Separation of serum carotenoids and vitamin A on chromsil-amino and -cyano phases by a bi-directional gradient elution technique.

Vitamin A, beta-carotene, lycopene, beta-cryptoxanthin, lutein and zeaxanthin can be simultaneously separated in human serum extracts by normal-phase liquid chromatography. Two stationary phases (containing amino and cyano groups, respectively) were investigated. With a bi-directional (up-down) gradient-elution technique both packings are useful for the determination of serum levels of carotenoids and retinol in serum extracts. The small sample size, the simplicity of extraction, and a good reproducibility render these procedures ideal for clinical use.