Which technique is typically categorized as potentiometry?

• A. ISE
• B. Polarography
• C. Coulometry
• D. Voltammetry

Answer: (A)

Potentiometry measures the electrical potential of a cell while drawing essentially no current, and the measured potential changes with the activity of a specific ion. Ion-selective electrodes are a classic example: the electrode develops a potential at the sensing interface that depends on the ion activity in solution, and with a stable reference electrode, this potential can be related directly to the ion concentration using the Nernst equation. That direct readout of ion activity from a measured potential is the hallmark of potentiometry, which is why ion-selective electrodes are the typical technique in this category.

The other techniques involve measuring current as the potential is varied. Polarography and voltammetry determine current as a function of applied potential, which is the essence of current-based electrochemical methods. Coulometry quantifies the total charge passed to drive a reaction, focusing on charge rather than potential measurement. Hence, they are not potentiometric techniques.