E nantioseparation of phenothiazines in cyclodextrin-modified micellar electrokinetic chromatography

In this study, enantioseparations of five phenothiazines in cyclodextrin (CD)-modified micellar electrokinetic chromatography
(MEKC) were investigated using a citrate buffer containing tetradecyltrimethylammonium bromide (TTAB) as a
cationic surfactant at low pH. b-Cyclodextrin (b-CD) and hydroxylpropyl-b-CD (HP-b-CD) were selected as chiral
selectors. The results indicate that the separation window is greatly enlarged by b-CD concentration and that the separability
and selectivity of phenothiazines are remarkably influenced by the concentrations of both b-CD and TTAB, as well as buffer
pH. The interaction of thioridazine with b-CDs is considerably reduced in the presence of TTAB micelles due to competitive
complexation of thioridazine with TTAB micelles, which is pH-dependent. As a result, effective enantioseparation of
thioridazine is simultaneously achievable with that of trimeprazine and promethazine or ethopropazine in MEKC with
addition of either b-CD or HP-b-CD, respectively, to a micellar citrate buffer containing TTAB at pH 3.5. Better
enantioresolution of thioridazine in MEKC than in capillary zone electrophoresis can be obtained.
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