Chemical Oxygen Demand (COD) Sensor Using a Stopped-Flow Thin Layer Electrochemical Cell

Abstract

A chemical oxygen demand (COD) sensor employing a stopped-flow thin layer electrochemical cell has been constructed. The coulometric charge required for exhaustive electrolysis of samples was measured and correlated with the COD evaluated by the Japanese conventional method using permanganate. A single measurement took 2–6 minutes, depending upon the kind or the concentration of the sample, much less than the two hours required in the conventional method. For lake water samples, a linear relationship (r=0.912, n=17) was observed between both methods in the range allowed by the Environmental Quality Standard of Japan. Linear sweep voltammetry was performed using both real samples and standard compounds considered to be of environmental significance (D-glucose, glycine, L-glutamate, phenol, hydroquinone, quinone, lignin, tannic acid, hemicellulose and humic acid) and exhaustive electrolyses of L-glutamate, lignin, tannic acid and hemicellulose were performed. The overall results indicated that lignin accurately represented the behavior of the real samples.