A glass electrode is a type of ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion. It is an important part of the instrumentation for chemical analysis and physico-chemical studies. In modern practice, widely used membranous ion-selective electrodes (ISE, including glasses) are part of a galvanic cell. The electric potential of the electrode system in solution is sensitive to changes in the content of a certain type of ions, which is reflected in the dependence of the electromotive force (EMF) of galvanic element concentrations of these ions.

A glass electrode is a type of ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion.

A glass electrode is perhaps the most successful and ubiquitous
electrochemical sensor. It provides information about
the activity of hydronium ions, H3O+, in water. Because
water, which mildly dissociates to H3O+ and OH- ions, is
the most common solvent medium, and chemical reactions
in water largely depend on H3O+ activity, the ability
to measure it is essential. And conversely, because H3O+
activity, or rather, its negative logarithm, the pH, is so easy
to measure, pH is the most commonly monitored and
recorded parameter of liquid samples.

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