Conformational arrangement of dissolved humic substances. Influence of solution composition on association of humic molecules
- Univ. di Napoli Federico II, Portici (Italy). Dipt. di Scienze Chimico-Agrarie
The characteristics and quantity of humic substances greatly affects the environmental fate of organic pollutants in soils and natural waters. The authors studied the conformational changes of humic and fulvic acids of different chemical nature by high-pressure size-exclusion chromatography (HPSEC) after dissolution in mobile phases differing in composition but constant in ionic strength. Modification of a neutral mobile phase by addition of methanol, hydrochloric acid, and acetic acid produced, in the order, a progressive decrease in molecular size. Size diminishing was shown by increasingly larger elution volumes at a refractive index detector and by concomitant reductions of peaks absorbance at a UV-vis detector. The decrease of molecular absorptivity (the phenomenon of hypochromism) proved that size reduction of dissolved humic substances was due more to disruption of an only apparent high-molecular-size arrangement into several smaller molecular associations than to coiling down of a macromolecular structure. The most significant conformational changes occurred in acidic mobile phases where hydrogen bondings formation was induced, suggesting that the large and easily disruptable humic conformation was held together predominantly by weak hydrophobic forces.
- OSTI ID:
- 355497
- Journal Information:
- Environmental Science and Technology, Vol. 33, Issue 10; Other Information: PBD: 15 May 1999
- Country of Publication:
- United States
- Language:
- English
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