Fabrication of porphyrin-based magnetic covalent organic framework for effective extraction and enrichment of sulfonamides.

The dehydration reaction of tetraamino porphyrin and 4,4′-biphenyldicarboxaldehyde was performed for the synthesis of a novel covalent organic framework (COF), which was decorated on magnetic Fe3O4 to obtain core-shell structured Fe3O4@COFs nanospheres for the first time, for effective extraction and enrichment of sulfonamides (SAs). The morphology and structure of the synthesized nanospheres were characterized through various methods. The extraction conditions for six SAs including sulfadiazine, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfamethoxazole, sulfadimethoxine were systematically optimized. Fe3O4@COFs nanospheres were evaluated for magnetic solid-phase extraction. By coupling with high-performance liquid chromatography, a facile and sensitive method was established for the quantitation analysis of six SAs. The method showed good linearity ranging from 1 to 500 ng mL−1 with R2 > 0.99, high sensitivity with LODs in the range of 0.2–1 ng mL−1, and high precision with RSDs≤6.3%. This method was further applied into determination of SAs in environmental water and food samples, with recoveries in the range of 65.3%–107.3% and RSDs≤6.7%. These successful applications suggest that the core-shell structured Fe3O4@COFs nanospheres could be used as a potential adsorbent for efficient extraction and analysis of trace SAs.