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Focussing Review
Method Development of Enantiomer Separations by Affinity Capillary Electrophoresis, Cyclodextrin Electrokinetic Chromatography and Capillary Electrophoresis-Mass Spectrometry |
| Yoshihide Tanaka | |
Department of Analytical Chemistry, Nippon Boehringer Ingelheim Co. Ltd., 3-10-1, Yato, Kawanishi, Hyogo 666-0193, Japan |
Capillary electrophoresis (CE) has become a powerful tool for enantiomer separations during the last decade. Since 1993, the author has investigated
enantiomer separations by affinity capillary electrophoresis (affinity CE) with some proteins and by cyclodextrin electrokinetic
chromatography (CDEKC) with some charged cyclodextrins (CDs). Many successful enantiomer separations are demonstrated from our study
in this review article. In the enantiomer separations by affinity CE, the deterioration of detection sensitivity was observed under high concentration
of the protein in running solutions. The partial filling technique was practically useful to solve the serious problem. It allowed operation
at high protein concentrations, such as 500 μM, without the detection problem. Charged CDs had several advantages for the enantiomer
separations over neutral ones. Strong electrostatic interactions between a charged CD and oppositely charged analytes should be effective for
the formation of the complex. A large difference in electrophoretic mobility between the free analyte and the inclusion complex should also
enhance the enantiomeric resolution. In CE-mass spectrometry (CE-MS), the partial filling technique was applied to avoid the introduction of
nonvolatile chiral selectors into the CE-MS interface. By replacing the nonvolatile electrolytes in the running buffer by volatile ones, the separation
conditions employed in CE with the UV detection method could be transferred to CE-MS.
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| Keywords: | enantiomer separation, capillary electrophoresis, capillary electrophoresis-mass spectrometry, partial filling technique, protein, charged cyclodextrin |
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