B. Varga et al., Secondary structure of humic acids. Can micelle-like conformation be proved by aqueous size exclusion chromatography?, ENV SCI TEC, 34(15), 2000, pp. 3303-3306
Citations number
27
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
Understanding the chemical and secondary structures of humic substances is
essential to predict their interactions with organic and inorganic pollutan
ts in the environment. Humic substances are suggested by some to form micel
les under certain conditions. Disruption of the hypothesized micelle-like s
tructure by the addition of organic acids was reported earlier based on obs
erved retention shift in size exclusion chromatographic analyses. In this w
ork the effects of added organic and inorganic acids on the retention shift
are studied in humic acid samples. Parameters such as eluent pH, salt conc
entration, and buffer capacity were examined simultaneously with the additi
on of organic and inorganic acids to the samples. The results suggest that
the retention shift was not the consequence of micellar disaggregation but
secondary (mainly hydrophobic) interactions caused by the pH change on the
stationary phase were responsible. Therefore, micellelike structure of humi
c substances cannot be confirmed solely on the basis of the change in reten
tion volumes. For the characterization of humic substances by size exclusio
n chromatography secondary interactions (ionic and hydrophobic) should also
be considered.