OPTIMIZATION OF MOBILE PHASES FOR HPLC OF CIS-TRANS CAROTENE ISOMERS

Various methanol-based, binary and ternary solvent systems were compared with respect to resolution of cis isomers of alpha and beta-carotene by reversed-phase HPLC. A ternary system : acetonitrile-methanol-methylene chloride (75:15:10), or a binary system : acetonitrile-methanol (90:10 or 5:95) provided the best separation of beta-carotene and its four cis isomers, 9-cis, 13-cis, 15-cis and 13,15-di-cis-beta-carotene. The elution order of 9-cis and 13-cis-beta-carotene was dependent on the methanol concentration. Methanol-methylene chloride (99:1) resolved alpha-carotene and its three cis isomers, 9-cis, 13-cis, and 15-cis-alpha-carotene. It also proved the best for simultaneous separation of cis isomers of alpha and beta-carotene. Sample solvent can affect the separation efficiency of each isomer. The presence of cis isomers of alpha and beta-carotene in fresh and cooked carrots was also determined.