pH and CO2 Electrodes

pH electrodes are used to quantify the concentration of protons in solution, then described in the logarithmic pH scale. This is achieved through the application of the Nernst equation to calculate the potential difference generated in a redox cell across the “pH-sensitive glass”. This compares the unknown H+ concentration with a known buffered reference. CO2 (Severinghaus) electrodes use this same principle, but the pH being detected is in turn controlled by the CO2 dissolved in the solution/blood sample.