Microcell for Cyclic Voltammetry Cyclic voltammetry has become a very popular tool in the laboratory for studying redox properties of organic and inorganic compounds. It is simple to set up, requires no expensive instrument, and can yield a large amount of information. (For an introduction of this technique, see articles in April and September 1983 issues THIS JOURNAL.) While eom, mercial electrochemical cells for CV experiments are available or can be readily built using common, standard glassware, a minimum of a couple of milliliters of solution is required. This presents a problem when the compound of interest is available only in submilligram quantities. A PlexiglasQthin-layer cell which requires very little solution has been reported [Jarhawi, T. B., Heineman, W. R., Patriarehe, G. J.,Anal. Chim. Acta, 126,57 (1981)] and Bioanalytiull System (West Lafayette, IN) offers a microcell that employs a carbon paste electrode to do CV. However, these are not useful for organic solvents such as methylene chloride or acetonitrile which offer a wide voltage window for organic and inorganic compounds. We describe here the design of a micro CV cell. As shown hy the drawing, the actual cell is a t the interface between the capillary tubing and the large tube in which the reference electrode is placed. The reference electrode (or salt bridge) can either rest on top of the chamber or be self-supported by the O-ring, which also acts as a gas seal. The working and suxillary electrodes are two platinum beads sealed on the glass wall. (For best results, the platinum wire behind the bead should be flattened before sealing so as to minimize thermal expansion.) The volume of solution required in this cell is typically 0.3 mL and voltammograms of compounds as little as 80 pg have heen obtained. Periodidly, the cell should be soaked in cone. HN03 overnight for cleansing the platinum surface. The side-tube is optional. The usual technique in our laboratories is to place the electrolyte solution in the cell, buhble argon through briefly, and take a background CV. We then lift up the reference electrode slightly, add sample from the side-tube via a pipet tip, deaerate the solution, and measure the CV again. Even minor changes can he detected readily. The addition of a manifold tothe gas inlet and avent via the side-tube makes this cell a versatile reaction chamber for studies involving toxic gases, e.g., CO and NO. This work was supported by the Division of Chemical Sciences, US. Department of Energy, under contract No. DEAC02-76CH00016 a t BNL and NSF a t MSU. We thank J. Fajer for helpful discussions.
I. Fujlta (deceased) DepaRment of Applied Science Brwkhaven National Labwatory Upton. NY 11973 C. K. Chang Michigan State University East Lansing, MI 48824
Volume 61
Number 10
October 1984
913
