https://doi.org/10.1351/goldbook.09107
Chemically-modified electrode in which the products of a reaction between enzymes in an immobilized enzyme layer and the enzyme reaction substrate are electrochemically active and are measured usually by amperometry or potentiometry.
Example: Glucose electrode in which glucose oxidase converts β-D-glucose and oxygen to gluconolactone and hydrogen peroxide, the concentration of which is measured amperometrically. In modern devices, a redox mediator, e.g. ferrocenium ion and its derivatives, recycles the reduced form of the enzyme and is itself reoxidized in the reaction that is monitored.
Schematic of the mediated oxidation of glucose to gluconolactone by glucose oxidase. The current passed to re-oxidise the mediator is proportional to the amount concentration of glucose.