Preparation of a pyridyl covalent organic framework via Heck cross-coupling for solid-phase microextraction of perfluoropolyether carboxylic acids in food

The growing detection of emerging perfluoropolyether carboxylic acids (PFECAs) in food has raised considerable concerns about their high persistence, bioaccumulation, and toxicity. In this study, a pyridine-functionalized covalent organic framework (Py-COF) was synthesized by introducing basic pyridyl groups into Br-COF via Heck cross-coupling. According to density functional theory, PFECAs were adsorbed in the pore sites of Py-COF via O–···HN+ interaction, which was the stable and predominant adsorption configuration. After systematic characterization, Py-COF was used as the coating for solid-phase microextraction combined with high-performance liquid chromatography-tandem mass spectrometry (SPME-HPLC-MS/MS) for the efficient determination of PFECAs in food. Under the optimum conditions, the method showed satisfactory linearity (R2 ≥ 0.998), low limits of detection (0.001–0.004 ng g−1), and good relative recoveries (82.5 %–112 %). The established method was satisfactorily used for the analysis of trace PFECAs in food samples.