Capillary zone electrophoresis at subzero temperatures II: chiral separation of biogenic amines.
Capillary zone electrophoresis at subzero temperatures II: chiral separation of biogenic amines.
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零度以下毛细管区带电泳 II：生物胺的手性分离。
DOI：
10.1002/elps.1150180605
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Horvath,C
中科院分区：
文献类型：
--
作者：
Ma,S;Horvath,C
以七（2，6-二-O-甲基）-β-环糊精为手性选择剂，在-20 ° C ~ 40°C的温度范围内，采用毛细管区带电泳（CZE）分离8种生物胺对映体。在1.5°至40°C和−20°至40°C下，分别使用熔融石英毛细管在pH为2.5的纯净水溶液和甲醇介质中的磷酸钠（通过玻璃pH电极测量）。温度对对映体选择性的影响取决于分子中酚羟基的数目。当温度从40° C降低到−20°C时，通过相对迁移率差测量，对于具有两个邻位酚羟基的胺，系统的手性选择性增加了10倍，而对于没有酚羟基的胺，增加不明显。测定了3种分子结构相同但酚羟基数目不同的胺在不同温度下的络合物形成常数，并对该过程的热力学参数和补偿温度进行了估算。不含酚羟基的胺的补偿温度为690 K，而含一个或两个酚羟基的胺的补偿温度< 400 K。补偿温度的差异表明，它们与手性选择剂络合的内在机制是不相同的;这可能是在手性选择性的温度依赖性中观察到的差异的原因。每个酚羟基的焓变为2.5 kcal mol−1，这与单个氢键的典型值相比是有利的。因此，当胺具有酚羟基时，随着温度降低，手性选择性的强烈增加可能是由于在本研究中使用的条件下环糊精和酚羟基之间的氢键增强。
The separation of enantiomer pairs of eight biogenic amines by capillary zone electrophoresis (CZE) was investigated with heptakis (2,6‐di‐O‐methyl)‐β‐cyclodextrin as the chiral selector at temperatures ranging from −20° to 40°C by using a commercial electrophoresis unit retrofitted with an external thermostated refrigerated circulating bath in order to assist the original cooling system. Sodium phosphate in both neat aqueous and methanolic media at pH 2.5, as measured by the glass pH electrode, were used with the fused silica capillary from 1.5° to 40°C and −20° to 40°C, respectively. The effect of temperature on enantioselectivity was found to depend on the number of phenolic hydroxyl groups in the molecule. Upon lowering the temperature from 40° to −20°C, the chiral selectivity of the system, as measured by the relative mobility difference, increased tenfold for the amines with two vicinal phenolic hydroxyls, whereas the increase was insignificant for those having no phenolic hydroxyl groups. The complex formation constants of three amines which have the same molecular structure but the number of phenolic hydroxyl groups were determined at different temperatures and the thermodynamic parameters as well as compensation temperatures for the process were evaluated. Whereas the compensation temperature was 690 K for the amine without phenolic hydroxyl group, it was < 400 K for the amines with one or two phenolic hydroxyl groups. The difference in the compensation temperatures indicates that the intrinsic mechanisms of their complexation with the chiral selector are not the same; this may account for the discrepancies observed in the temperature dependency of the chiral selectivity. The enthalpy change per phenolic hydroxyl group was 2.5 kcal mol−1, which compares favorably with the typical value for a single hydrogen bond. Therefore, when the amines have phenolic hydroxyl groups, the strong increase in chiral selectivity with decreasing temperature may be due to enhanced H‐bonding between the cyclodextrin and the phenolic hydroxyls under the conditions employed in this study.