CAPILLARY ELECTROPHORESIS FOR THE CHARACTERIZATION OF HUMIC SUBSTANCES

The potential of capillary electrophoresis (CE) has been demonstrated for the analysis and characterization of humic substances (fulvic and humic acids). Humic substances were effectively separated by capillary gel electrophoresis (acrylamide gel CGE) and CE with cellulose deriva tive solutions using a 50 mM tris-borate buffer (pH 8.3) with 2 mM EDT A, or 5% polyvinylpyrrolidone (PNVP). They were detected by UV absorpt ion at 260 nm and by emission at 490 nm (excitation at 390 nm). The us ing these gel systems leads to the separation of humic substances into two fractions, which comprise lower-molecular weight components as we ll as higher ones. The addition of iron (III) chloride resulted in a d ecrease in the peak of the lower molecular-weight components, which mo st likely arose from an aggregation of the lower-molecular weight frac tion due to binding bond formation through the hydrolyzed Fe(III) ion. When sodium hypochlorite solution was added to the humic substance, s ome peaks decreased with increasing the residual chlorine concentratio ns. Therefore, the gel-mode CE enables one to monitor the reaction beh avior as well as the fate of humic substances in an aquatic system in relation to the binding of metal ions and the oxidation processes.