Chromatographic Separations
As illustrated below, in chromatography we pass a sample-free phase, which we call the mobile phase, over a second sample-free stationary phase that remains fixed in space. We inject or place the […]
Community Exchange Forums
Explore resources, experiments, and teaching materials shared by the analytical sciences community.
Liquid-Liquid Extractions
Shown here is an illustration outlining the progress of a traditional liquid–liquid extraction (LLE) using two identical extractions of a single sample with fresh portions of the extractant. The numbers give the […]
Multicomponent Analysis in Voltammetry
Voltammetry is a particularly attractive technique for the analysis of samples containing two or more analytes. Provided that the analytes behave independently, the voltammogram of a multicomponent mixture is a summation of […]
Clark Electrode for Dissolved Oxygen
In amperometry we apply a constant potential to the working electrode and measure current as a function of time. Because we do not vary the potential, amperometry does not result in a […]
Effect of Scan Rate in Cyclic Voltammetry
In a cyclic voltammetry experiment, scanning the potential in both directions provides with the opportunity to explore the electrochemical behavior of species generated at the electrode. This is a distinct advantage of […]
Cyclic Voltammetry
In cyclic voltammetry (CV) we scan the potential in both the cathodic and anodic directions. The illustration below shows a typical potential-excitation signal (a) in which we first scan the potential to […]
Anodic Stripping Voltammetry
As illustrated here, anodic stripping voltammetry (ASV) consists of two steps. The first step is a controlled potential electrolysis in which we hold the working electrode—usually a hanging mercury drop or a […]
Pulse Polarography
Normal polarography has been replaced by various forms of pulse polarography, several examples of which are shown here. Normal pulse polarography (a), for example, uses a series of potential pulses characterized by […]
Normal Polarography
The first important voltammetric technique to be developed—polarography—uses the dropping mercury electrode as the working electrode. As shown here, the current flowing through the electrochemical cell is measured while applying a linear […]
Shape of Voltammograms
In voltammetry we measure current as a function of the applied potential. The shape of a voltammogram is determined by several experimental factors, the most important of which are how we measure […]
Origin of Faradaic Current in Voltammetry
Let’s assume we have a solution that is 1.0 mM in Fe(CN)63– is 1.0 mM. The standard state potential for the reduction of Fe(CN)63– to Fe(CN)64– is +0.356 V. If we apply a potential of […]
Electrochemical Cell for Voltammetry
A typical arrangement for a voltammetric electrochemical cell is shown here. In addition to the working electrode, the reference electrode, and the auxiliary electrode, the cell also includes a N2-purge line for […]