Rapid method for determining ascorbic acid concentration

Abstract

In the course of investigations on the effect of citrus fruits upon the human organism it was found n ecessary to develop a method of determining the vitamin C content of the blood of a lar ge number of individuals in a short time. In this method the plasm a is n ot deproteinized but is diluted with 5-percent a cetic a cid and used directly in a sp ecially constructed photoelectric compara tor with the d ye 2,6-dichlorophenolindop henol.2 The ascorbic acid content of t he plasma sample is read directly from empirical calibra t ion curves determined by adding k nown amounts of ascorbic acid to blood plasm a. The comparator is operat ed so as to compensate autom atically for the us ual variation in the turbid ity and color of plasma samples. While the method is qui te rapid, once it is in opera tion, some time must be sp ent in preparing calibrat ion curves. The maximum t ot al errol' in the determination on p lasma samples containing fr om 0 to 3.5 mg of reduced ascorbic acid per 100 ml of plasma was estimated to b e ± 0.1 mg/ 100 m1. CONTENTS P age I. Introduction__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 117 II. Apparatus __ ____ ________ __ ____ ____________ ____ ________ _________ _ 11 9 III. Procedure ______ ________ ________ __ ____ ___ ___ ____________________ 121 IV. Calibration curves __ ______ ____________ _____ ___ ____ ___ ___ _________ 122 1. Blood ana lyses ____________ ___ ___ _______ ___ ____ __ ____ _____ 122 2. Urine analyses ____ ______ ___ ___ __ ___ ____ _____ ____ __ ___ _____ 125 V. Sources of error _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 126 VI. R eferences _____ ___ ____ __ ______ ____ ___ _____ _____ ___ ____ ______ __ __ 128