ELECTROSORPTION BASED MODIFICATION OF POROUS GRAPHITIC CARBON - USE OF ELECTROCHEMICALLY MODULATED LIQUID-CHROMATOGRAPHY TO CREATE A CHIRALSTATIONARY-PHASE FOR ENANTIOMERIC SEPARATIONS

A novel approach for the modification of the separation capabilities o f electrochemically modulated liquid chromatography is described. The basis of the approach derives from the electrosorption of an organic a dditive from the mobile phase onto a porous graphitic carbon (PGC) sta tionary phase, resulting in a new dimension in the ability to alter re versibly the chemical composition at the surface of the stationary pha se. The viability of the approach is demonstrated by the enantiomeric separation of racemic mixtures of the pharmaceutical agents hexobarbit al and mephenytoin. These separations are achieved by the electrosorpt ion of the organic additive P-cyclodextrin to form a PGC surface that is coated with a chiral selector. Results indicate that changes in app lied potential can not only manipulate the effectiveness of these sepa rations but can also reverse the enantiomeric elution order. A general mechanism for these separations is proposed and the potential applica bility of the strategy to other types of LC separations is briefly not ed.