the bulk of the analyte solution and conducts well. A common voltammetry method, polarography, uses mercury as a working electrode e.g. DME and HMDE, and as an auxiliary electrode. The reference is the most complex of the three electrodes; there are a variety of standards used and it is worth investigating elsewhere. For non-aqueous work, IUPAC recommends the use of the ferrocene/ferrocenium couple as an internal standard. In most voltammetry experiments, a bulk electrolyte (also known as a supporting electrolyte) is used to minimize solution resistance. It is possible to run an experiment without a bulk electrolyte, but the added resistance greatly reduces the accuracy of the results. With room temperature ionic liquids, the solvent can act as the electrolyte. Voltammograms A voltammogram is a graph that measures the current of an electrochemical cell as a function of the potential applied. This graph is used to determine the concentration and the standard potential of the analyte. To determine the concentration, values such as the limiting or peak current are read from the graph and applied to various mathematical models. After determining the concentration, the applied standard potential can be identified using the Nernst equation. There are three main shapes for voltammograms. The first shape is dependent on the diffusion layer. If the analyte is continuously stirred, the diffusion later will be a constant width and produce a voltammogram that reaches a constant current. The graph takes this shape as the current increases from the background residual to reach the limiting current (il). If the mixture is not stirred, the width of the diffusion layer eventually increases. This can be observed by the maximum peak current (ip), and is identified by the highest point on the graph. The third common shape for a voltammogram measures the sample for change in current rather than current applied. A maximum current is still observed, but represents the maximum change in current (ip). Mathematical models To determine analyte concentrations, mathematical models are required to link the applied potential and current measured over time. The Nernst equation relates electrochemical cell potential to the concentration ratio of the reduced and oxidized species in a logarithmic relationship. The Nernst equation is as follows: Where: Reduction potential : standard potential : universal gas constant : temperature in kelvin : ion charge (moles of electrons) : Faraday constant : Reaction quotient This equation describes how the changes in applied potential