Alkaline hydrolysis of humic substances - spectroscopic and chromatographic investigations

To find out more on the structure of humic substances (HS), isolated dissol ved organic carbon (DOC) samples from a brown water lake and a wastewater e ffluent were fractionated and subjected to alkaline hydrolysis. UV/Vis and fluorescence spectroscopy, as well as size-exclusion chromatography with on -line detection of UV absorption, fluorescence and DOC concentration were u sed to investigate the structural changes caused by the hydrolysis reaction . Following hydrolysis, the fluorescence intensity increased considerably d espite a decrease in the UV absorption. The UV absorption and the DOC data from the SEC experiments revealed a strong shift to smaller molecular sizes after hydrolysis. The spectra of the hydrolysed samples, as well as the si ze-exclusion chromatograms, were compared to spectra of hydroxybenzoic acid s and hydroxycinnamic acids. From this comparison, it can be concluded that the hydrolysis products have a structure similar to these organic acids. ( C) 2001 Elsevier Science Ltd. All rights reserved.