Enantioselective separation of ketoconazole enantiomers by membrane extraction

Abstract

A new process has been developed to separate ketoconazole (KTZ) enantiomers by membrane extraction, with the oppositely preferential recognition of hydrophobic and hydrophilic chiral selectors in organic and aqueous phases, respectively. This system is established by adding hydrophobic l-isopentyl tartrate ( l-IPT) in organic strip phase (shell side) and hydrophilic sulfobutylether-β-cyclodextrin (SBE-β-CD) in aqueous feed phase (lumen side), which preferentially recognizes (+)-2R,4S-ketoconazole and (−)-2S,4R-ketoconazole, respectively. The studies performed involve two enantioselective extractions in a biphasic system, where KTZ enantiomers form four complexes with SBE-β-CD in aqueous phase and l-IPT in organic phase, respectively. The membrane is permeable to the KTZ enantiomers but non-permeable to the chiral selector molecules. Fractional chiral extraction theory, mass transfer performance of hollow fiber membrane, enantioselectivity and some experimental conditions are investigated to optimize the separation system. Mathematical model of I/II = 0.893 e 0.039NTU for racemic KTZ separation by hollow fiber extraction, is established. The optical purity for KTZ enantiomers is up to 90% when 9 hollow fiber membrane modules of 30 cm in length in series are used.