Voltammetry

The term voltammetry is used to describe the process of measuring the current passed though an electrolytic system as a function of the applied voltage. There are a number of voltammetry techniques employed in analytical chemistry which, among others, include linear scan voltammetry, pulsed voltrammetry, cyclic voltammetry, stripping voltammetry and polarography. If a potential is applied across two electrodes immersed in an electrolyte, a current is generated due to the reduction of the analyte at an electrode surface. In practice the voltage is scanned and the resulting current presented as a curve relating current to applied voltage. The applied potential must reach a value that is sufficient to initiate the redox reaction which results in the initiation or an increase in the current flowing through the cell, a process that has been defined as electrolysis. The electrochemical reactions can be completely controlled by varying the applied potential.

The cell employed in voltammeric measurements normally contain three electrodes a diagram of and a general form of the instrument is shown in figure  14.

Figure 14. A Typical Voltammetry Cell

The working electrode is the electrode where the analyte is oxidised or reduced. The reference electrode is necessary to measure the potential of the working electrode and the counter electrode is the complementary electrode to the working electrode across which the potential is applied to achieve the oxidation or reduction.