Principle for Measurement of Partial Pressure of Carbon Dioxide

The electrodes used for measurement of partial pressure of CO2 in blood are based on measuring the pH as demonstrated in the figure below:

Principle of carbon dioxide sensor
Figure 1.0 principle of carbon dioxide sensor

The measurement is based on the fact that when CO2 is dissolved in water, it forms a weakly dissociated carbonic acid (H2CO3) that subsequently forms free hydrogen and bicarbonate ions per the following chemical reaction:

CO2 + H2O ⟷ H2CO3 ⟷ H+ + HCO3–

As a consequence of this chemical reaction, the pH of the solution is changed. This change generates a potential between the glass pH and a reference e.g. Ag/AgCl electrode that is proportional to the negative logarithm of the pCO2.

Related: How Estimation of Oxygen and Carbon dioxide is Carried out in Biological Solutions

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Author: John Mulindi

John Mulindi has a background in Instrumentation, and he writes on various topics ranging from Technical, Business to Internet marketing fields. He likes reading, watching football, writing and taking on adventure walks in free time.

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