Enantioselective supercritical fluid chromatography using Ristocetin A chiral stationary phases

Racemic mixtures of five acidic drugs have been successfully separated by supercritical fluid chromatography (SFC) using macrocyclic antibiotic chiral stationary phases (CSPs). A ristocetin A CSP has been prepared 'in-house' and effectively applied in packed capillary SFC to separate the enantiomers of dichlorprop (R-s = 1.4), ketoprofen (R-s = 0.9) and warfarin (R-s = 0.9). The commercial ristocetin A CSP (Chirobiotic R(TM)) was subsequently studied in packed column SFC with similar results where the enantiomers of warfarin (R-s = 2.2), coumachlor (R-s = 2.5) and thalidomide (R-s = 0.6) were separated. Interestingly, differences were observed between the two differently immobilised CSPs where the enantiomers of dichlorprop and ketoprofen, which were separated on the 'in-house' CSP, could not be separated on the commercial phase.