Enantiomeric separation of acidic compounds using single-isomer amino cyclodextrin derivatives in nonaqueous capillary electrophoresis

The enantiomeric separation of a series of acidic pharmaceuticals (mostly nonsteroidal anti-inflammatory drugs) has been investigated in NACE systems using single-isomer amino beta-CD derivatives. The first part of this study consisted of the selection of the basic experimental conditions to separate efficiently the enantiomers of acidic drugs. Several parameters, such as the nature of the ionic BGE components, were studied and a methanolic solution of ammonium acetate containing the cationic CD was selected as BGE. A D-optimal design with 20 experimental points was then applied and the nature and concentration of the CD were found to have a significant effect on the enantiomeric resolution for all studied compounds. Resolution (R(s)) values were always higher with 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-CD (PA-beta-CD) compared to those obtained with 6-monodeoxy-6-mono(2-hydroxy)propylamino-beta-CD (IPA-beta-CD). However, the latter led to shorter migration times. Generic NACE conditions were then selected by means of the multivariate approach in order to obtain the highest R(s) values in a minimum amount of time. Finally, dependence of separation selectivity, resolution, as well as mobility difference on chiral selector concentration was discussed and binding constants with PA-beta-CD were estimated for the two enantiomers of one of the model compounds, suprofen in these NACE systems.