Vol. 5, Issue 10, Part E (2019)

Abstract
The determination of reducing sugars, especially glucose, is of considerable interest. An assay attributed to Miller using 3, 5-dinitrosalicyclic acid (DNS) is widely used but suffers from some limitations. It is, nonetheless, convenient and recommended by the IUPAC Commission on Biotechnology for measuring cellulase activity. We found that 5-10% concentrations of methanol, ethanol, 1- and 2-propanol interfered with the DNS assay and gave a positive error (an apparent increase in glucose) when aqueous standards were used for calibrating the assay. For ethanol concentrations beyond about 15%, the assay gave a negative error. In the case of ethanol, this was due to an effect of ethanol on the color- forming reaction as well as a slight effect on the spectral absorbance of the product.