Enantioseparation of rabeprazole and omeprazole by nonaqueous capillary electrophoresis with an ephedrine-based ionic liquid as the chiral selector

An ephedrine‐based chiral ionic liquid, (+)‐N,N‐dimethylephedrinium‐bis(trifluoromethanesulfon)imidate ([DMP]⁺[Tf₂N]^‐), served as both chiral selector and background electrolyte in nonaqueous capillary electrophoresis. The enantioseparation of rabeprazole and omeprazole was achieved in acetonitrile–methanol (60:40 v/v) containing 60 mm [DMP]⁺[Tf₂N]^‐. The influences of separation conditions, including the concentration of [DMP]⁺[Tf₂N]^‐, the electrophoretic media and the buffer, on enantioseparation were evaluated. The mechanism of enantioseparation was investigated and discussed. Ion‐pair interaction and hydrogen bonding may be responsible for the main separation mechanism. Copyright © 2010 John Wiley & Sons, Ltd.