Spectrophotometric Titration for Fulvic Acids Extracted from Soil and Water

摘要

Structural studies of humic substances are done mainly by NMR methods. Knowing about two different humic acid fractions with different adsorption characteristic, it has become apparent that the positional relationship of the acid dissociation functional group and the hydrophobic skeleton part as well as the quantity ratio of the two parts is important to grasp a function characteristic of humic substances. Thinking about a characteristic of the binding to metal ions, information about kind and quantity of coordination atoms and functional groups is essential. As a second point to understand the binding selectivity, information of adjacent molecular groups to coordinate the functional group which affects the donor-acceptor property of the coordination atom and the solvation state around the coordinate functional group must be important. UV-Vis absorption spectroscopy of humic substances tend to be abandoned because of the insufficient information. On the other hand, two dimensional NMR methods are useful to get information about the neighboring group, but one has to consider low sensitivity, long measuring time and high costs. We expect to develop a information extraction technology and get useful information about neighboring group around the ligand by using UV-Vis absorption spectroscopy which has relatively low costs and high versatility.