State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmaceutical Science, Guangxi Normal University, Guilin 541004, PR China; Department of Food and Chemical Engineering, Liuzhou Institute of Technology, Liuzhou 545616, PR China.
Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, PR China.
J Chromatogr A. 2022 Jul 19;1675:463188. doi: 10.1016/j.chroma.2022.463188. Epub 2022 Jun 1.
Perfluorinated substances (PFASs) are harmful pollutants that have environmental persistence and high bioaccumulation. Effective sample pretreatment must be performed to detect trace or even ultra-trace PFASs in actual samples because of their extremely low contents in complex samples. In this study, a cationic hierarchical porous covalent organic frameworks (C-H-COF) were customized via a template-assisted strategy using polystyrene spheres (PS) as sacrificial materials and a post-synthetic modification method. C-H-COF showed good adsorption selectivity for PFASs owing to the dual effects of the full utilization of the internal adsorption sites and electrostatic interaction. The key role of electrostatic attraction in the extraction of PFASs using C-H-COF was further proven by density functional theory (DFT) calculations. The maximum adsorption capacity of the C-H-COF for perfluorooctanoic acid (PFOA) was 400 mg·g⁻, which was superior to that of microporous COFs (M-COF) and hierarchical porous COFs without cationic functionalization (H-COF). Accordingly, an analytical method for sensitively detecting five PFASs was established by employing C-H-COF as a dispersive solid phase extraction (DSPE) adsorbent combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the limits of detection were 0.011‒0.29 ng·L⁻. Moreover, the hierarchical porous structure of the C-H-COF accelerated the mass transfer of analytes so that the extraction process could be completed within 10 min. This method was employed to analyze PFASs in dairy products, in which the ultra-trace levels of analytes were quickly determined with spiked recoveries of 80.1‒112.6%. This work not only provides a rational synthetic strategy for novel ionic hierarchical porous COFs but also helps to expand the application of COFs in sample pretreatment.
全氟化合物（PFASs）是具有环境持久性和高生物累积性的有害污染物。由于复杂样品中 PFASs 的含量极低，因此必须进行有效的样品前处理，才能检测痕量甚至超痕量的 PFASs。在本研究中，采用模板辅助策略，以聚苯乙烯球（PS）为牺牲材料，通过后合成修饰方法，定制了一种阳离子分级多孔共价有机骨架（C-H-COF）。由于充分利用了内部吸附位和静电相互作用的双重作用，C-H-COF 对 PFASs 表现出良好的吸附选择性。通过密度泛函理论（DFT）计算进一步证明了静电吸引在使用 C-H-COF 提取 PFASs 中的关键作用。C-H-COF 对全氟辛酸（PFOA）的最大吸附容量为 400 mg·g⁻¹，优于微孔 COFs（M-COF）和无阳离子功能化的分级多孔 COFs（H-COF）。因此，采用 C-H-COF 作为分散固相萃取（DSPE）吸附剂，结合超高效液相色谱-串联质谱（UPLC-MS/MS），建立了一种灵敏检测五种 PFASs 的分析方法，检出限为 0.011‒0.29 ng·L⁻。此外，C-H-COF 的分级多孔结构加速了分析物的质量传递，使萃取过程在 10 min 内完成。该方法用于分析乳制品中的 PFASs，快速测定了痕量水平的分析物，加标回收率为 80.1‒112.6%。这项工作不仅为新型离子分级多孔 COFs 的合理合成策略提供了参考，而且有助于扩展 COFs 在样品预处理中的应用。
