Analysis of water‐soluble polymers using hydrodynamic chromatography

Hydrodynamic chromatography (HDC) has been successfully applied to measurements of the molecular size and molecular size distribution of high molecular weight, water‐soluble polymers. The scope of the method has been probed by experiments with xanthan, a comparatively stiff polysaccharide, and hydrolyzed polyacrylamide, which possesses a more flexible backbone. Separation occurs during convection of dissolved polymer through the interstitial volume of a chromatography column packed with nonporous beads. Nonequilibrium polymer configurations are readily created by the complex flow between these beads. Such altered configurations strongly affect molecular size measurements. To maximize resolution, hydrodynamic stress must be reduced by employing extremely low flow rates. These low flow rates, particularly important for ultrahigh molecular weight samples, unavoidably lengthen analysis time. Conditions under which chromatograms reflect the size distribution of an injected sample are elucidated. A complete description includes selection of column packing, solvent composition, flow rate, column calibration, and sample detection.