SEPARATION OF TRANS/CIS ALPHA-CAROTENE AND BETA-CAROTENE BY SUPERCRITICAL FLUID CHROMATOGRAPHY .2. EFFECT OF THE TYPE OF OCTADECYL-BONDED STATIONARY PHASE ON RETENTION AND SELECTIVITY OF CAROTENES

Described in this paper are the effects of the type of bonding (monomeric versus arborescent-polymeric) of 22 octadecyl-bonded phases and of carbon loading on the separation of cis and trans isomers of alpha- and beta-carotenes. Only arborescent-polymeric phases afforded the separation of cis and trans isomers, regardless of the degree of carbon loading. Incomplete separation of the alpha- and beta-carotenes is obtained if the capacity factor for alpha-carotene is below 6. Also described is a method for estimating the void volume in supercritical fluid chromatography, derived from the two-solvent weight-difference method used in high-performance liquid chromatography. The porosity values are in good agreement with those reported in the literature.