Voltammetrty


Dr. Betts w KU Chemistry Instrumentation w KU Chemistry Home w KU Home
Voltammetry and Other Electrochemical Techniques
About Voltammetry Bioanalytical Systems Epsilon Electrochemical Analyzer Applications Links

About Voltammetry Voltammetric methods of analysis involve the application of a potential (volts) in an electrochemical cell, and measuring the current (amps) that flows. Many different voltammetric techniques have been developed based on this current-voltage relationship, and have proven to be be extremely valuable tools for analyzing trace metals in solutions, determining complexation in organic and inorganic systems, studying kinetics and diffusion, etc.
One type of electrochemical cell used in voltammetry is the 3-electrode cell. This cell consists of working, reference and counter electrodes. The potential is applied between the working and reference electrodes, and the current flow is measured between the working and counter electrodes. The working electrode provides the surface for electron transfer to occur for the system under investigation. For example, during cyclic voltammetry of a iron complex the potential at the working electrode becomes more and more negative during the first part of the experiment. Essentially no current flows until the potential of the working electrode becomes sufficiently negative to cause Fe3+ to be reduced to Fe2+. Fe3+ + electron —› Fe2+ When the reduction of Fe3+ begins to occur, the current flowing through the working/counter electrode pair increases. During the second part of the cyclic voltammetry experiment, the potential scan is reversed causing the oxidation of the Fe2+ (that was generated during the initial potential sweep) back to Fe3+. Scanning the potential as a function of time first negative, then in a positive direction can be shown graphically (see diagram to right).


		A cyclic voltammogram consists of plotting the current that flows as a function of the applied potential. The trace on top [1] represents the reduction of Fe3+ to generate Fe2+. The trace on the bottom [2] represents the current that flows as the reverse reaction occurs (Fe2+ is oxidized to Fe3+). Under the correct conditions the amount of current that flows is related to the amount of the species present makeing this a valuable quantitative technique.
Many types of electrodes can be used as the working electrode: dropping mercury, glassy carbon, gold, copper, platimun, etc., and the timing of the applied potential can be varied to extract a variety of information. Overall, voltammetry is a powerful analytical technique that can be applied in many situations.

BioAnalytical Systems Epsilon Electrochemical Workstation The BAS Epsilon is a computer-interfaced ectrochemical analyzer capable of many types of electrochemical measurements. Cyclic Voltammetry/Linear Sweep Voltammetry Chronoamperometry/Chronocoulometry Controlled Potential Electrolysis DC Potential Amperometry Chronopotentiometry Sampled Current Polarography Normal Pulse Voltammetry/Polarography Differential Pulse Voltammetry/Polarography Square Wave Voltammetry Stripping Voltammetric Techniques


	BAS C-3 Cell Stand The portion of the instrument where the actual electron transfer processes occur is in the electrochemical cell. The cell that we use is a 3-electrode cell consisting of reference, working and counter electrodes, with stirring and purging capabilities. The C-3 cell stand is interfaced to the potentiostat which, in turn, is interfaced to the PC.

Applications of Electrochemistry The broad array of electrochemical techniques listed above has been applied to diverse areas of investigation. Below are listed a few examples of the application of electrochemical techniques in a variety of situations. Characterization of transition metal complexes Characterization of biosensors Characterization of battery electrodes Investigation of fuel cells Investigation of corrosion and corrosion inhibitors Corrosion behavior of surgical implant alloys Development of microelectrodes to quatify neurotransmitters in synapses Analysis of gunshot residue Determination of metals in drinking water Determination of trace levels of paraquat Determination of carboplatin in serum Determination of food colors in corks Evaluation of natural oxide film on aluminum for food and drink containers Evaluation of polymer coatings applied to aluminum food containers Probing protein interactions by direct electrochemistry Electrochemistry of semiconductors Control of plating chemistry by voltammetric techniques

Links to Electrochemistry Resources Vendors of Electrochemical Analyzers Bioanalytical Systems, Inc. http://www.bioanalytical.com/ Princeton Applied Research http://www.princetonappliedresearch.com/index.html Topac http://www.topac.com/ Pine Instrument Company http://www.pineinst.com/ecweb/index.htm Analytical Instrument Systems, Inc. http://www.aishome.com/index.html Electrochemistry Resources Bioanalytical Systems Application Capsules http://www.epsilon-web.net/Ec/EC_apps.html Princeton Applied Research Application Notes http://www.princetonappliedresearch.com/applications/application_notes/appnotes_archive.htm A Cyclic Voltammetry Primer http://www.cce.paisley.ac.uk/marco/Enzyme_Electrode/Chapter1/Cyclic_Voltammetry1.htm Electrochemistry Resource Page http://home.nas.net/~dbc/cic_hamilton/electro.html Electroanalysis http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2049/ Journal of Applied Electrochemistry http://www.kluweronline.com/issn/0021-891X/contents Electrochemical Concept Map http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/echemcon.html