In general, ion-selective electrode measurements rely on which physical quantity to determine analyte concentration?

In general, ion-selective electrode measurements rely on which physical quantity to determine analyte concentration?

• A. Current
• B. Potential difference
• C. Flux
• D. Capacitance

Answer: (B)

Ion-selective electrodes are potentiometric sensors. They generate a voltage, rather than relying on a flow of current, in response to the activity of a specific ion in solution. The measured potential difference between the ion-selective electrode and a reference electrode changes with ion activity according to the Nernst equation, so the analyte concentration is inferred from this voltage. In these measurements, current is ideally zero and is not the quantity used to quantify the concentration; flux and capacitance do not provide the primary readout for the concentration.