Šolínová Veronika, Koval Dušan, Kašička Václav
Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic.
Electrophoresis. 2025 Jul;46(13-14):820-828. doi: 10.1002/elps.202400207. Epub 2024 Nov 28.
Sulfated cyclodextrins (CDs) are multiply negatively charged molecules widely used as chiral selectors in capillary electrophoresis (CE). In some of their applications, the effective charge numbers of their molecules were observed to be lower than the numbers of the attached sulfated groups due to strong binding of counterions. However, degree of reduction of the theoretical charge was not quantified. For that reason, in this study, capillary isotachophoresis (CITP) and capillary zone electrophoresis (CZE) were applied for the determination of the effective charge numbers and actual ionic mobilities of two kinds of sulfated CDs: single isomer sulfated α-, β-, and γ-CDs (SI-CDs) and randomly highly sulfated α-, β-, and γ-CDs (HS-CDs). The effective charge numbers of the SI-CDs and HS-CDs were determined from the length of their ITP zones, the ionic mobilities determined by CZE, and molar concentrations of their solutions applied for CITP analysis, and from the same parameters of reference compounds, formic acid for SI-CDs and dichloroacetic acid for HS-CDs. The determined effective charge numbers of the SI-CDs were equal to or only slightly lower than the numbers of sulfate groups in their molecules but the effective charge numbers of randomly HS-CDs were significantly (22.2%-27.8%) reduced as compared to the average numbers of sulfate groups in their molecules. In accordance with a lower number of sulfate groups in SI-CDs than in HS-CDs, the absolute values of the actual ionic mobilities of SI-CDs (35.5-37.5) × 10 m V s were lower than those of HS-CDs (43.5-44.1) × 10 m V s.
硫酸化环糊精（CDs）是带多个负电荷的分子，在毛细管电泳（CE）中广泛用作手性选择剂。在它们的一些应用中，由于抗衡离子的强烈结合，观察到其分子的有效电荷数低于连接的硫酸根基团数。然而，理论电荷的降低程度并未量化。因此，在本研究中，采用毛细管等速电泳（CITP）和毛细管区带电泳（CZE）来测定两种硫酸化CDs的有效电荷数和实际离子迁移率：单异构体硫酸化α-、β-和γ-环糊精（SI-CDs）以及随机高度硫酸化的α-、β-和γ-环糊精（HS-CDs）。SI-CDs和HS-CDs的有效电荷数由其ITP区的长度、通过CZE测定的离子迁移率、用于CITP分析的溶液的摩尔浓度以及参考化合物的相同参数（SI-CDs用甲酸，HS-CDs用二氯乙酸）确定。所测定的SI-CDs的有效电荷数等于或仅略低于其分子中的硫酸根基团数，但随机HS-CDs的有效电荷数与其分子中硫酸根基团的平均数相比显著降低（22.2%-27.8%）。与HS-CDs相比，SI-CDs中的硫酸根基团数较少，其实际离子迁移率的绝对值（35.5-37.5）×10 mV s低于HS-CDs的（43.5-44.1）×10 mV s。
