Enantioseparation of phenothiazines in cyclodextrin-modified capillary zone electrophoresis using sulfated cyclodextrins as chiral selectors

Abstract

In this study, enantioseparations of five phenothiazines, including promethazine, ethopropazine, trimeprazine, methotrimeprazine, and thioridazine, in CD-modified CZE using dual CD systems consisting of randomly sulfate-substituted CD (MI-S-beta-CD) and a neutral CD as chiral selectors in a citrate buffer (100 mM) at pH 3.0 were investigated. The results indicate that MI-S-beta-CD is an excellent chiral selector for enantioseparation of ethopropazine. The enantiomers of promethazine can also be baseline-resolved with MI-S-beta-CD at concentrations in the range of 0.5-1.0% w/v. On the other hand, thioridazine and trimeprazine interact strongly with neutral CDs. As a result, the enantioselectivity of these two phenothiazines is remarkably and synergistically enhanced with increasing the concentration of neutral CDs in the presence of MI-S-beta-CD and simultaneous enantioseparations of these phenothiazines, except for methotrimeprazine, could favorably be achieved with the use of dual CD systems. Moreover, by varying the concentration of beta-CD or gamma-CD at a fixed concentration of MI-S-beta-CD (0.75% w/v) reversal of the enantiomer migration order of promethazine occurred. This may be attributable to the opposite effects of charged and neutral CDs on the mobility of the enantiomers of promethazine.

Enantioseparation of phenothiazines in CD‐modified CZE using single isomer sulfated CD as a chiral selector

“…It was concluded that the differences in the binding constants and limiting mobility of the complexes were responsible for the enantiomer migration reversal with g-CD as chiral selector. Compared with the results obtained using a phosphate buffer, citrate buffer, which involved competitive complexation with chiral selector, should play a significant role in the enantiomer migration reversal [54]. Recently, enantioseparations of phenothiazines in CD-modified CE with randomly sulfate-substituted b-CD (MI-S-b-CD) and with dual CD systems consisting of MI-S-b-CD and neutral CDs as chiral selectors in a citrate buffer at pH 3.0 were reported [54].…”

“…Compared with the results obtained using a phosphate buffer, citrate buffer, which involved competitive complexation with chiral selector, should play a significant role in the enantiomer migration reversal [54]. Recently, enantioseparations of phenothiazines in CD-modified CE with randomly sulfate-substituted b-CD (MI-S-b-CD) and with dual CD systems consisting of MI-S-b-CD and neutral CDs as chiral selectors in a citrate buffer at pH 3.0 were reported [54]. MI-S-b-CD was found to be an excellent chiral selector for the enantioseparation of ethopropazine; the enantiomers of promethazine can be baseline resolved with MI-S-b-CD [54].…”

“…MI-S-b-CD was found to be an excellent chiral selector for the enantioseparation of ethopropazine; the enantiomers of promethazine can be baseline resolved with MI-S-b-CD [54]. Moreover, reversal of the enantiomer migration order of promethazine occurs by varying the concentration of g-CD or b-CD in the presence of MI-S-b-CD at low concentrations [54].…”

“…Phenothiazines and the enantiomers as well have previously been separated by CE [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], mostly by CZE [41,[43][44][45][46][47][48][49][50][52][53][54][55][56][57]. The applications of the CE technique to the enantioseparations of phenothiazines using CDs as chiral selectors have been reported [41,42,47,48,[50][51][52][53][54]. (1)-Promethazine was found to have a greater binding strength than (2)-promethazine with b-CD [42].…”

“…Recently, enantioseparations of phenothiazines in CD-modified CE with randomly sulfate-substituted b-CD (MI-S-b-CD) and with dual CD systems consisting of MI-S-b-CD and neutral CDs as chiral selectors in a citrate buffer at pH 3.0 were reported [54]. MI-S-b-CD was found to be an excellent chiral selector for the enantioseparation of ethopropazine; the enantiomers of promethazine can be baseline resolved with MI-S-b-CD [54]. Moreover, reversal of the enantiomer migration order of promethazine occurs by varying the concentration of g-CD or b-CD in the presence of MI-S-b-CD at low concentrations [54].…”