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Electrochemical voltammetric

Electrochemical, voltammetric Winquist (Sweden) Characterization of waters with an array of noble metals [17]... [Pg.723]

In conclusion, UVAds/NIR spectroelectrochemistry in both transmission and reflection mode are extremely useful techniques that yield a wealth of complementary data additional to those obtained in pure electrochemical voltammetric experiments. Especially when based on computer simulation models, this data may be used to unravel the kinetics and thermodynamics of complex electrode processes. [Pg.198]

Electrochemical cell/voltammetric cell A cell where electrochemical/voltammetric measurements are performed. It incorporates an ionic conductor (electrol3rte, sample solution) and typically three electrodes a working electrode (a microelectrode), a current-... [Pg.18]

The electrochemical voltammetric data on fabrics are shown in Table 12.21. This suggests the possiblity of the involvement of nitrogen PAn in the surface coordination to the substrate material to explain the negligible electrochromic response. Otherwise data indicate that the basic grafted polymer polyaniline is almost identical to the electrochemically synthesized polymer. [Pg.562]

Table 12.21 Electrochemical voltammetric data on fabrics Table 12.22 Resistivity data of PAn grafted surfaces... Table 12.21 Electrochemical voltammetric data on fabrics Table 12.22 Resistivity data of PAn grafted surfaces...
When the complexes can be reduced or oxidized so that electrochemical (voltammetric) detection can be employed, the most common method involves amperometric detection at a constant DC potential. With this method, the current, which is proportional to the metal concentration. [Pg.170]

In voltammetry a time-dependent potential is applied to an electrochemical cell, and the current flowing through the cell is measured as a function of that potential. A plot of current as a function of applied potential is called a voltammogram and is the electrochemical equivalent of a spectrum in spectroscopy, providing quantitative and qualitative information about the species involved in the oxidation or reduction reaction.The earliest voltammetric technique to be introduced was polarography, which was developed by Jaroslav Heyrovsky... [Pg.508]

A typical arrangement for a voltammetric electrochemical cell is shown in Figure 11.28. Besides the working, reference, and auxiliary electrodes, the cell also includes a N2 purge line for removing dissolved O2 and an optional stir bar. Electrochemical cells are available in a variety of sizes, allowing for the analysis of solution volumes ranging from more than 100 mL to as small as 50 )+L. [Pg.510]

Influence of the Kinetics of Electron Transfer on the Faradaic Current The rate of mass transport is one factor influencing the current in a voltammetric experiment. The ease with which electrons are transferred between the electrode and the reactants and products in solution also affects the current. When electron transfer kinetics are fast, the redox reaction is at equilibrium, and the concentrations of reactants and products at the electrode are those specified by the Nernst equation. Such systems are considered electrochemically reversible. In other systems, when electron transfer kinetics are sufficiently slow, the concentration of reactants and products at the electrode surface, and thus the current, differ from that predicted by the Nernst equation. In this case the system is electrochemically irreversible. [Pg.512]

In the previous section we saw how voltammetry can be used to determine the concentration of an analyte. Voltammetry also can be used to obtain additional information, including verifying electrochemical reversibility, determining the number of electrons transferred in a redox reaction, and determining equilibrium constants for coupled chemical reactions. Our discussion of these applications is limited to the use of voltammetric techniques that give limiting currents, although other voltammetric techniques also can be used to obtain the same information. [Pg.527]

Scale of Operation Voltammetry is routinely used to analyze samples at the parts-per-million level and, in some cases, can be used to detect analytes at the parts-per-billion or parts-per-trillion level. Most analyses are carried out in conventional electrochemical cells using macro samples however, microcells are available that require as little as 50 pL of sample. Microelectrodes, with diameters as small as 2 pm, allow voltammetric measurements to be made on even smaller samples. For example, the concentration of glucose in 200-pm pond snail neurons has been successfully monitored using a 2-pm amperometric glucose electrode. ... [Pg.531]

In voltammetry we measure the current in an electrochemical cell as a function of the applied potential. Individual voltammetric methods differ in terms of the type of electrode used, how the applied potential is changed, and whether the transport of material to the electrode s surface is enhanced by stirring. [Pg.533]

Many anodic oxidations involve an ECE pathway. For example, the neurotransmitter epinephrine can be oxidized to its quinone, which proceeds via cyclization to leukoadrenochrome. The latter can rapidly undergo electron transfer to form adrenochrome (5). The electrochemical oxidation of aniline is another classical example of an ECE pathway (6). The cation radical thus formed rapidly undergoes a dimerization reaction to yield an easily oxidized p-aminodiphenylamine product. Another example (of industrial relevance) is the reductive coupling of activated olefins to yield a radical anion, which reacts with the parent olefin to give a reducible dimer (7). If the chemical step is very fast (in comparison to the electron-transfer process), the system will behave as an EE mechanism (of two successive charge-transfer steps). Table 2-1 summarizes common electrochemical mechanisms involving coupled chemical reactions. Powerful cyclic voltammetric computational simulators, exploring the behavior of virtually any user-specific mechanism, have... [Pg.35]

Shipping analysis is an extremely sensitive electrochemical technique for measuring trace metals (19,20). Its remarkable sensitivity is attributed to the combination of an effective preconcentration step with advanced measurement procedures that generate an extremely favorable signal-to-background ratio. Since the metals are preconcentrated into the electrode by factors of 100 to 1000, detection limits are lowered by 2 to 3 orders of magnitude compared to solution-phase voltammetric measurements. Hence, four to six metals can be measured simultaneously in various matrices at concentration levels down to 10 10 i. utilizing relatively inexpensive... [Pg.75]

The nature of electrochemical instruments makes them very attractive for decentralized testing. For example, compact, battery-operated voltammetric analyzers, developed for on-site measurements of metals (9,10), readily address the growing needs for field-based environmental studies. Similarly, portable (hand-held) instruments are being designed for decentralized clinical testing (11). [Pg.107]

These equations contain useful information about how the relaxation control affects the voltammetric peaks when different electrochemical, chemical, structural, and geometric variables are changed. If we assume that the peak overpotential (tjp) is much greater than the nucleation overpotential, the maximum of Eq. (58) can be written as... [Pg.412]

T. Chao, K.J. Walsh, and P.S. Fedkiw, Cyclic voltammetric study of the electrochemical formation of platinum oxide in a Pt/yttria-stabilized zirconia cell, Solid State Ionics 47, 277-285 (1991). [Pg.275]


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See also in sourсe #XX -- [ Pg.510 , Pg.511 ]




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