Electrochemistry polarography

It is of interest to examine the development of the analytical toolbox for rubber deformulation over the last two decades and the role of emerging technologies (Table 2.9). Bayer technology (1981) for the qualitative and quantitative analysis of rubbers and elastomers consisted of a multitechnique approach comprising extraction (Soxhlet, DIN 53 553), wet chemistry (colour reactions, photometry), electrochemistry (polarography, conductometry), various forms of chromatography (PC, GC, off-line PyGC, TLC), spectroscopy (UV, IR, off-line PylR), and microscopy (OM, SEM, TEM, fluorescence) [10]. Reported applications concerned the identification of plasticisers, fatty acids, stabilisers, antioxidants, vulcanisation accelerators, free/total/bound sulfur, minerals and CB. Monsanto (1983) used direct-probe MS for in situ quantitative analysis of additives and rubber and made use of 31P NMR [69]. 

In 1922 he invented the polarographic method in electrochemistry (polarography is based on electrolysis using a dropping mercury electrode), and he continued development of this new branch of electrochemistry for decades. In 1926 he married Marie Koranova and had two children. In 1950 he was appointed director of the newly established Polarographic Institute (incorporated into the Czechoslovak Academy of Sciences in 1952). In 1959 he was awarded the Nobel Prize in chemistry for his discovery and development of the polarographic methods of analysis. ... 

Electrochemistry voltammetry, anodic stripping (ASV), cathodic stripping (CSV), polarography, differential pulse polarography (DPP), ion selective electrode (ISE)... 

Principles and Characteristics A substantial percentage of chemical analyses are based on electrochemistry, although this is less evident for polymer/additive analysis. In its application to analytical chemistry, electrochemistry involves the measurement of some electrical property in relation to the concentration of a particular chemical species. The electrical properties that are most commonly measured are potential or voltage, current, resistance or conductance charge or capacity, or combinations of these. Often, a material conversion is involved and therefore so are separation processes, which take place when electrons participate on the surface of electrodes, such as in polarography. Electrochemical analysis also comprises currentless methods, such as potentiometry, including the use of ion-selective electrodes. 

Heyrovsky, Jaroslav (1890-1967) received the 1959 Nobel Prize in Chemistry for his discovery of polarography and for his role in the development of this technique which has become such an important tool in electrochemistry, analytical chemistry and many other areas of science and technology. He was for many years a professor of physical chemistry at the Charles University of Prague. When the Prague Polarographic Institute was founded in 1950, Heyrowski became its first director. Obituary notices for Prof Heyrowski appeared in many scientific journals attesting to his widespread recognition and esteem Refs 1) Anon, C EN 45,16 83 (1967) ... 

Most of the work on the boric acid-diol reaction during the last twenty years has been done to determine the coordination number of the diol (number of diol molecules) in the complex and to evaluate the equilibrium constant (often called a stability constant) for a number of diol-boric acid reactions. Several techniques have been used to study these questions, including polarimetry (7), optical rotatory dispersion (8), polarography (9), conductivity (3), vapor pressure osmometry (10), and electrochemistry (II, 12, 13). The most frequently studied system has been the electrochemical (pH) titration of boric acid or borax solutions with various diols. 

Electrochemistry finds wide application. In addition to industrial electrolytic processes, electroplating, and the manufacture and use of batteries already mentioned, the principles of electrochemistry are used in chemical analysis, e.g.. polarography, and electrometric or conductometric titrations in chemical synthesis, e.g., dyestuffs, fertilizers, plastics, insecticides in biolugy and medicine, e g., electrophoretic separation of proteins, membrane potentials in metallurgy, e.g.. corrosion prevention, eleclrorefining and in electricity, e.g., electrolytic rectifiers, electrolytic capacitors. 

Delahay, JACS 75, 555-59 (1953) (Oscillographic polarography with controlled potential) 3)C.A.Streuli W.D.Cooke, AnalChem 26, 963 70 (1953) (Chronoamperometry with linearly varied potential using polarized Hg pool cathode) 4)P.Delahay, "New Instrumental Methods in Electrochemistry ,Inter science,... 

The Dimensionless Parameter is a mathematical method to solve linear differential equations. It has been used in Electrochemistry in the resolution of Fick s second law differential equation. This method is based on the use of functional series in dimensionless variables—which are related both to the form of the differential equation and to its boundary conditions—to transform a partial differential equation into a series of total differential equations in terms of only one independent dimensionless variable. This method was extensively used by Koutecky and later by other authors [1-9], and has proven to be the most powerful to obtain explicit analytical solutions. In this appendix, this method will be applied to the study of a charge transfer reaction at spherical electrodes when the diffusion coefficients of both species are not equal. In this situation, the use of this procedure will lead us to a series of homogeneous total differential equations depending on the variable, v given in Eq. (A.l). In other more complex cases, this method leads to nonhomogeneous total differential equations (for example, the case of a reversible process in Normal Pulse Polarography at the DME or the solutions of several electrochemical processes in double pulse techniques). In these last situations, explicit analytical solutions have also been obtained, although they will not be treated here for the sake of simplicity. 

J. Thompson, 1893) and the development of chemical thermodynamics (G. N. Lewis, 1923). Building on this foundation, the utilization of electrochemical phenomena for thermodynamic characterization and analysis of molecules and ions (electroanalytical chemistry) began at the beginning of this century [po-tentiometry (1920) and polarography (1930)]. Relationships that describe the techniques of potentiometry and polarography derive directly from solution thermodynamics. In the case of polarography, there is a further dependence on the diffusion of ionic species in solution. The latter is the basis of conductivity measurements, another area that traces its origin to the nineteenth century. These quantitative relationships make it possible to apply electrochemistry to... 

For chemists, the second important application of electrochemistry (beyond potentiometry) is the measurement of species-specific [e.g., iron(III) and iron(II)] concentrations. This is accomplished by an experiment in which the electrolysis current for a specific species is independent of applied potential (within narrow limits) and controlled by mass transfer across a concentration gradient, such that it is directly proportional to concentration (/ = kC). Although the contemporary methodology of choice is cyclic voltammetry, the foundation for all voltammetric techniques is polarography (discovered in 1922 by Professor Jaroslov Heyrovsky awarded the Nobel Prize for Chemistry in 1959). Hence, we have adopted a historical approach with a recognition that cyclic voltammetry will be the primary methodology for most chemists. 

The majority of controlled-potential electrochemistry has been carried out at mercury-pool electrodes. This is because of the vast amount of reference data available from polarography. Furthermore, the uniform and reproducible surface, and the high voltage for solvent reduction make the mercury pool particularly attractive relative to solid electrodes. As with electrodeposition, controlled-potential electrolysis rates are dependent on electrode area, stirring rates, solution volume, solution temperature, and supporting electrolyte. If the diffusion layer is uniform and the applied potential is such that one is on the diffusion plateau, the electrolysis obeys the relation... 

Twenty years ago the main applications of electrochemistry were trace-metal analysis (polarography and anodic stripping voltammetry) and selective-ion assay (pH, pNa, pK via potentiometry). A secondary focus was the use of voltammetry to characterize transition-metal coordination complexes (metal-ligand stoichiometry, stability constants, and oxidation-reduction thermodynamics). With the commercial development of (1) low-cost, reliable poten-tiostats (2) pure, inert glassy-carbon electrodes and (3) ultrapure, dry aptotic solvents, molecular characterization via electrochemical methodologies has become accessible to nonspecialists (analogous to carbon-13 NMR and GC/MS). 

Liquid chromatography/electrochemistry Low-energy electron diffraction Mercury flow rate (in polarography)... 

Lingane was a leader in the field of - electro analytical chemistry and wrote, with Kolthoff, the definitive, two volume monograph, Polarography [i] that remains a useful reference work. He also helped develop other electroanalytical techniques, like controlled potential electrolysis, -> coulometry, -> coulometric titrations, and developed an early electromechanical (Lingane-Jones) potentiostat, He wrote the widely-used monograph in this field, Electroanalytical Chemistry (1st edn., 1953 2nd edn., 1958). Lingane received a number of awards, including the Analytical Chemistry (Fisher) Award of the American Chemical Society in 1958. Many of his Ph.D. students, e.g., -> Meites, Fred Anson, Allen Bard, Dennis Peters, and Dennis Evans, went on to academic careers in electrochemistry. 

Refs. [i] Bard A], Lund H (eds) (1978-1984) Encyclopedia of electrochemistry of elements, vols. XI-XV. Marcel Dekker, New York [ii] Lund H, Hammerich O (eds) (2001) Organic electrochemistry, 4th edn. Marcel Dekker, New York [in] Meites L, Zuman P (1976-1983) Handbook series in organic electrochemistry, vols. I-VI. CRC Press, Boca Raton [iv] Zuman P (1971) Substituents effects in organic polarography. Plenum Press, New York... 

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. 

For a more detailed discussion of these points the reader is referred to G. Kortum and J. O M. Bockris, Textbook of Electrochemistry, Elsevier Publishing Company, Amsterdam, 1951, and to I. M. Kolthoff and J.. 1. I ingane, Polarography, Interscience Publishers, Inc., New York, 1952. More quantitative treatments will be found in J. O M. Bockris, Modern Aspects of Electrochemistry, Butterworth Co. (Publishers) Ltd., I ondon, 1954, and in P. Delahay, New Instrumental Methods in Electrochemistry, Interscience Publishers, Inc., New York, 1954. 

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