Investigations on the water pollution index. VII On the chemical oxygen demand of amino acids using permanganate.

Amino acids are contained in various effluents and environmental waters and their COD values are adopted as a water pollution index. In this report, chemical oxygen demand (COD) originated from each amino acid was investigated. Acidic and alkaline COD determination was carried out with semimicro method using permanganate. The COD values of most amino acids were linearly increased with their molar concentration. The effect of AgNO3 added into the reaction mixture was evidently recognized and the acidic values of amino acid, L-aspartic acid, increased by 27.5 times compared with those when it was not added. Big differences in COD values were shown among different groups of amino acids. Acidic COD values of amino acids did not reach the plateau values after 30 min's heating as the official method. In the alkaline method, COD values differed very little and showed higher values compaired with the acidic method. Heating time (60 min) was considered to be adequate. The decomposition rate to the theoretical values (complete oxidation) was 19.4% in the acidic and 43.9% in the alkaline method. Therefore the alkaline method will be utilized as a water pollution index of effluents containing amino acids.