Potentiometry

Potentiometry is an electroanalytical method that determines chemical information from voltage differences measured under conditions of negligible current. It commonly uses an indicator electrode and a reference electrode.

Nernst equation: An equation relating an electrode’s equilibrium potential to the activities of chemical species involved in its reaction. It predicts how potentiometric voltage changes with the activity of the target ion.
pH meter: An instrument that measures solution acidity by sensing an electrode voltage related to hydrogen-ion activity. It is the best-known instrument built around potentiometric measurement.
Electrode potential: The electrical potential difference that develops between an electrode and an electrolyte at their interface. Potentiometry compares electrode potentials to obtain its measured voltage.
Amperometry: An electroanalytical method that determines analyte information by measuring current at a controlled potential. It measures current as the signal, whereas potentiometry measures voltage with negligible current.
Reference electrode: An electrode designed to maintain a stable, known potential during electrochemical measurements. Its stable potential provides the baseline for the measured cell voltage.
Ion-selective electrode: An electrode whose membrane potential responds preferentially to a particular ion in solution. It extends potentiometry from acidity to selective measurements of many ions.
Chemical activity: A thermodynamic measure of a species’ effective concentration in a non-ideal mixture. Electrode response generally tracks ion activity rather than concentration alone.
Voltammetry: An electroanalytical method that studies current as applied electrode potential is varied. Its deliberate potential sweeps and current measurements differ from potentiometric operation.
Indicator electrode: An electrode whose potential responds to the composition of the solution being measured. Its composition-dependent potential supplies the analytical signal.
Potentiometric titration: A titration in which electrode potential is monitored as titrant is added to locate a reaction endpoint. It uses voltage changes to identify endpoints without relying on a visual indicator.

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