Development of a miniature pCO₂ electrode for biomedical applications

A miniature pCO₂ electrode for possible CO₂ measurement in a biological system was constructed and evaluated. The pCO₂ electrode employed a miniature pH glass electrode and the Severinghaus configuration. The electrode was evaluated in both gas and liquid phases. A good linear relation existed between the measured electrode potential of the pCO₂ electrode and the logarithm of the CO₂ concentration at 20°C in both gas and liquid phases. The temperature dependence of the electrode over the temperature range of 20-60°C was evaluated. From 20 to 40°C, a change of CO₂ of 0·15%/°C at a CO₂ level of 9·6 mole% was observed. The response time, pCO₂ and temperature-hysteresis effects, and long-term stability of the pCO₂ electrode were also investigated and discussed.