Separation of carotenes on cyclodextrin-bonded phases

The separation of carotenoids and retinoids on a beta-cyclodextrin-bonded stationary phase with conventional mobile phases is reported. Compounds studied include beta-carotene (all-trans), 15,15'-cis-beta-carotene, 7,8,7',8'-dihydro-beta-carotene, alpha-carotene, lycopene, lutein, zeaxanthin, retinal, retinol, retinol palmitate and retinol acetate. The best resolution of carotenes was obtained with low concentrations (less than or equal to 1%) of polar solvents (e.g., 2-propanol or ethyl acetate) in hexane or cyclohexane. Xanthophylls required much higher concentrations of polar solvents. The best solvent for the resolution of lutein and zeaxanthin was found to be dichloromethane. The resolution of cis/trans-isomers and the tentative identification of other isomers present in newly synthesized carotenoid standards is also reported. All-trans-isomers were found to be eluted before cis-isomers.