What is an electrode junction?

An electrode junction is a reference to which voltage potentials within the electrode are compared. The reference junction completes the electrical circuit and produces along with the glass sensing membrane voltage potential that is sent to the pH meter to produce the pH reading. The reference electrode junction is porous and allows the reference fill solution to come into contact with the sample. Due to this contact between reference junction and the internal electrode electrolytic fill solution and the sample being tested the porous reference junction can and will become contaminated.

Contamination is normal and is why electrode cleaning solution is used to clean the electrode after which deionized water which is depleted of ions is used to rinse the electrode and its’ junction. The depleted deionized water will draw out any remaining contaminating ions since deionized water is in effect hungry to absorb ions.