Electrochemical determination of the anionic particle charge of aquatic fulvic acids

The fulvic acid (FA) fractions of humic substances from river water and bog lakes and of humic-like substances from landfill leachates were isolated by the XAD-method and titrated by a cationic polyelectrolyte. The isoelectric point of net charge of the FA samples was calculated by the streaming current detection (SCD)-technique and a new parameter of charge density (aPC) was calculated from the titer volume. The aPC-values of the FA are low for humic like substances (0.22–1.76 μeq/mg DOC) and high (2.41–5.60 μeq/mg DOC) for humic substances. Polarographically determined Cu(II)-complexation capacities (CuCC) of humic-like substances are in good linear relationship to their aPC-values. Even though SCD-signals only supply qualitative information, a useful fingerprint of the FA sample is given by the shape of the titration curve.