Absence of unwinding of double-helical DNA in the surface of mercury electrode charged to DNA reduction potentials at neutral pH

1979 ◽  
Vol 44 (2) ◽  
pp. 448-455 ◽  
Author(s):  
Emil Paleček ◽  
Sianette Kwee
Keyword(s):  
Conformational Changes ◽  
Electrode Surface ◽  
Mercury Electrode ◽  
Linear Sweep Voltammetry ◽  
Reduction Product ◽  
Potential Range ◽  
Acid Media ◽  
Reduction Potentials ◽  
Dropping Mercury Electrode ◽  
Neutral Media

The influence of adsorption of DNA on its double-stranded (ds) structure was studied with the aid of hanging mercury drop electrode (HMDE) in neutral media. Changes in DNA reducibility followed by linear sweep voltammetry served as an indication of the DNA conformational changes in the electrode surface. It has been shown that, due to contact of ds DNA with the electrode for periods many times longer than those which can be reached at the dropping mercury electrode, extensive surface denaturation of DNA can be detected only in a narrow potential range around -1.2 V. At potentials more negative than this region neither surface denaturation nor blocking of the electrode by the reduction product were observed. On the other hand, interaction of the denatured DNA with the mercury surface under the same conditions, resulted in blocking of the electrode surface by the reduction product. In agreement with the previous studies in acid media similar blocking of the surface was observed at pH 5 both with thermally denatured and ds DNAs. On the basis of the experimental data the following conclusions have been drawn: i) in neutral media the course of interfacial events of DNA is strongly dependent on DNA conformation and differs from the course suggested for acid media; ii) the deduction concerning the behavior of ds DNA on the electrode in neutral media made by other authors on the basis of their measurements in acid media is not justified.

Polarographic and voltammetric determination of N,N’-dinitrosopiperazine

1991 ◽  
Vol 56 (7) ◽  
pp. 1434-1445 ◽  
Author(s):  
Jiří Barek ◽  
Ivana Švagrová ◽  
Jiří Zima
Keyword(s):  
Mercury Electrode ◽  
Linear Sweep Voltammetry ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Polarographic Reduction ◽  
Concentration Region ◽  
Pulse Polarography ◽  
Chemical Efficiency ◽  
Dropping Mercury Electrode

Polarographic reduction of the genotoxic N,N’-dinitrosopiperazine was studied and its mechanism was suggested. Optimum conditions were established for the determination of this substance by tast polarography over the concentration region of 1 . 10-3 to 1 . 10-6 mol l-1 and by differential pulse polarography on the conventional dropping mercury electrode or by fast scan differential pulse voltammetry and linear sweep voltammetry on a hanging mercury drop electrode over the concentration region of 1 . 10-3 to 1 . 10-7 mol l-1. Attempts at increasing further the sensitivity via adsorptive accumulation of the analyte on the surface of the hanging mercury drop failed. The methods are applicable to the testing of the chemical efficiency of destruction of the title chemical carcinogen based on its oxidation with potassium permanganate in acid solution.

The Influence of N,N'-Dialkylthioureas on the Two-Step Electroreduction of Zn(II) Ions

1998 ◽  
Vol 63 (6) ◽  
pp. 749-760 ◽  
Author(s):  
Grażyna Dalmata
Keyword(s):  
Electron Transfer ◽  
Double Layer ◽  
Rate Constant ◽  
Electrode Surface ◽  
Mercury Electrode ◽  
Impedance Method ◽  
Dropping Mercury Electrode ◽  
Wide Potential ◽  
Orientation Of Molecules

A two-step reduction of Zn(II) ions at the dropping mercury electrode in 1 M NaClO4/0.001 M HClO4 in the presence of N,N'-dialkylthioureas was examined in wide potential and frequency ranges, using the impedance method. The rate constant of the first electron transfer increases with increasing concentration of N,N'-dialkylthioureas, whereas that of the second electron transfer depends largely on the double layer effects, particularly, on the orientation of molecules on the electrode surface.

Polarographic determination of alkaline earths with azo dyes

1991 ◽  
Vol 56 (1) ◽  
pp. 206-215 ◽  
Author(s):  
L. S. Kopanskaya ◽  
V. T. Meryan ◽  
V. A. Smelov
Keyword(s):  
Azo Dyes ◽  
Calcium Concentration ◽  
Mercury Electrode ◽  
Linear Sweep Voltammetry ◽  
Magnesium Concentration ◽  
Linear Sweep ◽  
Limit Of Determination ◽  
Dropping Mercury Electrode ◽  
Alkaline Earths

Magnesium and calcium can be determined in an alkaline medium as complexes with azo dyes by square-wave polarography on the dropping mercury electrode or by linear sweep voltammetry on the hanging mercury drop. The linear dependence of current on magnesium concentration in the presence of IREA magnezone is valid within half an order; in the presence of calcone in a wider range. The lower limit of determination is 2.10-7 mol 1-1. The dependence of current on calcium concentration in the presence of calcion is linear within the interval of 5.10-7 to 4.10-6 mol 1-1 in the voltammetric determination with accumulation.

Polarographic Determination of Famotidine in Dosage Forms

1989 ◽  
Vol 72 (4) ◽  
pp. 549-551
Author(s):  
Juan A Squella ◽  
Gladys Valencia ◽  
Igor Lemus ◽  
Luis J Nunez-Vergara
Keyword(s):  
Sample Preparation ◽  
Mercury Electrode ◽  
Dosage Forms ◽  
Polarographic Determination ◽  
Proton Reduction ◽  
Dropping Mercury Electrode ◽  
Neutral Media ◽  
Precision And Accuracy

Abstract Famotidine, which cannot be electrochemically reduced at the dropping mercury electrode, exhibits catalytic proton reduction waves. The peak obtained by in-phase ac polarography in neutral media is of analytical interest. Recovery studies and individual tablet assays are described. Results show adequate precision and accuracy. Sample preparation is not time consuming, and no excipient separation is required.

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