Abstract: An apparatus for measuring chemical oxygen demand (COD) in industrial waste water, based on the principle of flow injection analysis (FIA), is described. The apparatus is simple and inexpensive and constructed by components, such as a double plangent pump, sampling valve, flow cell, spectrophotometer and recorder, commercially available for high performance liquid chromatography. Polytetrafluoroethylene (Teflon) tubing is used for mixing coils and transmission lines. The operating conditions are determined by using glucose as the standard COD substance. The peak heights obtained for various concentrations of aqueous glucose solutions correspond to their manual COD values obtained by the JIS (Japan Industrial Standard) method.

Abstract: A flow cell was constructed from plexiglass. The cell was designed to allow insertion and removal of a Clark-type oxygen membrane electrode. It was used in a flow system to amperometrically determine glucose and glucose oxidase via oxygen depletion. Hydrogen peroxide was determined by oxidation at +0.9 V vs. the silver/silver chloride electrode by removing the electrode membrane. Alternatively, a lead dioxide catalyst electrode was constructed and inserted into the cell to catalytically decompose hydrogen peroxide to oxygen, which was detected. Molybdenum (VI) was determined by its catalytic effect on the reaction between hydrogen peroxide and thiosulfate.