Separation of acidic enantiomers by capillary electrophoresis–mass spectrometry employing a partial filling technique

Abstract

Enantiomer separations were performed by capillary electrophoresis–mass spectrometry (CE–MS). Because high concentrations of nonvolatile chiral selectors were not compatible for the CE–MS interface and/or the MS instrument, a partial filling technique was employed to avoid the problem. In this method, a separation solution containing a chiral selector was filled in only a part of the capillary. Since the electroosmotic flow (EOF) was almost completely suppressed in a polyacrylamide-coated capillary, neither the uncharged chiral selector nor the positively charged chiral selector migrated towards the MS detector under the negative polarity mode. Using either cyclodextrins (CDs) or avidin as a chiral selector, racemic mixtures of camphorsulfonic acid, tropic acid, arylpropionic acid and warfarin were successfully separated and detected by MS. This method was also applied to the optical purity test of commercial camphorsulfonic acid enantiomers.