Development of electrochemical in-situ pH-pCO2 sensor for deep-sea oceanography applications

In recent years, in-situ measurement using pH and pCO₂ sensors has attracted attention in relation to global warming issues. The high precision electrochemical in-situ pH-pCO₂ sensor was developed for measurement of these parameters in seawater. A new pH sensor was used an ion sensitive field effect transistor for the pH electrode and a chlorine ion selective electrode for the reference electrode. For a new pCO₂ sensor, the pH sensor was sealed with a gas permeable membrane filled with inner solution. The pH sensor can detect pCO₂ change as the inner solution pH changes which is caused by penetration of carbon dioxide through the membrane. Several sea tests using this sensor were carried out in various locations of the ocean. High accuracy, quick response, and long-term stability have been achieved. In the field, response speed of the pH sensor is 1 second or less, and measurement accuracy is plusmn0.005 pH. In-situ response time of the pCO₂ sensor was less than 60 seconds.