Development of polarograph

Recent developments of polarographic adsorptive complex waves and catalytic... 

J. Heyrovsky (Prague) discovery and development of the polarographic method of analysis. 

Polarograms are sometimes distorted by polarographic maxima, where the current in individual segments of the I vs. E curves is much higher (several times) than the limiting diffusion current. A number of reasons exist for the development of these maxima. 

The realization that current sampling on a step pulse can increase the detection sensitivity by increasing the faradaic/charging ratio is the basis for the development of various pulse voltammetric (or polarographic) techniques. Also, the pulses can be applied when it is necessary and can reduce the effect of diffusion on the analyte. Figure 18b. 11 shows the waveform and response for three commonly used pulse voltammetric techniques normal pulse voltammetry (NPY), differential pulse voltammetry (DPV), and square-wave voltammetry (SWV). 

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) ... 

Further development of direct reading instruments for analysis may be expected, for example in polarographs, x-ray and emission spectrometers. 

Like benzenoid hydrocarbons, pyridine-like heterocycles give well-developed two-electron waves on reduction at the dropping mercury electrode. The latter are polarographically much more reducible than the former. This can be explained easily in terms of the HMO theory It is assumed (cf. ref. 3) that the value of the half-wave potential is determined essentially by the energy of the lowest free 7r-molecular orbital (LFMO) of the compound to be reduced, and for models of hetero analogues this quantity is always lower than that for the parent hydrocarbons. Introduction of an additional heteroatom into the molecule leads to a further enhancement of the ease of polarographic reducibility.95 On the other hand, anodic oxidation of the heterocyclic compounds is so much more difficult in comparison with benzenoid hydrocarbons that they are not oxidizable under the usual polarographic conditions. An explanation in terms of the HMO theory is obvious. 

HF.YROVSKY, JAROSLAV (1890-1967). A Czechoslovakian physio-chcmist who won Ihe Nobel prize for chemistry in 1959. for his discovery and development of the polamgraphic and oscillo-polarographic methods of analysis. Although his Ph.D. was from the University of Prague, he later studied in London. 

Pulse polarography has been used to characterize the products of the photochemical oxidation of 3,4-dihydro-1-isoquinolineacetamide to 1-isoquinoline-acetamide (see Fig. 26.5) [73]. After photochemical oxidation, the polarographic activity that the compound had previously demonstrated in acid and neutral supporting electrolytes was destroyed. This was in agreement with the development of fluorescence activity due to the formation of the unsaturated derivative. 

The development of a simple fast-scan polarographic method for the determination of the A4-3-ketosteroid flurandrenolone in pharmaceutical preparations has been reported [134]. The polarographic peak due to the reduction of the carbon-fluorine bond is measured in ointments and creams to determine concentrations as low as 0.01 % w/w. Pulse polarographic procedures have been described for progesterones [135], A4-3-ketosteroids [136], hydrocortisone [137], and flucytosine [138] in pharmaceutical preparations. Recent studies have illus-... 

A review of the state of development of the various instrumental methods of analysis including polarography is presented (Ref 136). Whit-nack (Refs 24 101) also used the linear sweep polarograph to determine microgram quantities of TNT in milligram samples of warhead exudates. Brandone et al (Ref 102) determined polarographically the compn of expl mixts containing TNT... 

Fig. 2.7 A portrait of Jarovslav Heyrovsky, Nobel Prize for Chemistry in 1959 for his discovery and development of the polarographic methods of analysis. Source archiv UFCH J. Heyrovskeho AV CR, v.v.i. http //www.jh-inst.cas.cz...

Gipsy et al. have developed a polarographic method for determination of zaleplon in ethanol-0.1 M Britton Robinson buffer solution (30-70) which showed two irreversible, well-defined cathodic responses in the pH range... 

Belal et al [15] developed a polarographic method for the determination of EDTA in pharmaceutical dosage forms based on chelation with Eu(III) at pH 4, and followed by measuring the cathodic current. The current-concentration range was found to be linear over the ranges 8-160 pg/mL and over 2-120 pg/mL using direct current (DCt) and differential pulse (DPP) modes of detection, respectively, with minimum detectability of 0.1 pg/mL. 

Czech chemist Jaroslav Heyerovsky, recipient of the 1959 Nobel Prize in chemistry, for his discovery and development of the polarographic method of analysis. ... 

Song et al. [11] developed a polarographic method for the determination of mefenamic acid in tablets, which was based on rapid nitrosation of mefenamic acid with sodium nitrite in acetic acid, and subsequent measurement of the A-nitroso derivative of mefenamic acid by linear-sweep polarography. The method is simple, sensitive, and specific, and was characterized by a detection limit of 2 x 10 7 mol/L. 

The Frumkin epoch in electrochemistry [i-iii] commemorates the interplay of electrochemical kinetics and equilibrium interfacial phenomena. The most famous findings are the - Frumkin adsorption isotherm (1925) Frumkin s slow discharge theory (1933, see also - Frumkin correction), the rotating ring disk electrode (1959), and various aspects of surface thermodynamics related to the notion of the point of zero charge. His contributions to the theory of polarographic maxima, kinetics of multi-step electrode reactions, and corrosion science are also well-known. An important feature of the Frumkin school was the development of numerous original experimental techniques for certain problems. The Frumkin school also pioneered the experimental style of ultra-pure conditions in electrochemical experiments [i]. A list of publications of Frumkin until 1965 is available in [iv], and later publications are listed in [ii]. 

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