CHARACTERIZATION OF HUMIC SUBSTANCES BY CAPILLARY ISOTACHOPHORESIS

The use of capillary isotachophoresis (ITP) for the characterization of humic substances was studied. ITP separations of these complex mixtures were considerably improved on the addition of polyvinylpyrrolidone (PVP) to the leading electrolyte. It was preferred to work in the spike mode to improve the interpretability of the isotachopherograms obtained using a photometric detector (405 nm). Interaction of PVP with humic substances was found to differentiate humic and fulvic acids. ITP was useful also for characterizing differences in the molecular weights and hydrophobicities of humic substances fractionated by chromatography on Sephadex G-50 and on Phenyl-Sepharose CL-4B.