DETERMINATION OF CHEMICAL OXYGEN-DEMAND IN AQUEOUS ENVIRONMENTAL-SAMPLES BY SEGMENTED FLOW-INJECTION ANALYSIS

A method is described for the determination of chemical oxygen demand (COD) in aqueous environmental samples by segmented flow-injection analysis. KMnO4 solution is used as both an oxidant and a spectrophotometric reagent and D-glucose as a standard. When the reaction temperature is 95-degrees-C, the residence time is about 8 min and a sample throughput of 80 h-1 can be achieved. The detection limit and relative standard deviation are 2 mg l-1 and 0.7%, respectively, and the recovery is 85-95%. Chloride ion up to levels of 1500 mg l-1 does not interfere. COD values for aqueous environmental samples are compared with those obtained using the Japanese Industrial Standard method and agreed within an error range of +/- 10%.