Potentiometry: Types of Electrodes

Reference electrodes provide a constant baseline potential for potentiometric measurements, whereas indicator electrodes respond to changes in solution composition.

The standard hydrogen electrode, or SHE, has zero potential under standard state conditions but requires continuous hydrogen gas flow, making it unsuitable for routine laboratory or industrial applications.

One alternative is the saturated calomel electrode, or SCE, which is temperature-sensitive and may cause mercury contamination.

Another option is the silver–silver chloride reference electrode, which handles higher temperatures but may experience junction plugging from reacting with the analyte solution.

In contrast, many metallic indicator electrodes are designed to react directly with their cations, with anions with which they form sparingly soluble salts, or with different cations through an intermediary compound.

Inert metallic electrodes act as electron donors or acceptors in redox reactions instead.

Meanwhile, membrane electrodes use ion-selective membranes to determine specific ion concentrations in solutions.