ORP/Redox Sensors

The terms ORP or Redox are given to the voltage seen by the transfer of electrons between atoms or molecules in a redox reaction. To measure potential ORP/Redox it uses sensors made of metal, usually platinum, gold or silver. These sensors are inert and applied in chemical reactions that operate only by electron transfer. Such reactions occur with elements and compounds which presents two or more oxidation states. With the exchange of electrons from the redox system, the sensor receives a voltage equal to the electrochemical potential of this system. The application of redox measurements to a practical situation requires prior knowledge of some factors: - Presence of contaminants that can compete with the main redox reaction (Pt, Ag or Au); - Approximate values of ions activity coefficients, - Approximate speed of the reaction to be controlled, - Necessity or not of the control pH. One form of control is often used to maintain the redox potential above.