| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 91 === ABSTRACT
The influence of pH on the electrophoretic behavior of six quinolones with a piperazino substituent, together with two quinolones without a piperazino substituent and
1-phenylpiperazine, in capillary zone electrophoresis (CZE) was investigated. We focussed our attention on the examination of the mobility equations involving three protolytic equilibria for describing the electrophoretic behavior of quinolones with a piperazino moiety and the significance of the contribution of the zwitterionic species of these quinolones to the effective mobility. The results indicate that quinolones with a piperazino moiety should involve three protolytic equilibria and that, due to a stronger dissociation of the carboxylic group as compared with the protonation of the piperazino moiety in the pH range 6.0-8.0, the zwitterionic species of these quinolones are slightly negatively charged, thus resulting in a significant contribution of the zwitterionic species of these quinolones to the effective mobility. With the use of an appropriate mobility equation and with the aid of computer simulation through the analysis of mobility curves, not only the pKa1 value due to the doubly protonated piperazino moiety can be affirmatively estimated, but also the pKa2 and pKa3 values due to the dissociation of the carboxylic group and the singly protonated piperazino moiety, respectively, can be more precisely determined. The determination of pKa values allows us to rationalize the influence of pH on the electrophoretic behavior of these compounds in CZE.
Capillary zone electrophoresis has proven to be a powerful technique for separation. In the second part of this study , seven quinolones with a piperizine substituent were separated by using cyclodextrins as additive. We focusesd on the separation of quinolones having a piperizine substituent with addition of sulfated cyclodextrins and the optimization of separation. Moreover, by mixing neutral cyclodextrin with sulfated cyclodextrins, the separation efficiency was considerably enhanced. Besides, the enantiomers of two quinolones with a piperizine substituent could be separated when cyclodextrins were used.
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