Glass Electrode:

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 important part of the instrumentation for chemical analysis and physico-chemical studies. In modern practice, widely used membranous ion-selective electrodes (ISE, including glasses) that 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.

Applications:

Glass electrodes are commonly used for pH measurements. Specialized ion sensitive glass electrodes are also often used for determination of concentration of lithium, sodium, ammonium, and other ions. Glass electrodes have been utilized in a wide range of applications - from pure research, control of industrial processes, to analyze foods, cosmetics and comparison of indicators of the environment and environmental regulations: a microelectrode measurements of membrane electrical potential of a biological cell, analysis of soil acidity, etc.

Types:

Almost all commercial electrodes respond to single charged ions, like H+, Na+, Ag+. The most common glass electrode is the pH-electrode. Only a few chalcogenide glass electrodes are sensitive to double-charged ions, like Pb2+, Cd2+ and some others.

There are two main glass-forming systems:

silicate matrix based on molecular network of silicon dioxide (SiO2) with additions of other metal oxides, such as Na, K, Li, Al, B, Ca, etc.

chalcogenide matrix based on molecular network of AsS, AsSe, AsTe.

Because of the ion-exchange nature of the glass membrane, it is possible for some other ions to concurrently interact with ion-exchange centers of the glass and to distort the linear dependence of the measured electrode potential on pH or other electrode function. In some cases it is possible to change the electrode function from one ion to another. For example, some silicate pNa electrodes can be changed to pAg function by soaking in a silver salt solution.