COMPLEXOMETRIC GEL-PERMEATION CHROMATOGRAPHY OF SOLUBLE HUMIC SUBSTANCES USING SEPHADEX G-25

Sephadex G-25 was used with 0.01 m sodium acetate containing a concent ration of 3 x 10(-5) M Cu(II) as eluent to establish the molecular-siz e distribution (MSD) and the Cu-complexation of molecular-weight fract ions of organic solutes. The appropriateness of this modified gel perm eation method for complexometric measurements on soluble humic substan ces was investigated employing various types of soil solutions. The pr esence of Cu in the eluent had an effect on the MSD obtained by elimin ation of electrostatic repulsion between gel and solutes. No evidence was found that the presence of Cu in the chromatographic system induce d aggregation of the organic substances. The Cu-binding capacity of th e samples as obtained with this gel permeation method was found to inc rease linearly over a wide sample concentration range varying from 40- 2000 mg Cd m-3. No interference was observed between the Cu-complexati on by exclusion and inclusion peaks in the chromatograms. The analyses revealed that the fraction apparently low in molecular weight makes a large contribution to the complexation potential of forest soil solut ions.