The influence of tocopherols on U. S. P. XIV vitamin A assay

Abstract

The Morton-Stubbs procedure in the assay of vitamin A is subject to considerable over-correction when tocopherols are present. A procedure is described which circumvents the difficulty by employing a tocopherol-containing blank. The blank is prepared by shaking the vitamin A-tocopherol solution in hexane with 60 per cent sulfuric acid, followed by reading the acid-treated solution against the untreated solution. Data are presented indicating the effectiveness of the procedure in eliminating the difficulty.