Hu Shaoqiang
Henan Key Laboratory of Function-Oriented Porous Materials, College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471934, China.
Molecules. 2023 Aug 6;28(15):5908. doi: 10.3390/molecules28155908.
Despite the fact that the self-disproportionation of enantiomers (SDE) has been found for several decades and has been widely used in crystallization, sublimation and chromatography for the purification or separation of nonracemic compounds, the phenomenon of SDE in capillary electrophoresis (CE) has never been reported up to now. Here, a new approach to separate enantiomers in CE based on SDE was demonstrated by introducing copper (II) ions into the separation media. The enantiomers of atenolol interact with copper ions to produce positively charged complexes with different electrophoretic mobilities from the single molecules. The dynamic equilibrium between homo- or heterochiral complexes (associates) and single molecules of atenolol enantiomers supports the manifestation of SDE. Different mobilities of the single molecules and associates, and different distribution of two enantiomers between the single molecules and associates caused by their different concentrations, produce a net difference in electrodriven migration velocities of the two enantiomers. The relative movement of two enantiomers causes a zone depleted in one enantiomer at the rear end of sample segment, giving a trapezoidal CE curve with a step at the end. Quantification of enantiomers is achieved according to the step height. The analysis does not rely on the use of enantiomerically pure chiral selector and the result agrees with that obtained by conventional chiral CE using a chiral selector.
尽管对映体自歧化现象（SDE）已被发现数十年，且已广泛应用于结晶、升华和色谱法中以纯化或分离非外消旋化合物，但毛细管电泳（CE）中的SDE现象至今从未被报道过。在此，通过将铜（II）离子引入分离介质，展示了一种基于SDE在CE中分离对映体的新方法。阿替洛尔的对映体与铜离子相互作用，生成带正电荷的络合物，其电泳迁移率与单个分子不同。阿替洛尔对映体的同手性或异手性络合物（缔合物）与单个分子之间的动态平衡支持了SDE的表现。单个分子和缔合物的迁移率不同，以及两种对映体因其浓度不同而在单个分子和缔合物之间的不同分布，导致两种对映体的电驱动迁移速度产生净差异。两种对映体的相对移动会在样品段后端导致一种对映体耗尽的区域，从而得到一条在末端有台阶的梯形CE曲线。根据台阶高度实现对映体的定量分析。该分析不依赖于使用对映体纯的手性选择剂，且结果与使用手性选择剂的传统手性CE所获得的结果一致。
