An improved technique for concentration measurement of galactomannan solutions by differential refractive index

Galactomannans such as guar gum and locust bean gum are naturally occurring polysaccharides which have been widely used in various industries. One of the issues when dealing with these galactomannans is that they do not dissolve completely into water; therefore the actual dissolved concentration of the solution will always be ambiguous. In this article, we present an easy and robust method for determining the concentration of galactomannan solutions by utilizing a Differential Refractive Index (DRI) detector. Calibration charts for guar gum and locust bean gum were constructed for the DRI method, with the accuracy of results being compared to that of the traditional phenol–sulfuric acid method. The results of this investigation showed that the DRI method is a more accurate and reliable technique for determining the concentration of galactomannan solutions, having an average error of ±0.5% compared to ±5.0% for the phenol–sulfuric acid method.