General concepts of voltammetry

Fig-1 Schematic diagram representing the process of examining an electrode reaction mechanism using voltammetric techniques. 

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The two major classes of voltammetric technique 4 Evaluation of reaction mechanisms 6 General concepts of voltammetry 6 Electrodes roles and experimental considerations 8 The overall electrochemical cell experimental considerations 12 Presentation of voltammetric data 14 Faradaic and non-Faradaic currents 15 Electrode processes 17 Electron transfer 22 Homogeneous chemical kinetics 22 Electrochemical and chemical reversibility 25 Cyclic voltammetry 27 A basic description 27 Simple electron-transfer processes 29 Mechanistic examples 35... 

This chapter is meant to serve both as a guide for the beginner and as an overview for the nonelectrochemist with a need to know the methods available. Approximately half of the chapter is concerned with various aspects of linear sweep and cyclic voltammetry in view of the importance and widespread use of these techniques. Some general aspects of the heterogeneous electron transfer process, and the chemical reactions associated with it, are introduced in this part. Electrochemical reactions in which the electroactive substrate is formed in a chemical reaction in solution prior to the electron transfer [1-5] and catalysis of chemical reactions by electron transfer [6] are not included in this chapter. The reader interested in the details of such reactions should consult the presentations referred to. The reader is encouraged also to consult Chapter 1, where a number of basic electrochemical concepts are discussed in detail. 

The book offers the reader in its first part a general and as detailed as necessary introduction into the basic principles and methods, starting with sampling, sample storage and sample treatment. These steps are of utmost importance for each analytical procedure. This is followed by the description of the potential of a number of modern trace analytical methods, i.e. atomic absorption and emission spectrometry, voltammetry, neutron activation and isotope dilution mass spectrometry. The latter method is an important reference method within a general concept for quality control and the generation of reference materials which are an absolute must in this context. 

Now suppose we sample the current at some fixed time r into each of these step experiments then we can plot the sampled current, /(r), V5. the potential to which the step takes place. As shown in Figures 5A.3b and 5.1.3c, the current-potential curve has a wave shape much like that encountered in earlier considerations of steady-state voltammetry under convective conditions (Section 1.4.2). This kind of experiment is called sampled-current voltammetry, several forms of which are in common practice. The simplest, usually operating exactly as described above, is called normal pulse voltammetry. In this chapter, we will consider sampled-current voltammetry in a general way, with the aim of establishing concepts that apply across a broad range of par-... 

We will consider five subtopics tast polarography and staircase voltammetry, normal pulse voltammetry, reverse pulse voltammetry, differential pulse voltammetry, and square wave voltammetry. Tast polarography, normal pulse voltammetry, and differential pulse voltammetry form a sequence of development rooted historically in polarography at the DME. To illustrate the motivating concepts, we will introduce each of these methods within the polarographic context, but in a general way, applicable to both the DME and SMDE. Then we will turn to the broader uses of pulse methods at other electrodes. Reverse pulse voltammetry and square wave voltammetry were later innovations and will be discussed principally outside the polarographic context. 

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