For most people, the word electrochemistry may conjure up the image of the humble pH meter, but this field of laboratory analysis is actually very multi-faceted, with numerous distinct techniques. Fundamentally, these techniques all measure aspects of chemical reactions that involve the transfer of electrons in solution. This transfer of electrons can be measured as the flow of electricity, and the chemical reaction can be altered and studied through the application and/or measurement of a voltage between electrodes inserted into the solution. One of the more sophisticated techniques within electrochemistry is voltammetry.

At its most basic, voltammetry is the measurement of current in an electrolytic solution, as a varying potential is applied. In principle, this can be accomplished with a simple two-electrode set-up, but there are difficulties in maintaining a fixed potential under these conditions. In practice, three electrodes are used: a working electrode that applies the varying potential, a reference electrode held at constant potential, and an auxiliary electrode that provides a source of electrons to balance the current in the cell. More complicated systems with additional electrodes are also possible.

The variation of the potential allows numerous individual methods to be conducted. In a simple linear sweep, the current is measured as the potential of the working electrode increases in a linear fashion from a starting potential to the end potential. Peaks in the measured current indicate the presence of species in the solution, with identification provided by the potential at which the peak occurs. In cyclic voltammetry, the potential is varied in a sawtooth wave, creating a cyclical reaction as the target analyte is alternately oxidized and reduced, providing information on reaction rates and frequency response.

Another variation is anodic stripping voltammetry (ASV). The working electrode is first held at a high potential in order to remove any deposited analyte. Next, the electrode is held at a low potential to induce the analyte to deposit onto the electrode and equilibrate. Finally, a linear potential sweep is carried out, which strips the electrode of the analyte, causing an electron flow that can be measured. ASV is helpful in measuring trace amounts of analyte in solution.

Among the many electrochemical applications for voltammetry, water quality testing and other environmental applications predominate. One specific method approved by the National Institute of Occupational Safety and Health (NIOSH) is for lead-in-air. Ultrasonic extraction is used to obtain a solution from an air filter, and ASV provides the measurement of lead content. Although NIOSH also has other lead-in-air methods, the ASV method can be used with portable instruments.

The total market for voltammetry was about $18 million in 2007, and growth is relatively slow. The major vendors are Metrohm and Danaher, although many smaller vendors compete in this area of electrochemistry.

Voltammetry at a Glance:

Leading Suppliers

• Metrohm AG

• Radiometer Analytical

(Danaher)

Largest Markets

• Water

• Food

• Metals

• Agriculture

Instrument Cost

• $4,000–$30,000