A COLORIMETRIC METHOD FOR MEASURING INDICAN

Abstract

A qualitative test for indican (indoxyl-O-sulphate, usually as the potassium salt) has been adapted for the quantitative measurement of indican. The method involves the condensation of indican and p-dimethylaminobenzaldehyde in the presence of acid to yield an orange-colored compound. When an excess of sodium acetate is added, the orange-colored reaction product is converted to a cherry-red derivative. The effects of time, acids, temperature, and concentration of reagents on the reaction have been studied and optimum conditions have been selected to obtain a standard curve.Unsatisfactory analytical results are obtained when this method is applied directly to urine samples and a method for the quantitative elution of indican from charcoal columns has, therefore, been devised. With this modification quantitative recoveries have been achieved with indican alone and with indican added to urine samples.In addition a review of the literature pertaining to indican measurement and indigoid pigments is presented.