SEPARATION OF TRANS/CIS-CAROTENE ALPHA-CAROTENE AND BETA-CAROTENE BY SUPERCRITICAL FLUID CHROMATOGRAPHY .1. EFFECTS OF TEMPERATURE, PRESSURE AND ORGANIC MODIFIERS ON THE RETENTION OF CAROTENES

A partial separation of the isomers of alpha- and beta-carotenes has previously been achieved by non-aqueous reversed-phase chromatography on octadecyl silica columns eluted with mixtures of hexane and polar modifiers. We show that improved results are obtained by the use of mobile phases based on liquid or supercritical carbon dioxide. Polar modifiers have similar effects on chromatographic selectivity in the non-aqueous reversed-phase and supercritical fluid chromatography systems, suggesting that the retention mechanism is the same in both cases (predominantly partition). With the carbon dioxide-based mobile phases, it was possible to optimize chromatographic efficiency by varying the temperature and pressure. The use of both binary and ternary mixtures was investigated.