Two commonly used ultrafiltration membranes are evaluated for the determination of molecular weights of humic substances. Polyacrylic acids of Mr 2000 and 5000 and two well-characterized fulvic acids are used as standards. Molecular size characteristics of standards, as determined by small-angle X-ray scattering, are presented. Great care in evaluating molecular weight data obtained by ultrafiltration is needed because of broad nominal cutoffs and membrane-solute interactions.
Additional publication details
Evaluation of ultrafiltration for determining molecular weight of fulvic acid