Voltammetric and Polarographic Methods

Since the area of the microelectrode is very small, and the associated current minute, the iR drop through the solution will also be very small. On this basis, 

James G. Dick, McGraw-Hill, Inc., (1973), Chapter 12, Section 12.5 (with 

In order for the current to be directly related to the concentration of the analyte of interest it must be a current that has no significant component other than that associated with the analyte. The sources of current which might contribute to the total current are the following  

The current resulting from the attraction of the charge on the working electrode for the oppositely-charged analyte substance, sometimes called the electrostatic attraction current. 

The current required to sustain the charge on the working electrode against leakage losses. This is the charging or condenser current and forms part of the residual current. 

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The lower detection limits cited above for these pulsed voltammetric and polarographic methods are summarized below in Table 6.7. Whenever we cite a concentration limit, we are saying in effect that this is the very lowest that it is possible to achieve. It should be emphasized, however,... 

Differential pulse voltammetric and polarographic methods described in this section represent a significant enhancement of the available instrumental analysis capabilities for the quantitative speciation of sulfide, thiosulfate, sulfite and of heteroaromatic sulfur moieties in coal conversion process streams and products. 

G. D. Christian, Analytical Chemistry, 4th edition, Wiley, New York (1986). Voltammetric and Polarographic Methods... 

Voltammetric and polarographic methods were, and still are, only exceptionally used for determining the main component of a sample (pure substance determination) since the accuracy of about 2 to 3% is not sufficient here. The other electroanalytical methods, e.g. coulometry and coulometric titrations are to be recommended here because of their higher accuracy. 

All these topics are discussed very briefly here. The emphasis of this chapter is on the voltammetric and polarographic behavior of proteins, polysaccharides, and nucleic acids. In contrast to most of the other physicochemical methods. 

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. 

The unique feature of polarographic methods that sets them apart from other voltammetric techniques is the use of a dropping mercury electrode as the working electrode. In this section we shall deal with the properties of mercury as an electrode material and the characteristics of the electrode in use. 

II. Practical Application of Polarographic/Voltammetric, Tensammetric Techniques and Hybrid Methods (HPLC-EC)... 

The days where a polarographic method was always the last resort and where it had to prove its efficacy several times over are coming to a close. On the other hand, overoptimistic views predicting a bright future for the polarographic and voltammetric techniques are out of... 

Other analytical techniques. Electroanalytical methods can also be used to differentiate between ionic species (based on valence state) of the same element by selective reduction or oxidization. In brief, the electroanalytical methods measure the effect of the presence of analyte ions on the potential or current in a cell containing electrodes. The three main types are potentiometry, where the voltage difference between two electrodes is determined, coulometry, which measures the current in the cell over time, and voltammetry, which shows the changes in the cell current when the electric potential is varied (current-voltage diagrams). In a recent review article, 43 different EA methods for measuring uranium were mentioned and that literature survey found 28 voltammetric, 25 potentiometric, 5 capillary electrophoresis, and 3 polarographic methods (Shrivastava et al. 2013). Some specific methods will be discussed in detail in the relevant chapters of this tome. 

Voltammetric/polarographic methods are not very important for anion analysis. Only bromate, iodate, and periodate can be determined by means of polarographic reduction currents. Indirect determinations are possible for those anions that form compounds of low solubility or stable complexes with the Hg ions formed in the anodic oxidation of the electrode mercury. The current caused by the dissolution of the mercury is proportional to the concentration of these anions in the sample... 

The incorporation of computers into SIA systems has also facilitated the implementation of stopped-flow methods. It suffices to calculate the volume of carrier to be delivered and stop the system when a peak is obtained at the detector in order to readily implement various analytical methodologies including classical kinetic, spectrophotometric, polarographic, voltammetric and anodic stripping... 

Institute of Chemistry and Metallurgy Ural Branch USSR AS and Tomsk Polytechnic Institute. Dr. A.G. Stromberg. The early works on organic polarography in the USSR [144-146] and polarographic and voltammetric methods for determining the trace of organic substances [147]. 

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