The structural characterization of humic acids (HAs) is a focal point in understanding and establishing a relationship between their structure and biological properties. However, the complexity of HAs seriously limits the application of a single analytical technique. For a better understanding of HAs role in the environment, it is necessary to develop methods which can provide a complete characterization of HA structure. Humic acid extracted from the A horizon of a Chernozem (Boroll, USDA Soil Taxonomy) soil and their fractions (A, B and C+D) with different molecular size (MS) obtained by coupling size exclusion chromatography and polyacrylamide gel electrophoresis (SEC-PAGE) were investigated using thermal (TG-DTA), spectroscopic (DRIFT) and isotopic ( d 13C) analyses. Moreover, the molecular structure of the high temperature stable fraction (residues obtained by stopping the heating of the sample in TG-DTA apparatus at 400°C) was studied by DRIFT spectroscopy. The highest MS fraction (A) were characterized by the highest contents of aliphatic, carboxyl groups, carbohydrates and amino acids than the B and C+D fractions. Instead, the C+D fraction, that was 36% of HA (w/w), seems to be characterized by a higher content in aromatic compounds, in particular in benzoic derivatives, than the other fractions. A shift of δ 13C to more negative values was observed in the lowest MS fractions (B and C+D). The aromatic structure of A and B residues seems to be more complex than that of C+D residue.
Montecchio D., Cavani L., Gioacchini P., Francioso O., Trubetskaya O., Trubetskoj O., et al. (2009). Thermal and Spectroscopic Analyses applied to the study of different molecular size humic acids. COLORADO SPRINGS : Colorado State University.
Thermal and Spectroscopic Analyses applied to the study of different molecular size humic acids
MONTECCHIO, DANIELA;CAVANI, LUCIANO;GIOACCHINI, PAOLA;FRANCIOSO, ORNELLA;CIAVATTA, CLAUDIO
2009
Abstract
The structural characterization of humic acids (HAs) is a focal point in understanding and establishing a relationship between their structure and biological properties. However, the complexity of HAs seriously limits the application of a single analytical technique. For a better understanding of HAs role in the environment, it is necessary to develop methods which can provide a complete characterization of HA structure. Humic acid extracted from the A horizon of a Chernozem (Boroll, USDA Soil Taxonomy) soil and their fractions (A, B and C+D) with different molecular size (MS) obtained by coupling size exclusion chromatography and polyacrylamide gel electrophoresis (SEC-PAGE) were investigated using thermal (TG-DTA), spectroscopic (DRIFT) and isotopic ( d 13C) analyses. Moreover, the molecular structure of the high temperature stable fraction (residues obtained by stopping the heating of the sample in TG-DTA apparatus at 400°C) was studied by DRIFT spectroscopy. The highest MS fraction (A) were characterized by the highest contents of aliphatic, carboxyl groups, carbohydrates and amino acids than the B and C+D fractions. Instead, the C+D fraction, that was 36% of HA (w/w), seems to be characterized by a higher content in aromatic compounds, in particular in benzoic derivatives, than the other fractions. A shift of δ 13C to more negative values was observed in the lowest MS fractions (B and C+D). The aromatic structure of A and B residues seems to be more complex than that of C+D residue.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
