Continuous-flow injection analysis of aqueous environmental samples for chemical oxygen demand

Abstract

A method is described for the continuous, rapid determination of chemical oxygen demand (COD). The method is based on flow injection analysis (FIA) and uses acidic potassium permanganate solution as both an oxidant and a spectrophotometric reagent, and glucose as a standard. COD values for aqueous environmental samples, such as industrial wastewaters, are compared with those obtained using the Japanese Industrial Standard (JIS) method and are found to be within an error range of ±30%. The method is comparable to other manual and automatic methods and has several advantages. A sampling rate of 20 samples per hour can be achieved, and the detection limit and precision are 5 mg l^–1 as COD and 0.6%, respectively. Chloride ion up to levels of 6000 mg l^–1 does not interfere, even in the absence of silver salts.