| Abstract: | A β-cyclodextrin-bonded phase has been used to investigate the separation of the enantiomers of atenolol, oxprenolol, celiprolol, tertatolol, terbutaline, fluoxetine, norfluoxetine, and zopiclone, focusing on the importance of solvent selectivity. With cyclodextrin (CD)-bonded phases, chiral discrimination occurs because the two enantiomers of a racemate form inclusion complexes of different strengths within the CD cavity. The organic modifier molecules tend to compete with solutes for a definite number of adsorption sites on the stationary phase. Moreover, the ternary complex formation may play an important role in chiral recognition. In this study, it was of interest to estimate the influence of mobile phase modifiers with respect to solvent type (i.e., ACN, MeOH, EtOH, THF, i-PrOH, PrOH and t-BuOH), size and shape, and concentration. Solvent selectivity has been investigated by using different organic modifiers in mobile phases with the same polarity, and relationships were established between the logarithm of solvent partition coefficient (log Ps) and the three most important chromatographic parameters: retention time (t), resolution (R), and enantioselectivity (α). Thus, it seems that the hydrophobicity of the organic modifier becomes one of the dominant factors affecting the inclusion process phenomena. Further, the apparent partition coefficients of the compounds under study have been determined and a comparison has been attempted regarding the degree of their enantiomeric resolution. © 1995 Wiley-Liss, Inc. |
