Volatile Organic Acids in Lake Water;Their Gas Chromatographic Determination and Ecological Significance

Abstract

Gas chromatographic analysis of volatile organic acids dissolved in lake water was conducted by using their benzyl esters, which were well separated and determined in the ng order of magnitude. Thus, only 50-250ml of the lake water was needed for the determination of the volatile organic acids. The identification of benzyl esters of these organic acids was conducted by combined gas chromatography-mass spectrometry. Acetic, propionic, n-butyric and lactic acids were found in the water samples from Lake Kizaki. However, formic acid was identified only by the retention time from gas chromatography. Formic, acetic and propionic acids measured were in the range of 0-30μgC/l, 30-120μgC/l and 0-90μgC/l, respectively, in the various depths of Lake Kizaki.Gel-filtration using Sephadex G-25 was applied to determine the molecular weight distribution of dissolved organic matter of the water sample from the surface of Lake Kizaki. Volatile organic acids consisting of formic, acetic and propionic acids accounted for 59% of the dissolved organic carbon in the fraction of organic matter with a molecular weight of less than 200. Considering the short residence time as reported by several authors, the volatile organic acids were suggested to be the most ecologically significant materials in the matter cycle in the lake waters.