Evaluation of carbon nanostructures as chiral selectors for direct enantiomeric separation of ephedrines by EKC.

Single-walled nanotubes and multi-walled nanotubes (MWNTs) have been evaluated as chiral selectors for the enantiomeric separation of ephedrines by using EKC with surfactant-coated carbon nanotubes. The analysed compounds were (+/-)-ephedrine, (+/-)-norephedrine and (+/-)-N-methylephedrine. The potential of those carbon nanostructures as chiral selectors has been evaluated by changing different experimental variables such as pH, addition of organic modifiers, potential and injection time. The capability of MWNTs to resolve enantiomeric mixtures was demonstrated by using partial filling of the capillary with concentrated surfactant-coated MWNTs. Differences in the enantioselectivity were discussed.