Which electrode is used to measure pCO2?

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Multiple Choice

Which electrode is used to measure pCO2?

Measuring pCO2 relies on turning a gas partial pressure into a signal your sensor can read. The Se­veringhaus electrode is built for this: CO2 from the sample diffuses through a gas-permeable membrane into a bicarbonate buffer inside the electrode. There CO2 forms carbonic acid and then releases H+, lowering the pH. A pH electrode inside the assembly senses this pH change, which is tied to the CO2 level through the known buffer chemistry (pH shifts correspond to specific CO2 partial pressures). Because this setup responds to gas pressure of CO2 rather than to a single ion in solution, it’s specifically designed for pCO2. The other options aren’t suited for CO2 measurement. A glass membrane pH electrode responds to H+ activity to give pH, not directly to CO2 partial pressure. A solid-state crystal membrane sensor and the vancomycin-based liquid polymer aren’t designed to translate CO2 pressure into a pH signal in this gas-sensing manner. So the gas-sensing Severinghause electrode is the appropriate choice for pCO2.

Measuring pCO2 relies on turning a gas partial pressure into a signal your sensor can read. The Se­veringhaus electrode is built for this: CO2 from the sample diffuses through a gas-permeable membrane into a bicarbonate buffer inside the electrode. There CO2 forms carbonic acid and then releases H+, lowering the pH. A pH electrode inside the assembly senses this pH change, which is tied to the CO2 level through the known buffer chemistry (pH shifts correspond to specific CO2 partial pressures). Because this setup responds to gas pressure of CO2 rather than to a single ion in solution, it’s specifically designed for pCO2.

The other options aren’t suited for CO2 measurement. A glass membrane pH electrode responds to H+ activity to give pH, not directly to CO2 partial pressure. A solid-state crystal membrane sensor and the vancomycin-based liquid polymer aren’t designed to translate CO2 pressure into a pH signal in this gas-sensing manner. So the gas-sensing Severinghause electrode is the appropriate choice for pCO2.

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