Method for simultaneous direct estimation of glucose and xylose in serum.

A direct procedure for measuring serum monosaccharides is presented. Borate intensifies the colors produced when these substances react with o-toluidine, which, in the case of glucose and xylose, have absorption maxima at 480 nm and 630 nm, respectively. Thus, these sugars may be determined singly or simultaneously in a single sample by differential spectrophotometry. An alternative technique in which glucose oxidase and o-toluidine are used is also presented for the estimation of xylose and other pentose sugars in the presence of glucose. These two techniques permit the measurement of a pentose and a hexose other than glucose in protein solutions containing glucose. The techniques have a high degree of correlation and reproducibility. The effects of such variables as reagent concentration, reaction time, and borate concentration on the o-toluidine reaction are presented, along with an evaluation of bilirubin and hemoglobin interference.