Development of a dissolved carbon dioxide sensor based on a coulometric titration

This paper presents a sensor for the determination of dissolved carbon diox ide in water and seawater, respectively. The gas diffuses through a hydroph obic gas-permeable membrane and reacts with an alkaline electrolyte causing a ptr-value shift which is detected by an iridium oxide pH-electrode. The duration of the pH-shift within a specified pH-interval is measured and thi s so-called measuring period is correlated with the partial pressure of dis solved carbon dioxide in the sample. To start a new cycle, the initial pH-v alue is reached again by generating hydroxide ions electrochemically. The s ensor allows determination of dissolved carbon dioxide in water in the rang e from 30 to 180 ppm. (C) 1999 Elsevier Science S.A. All rights reserved.