Characterization of Humic Substances by Functional Groups and Spectroscopic Methods

The present study was carried in the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Rajendranagar. The humic and fulvic acids were extracted, isolated and purified from manures and were studied for their functional groups and spectroscopic methods. It has been found that the total acidity (9.4 me g-1), carboxyl group (6.2 me g-1) and phenolic-OH (3.2 me g-1) groups were higher in case of fulvic acid compared to humic acid (7.2, 4.2 and 3.0 me g-1 respectively). Among these functional groups, the percent contribution of carboxylic groups towards total acidity was higher than that of phenolic-OH groups in both humic fractions. The ratio of optical densities at 465 and 665 nm i.e. E4/E6 ratio was higher in case of fulvic acid (6.17) compared to humic acid (4.34). The UV spectra of humic and fulvic acid were similar in nature in spite of the differences in their composition and showed a decreasing optical density with increasing wavelength.