EVALUATION OF HUMIC-ACID FRACTIONS BY FLUOROMETRY AND C-13 NMR-SPECTROSCOPY

Freeze-thaw cycles were used to produce morphologically dissimilar hum ic acid fractions that showed evidence of possessing distinctly differ ent molecular features. The kinetics of fluorescence enhancement produ ced by the addition of Sm3+ ions to pyrene/humic acid solutions indica ted that the ability to form pseudomicellar domains was vastly differe nt among the fractions. C-13 NMR spectra bore out the suggestion that the tendency of humic acid fractions to undergo intramolecular coiling is related to their aliphatic content. Published by Elsevier Science B.V. All rights reserved.