Clarkelektrode

Clarkelektrode, commonly known as the Clark oxygen electrode, is an electrochemical sensor used to measure dissolved oxygen in liquids. It was developed by Leland C. Clark Jr. in the mid-20th century and became a foundational tool in physiology, biochemistry, and environmental monitoring. The electrode is an amperometric sensor in which oxygen is reduced at a working electrode, producing a current that is proportional to the concentration of dissolved oxygen in the sample. The current is typically diffusion-limited, meaning it depends on how fast oxygen can diffuse through a protective barrier to the electrode surface.

Construction and principle: A typical Clark-type sensor contains a platinum working electrode, a reference electrode (often Ag/AgCl), and an electrolyte housed in a diffusion cell. The sample is separated from the electrolyte by an oxygen-permeable membrane, such as a Teflon barrier. When a bias is applied, oxygen diffuses through the membrane, reaches the platinum surface, and is reduced. The resulting current is measured and related to the oxygen concentration in the sample through calibration.

Applications: The Clark electrode is widely used for blood gas analysis and monitoring dissolved oxygen in cell cultures and fermentation processes. It also serves in environmental monitoring of water quality and in basic research on cellular respiration and metabolic rates. Its real-time measurements and relatively simple electronics contributed to its long-standing utility, particularly before the advent of optical methods.

Limitations and developments: Limitations include oxygen consumption by the sensor during measurement, potential interference from other reducible species, and the need for regular calibration and maintenance of the electrolyte. Modern developments include non-consumptive optical oxygen sensors based on luminescent quenching and improved Clark-type designs with advanced membranes and microfabrication for smaller-scale applications.