10.24 : Amperometry: Overview

Amperometry is a technique commonly used to measure the concentration of specific analytes in a solution by monitoring the electric current generated during an electrochemical reaction. It involves applying a constant potential between a working electrode and a reference electrode to measure the resulting current, which is proportional to the concentration of the analyte. The Clark oxygen electrode operates based on this principle of amperometry. It consists of a cathode and an anode enclosed in a gas-permeable membrane. Typically, the cathode is platinum or gold, while the anode is made of silver. When a potential is applied between the cathode and the anode, oxygen molecules diffuse through the gas-permeable membrane and are reduced at the cathode surface, generating a current. This current is proportional to the concentration of dissolved oxygen in the sample.

Amperometry is widely used for blood glucose monitoring. A biosensor approach is employed in blood glucose amperometric sensors. The sensor consists of a platinum or gold electrode immobilized with the enzyme glucose oxidase. Glucose oxidase catalyzes the oxidation of glucose to produce gluconic acid and hydrogen peroxide. The amperometric sensor applies a potential between the enzyme-coated working electrode and a reference electrode. As glucose is present in the blood sample, it reacts with the immobilized enzyme to generate hydrogen peroxide. The hydrogen peroxide produced is then electrochemically oxidized at the working electrode, resulting in a measurable current. The magnitude of the induced current is directly proportional to the glucose concentration in the blood sample.