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Journal of Water Supply: Research and Technology—AQUA Vol 57 No 1 pp 35–44 © IWA Publishing 2008 doi:10.2166/aqua.2008.029

UV absorbance ratio index with size exclusion chromatography (URI-SEC) as an NOM property indicator

Namguk Her, Gary Amy, Jinsik Sohn and Urs von Gunten

Korea Army Academy at Yeong-cheon, PO Box 135-1, ChangHaRi GoGyeongMyeon, YeongCheon City GyeongBuk, 770-849, Korea Tel.: +82-10-5078-2894 Fax: +82-54-335-5790 namguk@daum.net
UNESCO-IHE Institute for Water Education, Westvest 7, 2601 DA, Delft, The Netherlands
Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul, 136-702, Korea
Swiss Federal Institute for Aquatic Science and Technology (EAWAG), Ueberlandstrasse 133, CH-8600, Dubendorf, Switzerland


An advanced approach is presented for identifying and characterizing biopolymers of natural organic matter (NOM) in water samples. It involves a simple method encompassing the ratio of peak heights of high performance size exclusion chromatography (HPSEC) chromatograms based on ultraviolet absorbance (UVA) detection at 210 nm and 254 nm. The HPSEC system eliminates inorganic interferences by separation and makes it possible to obtain ratio values associated with organic components as a function of molecular weight (MW). Certain biopolymers show a distinctive ultraviolet absorbance ratio index (URI, UVA210/UVA254) because they contain different compositional proportions of UV-absorbing functional groups and sp2-hybridized carbon. URI values were found to be the lowest for humic acids (1.59 for a humic acid, highest aromaticity), intermediate for fulvic acids (1.88 for a fulvic acid, intermediate aromaticity), and highest for proteins (13.5 for BSA, lowest aromaticity). URI increases with the degree of eutrophication of natural waters by the increase of microbially derived components that have a high functional group proportion with a low sp2-hybridized carbon, and increases with oxidation (e.g. ozonation) by the cleavage of unsaturated bonds (decrease in unsaturated bonds and increase in functional group proportions).

A particular functional group displays its characteristic chemical behaviour when it is present in a compound. The chemical behaviour of NOM is highly related to its functional groups. The concept of URI considers the main functional groups of NOM and can act as an important water quality index. It may be used as a surrogate for assessing the effects of oxidation of NOM. The method is simple and can be easily applied to characterization of bulk water samples.

Keywords: biopolymers; high performance size exclusion chromatography (HPSEC); natural organic matter (NOM); UV absorbance ratio index (URI UVA210/UVA254)

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