Voltammetric techniques experimental response

This method operating with the time window of about 100 to 3000 s is suitable to study reactions with rate constants, k, of the order of 10" to 10"" s" This voltammetric technique enables the determination of reaction products by the electroanalysis of the solution following the electrolysis and hence the interpretation of the overall reaction scheme. Moreover, the experiments are carried out at potentials of the limiting current this is why the electron transfer kinetics does not disturb the estimation of the results. The interpretation of the coulometric responses is usually much simpler than those of other voltammetric methods. The experimental parameters to be evaluated are as follows ... 

The non-reversible behavior is plotted in Fig. 7.46, which corresponds to the corrected (Jcv/v) — E curves (dashed lines) and the (QDSCVC/AE) — E ones (symbols) of the system 4-PhenylazoPhenol. From these curves, it can be seen that although the DSCVC curves are perfectly superimposable, the CV ones clearly show smaller peak heights in both scans. This systematic decrease of the CV signals, which cannot be theoretically predicted, is 5-10 %, and it has been reported when the response of electro-active monolayers in CV has been compared with other voltammetric and chronopotentiometric electrochemical techniques [71, 72], Due to the quasi-reversible nature of the charge transfer reduction of the 4-PhenylazoPhenol, no simple equations for the peak parameters are available. So, a numerical comparison between theoretical and experimental curves for different sets of parameters should be made in order to obtain the kinetic and thermodynamic parameters of the system. 

The basic concept is that the experimental voltammetric data are collected and a mechanism for the electrode reaction mechanism is postulated. The proposed mechanism may be theoretically simulated by solving the appropriate mathematical problem. Satisfactory agreement between experiment and theory is used to suggest a quantitative description for a particular mechanism, but as with most kinetic studies ideally the identity of proposed reaction intermediates must be confirmed by an independent technique, e.g. a spectroscopic technique. It is inherently dangerous to assume the structure of a reaction product or intermediate solely on the basis of a voltammetric response. 

Voltammetric and chronopotentiometric detection modes are mostly used [20]. Together with them, electrochemical impedance spectroscopy (EIS) becomes to be popular at DNA-based biosensors [13]. According to electrochemi-cally active species which responses are evaluated at the detection of damage to DNA, the experimental techniques can be classified as follows [1] ... 

At present, voltammetric investigations hold a prominent position among different techniques used for studies of electrochemical behavior of metal complexes. Currently available variations of voltammetry make it possible to accumulate the necessary experimental data readily and handily. The next step involves a quantitative interpretation of the data obtained, which could be modified in response to the respective theoretical relationships intended for application. Some selected transforms of voltammetric data are considered next. 

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