A modified QuEChERS method for the determination of sulfonamides in animal-derived food using enzymatic inhibition assay

Sulfonamides (SAs) are widely used, and their residues pose a serious threat to food safety and human health. Herein, we developed a green, accurate, and sensitive method for detecting SAs residues in animal-derived food using a modified QuEChERS method combined with enzyme inhibition–based colorimetry. Magnetic COF (TpPa-Cl)@Fe 3 O 4 was simple to synthesise, chemically stable and reusable. When used as an adsorbent in modified QuEChERS, it simplifies the purification process and has a high purification capacity. An environmentally friendly natural deep eutectic solvent synthesized using propylene glycol and betaine can serve as a green substitute for traditional organic extractants. SAs were detected by inhibiting the colorimetric reaction between carbonic anhydrase and p -nitrophenyl acetate, and were quantitatively analyzed by digital image colorimetry (DIC) of smartphone. Under optimal conditions, the limits of detection and quantification were 0.53–0.86   µg·kg −1 and 1.52–1.95   µg·kg −1 , respectively. The recoveries of SAs were in the range of 93.60%–101.60%, and the relative standard deviation was < 4.9%. Based on the combined results, our developed method has good applicability in the analysis of SAs residues in food.