The measuring electrode covering membrane for a pCO2 electrode is typically which material?

• A. Teflon/Silicone
• B. Glass
• C. Plastic
• D. Ceramic

Answer: (A)

The measuring electrode covering membrane in a pCO2 sensor must be a gas-permeable, chemically inert barrier that allows CO2 to diffuse into the sensing compartment while blocking liquids. This diffusion membrane is typically made from silicone rubber or PTFE (Teflon). Silicone has very high CO2 permeability and is flexible, making it easy to form as a thin, uniform layer over the electrode. PTFE is also highly inert and provides good gas diffusion properties with excellent resistance to wetting. Because the membrane needs to let CO2 pass but keep the electrolyte and sample contained, silicone or Teflon are the materials that best fit this role. Glass, plastic, and ceramic are not suitable diffusion membranes for CO2 in this context, as they are not effectively permeable to CO2 or fail to meet the practical requirements of the electrode setup.