Abstract: Ascorbic acid or dehydroascorbic acid is determined by reaction with a tetrazolium salt selected from 3-(4,5-dimethyl-thiazolyl-2)-2,5-diphenyl-tetrazolium bromide, nitrotetrazolium blue, tetrazolium blue chloride and distyryl-nitro blue tetrazolium chloride, in the presence of phenazine methosulphate and a detergent, at a weakly acidic pH value, and evaluating the coloration obtained as a measure of the initial acid content. The method is particularly efficacious in substantially eliminating disturbance of the reaction by foreign substances.

Abstract: In a conventional method for the quantitative determination of substances, particularly in serum, which, by action of an oxidase thereon, combine with oxygen to form hydrogen peroxide and wherein the hydrogen peroxide formed is converted, in the presence of methanol and catalase, to formaldehyde, the formaldehyde is reacted with hydrazone in the presence of ferric chloride, and the dye thus formed is determined photometrically, the improvement comprising using as the hydrazone, 3-methyl-2-sulfonylbenzothiazolone-hydrazone; use of this hydrazone results in the formation of a very easily soluble dye and is suited for use in automatic analyzers.