Enantioseparation of racemic paroxol on an amylose-based chiral stationary phase by supercritical fluid chromatography.

The separation of racemic paroxol, a key precursor of trans-(-)-paroxetine, on Chiralpak AD-H, an amylose-based chiral stationary phase, by supercritical fluid chromatography was studied. Pulse experiments were investigated using supercritical carbon dioxide modified with methanol (MeOH), ethanol and 2-propanol at 35°C and 15  MPa. Retention and separation factors were determined under analytical conditions for different mobile phase compositions. Among the modifiers used, MeOH was shown to be the best additive, and 5% v/v of MeOH was the preferable concentration at which selectivity of 1.14 and resolution of 3.0 was obtained. In order to evaluate the potential with respect to preparative separations, the adsorption isotherms of individual enantiomers of paroxol were estimated using the elution by characteristic point method. Isotherm parameters were determined from the overloaded elution profiles that were collected at pressure ranging from 15 to 24  MPa. The isotherms obtained were further validated by comparing experimentally recorded elution profiles with the predictions based on the equilibrium-dispersive model. The results are important to the process design and optimization of preparative supercritical fluid chromatography application.