Unlike potentiometry, where the free energy contained within the system generates the analytical signal, electrolytic methods are an area of electroanalytical chemistry in which an external source of energy is supplied to drive an electrochemical reaction which would not normally occur. The externally applied driving force is either an applied potential or current. When potential is applied, the resultant current is the analytical signal; and when current is applied, the resultant potential is the analytical signal. Techniques which utilize applied potential are typically referred to as voltammetric methods while those with applied current are referred to as galvanostatic methods.
Voltammetry refers to the measurementof current that results from the application of potential. Unlike potentiometry measurements, which employ only two electrodes, voltammetric measurements utilize a three electrode electrochemical cell. The use of the three electrodes (working, auxillary, and reference) along with the potentiostat instrument allow accurate application of potential functions and the measurement of the resultant current. The different voltammetric techniques that are used are distinguished from each other primarily by the potential function that is applied to the working electrode to drive the reaction, and by the material used as the working electrode. Common techniques to be discussed here include:
- Normal-pulse polarography (NPP)
- Differential-pulse polarography (DPP)
- Cyclic voltammetry
- Anodic-sttripping Voltammetry
Time Based Techniques