Controlled Potential Coulometry Purpose

Controlled Potential Coulometry can be used as an absolute (standards-less) analytical technique to determine many metals or compounds. By completely electrolyzing the analyte of interest and noting the total charge consumed, the quantity of the analyte is easily determined.

Controlled Potential Coulometry can also be used to determine the overall number of electrons in a faradaic reaction. Unlike voltammetric techniques where the electrode area and diffusion coefficient of the redox species must be known, Controlled Potential Coulometry can determine the overall number of electrons in the redox process without prior knowledge of the electrode area or diffusion coefficient.

In this technique, the potential of the electrode is held constant for a long time—minutes to hours—and the resulting integrated charge is recorded. All of the electrochemically active species which is being electrolyzed reacts, resulting in a 100% efficiency. The total charge passed in this technique obeys Faraday’s law, Q = nFN0, where Q is the total charge passed, n is the overall number of electrons consumed in the experiment, F is Faraday’s constant (9.64853 × 104 C/equiv), and N0 is the total moles of redox species present.