Glöckler David, Harir Mourad, Schmitt-Kopplin Philippe, Elsner Martin, Bakkour Rani
TUM School of Natural Sciences, Chair of Analytical Chemistry and Water Chemistry, Technical University of Munich, Garching 85748, Germany.
Research Unit Analytical BioGeoChemistry, Helmholtz Munich, Neuherberg 85764, Germany.
Anal Chem. 2023 Oct 3;95(39):14582-14591. doi: 10.1021/acs.analchem.3c01881. Epub 2023 Sep 18.
Cyclodextrin polymers (CDPs) are promising next-generation adsorbents in water purification technologies. The selectivity of the polymer derivate cross-linked with tetrafluoroterephthalonitrile (TFN-CDP) for nonionic and cationic micropollutants (MPs) over dissolved organic matter (DOM) renders the adsorbent also attractive for many analytical applications. The molecular drivers of the observed selectivity are, nonetheless, not yet fully understood. To provide new insights into the sorption mechanism, we (i) synthesized TFN-CDPs with different cavity sizes (α-, β-, γ-CDP); (ii) assessed their extraction efficiencies for selected nonionic MPs in competition with different DOM size fractions (<1, 1-3, 3-10, >10 kDa) to test for size-selectivity; and (iii) performed nontargeted, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry analysis on CDP-extracted DOM compounds (<1 kDa) to probe for molecular sorbate properties governing their selective sorption. First, no evidence of size-selectivity was obtained through either the different CD cavity sizes (i) or the two independent approaches (ii) and (iii). Second, we found a dominant impact of sorbate oxygenation and polarity on the extraction of DOM and MPs, respectively, with relatively oxygen-poor/nonpolar molecules favorably retained on all α-, β-, and γ-CDP. Third, our data indicates exclusion of an anionic matrix, such as carboxylic acids, but preferential sorption of cationic nitrogen-bearing DOM, pointing at repulsive and attractive forces with the negatively charged cross-linker as a likely reason. Therefore, we ascribe TFN-CDP's selectivity to nonpolar and electrostatic interactions between MPs/DOM and the polymer building blocks. These molecular insights can further aid in the optimization of efficient and selective sorbent design for environmental and analytical applications.
环糊精聚合物（CDP）是水净化技术中很有前景的下一代吸附剂。与四氟对苯二甲腈交联的聚合物衍生物（TFN-CDP）对非离子和阳离子微污染物（MPs）相对于溶解有机物（DOM）的选择性使该吸附剂在许多分析应用中也具有吸引力。然而，观察到的选择性的分子驱动因素尚未完全理解。为了深入了解吸附机制，我们（i）合成了具有不同空腔尺寸（α-、β-、γ-CDP）的TFN-CDP；（ii）评估了它们在与不同DOM尺寸级分（<1、1-3、3-10、>10 kDa）竞争时对选定非离子MPs的萃取效率，以测试尺寸选择性；（iii）对CDP萃取的DOM化合物（<1 kDa）进行非靶向、超高分辨率傅里叶变换离子回旋共振质谱分析，以探究控制其选择性吸附的分子吸附质特性。首先，通过不同的CD空腔尺寸（i）或两种独立方法（ii）和（iii）均未获得尺寸选择性的证据。其次，我们发现吸附质的氧化和极性分别对DOM和MPs的萃取有主要影响，相对贫氧/非极性分子更易保留在所有α-、β-和γ-CDP上。第三，我们的数据表明排除了阴离子基质，如羧酸，但阳离子含氮DOM有优先吸附，这表明与带负电荷的交联剂之间的排斥力和吸引力可能是原因。因此，我们将TFN-CDP的选择性归因于MPs/DOM与聚合物结构单元之间的非极性和静电相互作用。这些分子层面的见解可以进一步帮助优化用于环境和分析应用的高效且选择性的吸附剂设计。
