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首页> 外文期刊>Journal of chromatography, A: Including electrophoresis and other separation methods >Cinchona-based zwitterionic stationary phases: Exploring retention and enantioseparation mechanisms in supercritical fluid chromatography with a fragmentation approach
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Cinchona-based zwitterionic stationary phases: Exploring retention and enantioseparation mechanisms in supercritical fluid chromatography with a fragmentation approach

机译：基于CinChona的两性离子固定阶段：探索超临界流体色谱法的保留和映对机制，碎片方法

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Chiralpak ZWIX(+) and ZWIX(-), are brush-type bonded-silica chiral stationary phases (CSPs), based on complex diastereomeric Cinchona alkaloids derivatives bearing both a positive and a negative charge. In the present study, we aimed to improve the understanding of retention and enantioseparation mechanisms of these CSPs employed in supercritical fluid chromatography (SFC). For this purpose, 9 other stationary phases were used as comparison systems: two of them are commercially available and bear only a positive charge (Chiralpak QN-AX and QD-AX) and the 7 others were designed purposely to be structurally similar to the parent ZWIX phases, but miss some portion of the complex ligand. First, cluster analysis was employed to identify similar and dissimilar behavior among the 11 stationary phases, where ionic interactions appeared to dominate the observed differences. Secondly, the stationary phases were characterized with linear solvation energy relationships (LSER) based on the SFC analysis of 161 achiral analytes and a modified version of the solvation parameter model to include ionic interactions. This served to compare the interaction capabilities for the 11 stationary phases and showed in particular the contribution of attractive and repulsive ionic interactions. Then the ZWIX phases were characterized for their enantioseparation capabilities with a set of 58 racemic probes. Discriminant analysis was applied to explore the molecular structural features that are useful to successful enantioseparation on the ZWIX phases. In particular, it appeared that the presence of positive charges in the analyte is causing increased retention but is not necessarily a favorable feature to enantiorecognition. On the opposite, the presence of negative charges in the analyte favors early elution and enantiorecognition. Finally, a smaller set of 30 pairs of enantiomers, selected by their structural diversity and different enantioseparation values on the ZWIX phases, were analyzed on all chiral phases to observe the contribution of each structural fragment of the chiral ligand on enantioselectivity. Molecular modelling of the ligands also helped in understanding the three-dimensional arrangement of each ligand, notably the intra-molecular hydrogen bonding or the possible contribution of ionic interactions. In the end, each structural element in the ZWIX phases appeared to be a significant contributor to successful enantioresolution, whether they contribute as direct interaction groups (ion-exchange functions) or as steric constraints to orientate the interacting groups towards the analytes. (C) 2019 Elsevier B.V. All rights reserved.
机译：Chiralpak Zwix（+）和Zwix（ - ），是刷型粘合 - 二氧化硅手性固定阶段（CSP），基于复杂的非对映体Cinchona生物碱衍生物，均为正极和负电荷。在本研究中，我们旨在改善在超临界流体色谱（SFC）中使用这些CSP的保留和映对机制的理解。为此目的，其他固定相用作比较系统：其中两个是商业上可获得的并且仅承担正电荷（Chiralpak Qn-Ax和QD-AX），而其他7个是在结构上设计的，以便在结构上类似于父母zwix阶段，但错过了复杂配体的一些部分。首先，使用聚类分析来鉴定11个固定相之间的类似和不同行为，其中离子相互作用似乎占据了观察到的差异。其次，基于161个成立分析物的SFC分析和溶剂化参数模型的修饰形式的SFC分析以及包括离子相互作用的改性版本，以线性溶剂能量关系（LSER）表征了固定相。这用于比较11个固定阶段的相互作用能力，特别是有吸引力和排斥的离子相互作用的贡献。然后，Zwix阶段的特征在于它们的映对能力，具有一组58个外消旋探针。应用判别分析来探讨可用于Zwix阶段对映映的分子结构特征的分子结构特征。特别地，似乎在分析物中存在阳性电荷导致饲养增加，但不一定是对映射的有利特征。在相反的情况下，分析物中的负面收费的存在涉及早期洗脱和肾上腺症。最后，在所有手性相位上分析了通过它们结构分集和Zwix阶段的不同映对值选择的较小的30对对映体，以观察手性配体对对映选择性的每个结构片段的贡献。配体的分子模型还有助于理解每个配体的三维布置，特别是分子内氢键或离子相互作用的可能贡献。最后，Zwix阶段中的每个结构元素似乎是成功对脑筋的重要贡献者，无论它们是否有助于直接相互作用基团（离子交换功能）或作为空间约束，以使相互作用基团朝向分析物定向。 （c）2019 Elsevier B.v.保留所有权利。

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