Oxygen-containing functional groups of the main oxygen-containing functional groups of humic acid is a carbonyl group, a phenolic hydroxyl group, alcoholic hydroxyl group, a carboxyl group, an alkoxy group, quinone group, and various types of humic acid, the variation of the oxygen-containing functional groups is not obvious.
These functional groups are reflected in the following spectral analysis, such as electronic spin resonance (ESR) showed that humic acid has quinone and semi-quinone; Fourier transform infrared (FTIR) spectroscopy has revealed humic acid carbonyl, phenolic hydroxyl , hydroxyl, carboxyl, alkoxy, aromatic, etc.; ultraviolet absorption spectrum in a neighboring 210nm absorption peak derived from aromatic structures; dimensional fluorescence spectra to obtain humic fluorophore full spectral information.
E4/E6 about its meaning, there are different versions. At present, most scholars believe that the degree or with aromatic carbonyl Conjugate relevant. When measured using 0.05mol sodium bicarbonate as a solvent, in a certain concentration range (40 ~ 200mg/kg), in the visible spectrophotometer contrast 465nm (E4) and 665nm (E6) absorbance.
Humic acids from different sources at home and abroad characterization results showed that the differences in structure and composition, which is the source of humic acid, origin and extraction methods and other related.