Determination of Organic Acids in the Lake Sediment

Abstract

In order to study the detailed distribution and the composition of organic acids present in the lake sediments, a new analytical method was established and applied to the bottom sediments of Lake Biwa. Extraction of organic acids was carried out by the use of the method reported by Miyoshi and Neish. The ethyl ether extract was evaporated to dryness and converted to butyl esters by refluxing in butanol, H₂SO₄ and anhydrous sodium sulfate by Yamashita's method. Using a Hydrogen-flame ionization detector and glass column (3m×3mm i.d.) of SE-52 on chromosorb W on a Shimazu GC-6A, nitrogen flow rate of 40ml/min. and temperature program-ing between 45°C and 220°C at a rate of 6°C/min were selected as optimum condition of acid ester analysis. The average recovery of organic acids by the use of the above procedure was much higher than that of Koyama's silica-gel chromatography.
Identification and determination of organic acids in sediment samples from Lake Biwa were carried out and obtained:
In the bottom sediment, the organic acids detected were formic, acetic and regardless of the location and depth of the bottom sediments. In general Acetic acid was found in the highest concentration. The organic acids were not detected in the interstitial water of the sediment, but were found in adsorbed form on/in the sediment particles.