Replacement of toxic mobile phases commonly used in high performance liquid chromatography of retinoids

Vitamin A isomers are usually separated and analysed by high performance liquid chromatography (HPLC) using an eluent mixture which contains organic solvents such as n-hexane or 1,4-dioxane. However, both are toxic, n-hexane causes a degenerating nerve disease, whereas 1,4-dioxane is supposed to be carcinogenic. In order to avoid preventive handling and potential hazards to health these solvents have been replaced by various mobile phases of n-heptane/tert-butylmethylether. The advantages are better baseline separation of the main retinol isomers and discrimination of even several di- and tri-cis-retinol isomers, low solvent consumption and no known risk so far to health.