Heyrovsky polarography

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... 

Hey Heyrovsky, J., Kuta, J. Grundlagen der Polarographie, Berlin Akademie-Verlag, 1965. 65Nie Nieholson, R.S. Anal. Chem. 37 (1965) 1351. 

The first version of a polarographic technique was put forward in 1922 by the Czech scientist Jaroslav Heyrovsky. Classsical polarography is the measurement of quasisteady-state polarization curves with linear potential scans applied to the DME sufficiently slowly (v between 1 and 20mV/s), so that within the lifetime, of an individual drop, the potential would not change by more than 3 to 5 mV. With special instruments (polarographs), one can record the resulting 7 vs. E curves (polaro-grams) automatically. 

Because of these advantages, polarography became very popular immediately after its inception in 1922. For the development of this method, Heyrovsky was awarded a Nobel prize in 1959. Over the period from 1922 to 1960, several tens of thousands of papers concerned with the use and improvement of polarography were published. However, interest in this method declined markedly in the 1960s, due primarily to a drastic increase in the requirements to be met by methods of chemical analysis. With the production of new superpure materials and increasing awareness for ecological problems, it became necessary to develop much more sensitive methods of analysis able to detect the different impurities down to a level of 10 M. 

J. Heyrovsky and P. Zuman, Practical Polarography, Academic Press, New York, 1961. 

As a consequence of the particular geometry of the dme and its periodically altering surface area, the theory of polarography necessarily requires an amplification of what has already been stated about the theory of electrolysis in Sections 3.1 and 3.2. Such an amplification was given in 1934 by Ilkovic in close collaboration with Heyrovsky, and resulted in the well known Ilkovic equation ... 

H. P. Agarwal and M. Saxena, in Proceedings II (Abstracts), J. Heyrovsky Memorial Congress on Polarography, Prague, Czechoslovakia, 1980. 

Heyrovsky, J. and Kuta, J. (1966). Principles of Polarography. Publishing House of the Czechoslovak Academy of Sciences, Praha, and Academic Press, New York. 

Voltammetry is a part of the repertoire of dynamic electrochemical techniques for the study of redox (reduction-oxidation) reactions through current-voltage relationships. Experimentally, the current response (i, the signal) is obtained by the applied voltage (.E, the excitation) in a suitable electrochemical cell. Polarography is a special form of voltammetry where redox reactions are studied with a dropping mercury electrode (DME). Polarography was the first dynamic electrochemical technique developed by J. Heyrovsky in 1922. He was awarded the Nobel Prize in Chemistry for this discovery. 

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) ... 

For example, (a) Kolthoff, I.M., Lin-gane, J. J. Polarography, 2nd edn., Interscience Publishers, New York, 1952 (b) Meites, L. Polarographic Techniques, 2nd ed., Interscience Publishers, New York, 1965 (c) Heyrovsky, J., Kuta, J. Principles of Polarography, Academic Press, New York, 1966 (d) Bond, A. M. Modem Polarographic Methods in Analytical Chemistry, Marcel Dekker, New York, 1980 ... 

Figure 17-14 Polarography apparatus featuring a dropping-mercury working electrode. Polarography was invented by Jaroslav Heyrovsky in 1922, for which he received a Nobel Prize in 1959.

For many years, the study of the electrode—electrolyte interface and electrode kinetics was confined to the very reproducible mercury-aqueous system because of the availability of the dropping mercury electrode (DME) and development of polarography. Extensive leading work in this field was carried out by Heyrovsky, Frumkin, Grahame, and Randles. 

Since the invention of d.c. polarography [10, 11], numerous inorganic and organic compounds have been studied by means of this method in Heyrovsky s school and extensive knowledge gathered about the electrochemical properties of these compounds. Among them, many cases were discovered where the polarographic wave appeared to be influenced by the existence of chemical equilibria between the electroactive substance and other, in most cases electroinactive, species in the electrolyte solution, more particularly by the finite rate at which these equilibria relax after the electrochemical perturbation. In fact, the chemical reaction serves as either a source or a sink to deliver or to consume the electroactive reactants and products, in addition to diffusion. 

J. Heyrovsky and J. Kuta, Principles of Polarography, Academic Press, London,... 

J-Heyrovsky, Oszillographische Polarographie mit Weckselstrom , AkadVerlag, Berlin (1959) 28)J.D.Voorhies, UnivMicrofilms (Ann Arbor, Mich), LC Card No MIc 59-5237, 222pp Dissertation Abst 20, 2596-7... 

Heyrovsky, J., and J. Kuta Principles of Polarography. New York Academic Press 1966. 

Heyrovsky, J., and P. Zuman Practical Polarography, 230 pp. London Academic Press 1968. 

Although nowadays the DME electrode is scarcely employed, it is of a great historical importance since it allowed the development of the first voltammetrical technique, Polarography, designed by Jaroslav Heyrovsky (Fig. 2.7). A DME consists of a glass capillary of 0.05-0.1 mm of internal diameter from which mercury flows forming spherical drops (see Fig. 2.8). This electrode has two characteristic parameters the flow rate m (mass of mercury per unit of time) and the drop life time fj. By assuming that the electrode has spherical shape at any... 

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