Ampérométrie: Présentation

Amperometry is an electroanalytical method that measures electric current generated at an electrode while maintaining constant potential. The current produced is directly proportional to the analyte concentration, enabling detection and quantification. This principle allows amperometry to serve as a foundation for constructing chemical sensors that monitor specific substances in solutions.

The Clark oxygen electrode operates by applying voltage between a platinum cathode and silver-silver chloride anode enclosed in a gas-permeable membrane. Dissolved oxygen molecules diffuse across the membrane and undergo reduction at the cathode surface. The anode supplies electrons for this reaction, generating current proportional to oxygen concentration in the blood sample.

An amperometric glucose biosensor consists of a platinum or gold electrode immobilized with glucose oxidase enzyme. When glucose is present, the enzyme catalyzes its oxidation to produce gluconic acid and hydrogen peroxide. The sensor applies potential between the enzyme-coated working electrode and reference electrode, measuring current from hydrogen peroxide oxidation proportional to glucose concentration.

Amperometry enables real-time blood glucose monitoring through biosensor technology. The enzyme glucose oxidase catalyzes glucose oxidation, producing measurable hydrogen peroxide. The resulting current is directly proportional to glucose concentration, providing rapid, quantitative analysis essential for diabetes management and clinical diagnostics.

In amperometry, a constant potential is maintained between working and reference electrodes. This fixed potential drives electrochemical reactions at the electrode surface, generating current proportional to analyte concentration. The controlled potential ensures selective oxidation or reduction of target analytes while minimizing interference from other species.

The gas-permeable membrane in amperometric sensors selectively allows target molecules to diffuse while excluding interfering substances. In the Clark oxygen electrode, this membrane permits dissolved oxygen to reach the cathode while preventing direct contact with the electrolyte. This selective permeability ensures measurement specificity and sensor accuracy.

The anode supplies electrons necessary for reduction reactions occurring at the cathode surface. In oxygen sensors, the silver-silver chloride anode oxidizes to provide these electrons, completing the electrochemical circuit. This electron supply is essential for generating measurable current proportional to analyte concentration at the working electrode.