Protein molecules present in samples can react with the electrolyte to produce a solid precipitate.
These solids can block the porous junction on the electrode, making it impossible for the electrolyte to flow out as normal.
How can protein damage be avoided?
This type of failure is usually only seen in single junction electrodes, using a double junction one will avoid this.
Work with protein containing samples such as biological samples or food products should be performed with a double junction electrode.
How can I clean a protein damaged electrode?
If your pH electrode has failed and you suspect that protein contamination is the cause, you may be able to revive it.
Use an electrode cleaning solution that contains Pepsin and Hydrochloric Acid (HCl), such as the TRUEscience Electrode Cleaning Solution for Proteins.
Pour a small amount into a beaker and leave the electrode to soak in this for about 30 minutes.
Rinse the electrode under clean water to remove the cleaning solution, then test if the cleaning has worked by trying to measure the pH of a buffer.
If the electrode response is still incorrect leave the electrode to soak in the cleaning solution again for a further 2 hours. Rinse and test in buffer again.
If the electrode response is still incorrect after 8 hours of soaking then it may be beyond repair and need replacing. You may need to work with a double junction electrode to avoid protein damage in the future, so consider this when you're looking for a replacement electrode.
See our other blog posts for further information on pH electrode selection, cleaning and care or contact us here with any questions.