Electrochemical detection working electrode material

If the crystal is a semiconductor such as Si, it can be used as the working electrode itself and this was the means employed in the early experiments. However, the limited number of suitable electrode materials available was a severe restriction and attempts to use metal-coated crystals suffered severely from the low sensitivity caused by the attenuation of the IR beam by the coating. In addition, lock-in detection is mainly limited to those electrochemical systems capable of responding sufficiently rapidly to the imposed potential modulation. 

A number of other carbon materials have been used for electrochemical detection [6] however, at this point none of these appear to have a clear advantage over the electrodes described earlier. Nevertheless, these alternative materials certainly do work and there is little doubt that we will continue to see additional entries as the search for the ideal electrode continues. The chapter on carbon electrodes by McCreery and Kneten (Chap. 10) is a good place to review the fundamental issues. 

Electrochemical techniques have been used in analytical chemistry for more than 50 yr, but there was little interest in or understanding of them by biologists until the 1970s. A breakthrough occurred in 1973 when Ralph Adams and his colleagues (1) showed that it was possible to implant a working electrode in a rat brain and detect electroactive materials in vivo. This heralded a new chapter in electrochemistry because it now appeared to be possible to study the release of neurotransmitters in intact animals without the use of complicated radioactive labeling techniques. 

Recently, electrochemical detection methods, namely, conductimetry, amperometry, and potentio-metry, have also become accessible. All three variants of electrochemical detection are intrinsically simpler than the optical methods, and their success depends highly on the electrode materials and designs used. Conductivity detection relies on measurement of the differences between the conductivities of the analyte and the separation electrolyte this provides a direct relationship between migration times and response factor, and makes this detector universal. On the contrary, amperometric detection is restricted to electroactive species and potentiometric detection is not possible for certain small ions with multiple charges. Conductimetric detection works better for inorganic compounds since the higher mobility of... 

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