FLOW DETERMINATION OF DISSOLVED INORGANIC CARBON USING THE ALTERNATE WASHING SYSTEM EQUIPPED WITH A POTENTIOMETRIC GAS ELECTRODE

The alternate washing system equipped with a potentiometric carbon dioxide sensitive gas electrode was prepared for the determination of dissolved inorganic carbon. The design of this system is based on the alternate introduction of a sample solution and a washing stream into a flow cell by means of a four-way valve controlled by a microcomputer. This enables simple, quick, and selective determination of dissolved inorganic carbon in discrete samples. The limit of linear response was ca. 2 X 10(-4) M. Determination at pH 5 is proposed because the interference from various volatile weak acids such as nitrite, sulfide, or hydrogen sulfite can be much reduced without sacrificing sensitivity. This system was applied to natural water analysis, and the results were compared with those of alkalinity.