Carbon dioxide sensors

are made as single-use sensors, measure contact-free and belong to the optical sensors ²⁰. The sensors have a gas-permeable membrane and are based on a pH-sensitive dye in a HCO₃^--buffer solution. If CO₂ is present in the culture broth, it diffuses through the gas-permeable membrane into the HCO₃^--buffer solution and changes its pH value. This is detected with the sensor and allows the pCO₂ concentration to be determined afterwards using the Henderson-Hasselbach equation ²⁰.