Objective  Fe₃O₄@SNW-1 was prepared as an adsorbent in the magnetic solid phase extraction (MSPE) to pre-treat samples for HPLC determination on sulfonamides (SAs) in milk.

  Method  A magnetic covalent organic framework (COF) material, Fe₃O₄@SNW-1, was hydrothermally synthesized to serve as the adsorbent in MSPE for the sample pretreatment. Parameters for the pretreatment, including adsorbent usage, adsorption duration, eluent selection, and elution time that affected the extract recovery, were optimized. HPLC was used to evaluate and determine the validity of the methodology.

  Result  The optimized MSPE applying 2.0 mL ammonia-methanol (5 ∶ 95, V/V) as elution solvent, 60s for desorption, 4.0 mg of Fe₃O₄@SNW-1 as adsorbent, 120 s for adsorption at pH 6.0 to achieve linearities in the ranges between 10 ng·mL⁻¹ and 100 ng·mL⁻¹ on detecting 5 different SAs with correlation coefficients greater than 0.995. The HPLC detection limit on the SAs was 1.7-2.7 ng·mL⁻¹. The daytime RSDs of 5 extraction replicates on the SAs (50 ng·mL⁻¹ each) were 2.8–4.7%. The recovery rates on the SAs varied from 72.0% to 95.0%.

  Conclusion  The proposed HPLC method with the MSPE sample pretreatment was convenient, rapid, specific, and effective for the determination of trace amounts of SA residues in milk.