In the PCO2 electrode, diffusion of CO2 into the internal electrolyte causes a pH shift that is detected as the sensor signal. Which statement best describes this mechanism?

In the PCO2 electrode, diffusion of CO2 into the internal electrolyte causes a pH shift that is detected as the sensor signal. Which statement best describes this mechanism?

• A. A pH shift occurs
• B. A color change occurs
• C. Turbidity increases
• D. Temperature increases

Answer: (A)

The fundamental idea is that the PCO2 electrode detects a change in pH caused by CO2 entering the internal electrolyte. CO2 diffuses through the membrane into the internal buffer, where it reacts with water to form carbonic acid and then dissociates to increase hydrogen ion concentration. This rise in H+ lowers the pH inside the electrode, and the pH-sensitive transducer converts that pH shift into an electrical signal proportional to pCO2. Color changes, turbidity, or temperature changes are not involved in this mechanism, so they don’t describe how the sensor generates its signal.

The fundamental idea is that the PCO2 electrode detects a change in pH caused by CO2 entering the internal electrolyte. CO2 diffuses through the membrane into the internal buffer, where it reacts with water to form carbonic acid and then dissociates to increase hydrogen ion concentration. This rise in H+ lowers the pH inside the electrode, and the pH-sensitive transducer converts that pH shift into an electrical signal proportional to pCO2. Color changes, turbidity, or temperature changes are not involved in this mechanism, so they don’t describe how the sensor generates its signal.