Studies on the effect of alcohols on the chiral discrimination mechanisms of amylose stationary phase on the enantioseparation of nebivolol by HPLC

The chiral recognition mechanism of amylose CSPs has been described by achieving the enantiomeric resolution of (+/-)-nebivolol on Chiralpak AD and Chiralpak AD-RH columns with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol as mobile phases at different flow rates. The energies of interactions of methanol, ethanol, 1-propanol, 2-propanol and 1-butanol with both phases were calculated. The (+)-RRRS enantiomer eluted first when using methanol, ethanol and 1-propanol, while the elution order was reversed when using 2-propanol and 1-butanol as the mobile phases. It has been concluded that the reversal elution order observed was due in part to the chiral cavities on the amylose CSP which were responsible for the bondings of different magnitude between chiral stationary phase and enantiomers, which are influenced with the type of alcohol used as mobile phase on the conformation of the 3,5-dimethyl phenyl carbamate moiety on the pyranose ring system of the amylose.