The application of the Spekker photoelectric absorptiometer to the determination of vitamin C

Abstract

Interference from non-specific reductants in the titration of ascorbic acid with 2.6 dichlorophenolindophenol is minimized by a step-titration procedure, involving photo-electric measurement of the colour due to excess indophenol in a series of mixtures to which increasing amounts of indophenol have been added. Measurements on each mixture are corrected for fading of the color by an extrapolation method and the end point of the titration is detd. from a graph added. Satisfactory recovery of ascorbic acid was obtained in the presence of cysteine and glutathione in amts. up to 10 times that of the ascorbic acid itself.