Calibration of the pCO2 electrode requires which standard?

• A. Two gases of known pCO2
• B. Two phosphate buffers
• C. Two gases of known pO2
• D. Two solutions of known pH

Answer: (A)

Calibrating a pCO2 electrode relies on tying the sensor’s signal to actual carbon dioxide levels. Using two gas standards with known pCO2 provides two fixed reference points, letting you determine the sensor’s response line—its offset and slope. With a CO2-diffusing, bicarbonate-buffer sensor, the change in signal is driven by CO2 partial pressure, so knowing two precise pCO2 values lets you translate the output into an accurate pCO2 measurement across the range you’ll test. Using buffers or pH standards wouldn’t establish this CO2-specific relationship, and two gases of known pO2 would calibrate an oxygen sensor, not CO2, while two known pH solutions would calibrate a pH meter rather than a CO2 electrode.