Microvoltammetric electrodes

Wightman, R. M. (1981), Microvoltammetric electrodes. Anal. Chem., 53(9) 1125A-l 133A. 

Howell, J.O., and Wightman, R.M. 1984. Ultrafast voltammetry and voltammetry in highly resistive solutions with microvoltammetric electrodes. Analytical Chemistry 56, 524-529. 

The first references to the use of microelectrodes appear in the biochemical literature and relate not to microvoltammetric electrodes, as will largely be considered here, but rather to very small ion-sensitive electrodes (particularly pH electrodes) capable of making measurements inside a single biological cell. Biochemists have also used metal microelectrodes to provide direct electrical stimulation of nerves, for example in the design of auditory protheses [1]. Indeed, the two types of electrode have often been used in combination, i.e. an ion-sensitive electrode is used to detect changes caused by the electrical stimulation of a nerve. Applications of both these types of... 

E. W. Kristensen, R. L. Wilson, and R. M. Wightman, Dispersion in Flow Injection Analysis Measured with Microvoltammetric Electrodes. Anal. Chem., 58 (1986) 986. 

Figure 5. Chromatograms of 5 nmol each ME, E, and DHBA with microvoltammetric electrode near the center of the column and near the edge of the column. Flow rate — 1.0 mL min . (Reproduced from ref. 13. Copyright 1988 American Chemical Society.)...

Microvoltammetric electrodes based on carbon fibers have greatly enhanced the feasibility of making interpretable measurements in brain tissue[25]. Their size is sufficiently small (Figure 6) so that there is no visible tissue damage in the region of electrode implantation when examined by post-mortem histology. Characterization of the factors that... 

Fig. 6. Tip of a carbon fiber microvoltammetric electrode as viewed with a scanning electron microscope. The carbon fiber, viewed in the center of the assembly, has a radius of 10 pm.

Fig. 8. Oxidation current from a microvoltammetric electrode placed in the caudate nucleus of an anesthetized rat during an electrical stimulation of the medial forebrain bundle. Top chronoampero-metric current ya. time at 0.5 V ys. SCE. Bottom difference of voltammogram obtained at the peak (circles), compared to voltammograms obtained for dopamine (DA) and ascorbic acid (AA) in vitro. Current scales for voltammograms i = 16 pA, 25 yM dopamine i = 28 pA, 200 jjM ascorbic acid i 32 pA, stimulation. Insert chronoamperometric current ys. time for an Identical experiment with 2-s intervals between measured points. Reprinted with permission from reference 34 (copyright 1983 by the AAAS).

Kristensen EW, Knhr WG, Wightman RM (1987) Temporal characterization of per-fluorinated ion exchange coated microvoltammetric electrodes for in vivo use. Anal Chem 59 1752-1757. 

Dayton, M. A. Ewing, A. G. Wightman, R. M. Response of microvoltammetric electrodes to homogeneous catalytic and slow heterogeneous charge-transfer reactions. Ana/ Chem 1980, 52, 2392-2396. 

Wightman RM (1981) Microvoltammetric electrodes. Anal Chem 53 1125A-1134A... 

Dayton MA, Brown JC, Stutts KJ, Wightman RM (1980) Faradaic electrochemistry at microvoltammetric electrodes. Anal Chem 52 946-950... 

Nafion, a perfluorinated sulfonated polymer introduced by Rubinstein and Bard 4 5, which is able to immobilize electroactive cations by electrostatic binding, has been coated on gold electrodes in order to display the electrochemical behaviours of the ferrocene-ferricinium couple . Ru(NH3)e and Ru(bpy)3 have also been used as redox centers ". Nafion has been proposed to modify microvoltammetric electrodes for in vivo use . 

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