Polarographic methods of glucose assay are based on which principle?

• A. Nonenzymatic oxidation of glucose
• B. Rate of oxygen depletion measured
• C. Chemiluminescence caused by ATP formation
• D. Change in electrical potential as glucose is oxidized

Answer: (B)

Polarographic glucose assays rely on amperometric measurement of oxygen consumption. In these methods, glucose is oxidized by glucose oxidase, using oxygen as the electron acceptor and producing gluconic acid (and often hydrogen peroxide). The key signal comes from how quickly oxygen is depleted in the solution. A polarographic electrode pulls a fixed potential to reduce the dissolved O2 at the cathode, generating a current that is proportional to the O2 concentration (and thus to the rate of glucose-driven oxidation). As glucose concentration rises, more O2 is consumed per unit time, causing a greater change in the current. This is the fundamental principle: tracking the rate of oxygen depletion to determine glucose levels.

Nonenzymatic oxidation isn’t used here, chemiluminescence from ATP formation isn’t involved, and polarography measures current from oxygen reduction rather than a shift in electrical potential due to oxidation.