Hedeland Ylva, Haglöf Jakob, Beronius Per, Pettersson Curt
Department of Analytical Chemistry, Division of Analytical Chemistry, Uppsala University, Uppsala, Sweden.
Electrophoresis. 2006 Nov;27(22):4469-79. doi: 10.1002/elps.200600297.
The present work demonstrates the importance of the ionic composition in the BGE for enantioseparation. (-)-2,3:4,6-di-O-Isopropylidene-2-keto-L-gulonic acid ((-)-DIKGA) has been used as the chiral selector in methanolic and ethanolic BGEs. The influence of added alkali metal hydroxides on the EOF and the chiral separation of amines (atenolol, isoprenaline, pindolol and propranolol) have been studied. The ion-pair formation constants in ethanol were determined by precision conductometry for the enantiomers of pindolol with (-)-DIKGA, for Li(+), Na(+) and Cs(+) with (-)-DIKGA, and also for the corresponding alkali metal hydroxides. The effective mobilities and the enantiomeric mobility differences were affected by the type of alkali metal hydroxide (LiOH, NaOH, KOH, RbOH or CsOH) added to the BGE. The effective mobility and mobility difference were increased with decrease in solvated radius of the alkali metal cation. These differences could partly be correlated to the ion-pair formation constants of the alkali metal cations with the chiral selector, affecting the equilibrium concentration of the free selector. The electroosmosis was also affected by the alkali metal hydroxide added to the BGE. The cathodic electroosmosis decreased with decreasing solvated radius of the alkali metal cation added to the BGE. Interestingly, the cathodic EOF was even reversed, i.e. became anodic in the ethanolic BGEs containing KOH, RbOH or CsOH and the methanolic ones with RbOH and CsOH.
本研究表明了背景电解质（BGE）中离子组成对映体分离的重要性。（-）-2,3:4,6-二-O-异丙叉基-2-酮-L-古洛糖酸（（-）-DIKGA）已被用作甲醇和乙醇背景电解质中的手性选择剂。研究了添加碱金属氢氧化物对电渗流（EOF）以及胺类（阿替洛尔、异丙肾上腺素、吲哚洛尔和普萘洛尔）手性分离的影响。通过精密电导法测定了吲哚洛尔对映体与（-）-DIKGA、Li⁺、Na⁺和Cs⁺与（-）-DIKGA以及相应碱金属氢氧化物在乙醇中的离子对形成常数。添加到背景电解质中的碱金属氢氧化物类型（LiOH、NaOH、KOH、RbOH或CsOH）会影响有效迁移率和对映体迁移率差异。随着碱金属阳离子溶剂化半径的减小，有效迁移率和迁移率差异增大。这些差异部分可与碱金属阳离子与手性选择剂的离子对形成常数相关，从而影响游离选择剂的平衡浓度。添加到背景电解质中的碱金属氢氧化物也会影响电渗流。随着添加到背景电解质中的碱金属阳离子溶剂化半径的减小，阴极电渗流降低。有趣的是，阴极电渗流甚至发生了反转，即在含有KOH、RbOH或CsOH的乙醇背景电解质以及含有RbOH和CsOH的甲醇背景电解质中变为阳极电渗流。
