Fillet M, Hubert P, Crommen J
Department of Analytical, Pharmaceutical Chemistry, Institute of Pharmacy, University of Liège, Belgium.
Electrophoresis. 1998 Nov;19(16-17):2834-40. doi: 10.1002/elps.1150191608.
General strategies for the development of capillary electrophoretic methods for the enantiomeric separation of basic, acidic or neutral drugs were developed. For all kinds of compounds, the use of a buffer made of 100 mM phosphoric acid adjusted to pH 3 with triethanolamine and containing anionic and/or uncharged cyclodextrin (CD) derivatives as chiral selectors was recommended. Two different optimization schemes depending on the acidic or basic character of the analytes, were elaborated. For most basic compounds present in cationic form at pH 3, enantiomeric separation could be achieved in the normal polarity mode. Different beta-cyclodextrin derivatives were first tested at a given concentration. Five derivatives were found to be particularly useful for enantioseparations in capillary electrophoresis (CE): the anionic carboxymethyl-beta-CD (CMCD) and sulfobutyl-beta-CD (SBCD) and the neutral dimethyl-beta-CD (DMCD), trimethyl-beta-CD (TMCD) and hydroxypropyl-beta-CD (HPCD). After selection of the most suitable CD, its concentration was optimized with respect to chiral resolution. If necessary, a further improvement in resolution could often be obtained for the enantiomers of cationic solutes by increasing the buffer pH from 3 to 5 using CMCD as chiral additive. Another possible alternative for enhancement in chiral resolution was the addition of metharlol or cyclohexanol to the buffer. For acidic drugs, essentially present in uncharged form at pH 3, and for neutral solutes, anionic CD derivatives such as SBCD or CMCD were first tested at a given concentration in the reversed polarity mode. Dual systems, based on the simultaneous addition of a charged CD (SBCD or CMCD) and a neutral CD (TMCD or DMCD), could then be investigated for resolution improvement. After optimization of the CD concentrations, the use of dual systems with CMCD at pH 5 could also be tested if necessary, especially for very weak acidic and neutral drugs. By applying these optimization strategies, 48 of the 50 drugs examined as model compounds could be fully enantioseparated by CE in short analysis times (usually less than 10 min).
开发了用于碱性、酸性或中性药物对映体分离的毛细管电泳方法的通用策略。对于所有类型的化合物，建议使用由100 mM磷酸制成的缓冲液，用三乙醇胺将其pH值调至3，并含有阴离子和/或不带电荷的环糊精（CD）衍生物作为手性选择剂。根据分析物的酸性或碱性特征，制定了两种不同的优化方案。对于在pH 3时以阳离子形式存在的大多数碱性化合物，可以在正常极性模式下实现对映体分离。首先在给定浓度下测试不同的β-环糊精衍生物。发现五种衍生物对毛细管电泳（CE）中的对映体分离特别有用：阴离子羧甲基-β-CD（CMCD）和磺丁基-β-CD（SBCD）以及中性二甲基-β-CD（DMCD）、三甲基-β-CD（TMCD）和羟丙基-β-CD（HPCD）。选择最合适的CD后，针对手性拆分对其浓度进行优化。如有必要，通过使用CMCD作为手性添加剂将缓冲液pH值从3提高到5，通常可以进一步提高阳离子溶质对映体的拆分度。提高手性拆分度的另一种可能方法是向缓冲液中加入甲醇或环己醇。对于在pH 3时基本上以不带电荷形式存在的酸性药物以及中性溶质，首先在反相极性模式下以给定浓度测试阴离子CD衍生物，如SBCD或CMCD。然后可以研究基于同时加入带电CD（SBCD或CMCD）和中性CD（TMCD或DMCD）的双系统以提高拆分度。在优化CD浓度后，如有必要，也可以测试在pH 5时使用CMCD的双系统，特别是对于非常弱的酸性和中性药物。通过应用这些优化策略，作为模型化合物检测的50种药物中有48种可以通过CE在短分析时间内（通常少于10分钟）实现完全对映体分离。
