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

This paper presents a sensor for the determination of dissolved carbon dioxide in water and seawater, respectively. The gas diffuses through a hydrophobic 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 this so-called measuring period is correlated with the partial pressure of dissolved carbon dioxide in the sample. To start a new cycle, the initial pH-value is reached again by generating hydroxide ions electrochemically. The sensor allows determination of dissolved carbon dioxide in water in the range from 30 to 180 ppm. (C) 1999 Elsevier Science S.A. All rights reserved.