Enantiomerization of Thioridazine in Dynamic Capillary Electrophoresis Using Sulfated Cyclodextrins as Chiral Selectors
Date Issued
2008
Date
2008
Author(s)
Ko, Ting-Chang
Abstract
In this study, we investigated the enationmerization reaction of thioridazine, a commonly prescribed phenothiazine neuroleptic drug, in dynamic capillary zone electrophoresis.n the first part, the reversed voltage was applied with citrate buffer at low pH using randomly (degree of substitution: 7~11) sulfated -substituted beta-cyclodextrin (MI-S-b-CD) as chiral selectors and the enantiomers of thioridazine could be well-resolved. Interestingly, an unusual plateau signal was observed between the two enantiomeric peaks. The plateau height which depends on the temperature is an indication of a rapid interconversion of the enantiomers. With the plateau height, relative peak height and the peak widths at half height of each individual enatiomeric peak at different temperatures as parameters, the rate constants and dynamic parameters (ΔH≠, ΔS≠, and ΔG≠298K) of enationmerization can be evaluated using software ChromWin2005 and DcXplore. In the temperature range between 15 oC and 25 oC, the plateau height increases with increasing temperature. However, in the temperature range between 33 oC and 45 oC, the plateau height decreases with increasing temperature. The results reveal that additional chemical reactions other than the enantiomerization of thioridazine are involved. n the second part, other types of chiral selectors were used for enantioseperation of thioridazine in order to compare with the MI-S-b-CD system. We found that, with the use of other chiral selectors, except for the S-b-CD (18) system, the formation of plateau in the enantioseperation of thioridazine could not be observed. The results reveal that the position, as well as the number, of sulfate substituent of S-b-CD plays an important role in the enantiomerization reaction of thioridazine.
Subjects
enantiomerization
dynamic capillary electrophoresis
thioridazine
sulfated cyclodextrin
chiral selectors
activation parameters
plateau
Type
thesis
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