Covalent organic framework nanospheres for solid-phase extraction of pyrethroids from vegetables.

Although various advanced materials have been developed for the enrichment of pyrethroids in food samples, covalent organic frameworks (COFs) have been scarcely explored for their extraction. We hypothesize that the abundant benzene ring structures in imine-type COFs can facilitate π-π and hydrophobic interactions with pyrethroids in vegetable matrices, thereby enhancing extraction efficiency. To test this hypothesis, core-shell magnetic COF nanospheres (Fe3O4@TAPT-TFPB-COF) were synthesized via a facile monomer-mediated in situ growth strategy and applied to magnetic solid-phase extraction of pyrethroids, followed by high-performance liquid chromatography analysis. Under optimal conditions, the method demonstrated excellent linearity (R ≥ 0.9981), low limits of detection (0.600 μg kg-1) and satisfactory recoveries (78.89-103.45 %). Furthermore, adsorption experiments confirmed the hypothesis: pyrethroids were chemically adsorbed onto Fe3O4@TAPT-TFPB-COF nanospheres in a monolayer form, driven by π-π and hydrophobic interactions. The developed method was successfully validated and demonstrated superior sensitivity and lower detection limits compared to existing approaches.