CHIRAL PACKED-COLUMN SUBCRITICAL FLUID CHROMATOGRAPHY ON POLYSACCHARIDE AND MACROCYCLIC ANTIBIOTIC CHIRAL STATIONARY PHASES

The polysaccharide chiral stationary phases (CSPs) Chiralcel OD and Ch iralpak AD, and the macrocyclic antibiotic CSPs Chirobiotic V and Chir obiotic T were evaluated in packed column subcritical fluid chromatogr aphy (pSFC) for the separation of different types of racemic compounds (beta-blockers, beta-agonists, benzodiazipines, non-steroidal anti-in flammatory drugs, barbiturates, free and derivatized amino acids, etc. ). The same conditions and program could be applied to check the appli cability and enantioselectivity of one of the CSPs for a given racemic mixture. The conditions are: temperature 30 degrees C, pressure 200 b ar, flow-rate 2 ml/min, carbon dioxide, modifier methanol containing 0 .1% trifluoroacetic acid (TFAA) and 0.1% triethylamine (TEA) with a gr adient from 5% (5 min) to 30% at 5%/min. A resolution of 0.4 under tho se conditions generally indicates that baseline separation can be real ized on the CSP by fine-tuning the different parameters of the SFC sep aration. The best CSP for pSFC proved to be Chiralpak AD which provide d separation for 70% of the 44 substances tested, followed by Chiralce l OD (66%), Chirobiotic T (50%) and Chirobiotic V (48%). For compariso n, the enantioselectivity in pSFC of the brush type CSPs Chirex 3022 w ith pi-donor characteristics and Chirex 3005 with pi-acceptor characte ristics was also evaluated. As expected, these phases perform poorly u nder SFC conditions, on Chirex 3022 (34%) and on Chirex 3005 (20%). (C ) 1997 Elsevier Science B.V.