF as the conductivity enhancer. The EE-SPME method was applied for the extraction of sulfathiazole (ST), sulfamethazine (SM₂), and sulfadimethoxypyrimidine (SMM) from fish. Adsorption time, agitation speed, adsorption voltage, ionic strength, the pH of sample solution, desorption time, desorption voltage, and the composition of desorption solution were optimized. The results showed that the M@NGF-based EE-SPME method enriched ST, SM₂ and SMM by 74, 58 and 64 folds, respectively, and shortened the adsorption equilibrium time to 35 min. In the linear range of 5–5000 μg/kg, the limits of detection (LODs) of this method were 1.78, 3.16 and 1.84 μg/kg for ST, SM₂ and SMM, respectively, and the limits of quantification (LOQs) were 5 μg/kg for all analytes. Coefficients of determination (R²) for linear regression analysis of this method were all greater than 0.9990, and the recoveries from spiked samples ranged from 79.2% to 110.1%, with relative standard deviations (RSDs) ranging from 1.4% to 9.8% (n = 5). This method solved the problems of low extraction efficiency and serious matrix interference of SA residues in fish, and allowed the rapid, sensitive detection of SA residues in fish.