Chiral separation of racemic mexiletine hydrochloride using cyclodextrins as chiral additive by capillary electrophoresis

Enantiomeric separation of racemic mexiletine hydrochloride was performed using cyclodextrins (CDs) including alpha-CD, beta-CD, heptakis-2,6-di-O-methyl-beta-CD (DM-beta-CD), heptakis-2,3,6-tri-O-methyl-beta-CD (TM-beta-CD), 2-O-(2-hydroxypropyl)beta-CD and gamma-CD as chiral selectors. However, the enantiomers can be chirally separated only by methyl-beta-CDs. The enantiomers could be baseline separated when TM-beta-CD was used, and were only partially separated by DM-beta-CD and no chiral separation was obtained using beta-CD; thus, it is believed that methoxy groups of methyl-beta-CDs play a key role in the chiral recognition for racemic mexiletine. Effects of CD concentration, applied voltage and the organic additive on chiral separation were studied. Under the conditions of 40 mmol/l Tris-H3PO4 buffer at pH 2.5 containing 20 mmol/l TM-beta-CD,baseline separation (R-s=2.3) of the enantiomers can be achieved. (C) 1998 Elsevier Science B.V.