Separation and characterization of humic acids and metal humates by electrophoretic methods

A modified buffer for the separation of humic acids (HA) by capillary zone electrophoresis (CZE) was studied. The addition of hydroxycarboxylic acids to borate buffer makes a more efficient separation of HA possible. Two sharp peaks are obtained. Preparative isolation of these two fractions can be reached by applying the conditions used in CZE to free-flow electrophoresis (FFE). The fractions obtained were characterized by repetition of the CZE procedure. Also metal complexes of HA were investigated by electrophoretic methods. In the presence of metal cations, HA form stable complexes of different electrophoretic mobility. These complexes can be separated by free-flow isotachophoresis (FF-ITP). The different fractions are analyzed by CZE, ultraviolet-visible and atomic absorption spectrometry. Significant changes in both the ITP-pattern of the FFE and the 'humic hump' in CZE demonstrate the influence of complexation on the macromolecules.