What exactly is the function of the diaphragm on a pH electrode, and why is it important?
The diaphragm on a pH electrode allows a flow of electrolyte from the reference solution into the solution being measured. This completes the electrical circuit between the reference and sensing electrode and gives the potential difference which is measured by the pH meter. The type of diaphragm used will influence the outflow of electrolyte into the sample, which will in turn effect the response speed of the electrode. The common diaphragm types are listed below along with their inherent properties. For most common applications a platinum diaphragm is the one of choice.
