Time dependent interfacial behaviour of tributylphosphine oxide at the mercury-solution interface

1985 ◽  
Vol 50 (12) ◽  
pp. 2804-2813 ◽  
Author(s):  
Anastos Anastopoulos ◽  
Panaghiotis Nikitas ◽  
Demetrios Jannakoudakis
Keyword(s):  
Mercury Electrode ◽  
Quantitative Description ◽  
Differential Capacitance ◽  
Time Dependent ◽  
Large Drop ◽  
Adsorption Parameters ◽  
Capacitance Measurements ◽  
Dropping Mercury Electrode ◽  
Interfacial Behaviour ◽  
Drop Time

A series of methods are used for the quantitative description of the time dependent interfacial behaviour of tributylphosphine oxide (TBPO). These methods include measurements of the interfacial tension by a capillary electrometer as well as differential capacitance measurements with a dropping mercury electrode (D.M.E.) of short drop times (⪬5 s), a D.M.E. of large drop times (~20 s) and a hanging mercury drop electrode (H.M.D.E.). The capacitance measurements with large drop times reveal the existence of peculiarities during the development of the adsorption film. The adsorption equilibrium of TBPO, at the vicinity of the adsorption maximum, is generally established within times shorter than 10 s. At the region of the adsorption pseudocapacity, time intervals ranging from 200 to 400 seconds are required for the equilibrium. The adsorption parameters derived with the large drop time D.M.E., are in reasonable agreement with those obtained by electrocapillary measurements.

Reduction and tensammetric pulse-polarographic currents of polynucleotides

1987 ◽  
Vol 52 (11) ◽  
pp. 2810-2818 ◽  
Author(s):  
Emil Paleček ◽  
František Jelen ◽  
Vladimír Vetterl
Keyword(s):  
Diagnostic Criteria ◽  
Pulse Width ◽  
Mercury Electrode ◽  
Pulse Amplitude ◽  
Single Strand ◽  
Pulse Polarography ◽  
Dropping Mercury Electrode ◽  
Adenylic Acid ◽  
Drop Time

The behaviour of electrochemically reducible single-strand polynucleotides (poly(adenylic acid)) and poly(cytidylic acid)) was studied by the differential (derivative) pulse polarography (DPP) and by other methods. Measurements were performed with the help of the dropping mercury electrode under various conditions specified by the pulse width, pulse amplitude, drop time etc. For the faradaic and tensammetric DPP peaks the diagnostic criteria were proposed which make it possible to classify even very small DPP peaks of double helical polynucleotides.

Retardation of Cd2+and Zn2+ discharge at the dropping mercury electrode by adsorbed phenyl substituted phosphonium cations

1988 ◽  
Vol 66 (5) ◽  
pp. 1053-1058 ◽  
Author(s):  
A. Anastopoulos ◽  
A. Christodoulou ◽  
I. Moumtzis
Keyword(s):  
Direct Current ◽  
Mercury Electrode ◽  
Capacitance Measurements ◽  
Adsorption Characteristics ◽  
Dropping Mercury Electrode ◽  
Activated Complex ◽  
Phosphonium Cations

The effect of adsorbed propargyltriphenyl- and vinyltriphenylphosphonium cations on the discharge of Cd2+ and Zn2+ at dropping mercury electrode is studied by direct current polarographic measurements. Adsorption characteristics are determined by capacitance measurements. The size parameters of the activated complex and the surfactant particles are derived and an elucidation of the mechanism of the inhibited reaction is attempted.

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.

Studies on the adsorption and the association of cytidine sulphate at the dropping mercury electrode with phase-sensitive ac-polarography

1979 ◽  
Vol 57 (10) ◽  
pp. 1136-1140 ◽  
Author(s):  
Yassein M. Temerk
Keyword(s):  
Mercury Electrode ◽  
Threshold Value ◽  
Adsorption Potential ◽  
Buffer Solution ◽  
Adsorption Parameters ◽  
Solution Ph ◽  
Adsorbed Molecules ◽  
Oriented Molecules ◽  
Dropping Mercury Electrode ◽  
Phase Sensitive

The adsorption and association of cytidine sulphate have been studied by using phase-sensitive ac-polarography in acidic buffer solution (pH 3.24) at the dropping mercury electrode. At low bulk concentrations, adsorbed molecules of cytidine sulphate at maximal adsorption potential (−0.7 V) are orientated in 'dilute' adsorption layer planar to the electrode surface where the interaction of π-electrons with interface favours adsorption. At bulk concentrations above a threshold value (6.6 × 10−3 M), the stacking interactions between vertically oriented molecules lead to association and formation of a compact layer; and a pit is observed. The concentration dependence of the ac-capacity current at a maximal adsorption potential (−0.7 V) shows a two-step Frumkin isotherm due to association of the adsorbed molecules. The adsorption parameters are computed and discussed.

Polarographic behaviour of petroleum components in aqueous solutions: Application of electrocapillary measurements and convective adsorption accumulation

1986 ◽  
Vol 51 (8) ◽  
pp. 1595-1603 ◽  
Author(s):  
Ladislav Novotný ◽  
Robert Kalvoda
Keyword(s):  
Surface Activity ◽  
Mercury Electrode ◽  
Diesel Oil ◽  
Analytical Determination ◽  
Polarographic Behaviour ◽  
Petroleum Fractions ◽  
Dropping Mercury Electrode ◽  
Strong Surface ◽  
Drop Time

Electrocapillary investigations by the drop time method revealed a rather strong surface activity of aqueous petroleum solutions and some petroleum fractions in solutions of base electrolytes at the dropping mercury electrode, depending on the quality of the surfactant. The highest surface activity and sensitivity of analytical determination was found between -0.4 and -0.6 V (S.C.E.). The detection limit of the electrocapillary method was 10-20 μg/l for Diesel oil and up to 5 times higher for petroleum samples. The sensitivity of the measurements at lowest concentrations was increased by convective adsorption accumulation at the surface of the growing drop.

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