Cyclodextrin-assisted enantioseparation of warfarin and 10-hydroxywarfarin by capillary electrophoresis studied from the analytical and thermodynamic points of view.

In this work cyclodextrin-assisted enantioseparation of warfarin and 10-hydroxywarfarin by CE has been studied from the analytical and thermodynamic points of view. The role of cyclodextrin concentration and temperature has been analyzed in reference to three different analytical parameters, corresponding to selectivity, resolution and resolution/analysis time ratio. The optimal conditions for enantioseparation have been found, they have been selected on the basis of critical difference in electrophoretic mobility and possibly short analysis time. The values of complexation percentage have also been calculated, to provide a link between the state of complexation equilibrium and the effectiveness of enantioseparation. In the optimal conditions the difference in complexation degree between enantiomers reaches 2.5% and 7.3% for warfarin and 10-hydroxywarfarin, respectively. At each temperature the highest enantioresolution is observed when the average complexation degree is close to 50%. In each case complexation is exothermic and driven by some enthalpically favorable process. 10-hydroxywarfarin exerts the stronger affinity to cyclodextrin and the stronger stereoselective effect. The presented results may be helpful in optimization and understanding of chiral separations by CE.