Disposable amperometric CO2 sensor employing bacteria and a miniature oxygen electrode

We have developed a disposable bacterial CO2 sensor employing a miniature Clark‐type oxygen electrode and autotrophic bacteria. To make the sensitive area less vulnerable to stress, to facilitate CO2 diffusion through the sensitive area, and to make the application to biosensors easier, the sensor structure was simplified by immobilizing the bacteria in an oxygen electrode cell along with a 0.1 M KCl electrolyte solution. We developed a novel process that allows immobilization of bacteria in a small sensitive area, thereby improving the response time. The response time of this CO2 sensor ranged from 1 to 3 minutes. A linear relationship was obtained for NaHCO3 concentrations between 0.5 and 3.5 mM (at 32°C and pH 5.5). The CO2 sensor can be used up to 10 times before disposal.