Analytical Sciences

Simultaneous Determinations of the Concentration and Molecular Weight of Humic Substances in Environmental Water by GelChromatography with a Fluorescence Detector

Etsu YAMADA,*^,** Ž€Û¬enichi DOI,* Katsuya OKANO,* and Yasuro FUSE**

*Department of Chemistry and Material Technology, Kyoto Institute of Technology,Matsugasaki, Sakyo, Kyoto 606-8585, Japan
**Center for Environmental Science, Kyoto Institute of Technology,Matsugasaki, Sakyo, Kyoto 606-8585, Japan

Simultaneous determinations of the concentration and molecular weight of humic substances in concentrated andunconcentrated environmental water samples by gel chromatography with a fluorescence detector were carried out. Thecalibration curves of humic acid and fulvic acid were linear in the concentration range of 0.1 to 10 mg/l. The relativestandard deviations of humic substances were less than 10%. The concentrations of aquatic humic substances in riverswere high in the summer and low in the winter. The molecular weight of most humic substances in Katsura, Uji, Kidzuand Yodo Rivers was estimated to be about 3000 - 10000. The ratio of the higher molecular weight of humic substanceswas larger in the warmer season than that in the cooler season. The main origin of aquatic humic substances in riverwater may be humic substances from soils around the rivers.

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