Observations on the chemical method for the estimation of vitamin C

Abstract

Under controlled conditions, the method of Birch et al. (titration with 2:6 dichlorophenol-indophenol) for the estimation of vitamin C gave accurate results provided the conc. of vitamin C was greater than 2 mg./100 cc, that of trichloroacetic acid not greater than 5%, and the time of titration was short. Oxidized ascorbic acid causes erroneous results; 20-25% trichloroacetic acid appears to give the best extractions. The vitamin C value is reduced as much as 67% by allowing the shredded foodstuff to stand 2 hrs. in warm, moist air.