Polarography of azobenzene and its p-sulphonic acids

1964 ◽  
Vol 17 (10) ◽  
pp. 1085 ◽  
Author(s):  
TM Florence ◽  
YJ Farrar
Keyword(s):  
Ph Effect ◽  
Aqueous Media ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ammonium Ions ◽  
Current Time ◽  
Electrode Processes ◽  
Ph Values ◽  
Strong Adsorption ◽  
Dropping Mercury Electrode

The behaviour at the dropping mercury electrode of trans-azobenzene and its p-sulphonic acids has been studied by several techniques including d.c., a.c., single sweep, and Kalousek polarography. Current-potential curves recorded at the streaming mercury electrode provided information on the reversibility of the electrode processes, while current-time and electrocapillary curves aided in elucidating the effects of adsorption. The results show that the rate of the electrode reaction of the azo-hydrazo couple is dependent on pH, the minimum rate occurring near pH 9 for azobenzene-4-sulphonic acid in aqueous media. At very low and high pH values, the couple approaches full reversibility at the dropping mercury electrode. This pH effect is apparently due to strong adsorption of both the azo and hydrazo derivatives near the potential of the electrocapillary maximum. Ammonium ions associate with azobenzene-4-sulphonate, and improve the reversibility in intermediate pH regions.

Current-time characteristics of the rapidly dropping mercury electrode

1960 ◽  
Vol 23 ◽  
pp. 585-591 ◽  
Author(s):  
Reita Tamamushi ◽  
Sunao Momiyama ◽  
Nobuyuki Tanaka
Keyword(s):  
Mercury Electrode ◽  
Current Time ◽  
Dropping Mercury Electrode

Admittance Behavior of Electrode Reaction of Water at a Dropping Mercury Electrode

1971 ◽  
Vol 44 (10) ◽  
pp. 2880-2880 ◽  
Author(s):  
Kiyoshi Matsuda ◽  
Katsuo Takahashi ◽  
Reita Tamamushi
Keyword(s):  
Mercury Electrode ◽  
Electrode Reaction ◽  
Dropping Mercury Electrode

The polarography of beryllium

1964 ◽  
Vol 17 (10) ◽  
pp. 1072 ◽  
Author(s):  
PJ Shirvington ◽  
TM Florence ◽  
AJ Harle
Keyword(s):  
Aqueous Media ◽  
Electrode Reaction ◽  
Complexing Agents ◽  
Water Molecules ◽  
Hydroxyl Groups ◽  
Reduction Step ◽  
Current Time ◽  
Diffusion Controlled ◽  
Coordinated Water ◽  
Potentiometric Data

The polarography of beryllium in 0.5M lithium chloride has been investigated in some detail, using several polarographic and coulometric techniques. Current-time curves, microscopic examination and cinematography of the mercury drop, and the effect of complexing agents, aided in elucidating the electrode process. The experimental data show that the polarographic step for the tetraquoberyllium ion is diffusion-controlled but irreversible, and results from the reduction of two protons liberated from the coordinated water molecules, yielding beryllium hydroxide and hydrogen. The evidence suggests that this reduction takes place in a stepwise process, with a soluble beryllium hydroxy complex as an intermediate. The polarographic results can be correlated with published potentiometric data on the composition and stabilities of hydrolysed beryllium species in aqueous media. The number of electrons involved in the electrode reaction depends on the number of hydroxyl groups per beryllium atom in the beryllium complex. Beryllium oxalate and salicylate complexes also give a reduction step, but only if the complex contains coordinated water molecules. The diffusion coefficient of the tetraquoberyllium ion was found to be 6.2 � 0.3 x 10-6 cm2 sec-1 at 30�.

The reduction of doxorubicin at a mercury electrode and monitoring its interaction with DNA using constant current chronopotentiometry

2009 ◽  
Vol 74 (11-12) ◽  
pp. 1727-1738 ◽  
Author(s):  
Jan Vacek ◽  
Luděk Havran ◽  
Miroslav Fojta
Keyword(s):  
Double Helix ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Ex Situ ◽  
Constant Current ◽  
Adsorbed State ◽  
Electrode Processes ◽  
Dna Double Helix ◽  
First Time

In this report, voltammetry with linear scan and chronopotentiometric stripping (CPS) with constant current were used for the analysis of doxorubicin (DOX) at a hanging mercury drop electrode (HMDE). CPS was used for the study of DOX in situ electrochemical reduction in adsorbed state and for ex situ (adsorptive transfer) analysis of the drug. For the first time, CPS was used to study the reversible reduction of the DOX quinine moiety at –0.45 V (vs Ag|AgCl|3 M KCl) as well as electrode processes giving rise to an irreversible signal around –1.45 V at the HMDE in 0.2 M acetate or Britton–Robinson buffers at different pH values. The dependence of the latter signal on pH revealed involvement of protonation equilibria; however, neither CV nor CPS data confirmed the catalytic character of the electrode reaction previously suggested by other authors. The CPS method was also applied to monitor the DOX interaction with double- (ds) and single-stranded (ss) DNA. In the presence of dsDNA, more pronounced changes in DOX signal intensity were observed, in agreement with a strong intercalation of the DOX redox centre into the DNA double helix.

Electrode currents and concentrations for transfer by diffusion and chemical reaction

1968 ◽  
Vol 21 (8) ◽  
pp. 1953
Author(s):  
CHJ Johnson
Keyword(s):  
Weighting Function ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Graphical Form ◽  
Diffusion Field ◽  
Irreversible Reaction ◽  
Definite Integrals ◽  
Reaction Solution ◽  
Stable Species ◽  
Dropping Mercury Electrode

In the present paper we compute the time-dependent diffusion field around an electrode, which may be a plane or a sphere of constant radius, for an electrochemical system in which a single depolarizing species A through a rapid reversible electrode reaction gives rise to a transitory species B which is converted into a stable species C by a slow irreversible reaction solution. The mathematical solution method is such that by suitable choice of variables it is possible to solve the plane and sphere problems in one operation. The functions yielding concentrations and electrode currents are obtained as definite integrals which are evaluated numerically. By appropriate choice of weighting function the present results can be applied to the expanding sphere problem (dropping mercury electrode). The results are consistent with the spirit of the Ilkovic analysis. Numerical results for planar and spherical electrodes are presented in graphical form.

Polarography of n-butylthioglycolate in aqueous media, methanol, and acetonitrile

1984 ◽  
Vol 62 (9) ◽  
pp. 1817-1821
Author(s):  
K. C. Gupta ◽  
Kalpana K. Sharma
Keyword(s):  
Aqueous Media ◽  
Mercury Electrode ◽  
Wave Characteristics ◽  
Anodic Wave ◽  
Diffusion Controlled ◽  
Dropping Mercury Electrode ◽  
Drop Time ◽  
And Diffusion ◽  
Mechanism Of The Reaction

The polarographic behaviour of n-butylthioglycolate (RSH) at the DME in aqueous media, methanol, and acetonitrile has been investigated in the presence of 0.1 M KNO3 and 0.01% thymol. The effect of pH, concentration of RSH, and drop time on the wave characteristics and the mechanism of the reaction occurring at the surface of the mercury drop have been studied. Well-defined reversible and diffusion-controlled anodic waves were obtained in aqueous media (pH 4.2), 40% methanol (pH 3.22), and 40% acetonitrile (pH 2.96). Mathematical and analytical evidence was obtained to show that the anodic wave of RSH at a dropping mercury electrode in aqueous media, 40% methanol, and 40% acetonitrile is due to the formation of the mercury complex RSHg. The dissociation constant (pK) of the mercapto group in n-butylthioglycolate is 9.6 and the diffusion coefficient in the different media are 1.17 × 10−6 cm2 s−1 (in aqueous media) 1.23 × 10−6 cm2 s−1 (in 40% methanol), and 2.43 × 10−6 cm2 s−1 (in 40% acetonitrile). The linearity of id with RSH concentration provides a rapid and precise method for the determination of RSH, down to 0.4 mM in aqueous media, methanol, and acetonitrile.

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