Why Electroanalysis

In contrast to many chemical measurements, which involve homogeneous bulk solutions, electrochemical processes take place at the electrode-solution interface. The distinction between various electroanalytical techniques reflects the type of electrical signal used for the quantitation. The two principal types 

Analytical Electrochemistry, Third Edition, by Joseph Wang Copyright 2006 John Wiley Sons, Inc. 

Potentiometry (discussed in Chapter 5), which is of great practical importance, is a static (zero-current) technique in which the information about the sample composition is obtained from measurement of the potential established across a membrane. Different types of membrane materials, possessing different ion recognition processes, have been developed to impart high selectivity. The resulting potentiometric probes have thus been widely used for several decades for direct monitoring of ionic species such as protons or calcium, fluoride, and potassium ions in complex samples. 

This chapter attempts to give an overview of electrode processes, together with discussion of electron transfer kinetics, mass transport, and the electrode-solution interface. 

Controlled-potential (potentiostatie) teehniques deal with the study of eharge-transfer proeesses at the eleetrode-solution interfaee, and are based on dynamie (no zero eurrent) situations. Here, the eleetrode potential is being used to derive an eleetron-transfer reaetion and the resultant eurrent is measured. The role of the potential is analogous to that of the wavelength in optical measurements. Sueh a eontrollable parameter ean be viewed as eleetron pressure, whieh forees the ehemieal speeies to gain or lose an eleetron (reduetion or oxidation, respeetively). 

Technique Working Electrode Detection Limit (M) Speed (time per cycle) (min) Response Shape 

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