Amini A, Merclin N, Bastami S, Westerlund D
Analytical Pharmaceutical Chemistry, Uppsala University, Biomedical Centre, Sweden.
Electrophoresis. 1999 Jan;20(1):180-8. doi: 10.1002/(SICI)1522-2683(19990101)20:1<180::AID-ELPS180>3.0.CO;2-6.
The principles for the determination of conditional association constants of enantiomers by capillary zone electrophoresis employing a partial filling technique (PFT) using methyl-beta-cyclodextrin as chiral selector is presented. Orciprenaline was used as a model compound. Partial filling is a separation technique, where different lengths of the chiral selector solution are introduced into the capillary to a final zone length shorter than the effective length of the capillary, prior to application of the solutes. Lengthening of the separation zone results in improving enantioresolution in addition to decreasing electrophoretic mobility of the enantiomers, because of longer interaction time between the solute and chiral selector. The degree of the reduction in electromobility depends on the affinity of the solute to the chiral selector, i.e. strength of the complex formed between the solute and cyclodextrin. The decrease in the electrophoretic mobility with increasing length of the separation zone is used for determination of the association constant. The association constants of the enantiomers of orciprenaline and the chiral selector were evaluated from the slope of the plot, observed electrophoretic mobility versus the ratio between the length of the separation zone and the effective length of the capillary. It was found that the association constants were independent of the chiral selector concentration. The mean values were 110 M(-1) and 160 M(-1) for respective enantiomer. Constants obtained by a conventional CE technique were in good agreement with those from the PFT experiments. The highest enantioselectivityy was obtained when about 50% of the solute was distributed to the selector phase.
介绍了采用部分填充技术（PFT），以甲基-β-环糊精作为手性选择剂，通过毛细管区带电泳测定对映体条件缔合常数的原理。以奥西那林作为模型化合物。部分填充是一种分离技术，即在施加溶质之前，将不同长度的手性选择剂溶液引入毛细管中，使其最终区带长度短于毛细管的有效长度。分离区带的延长除了会降低对映体的电泳迁移率外，还会提高对映体分离度，这是因为溶质与手性选择剂之间的相互作用时间更长。电迁移率降低的程度取决于溶质对手性选择剂的亲和力，即溶质与环糊精形成的络合物的强度。利用分离区带长度增加时电泳迁移率的降低来测定缔合常数。根据观察到的电泳迁移率与分离区带长度和毛细管有效长度之比的关系图的斜率，评估了奥西那林对映体与手性选择剂的缔合常数。发现缔合常数与手性选择剂浓度无关。各对映体的平均值分别为110 M⁻¹和160 M⁻¹。通过传统毛细管电泳技术获得的常数与部分填充技术实验得到的常数吻合良好。当约50%的溶质分布到选择剂相中时，获得了最高的对映体选择性。
