What pH electrode should I use for substances containing Protein?

We get many people coming to us asking why their pH meter isn’t working and in a lot of cases it ends up to be their pH electrode that is damaged. It’s not hard to damage electrodes, they are very sensitive and will break if it gets exposed to the wrong substances or not stored correctly.

One of the substances to be careful with are any substances containing protein. Proteins will often precipitate within the porous junction if they come into contact with the reference electrolyte, usually KCL. The porous structure will get blocked with protein debris filling the junction and rendering the electrode useless. If the electrolyte cannot flow freely the reference potential will no longer be stable, and measurements are not possible.

How can I revive a protein blocked electrode?

If you have an electrode with a junction contaminated with proteins, this can sometimes be cleaned by soaking the electrode into 5 % pepsin in 0.1 mol/L HCl solution for several hours.

What type of electrode should I use?

A liquid junction electrode creates a junction with a thin film of filling solution at the tip of the probe. They usually have a pump function to allow you to create a fresh junction for every use. This feature allows the user to flush out any traces of protein from the junction after measurement which prevents precipitate lingering and forming. Liquid junctions are available in both epoxy and glass.

Another option would be to use a double junction electrode. These electrodes have an additional salt bridge to prevent reactions between the electrode fill solution and your sample which would otherwise cause a build up of debris.

For more information on the testing the pH of protein solutions or any other substance please get in touch with our technical support team; phone 01954233120, email support@camlab.co.uk or fill in the form below and we will get in touch.