Magnetic-solid phase extraction using magnetic mesoporous carbon as adsorbent coupled with high performance liquid chromatography for the determination of sulfonamides in aquaculture wastewater.

Magnetic mesoporous carbon (FeO-Fe/MMC) was prepared successfully by one-step method combined with calcination method and applied as adsorbents for magnetic-solid phase extraction (MSPE) to determine trace sulfonamides (SAs) in aquaculture wastewater samples. A series of characterization results showed Fe₂O₃-Fe/MMC featuring large surface area, rich active functional groups and high magnetism. Factors affecting MSPE such as adsorption time, solution pH, and types of elution solvents were evaluated and optimized. Under optimal conditions, a simple and sensitive method for the determination of sulfapyridine (SPY), sulfamethoxypyridazine (SMP), sulfamethoxazole (SMX), and sulfamonomethoxine (SMM) was established by combining MSPE with high-performance liquid chromatography. This method demonstrated a good linear relationship in the range of 0.005 mg·L to 0.1 mg·L, with the enrichment factor ranging from 41 to 49, the intra-day relative standard deviation (C=0.05 mg·L, n=5) between 3.46% and 4.98%, the inter-day relative standard deviation (C=0.05 mg·L, n=5) ranging from 3.49% to 6.27%, and low relative standard deviation (n=5) between 3.46 % and 4.98 % and low detection limit of 0.102-0.122 µg·L⁻¹. Finally, this method was applied to spike recovery analysis of aquaculture wastewater samples, with satisfactory recovery results ranging from 75.40 % to 122.12 %. Besides, adsorption mechanism study indicated SAs was absorbed by Fe₂O₃-Fe/MMC mainly due to coordination interaction, hydrogen bonding and electrostatic interaction, which could expand the application scope of Fe₂O₃-Fe/MMC. Compared with other reports, this method characterized by high sensitivity, convenient operation, and good reproducibility. This study shed light on the design of adsorbents for efficient removal of sulfonamide antibiotics.