School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China.
Anal Chem. 2019 Nov 5;91(21):13803-13809. doi: 10.1021/acs.analchem.9b03276. Epub 2019 Oct 25.
Identification and quantitation of enantiomers is a critical and challenging step in the process of chiral capillary electrophoresis (CE) analysis, especially when the optically pure enantiomers are expensive or commercially unavailable. Herein, a method of CE in combination with circular dichroism (CD) spectroscopy for the identification of enantiomeric peak independent of single enantiomer standard was proposed. By comparing the theoretical CD spectrum of the single enantiomer calculated by time-dependent density functional theory (TDDFT) with the experimental CD spectrum of the enantiomeric mixture, the configuration of the dominant enantiomer in the nonracemic mixture was determined. Considering that the dominant enantiomer showed bigger peak area on the CE electrophoretogram, the enantiomeric peak was easily identified. Three kinds of enantiomers including seven chiral compounds (i.e., tryptophan, tyrosine, phenylalanine, Boc-valine, Boc-leucine, ibuprofen, and naproxen) were used to evaluate the reliability of the method. The concentration of the single enantiomer in the mixture can be further accurately quantified based on the total concentration of the mixture and the peak area ratio of a couple of enantiomers, and the accuracy was assessed by taking ibuprofen as an example. The developed CE-CD method provides an alternative tool for the analysis of nonracemic mixture with good ECD signals.
对映异构体的识别和定量是手性毛细管电泳（CE）分析过程中的一个关键且具有挑战性的步骤，特别是当光学纯对映异构体昂贵或无法从商业途径获得时。在此，提出了一种 CE 与圆二色性（CD）光谱相结合的方法，用于在无需单个对映体标准品的情况下识别对映体峰。通过将通过时间相关密度泛函理论（TDDFT）计算的单个对映体的理论 CD 光谱与对映体混合物的实验 CD 光谱进行比较，可以确定非对映混合物中优势对映体的构型。由于优势对映体在 CE 电泳图谱上显示出更大的峰面积，因此很容易识别对映体峰。使用三种对映体（即色氨酸、酪氨酸、苯丙氨酸、Boc-缬氨酸、Boc-亮氨酸、布洛芬和萘普生）七种手性化合物来评估该方法的可靠性。可以根据混合物的总浓度和一对对映体的峰面积比进一步准确地定量混合物中单一对映体的浓度，并且以布洛芬为例评估了准确性。开发的 CE-CD 方法为具有良好 ECD 信号的非对映混合物分析提供了一种替代工具。
