Selective determination of sugars manifesting enediol isomerism by means of reaction with tetrazolium

Abstract

Tetrazolium derivatives in aqueous solution at pH 12.4 are readily reduced at 37[degree] by sugars manifesting enediol isomerism, but not by sugars in which such isomerism is impeded by presence of a substituent in a carbinol group vicinal to the carbonyl group. A method is presented for the determination of 6-R-fructose and fructose in the presence of 1-R-fructose, and of aldose in the presence of 2-deoxyaldose by means of reaction with tetrazolium derivatives. Conditions are defined in which the rate of the reduction is a linear function of the sugar concentration over a wide concentration range. The use of 2:5-diphenyl-3-(4-styrylphenyl)-tetrazolium in this reaction permits smaller amounts of sugar to be determined than was possible with the use of 2:3:5-triphenytetrazolium. The selectivity of reaction as between 6-R-and 1-R-fructose is abolished if certain alcohols at high concentration are present in the reaction mixture during formazan production.