Do you know pH electrode?
Electrodes are an integral part of a pH meter. pH measurement is accomplished by a chemical battery composed of a measuring electrode and a reference electrode.
(1) The pH measuring electrode is also called the pH indicating electrode, which responds to the activity of hydrogen ions in the solution, and the electrode potential changes accordingly. Almost all modern pH meters use glass electrodes as measuring electrodes.
(2) The reference electrode (inert electrode) has no response to the activity of hydrogen ions in the solution. In pH measurement, it acts as a half-cell with constant potential and forms a chemical battery with the pH measurement electrode, providing and maintaining a fixed reference potential.
(3) A composite electrode is an electrode that combines a pH measuring electrode and a reference electrode. Composite electrodes are not affected by oxidizing and reducing substances, have a fast equilibrium speed, and are widely used. Currently, these electrodes are basically used in pH measurement. Regardless of the glass indicator electrode or the glass composite electrode, they are all thin-film electrodes. The membrane potential has a Nernst relationship with the hydrogen ion activity in the measured solution, which reflects the unique properties of the thin-film electrode. These properties are affected by the electrode itself and the conditions of use. , and have an effect on the measurement results.
