The measuring electrode tip for a pH electrode is commonly made of which material?

• A. AgCl
• B. Pt
• C. Au
• D. Cu

Answer: (A)

The main idea is that pH measurement relies on a glass sensing electrode whose tip is made of special glass that responds to hydrogen ion activity. The glass surface develops a potential that changes with pH because of ion exchange at the glass–solution interface. In contrast, the reference electrode provides a stable baseline potential, and that part of the probe is typically a silver/silver chloride (AgCl) system. So AgCl is associated with the reference half-cell, not the sensing tip. The metals listed (Pt, Au, Cu) aren’t used as the pH-sensing tip. This distinction helps you see why the measuring tip material is glass, while AgCl serves in the reference electrode to stabilize the measurement.