Plasma Vitamin A Assay by Fluorometry and Use of a Silicic Acid Column Technique

Abstract

We investigated a new procedure in which silicic acid column chromatography and fluorometry are used to assay plasma vitamin A. Using tritium-labeled vitamin A acetate and vitamin A alcohol as radioactive standards, we identified two fluorescent components in plasma extracts chromatographed on silicic acid columns. One unidentified fluorescent component was eluted first with hexane or petroleum ether. Vitamin A, the second fluorescent peak, was quantitatively eluted with isopropanol. The isopropanol eluates could be immediately assayed fluorometrically without further treatment. The unidentified compound was sensitive to ultraviolet irradiation, which destroyed it slower than vitamin A is destroyed. Values correlated well for plasma vitamin A concentrations, determined by this procedure and by the Neeld and Pearson modification of the Carr-Price colorimetric method (r = 0.871). By our technique, we found 34 µg of vitamin A per 100 ml of plasma in 778 preschool children.