Amperometric sensor for monitoring of dissolved carbon dioxide in seawater

Characteristics of an amperometric CO2 sensor have been investigated for the measurement of CO2 concentration in air and CO2 partial pressure in seawater. Use of RuO2 for the gas permeable pH-dependent electrode, in place of PtO, leads to improved sensitivity. The sensor showed good current response for a wide range of CO2 concentrations in air. For seawater, the partial pressure of CO2 can be measured continuously with the sensor. CO2 from the sample solution permeates into the sensor electrolyte through the membrane in a similar manner as with gas sensing. The CO2 concentration or partial pressure can be detected as a current of pH dependent RuO2 reduction induced by hydrogen ions supplied from CO2.