In polarographic glucose oxidase assay, to prevent reformation of oxygen from hydrogen peroxide, which substances are added?

• A. Molybdate and iodide
• B. Catalase and ethanol
• C. Sodium azide
• D. Copper and chloride

Answer: (A)

In this polarographic glucose oxidase setup, the measured signal comes from oxygen involved in the enzyme’s reaction. Hydrogen peroxide is produced as a byproduct, and if it re-forms oxygen, it can distort the readout. The aim is to remove hydrogen peroxide efficiently so it cannot generate any extra O2 during the measurement.

Adding a scavenging system that rapidly converts hydrogen peroxide to water without releasing oxygen is the way to achieve this. The combination of molybdate and iodide serves that role: iodide participates in redox chemistry with hydrogen peroxide, effectively destroying it, while molybdate helps drive the process and prevents any reformation of oxygen from the peroxide. This keeps the oxygen level in the system stable and ensures the polarographic signal truly reflects the glucose-driven consumption of oxygen.

Other potential additives do not specifically prevent O2 reformation from hydrogen peroxide (for example, catalase would release oxygen when it breaks down H2O2), so they are not used here.