Absolute molecular weight and molecular weight distribution of guar by size exclusion chromatography and low-angle laser light scattering

A procedure to determine the absolute weight-average molecular weight (M_w) and molecular weight distribution (MWD) of guar by aqueous size exclusion chromatography coupled with low angle laser scattering is described. It is shown that for a rigorously purified sample of guar solution the values for M_w and MWD are 2·2×10⁶ and 1·9 respectively. The effect of sample preparation and purification on these molecular parameters are discussed. Limitations and challenges in the aqueous size exclusion chromatography of complex water soluble polymers such as guar are also explored.