Editorial Feature

What is a Redox Electrode?

Oxidation reduction, or redox reactions, involves the transfer of an electron from a donor to an acceptor. The donor loses an electron to change from the reduced to oxidized form and the acceptor gains an electron to change from reduced to oxidized form. The reduced and oxidized forms of a redox component are known as a redox couple.

Redox electrodes are sensitive measurement sensors with a life span based on the chemical and temperature conditions. These electrodes have a typical life span of 2 to 3 years but may vary if the electrodes are subjected to harsh conditions.

Types of Redox Electrode

The redox electrode consits of various types such as:

  • Laboratory electrodes – These electrodes are made of polymer, epoxy or glass. They are often used for in-line measurements, using a threaded adapter.
  • In-line electrodes – These electrodes are used to measure redox potential in a pipe. Care should be taken while installing these electrodes, in order to prevent the formation of air cavity around the sensing area of the electrode.
  • Submersible electrodes – These electrodes are combined with immersion assemblies for measuring redox potential in an open duct or viaduct.

Working Principle

The reaction components are separated such that the donor couple and acceptor couple are in separate reaction vessels that are connected by a salt bridge. An electrode in each vessel connects the reaction mixture in one cell to that in the other via a measuring device. Therefore, the electrochemical cell contains two half-cells, each consisting of the redox reactants.

The circuit principally enables the electrons to flow from one half-cell to the other across the gradient generated by the free energy difference of the electrons. The system is constrained by channeling this flow via the measuring device so that the flux is zero.

The zero flux is obtained by balancing the voltage difference between the two half-cell reactions via an applied potential. This difference is known as the redox potential difference, which is measured using several electrode, more commonly hydrogen half-cell.

Applications of Redox Electrodes

The following are the applications of redox electrodes:

  • Pharmaceuticals
  • Food industry
  • Radioactive and NMR samples
  • Environmental studies

Advanced Micro Oxidation-Reduction Potential System

ArrowDOXTM Oxidation-Reduction Potential System is an ideal system for measuring samples as small as 5 µl. It features solid state sensor and fluoropolymer capillary tube that make it unbreakable. It has a tip diameter of 1 mm and immersion depth of 0.5 mm.

The key benefits of advanced micro oxidation-reduction potential system include:

  • It simultaneously measures the oxidation-reduction potential and spectrophotometric absorption
  • It has lower output resistance than glass probes.

Redox Microsensor

Unisense’s Redox Microsensor offers a high quality research tool for quick and reliable measurements. It has a tip size of less than 10 µm, resolution of 1 mV and response time of less than 5 seconds. This microsensor finds application in wide range of research fields that require non-destructive, fast and accurate measurements.

Some of the application areas of Redox Microsensor include:

  • Microbiology
  • Biotechnology
  • Biomedical sciences
  • Environmental sciences.

References and Further Reading

 

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