Adsorption of three perfluoroalkyl sulfonate compounds from environmental water and human serum samples using cationic porous covalent organic framework as adsorbents and detection combination with MALDI-TOF MS

In this work, according to the structure of three perfluoroalkyl sulfonates (PFASs) (perfluorobutylenesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctylsulfonic acid (PFOS)) and the property of a medium, we synthesized good-compatibility and stable cationic covalent-organic frameworks (C-COFs). They were used as adsorbents to absorb and detect analytes with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The structures of the C-COFs were characterized. Enrichment parameters, including adsorbent amount, enrichment time, pH, and type and volume of dispersion solution, were optimized to achieve the best enrichment efficiency. After the enrichment, the loaded C-COFs were directly analyzed by MALDI-TOF MS. The results indicated that the C-COFs had a high surface area (1105 m2/g) and microporous structure (1.1 nm); they are rapid and highly efficient for tested PFASs adsorption. The equilibrium adsorption capacity of the C-COFs for PFBS was 334.46 mg g−1. Further, the detection limit for PFBS, PFHxS, and PFOS was 0.001, 0.01, and 0.3 ng mL−1, respectively. Moreover, adsorption and ionization mechanism was discussed. Owing to high selectivity and sensitivity, high adsorption performance, good reproducibility, and satisfactory recoveries, the method was successfully applied to detect PFASs in a real sample.