Essentially a REDOX electrode is very similar to a pH one.The electrochemical potential developed by the REDOX indicator electrode is measure compared to a stable reference potential provided by the reference electrode.
A standard silver chloride type reference electrode used in the TRUEscience combination electrode exhibits potentials on the hydrogen scale of +120mV at 15ºC 206mV at 20°C and 203mV at 25°C respectively.
Sometimes there is a need to check the performance of a REDOX electrode to ensure it is behaving satisfactorily. In this instance a standard solution can be used. If the measuring electrode is poisoned by the sample or miss-use it may be found that standardising with one known solution to a known mV value is fine, but when a second standard is measured the result is different to the stated mV value. If the reference electrode has been poisoned it is usually the case that the standard used will have a different value to the measured value in both standard solutions used.
REDOX electrodes are susceptible to being poisoned by oil and grease deposits on the surface of the electrode in the same way that pH electrodes are. Poisoning of the electrode shows as drifting readings, or a sluggish response.
Usually we see this issue if the platinum pin/band has small deposits on the surface. Take 0.1 Molar HCl and using a cotton bud rub the surface, than rinse well with DI water. After cleaning the electrode will be hyper-active so it should be immersed in a REDOX solution for a couple of hours to restore normal operating conditions. The electrode should start to work.
Checking the electrode:
REDOX standards are available but the electrode should be working optimally after following the guidelines above for the standard solution to give the correct value.
TRUEscience REDOX measurements can be performed using the same TRUEscience Bluetooth Cap used for pH. The pH electrode will need to be changed for a REDOX electrode with the same S7 screw connector. The TRUEscience App has been updated to include REDOX as well as Dissolved Oxygen and a comprehensive range of Ion Selective Electrodes.
With so much flexibilty you might need a couple of Blutooth redox TRUEscience caps to run experiments simultaneously.