Performance of a lifetime-based optode for measuring partial pressure of carbon dioxide in natural waters

This article reports the performance of an improved, newly developed, compact, low power, lifetime-based optical sensor (optode) for measuring partial pressure of dissolved CO2 gas (pCO(2)) in natural waters. The results suggest that after preconditioning, these sensors are stable in water for time periods longer than 7 months. The wide dynamic range of about 0-50000 mu atm opens possibilities for numerous applications of which some are presented. In normal marine environments with pCO(2) levels of 200-1000 mu atm, the best-obtained precision was about +/- 2 mu atm, and the absolute accuracy was between 2-75 mu atm, depending on the deployment and the quality of the collected reference water samples. One limitation is that these sensors will become irreversibly poisoned by H2S and should thus not be deployed in sulphidic environments.