Abstract
Two methods of estimating actual vitamin A are described, one is the indirect and the other is the direct. The indirect method is the estimation of the actual vitamin A by substracting the non-A values from the total. The unsaponifiable matter of liver oil is usually composed of 4 fractions and can be detected by the fluorescence in ultraviolet light or color reaction with SbCl3 reagent. The non-A fractions are stable but vitamin A is destroyed in the course of chromatography, which takes about two hours.
Using weakly activated alumina in form of adsorption column of short length the actual vitamin A fraction can be rapidly collected and estimated with complete recovery. The collected A fraction shows the absorption curve corresponding to the pure vitamin A alcohol, free from kitol. Vitamin A and kitol can be chromatographically sharply fractionated.
Kitol shows about 1/1000 of fluorescence of vitamin A alcohol and by GDH method about 1/71, by Carr-Price method about 1/20 of vitamin A on the weight basis.
The vitamin A values determined by the direct method agree quite well with those by the indirect method.
