Fractionation of humic acids according to their hydrophobicity, size, and charge-dependent mobility by the salting-out method

Humic acids (HAs) represent heterogeneous and polydisperse mixture of molecules that differ in their chemical structure, composition, and functional properties. Fractionation of HAs is of key importance for understanding their interactions with various organic and inorganic compounds, for studying t...

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Bibliographic Details
Published in:Eurasian soil science 2008-12, Vol.41 (12), p.1294-1301
Main Authors: Zavarzina, A. G., Vanifatova, N. G., Stepanov, A. A.
Format: Article
Language:English
Subjects:
Acids
Agricultural ecosystems
Ammonium
Ammonium sulphate
Analysis
Chromatography
Earth and Environmental Science
Earth Sciences
Fractionation
Geochemistry
Geotechnical Engineering & Applied Earth Sciences
Humic acid
Humic acids
Inorganic compounds
Methods
Natural environment
Physiological aspects
Salt
Soil Chemistry
Soil sciences
Sulfates
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Summary:Humic acids (HAs) represent heterogeneous and polydisperse mixture of molecules that differ in their chemical structure, composition, and functional properties. Fractionation of HAs is of key importance for understanding their interactions with various organic and inorganic compounds, for studying their physiological activity, and for predicting their behavior in natural environments and agroecosystems. Existing fractionation methods are rather laborious and time consuming, which limits their application in fundamental science and industry. It is shown that fractionation of humic acids with ammonium sulfate ensures their preparative separation with respect to (a) hydrophobicity, (b) molecular size, and (c) charge dependent on the amount of functional groups. Salting out at the lowest and highest degrees of saturation with ammonium sulfate, upon which precipitation of the molecules occurs, makes it possible to separate humic acids into functionally different high-molecular-weight/hydrophobic and low-molecular-weight/hydrophilic fractions. The first fraction is characterized by a lower electrophoretic mobility than the second fraction. The weight percentage of the components coagulated at the lowest degree of salt saturation can be used as a quantitative parameter for comparing hydrophobic properties of humic acids. Salting out is recommended as a fast, simple, and cheap alternative to chromatographic methods for preparative separation of humic acids if large amounts of functionally different fractions need to be obtained.
ISSN:1064-2293
1556-195X
DOI:10.1134/S1064229308120065