Pulse voltammetry Polarography

Normal-pulse voltammetry consists of a series of pulses of increasing amplitude applied to successive drops at a preselected time near the end of each drop lifetime (4). Such a normal-pulse train is shown in Figure 3-4. Between the pidses, the electrode is kept at a constant (base) potential at which no reaction of the analyte occurs. The amplitude of the pulse increases linearly with each drop. The current is measured about 40 ms after the pulse is applied, at which time the contribution of the charging current is nearly zero. In addition, because of the short pulse duration, the diffusion layer is thinner than that in DC polarography (i.e., there is larger flux of... 

Fig. 5.18 Potentiostatic methods (A) single-pulse method, (B), (C) double-pulse methods (B for an electrocrystallization study and C for the study of products of electrolysis during the first pulse), (D) potential-sweep voltammetry, (E) triangular pulse voltammetry, (F) a series of pulses for electrode preparation, (G) cyclic voltammetry (the last pulse is recorded), (H) d.c. polarography (the electrode potential during the drop-time is considered constant this fact is expressed by the step function of time—actually the potential increases continuously), (I) a.c. polarography and (J) pulse polarography...

Detection sensitivity better than that in NPV can be achieved by differential current sampling with small pulses. Figure 18b.lib shows this scheme known as differential pulse voltammetry (DPV). Here, the potential is changed from an initial potential in small steps (2-5 mV) and a voltage pulse of a short duration (50 ms) is superimposed at the end of a long step (500-5000 ms). The current is sampled before the beginning of the pulse and near the end of the pulse as shown in Fig. 18b. 12b. In differential pulse polarography (DPP), this is near the... 

The polarographic behavior of l-(2-nitrophenyl)-3,3-dimethyltriazene (255) in a mixed aqueous-methanolic solvent was investigated by test polarography, differential pulse polarography and fast scan differential pulse voltammetry at a hanging mercury drop electrode529. 

In many respects, differential pulse voltammetry is more similar to classical polarography than to the normal pulse methods (see above). A linear potential ramp of dE/dt is applied to the working electrode (see Figure 6.24). However, in common with normal pulse voltammetry, a succession of pulses are also applied to the working electrode. (The WE is often a DME, and then we refer to differential pulse polarography .)... 

Large-amplitude ( normal ) pulse voltammetry techniques were introduced in Chapter 3. The differential normal pulse (DNP) method combines several features of both the small- and large-amplitude pulse techniques. This technique is normally performed at a DME and is actually a form of polarography. The... 

Potentiodynamictechniques— are all those techniques in which a time-dependent -> potential is applied to an - electrode and the current response is measured. They form the largest and most important group of techniques used for fundamental electrochemical studies (see -> electrochemistry), -> corrosion studies, and in -> electroanalysis, -+ battery research, etc. See also the following special potentiodynamic techniques - AC voltammetry, - DC voltammetry, -> cyclic voltammetry, - linear scan voltammetry, -> polarography, -> pulse voltammetry, - reverse pulse voltammetry, -> differential pulse voltammetry, -> potentiodynamic electrochemical impedance spectroscopy, Jaradaic rectification voltammetry, - square-wave voltammetry. 

NPV), differential pulse voltammetry (DPV) and SWV, and polarography methods (use of a mercury drop electrode) like normal (normal and pulse polarography (NPP)) and DPP, although sometimes these polarographic versus voltammetric terms are used interchangeably. These step methods do not typically use return scans and therefore often do not provide information about reversibility of the redox process and can sometimes give data that, unknown to the researcher, are characteristic of decomposition products. 

Differential pulse polarography using glassy carbon, SCE, and auxilliary Pt electrodes 266 Double pulse voltammetry using Pt surfaces 267... 

Because these methods are so deeply rooted in the polarographic tradition and even now are frequently used with polarographic electrodes, we begin with a discussion of phenomena at dropping mercury electrodes and then develop the subject through conventional polarography and into various forms of pulse voltammetry. 

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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