A METHOD FOR DETERMINING CONCENTRATIONS OF RETINOL, TOCOPHEROL, AND 5 CAROTENOIDS IN HUMAN PLASMA AND TISSUE SAMPLES

To explore the relation between plasma and tissue concentrations of seven fat-soluble micronutrients (retinol, alpha-tocopherol, lutein, cryptoxanthin, lycopene, alpha-carotene, and beta-carotene), we developed methods for clarifying plasma and tissue samples and quantitating these seven analytes simultaneously by using HPLC with ultraviolet detection. Clarification of tissue samples was performed by using enzymatic digestion followed by mechanical homogenization; saponification was avoided and tocopherol nicotinate was used as an internal standard. Precision and sensitivity for small samples of plasma and solid tissues were determined. Accuracy for plasma samples was assessed by comparing results obtained by using this method with those obtained by using older, standard methods. Results from application of this method to patient samples of plasma and various tissues are presented. This method will be of interest to investigators seeking to quantitate these seven micronutrients in solid tissue samples, but desiring to avoid the usual saponification step required in most other reported techniques.