A colorimetric method for the determination of glucosamine and chondrosamine.

A COLORIMETRIC method for the determination of glucosamine has recently been described by Zuckerkandl and Messiner-Klebermass [1931]. According to their procedure the test-solution, which should contain between 1 and 4 mg. glucosamine hydrochloride, is evaporated to dryness and treated with a freshly prepared solution of sodium methoxide. The free glucosamine base is then cautiously acetylated with acetic anhydride to yield the N-monoacetyl derivative which can be estimated by means of the intense reddish-purple colour that develops when, after a preliminary treatment with dilute alkali, p-dimethylaminobenzaldehyde in acid solution (Ehrlich's reagent) is added. We have found this method unsatisfactory. The acetylation of glucosamine which yields the Nmonoacetyl derivative, under the conditions described by Zuckerkandl and Messiner-Klebermass does not appear to be quantitative and, moreover, rapid fading of the colour that develops on the addition of the p-dimethylaminobenzaldehyde reagent increases the difficulty of colorimetric estimation. That Zuckerkandl and Messiner-Klebermass were aware of the difficulties involved in the use of the method for quantitative purposes is evident from their description of the reaction. They state that the error of estimation is, at the most, 6 %. CH-C. CO. OC2H8 H H OH