A routine method for the simultaneous measurement of retinol, alpha-tocopherol and five carotenoids in human plasma by reverse phase HPLC.

We describe a simple isocratic HPLC method for the accurate and precise measurement of retinol, alpha-tocopherol and the major carotenoids in plasma using UV detection. Reference ranges for retinol, alpha-tocopherol and five carotenoids are determined in a healthy population group. The most abundant carotenoids found in plasma were beta-carotene, lycopene, lutein and cryptoxanthin. Retinol, alpha-tocopherol and carotenoids were determined simultaneously using two internal standards, retinol acetate for retinol and tocopherol acetate for alpha-tocopherol and carotenoids. The use of echinenone as an internal standard for carotenoids was investigated. The protective effect of an antioxidant (ascorbic acid) on the stability of samples and extracted material is documented. The method is useful for the routine measurement of plasma retinol, alpha-tocopherol and carotenoids and could also be used in large scale epidemiological studies.