Showing papers on "Polarography published in 1991"
Patent•
22 Jan 1991
TL;DR: An electroanalytical electrode assembly comprises an electrically conductive working electrode which includes an electrical conductor having a body of electrolyte material, thereupon and separated from the analytical environment by a hydrophobic membrane as mentioned in this paper.
Abstract: An electroanalytical electrode assembly comprises an electrically conductive working electrode which includes an electrical conductor (15) having a body of electrolyte material (16) thereupon and separated from the analytical environment by a hydrophobic membrane (18). The membrane has an electrical conductivity greater than the electrical conductivity of the remainder of the measuring circuit and is selectably permeable for a preselected and ionic species, so as to provide a stable membrane potential. Use of an assembly of this type allows for placement of a reference electrode (20) external of the membrane (18).
74 citations
TL;DR: In this paper, a linear sweep polarographic method for the determination of progesterone was proposed, which exhibits a sensitivity that is 40 times greater than that in the absence of CTAB.
60 citations
TL;DR: In this article, the complex formation of Zn(II) and Cd(II), with polymethacrylic acid (PMA) and polyacrylic acids (PAA), was studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography and by differential pulse anodic stripping voltammetry (DPASV).
Abstract: Complex formation of Zn(II) and Cd(II) with polymethacrylic acid (PMA) and polyacrylic acid (PAA) is studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography and by differential pulse anodic stripping voltammetry (DPASV). Titrations of Zn(II) or Cd(II) with partially neutralized PMA or PAA by DPASV allow the precise determination of the apparent formation constant K of the four systems. The two Zn(II) systems appear to be labile on the different time scales of the several techniques, without remarkable complications due to secondary phenomena. Their K values, determined by all techniques, agree satisfactorily. The two Cd(II) systems, and especially the Cd/PAA system, show rather involved behavior, which tends to normality when the degree of neutralization αn of the polycarboxylates increases. Both slow kinetics and ligand adsorption coupled with induced Cd(II) adsorption (evidenced by maxima on the normal pulse polarograms) seem to be present. For all αn values, DPASV yields higher estimates of K than do polarographic techniques.
27 citations
TL;DR: A coated-wire ion-selective electrode (CWE) based on the bidentate neutral carrier 4,4′-di(5-nonyl)-2,2′-bipyridine (DNBP) was developed for the determination of divalent cadmium as discussed by the authors.
27 citations
TL;DR: In this paper, the results were confirmed by adsorptive stripping cathodic voltammetry and differential pulse polarography, and the characterization of different species formed in alcohol on addition of water was carried out using absorption, fluorescence and circular dichroism spectroscopic techniques.
Abstract: Chlorophyll a (Chl a ) aggregation in alcohol was examined as a function of the type of alcohol, Chl a concentration and water content. The sample preparation procedure was observed to play an important role in determining whether the dihydrate dimer or the monohydrate dimer was formed. The characterization of the different species formed in alcohol on addition of water was carried out using absorption, fluorescence and circular dichroism spectroscopic techniques. The results were confirmed by adsorptive stripping cathodic voltammetry and differential pulse polarography.
23 citations
TL;DR: The complex formation of Cd(II) with alginic and polygalacturonic acids is studied by normal pulse (NPP), reverse pulse (RPP), and differential pulse polarography (DPP) as discussed by the authors.
Abstract: Complex formation of Cd(II) with alginic and polygalacturonic acids is studied by normal pulse (NPP), reverse pulse (RPP), and differential pulse polarography (DPP), as well as by cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV). Titrations of Cd(II) with partially neutralized alginic or polygalacturonic acids, at different ionic strengths, by DPP and DPASV allow the precise determination of the apparent formation constant K of both systems. The systems appear to be labile on the different time scales of the various techniques. Adsorption of both polysaccharides, and the further induced adsorption of Cd(II), is evidenced clearly by NPP. On the other hand, the induced adsorption of Cd(II) is minimized under the conditions of RPP. The reversibility of the redox couple Cd2+/Cd(Hg) is not strongly affected by the presence of polysaccharides. Dependence of the apparent formation constants on the total ionic strength is reported.
22 citations
TL;DR: In this paper, a Fourier transform method is used for the resolution enhancement of the closely overlapping diffusion-controlled main peak and the post-peak caused by adsorption in differential pulse polarography (DPP).
22 citations
20 citations
TL;DR: The mechanism of transfer of Mn2+ ion from an aqueous to a dichloroethane (DCE) solution of a phenanthroline derivative (Phen) was investigated by current scan polarography with the ascending water electrode.
Abstract: The mechanism of transfer of Mn2+ ion from an aqueous to a dichloroethane (DCE) solution of a phenanthroline derivative (Phen); 1, 10-phenanthroline (phen), 4, 7-dimethyl-1, 10-phenanthroline (4, 7-DMP), 4, 7-diphenyl-1, 10-phenanthroline (4, 7-DPP) and 2, 9-dimethyl-1, 10-phenanthroline (2, 9-DMP), was investigated by current scan polarography with the ascending water electrode. The transfer process involves (a) diffusion of Phen to the aqueous/DCE interface, (b) formation of 1:1 Mn2+-Phen complex, whose kinetics are sufficiently slow to influence but not entirely control the polarographic process, (c) transfer of the 1:1 complex from the aqueous into the DCE phase and (d) further reaction of this complex with two additional Phen molecules at the interfacial area in DCE phase. The apparent reaction rates of step (b) were determined in the dimension of the ordinary electrode reaction rate; 8.2×10-2, 5.5×10-2 and 9.3×10-3dm M-1 s-1 for phen, 4, 7-DMP and 4, 7-DPP, respectively. The rate for Mn2+-2, 9-DMP complex was too slow to be determined.
19 citations
TL;DR: In this article, the transfer mechanism of Ni2+, Co2+, Zn2+ and Cd2+ ions from an aqueous to a dichloroethane (DCE) solution of phenanthroline derivatives (Phen) was studied.
Abstract: The transfer mechanism of Ni2+, Co2+, Zn2+ and Cd2+ ions from an aqueous to a dichloroethane (DCE) solution of phenanthroline derivatives (Phen) was studied. Included were 1, 10-phenanthroline (phen), 4, 7-dimethyl-1, 10-phenanthroline (4, 7-DMP), 4, 7-diphenyl-1, 10-phenanthroline (4, 7-DPP) and 2, 9-dimethyl-1, 10-phenanthroline (2, 9-DMP). The investigation was carried out by current-scan polarography at the ascending water electrode (AWE). Some polarographic waves were observed that can be attributed to the slow formation of 1:1 M2+-Phen complexes. In some cases, as with the Ni2+-Phen systems and the Co2+-4, 7-DPP system, no wave was observed, because the complexation rates are too slow. All of the Cd2+-Phen and all of the Zn2+-Phen systems, except for the Zn2+-4, 7-DPP system which exhibits a kinetic wave, yielded diffusion-controlled waves. Furthermore, a number of these systems appear to be affected by significant interfacial adsorption of the M2+-Phen complexes.
19 citations
TL;DR: In this paper, the electrochemical behavior of nitrofurantoin was studied by employing do polarography, cyclic voltammetry, and differential pulse polarography in universal buffers of pH 2.0-12.0.
Abstract: The electrochemical behavior of nitrofurantoin was studied by employing do polarography, cyclic voltammetry, and differential pulse polarography in universal buffers of pH 2.0–12.0. Kinetic parameters such as transfer coefficients, diffusion coefficients, and heterogeneous forward rate constant values were evaluated using these techniques. Differential pulse polarography was employed for the estimation of this drug in several pharmaceutical formulations.
TL;DR: In this article, a single drop square wave polarography was used to investigate the contribution of adsorption by interpretation of ipdashtp relationships, and the use of the automated cell together with rapid scan square wave voltammetry for the determination of these drugs singly, in formulations and in mixtures with each other was investigated.
Book•
01 May 1991
TL;DR: Polarographic Apparatus Currents in Polarography Simple Reversible Systems Complex Systems Irreversible Electrode Processes Kinetic and Catalytic Currents Adsorption Current Polarography in Non-Aqueous Solvents Organic Polarography Other Indicator Electrodes Special Polarographic Techniques Amperometry List of Abbreviations List of Symbols Polarographic Literature Appendix Index as discussed by the authors
Abstract: Polarographic Apparatus Currents in Polarography Simple Reversible Systems Complex Systems Irreversible Electrode Processes Kinetic and Catalytic Currents Adsorption Current Polarography in Non-Aqueous Solvents Organic Polarography Other Indicator Electrodes Special Polarographic Techniques Amperometry List of Abbreviations List of Symbols Polarographic Literature Appendix Index.
TL;DR: The linear relationship between partial pressure of oxygen and the oxygen concentration indicated that the Clark oxygen electrode can be used to study enzyme reactions consuming or evolving oxygen in non-Newtonian media.
TL;DR: In this paper, the composition of the complex attached to the electrode surface was calculated from the maximum potential shift (Δ Em) with increasing ligand concentration at a constant ionic strength maintained with sodium perchlorate.
Patent•
29 May 1991TL;DR: In this paper, the difference in oxidation-reduction potential DELTA E between the aminoindoles and quinone derivatives was shown to be at most 1.470 mV.
Abstract: Process for dyeing keratinous fibres, wherein at least one composition (A) containing at least one aminoindole in a medium suitable for dyeing is applied on these fibres, the application of the composition (A) being preceded or followed by the application of a composition (B) containing at least one quinone derivative chosen from ortho- or para-benzoquinones, ortho- or para-benzoquinone monoimines or diimines, 1,2- or 1,4-naphthoquinones, ortho- or para-benzoquinone sulphonimides, alpha , omega -alkylene bis(1,4-benzoquinones) or 1,2- or 1,4-naphthoquinone monoimines or diimines in a medium suitable for dyeing, the aminoindoles and the quinone derivatives being chosen in such a way that the difference in oxidation-reduction potential DELTA E between the oxidation-reduction potential Ei of the aminoindoles, determined at pH 7 in a phosphate medium with a vitreous carbon electrode by voltammetry, and the oxidation-reduction potential Eq of the quinone derivative, determined at pH 7 in phosphate medium by polarography with a mercury electrode relative to the saturated calomel electrode, is such that:
DELTA E = Ei-Eq
TL;DR: In this paper, a model of pulse polarograms influenced by anion induced adsorption of metal complexes is developed and the dependence of peak potentials on the logarithm of the ligand concentration is a curve with a flat segment, the slope of which depends on both the number of ligands in a dissolved surface active complex and the relationship between the surface concentration of the adsorbed ligand and its bulk concentration.
TL;DR: In this paper, the electrochemical properties of 3′-azido-3′-deoxythymidine (AZT) were investigated using cyclic voltammetry, differential-pulse voltammetric and chronocoulometry.
TL;DR: It is shown here that flash polarographic measurements require properly cleaned electrodes, a precise polarization voltage, as well as a short polarization time of the electrodes, and a model of the electrode response taking into account these factors is presented, which finds an oxygen release time of 1.7 ms.
Abstract: The time for oxygen release in photosynthesis has been reported to be 30–130 ms when measured by flash polarography under low polarization voltages (Plijter et al. 1988), in opposition to 1–3 ms with light modulated oxygen polarography (Jolio et al. 1966), with the detection of produced oxygen in a flowing sample (Etienne 1968) or with photoacoustic detection of oxygen evolution (Canaani et al. 1988). However, we show here that flash polarographic measurements require properly cleaned electrodes, a precise polarization voltage, as well as a short polarization time of the electrodes. When these criteria were met, an oxygen release in less than 2 ms could be measured by flash polarography under low polarization voltages, in accordance with the other techniques. But under high polarization voltages, the interpretation of the polarographic response to oxygen production must take into account the diffusion of oxygen, the capacitance of the platinum electrode and the oxygen release time. We present a model of the electrode response taking into account these factors; by interpreting the response of the electrodes with this model, we found an oxygen release time of 1.7 ms. These evidences support strongly a short oxygen release time of 1–3 ms.
TL;DR: In this paper, a tricyclic antidepressants detection with glassy carbon, carbon paste and antimony doped tin oxide electrodes was conducted with a flow-injection analysis and differential pulse polarization.
Abstract: Electrochemical detection of tricyclic antidepressants was conducted with glassy carbon, carbon paste and antimony doped tin oxide electrodes. We find that glassy carbon electrodes undergo passivation due to an adsorption process. Reliable calibration curves can only be obtained by polishing the electrode surface between scans. Carbon paste electrodes result in nonlinear calibration curves due to partitioning of the analyte and/or oxidized products of the analyte into the organic phase of the carbon paste. The extent of partitioning is dependent on the number of scans in the presence of the analyte. Antimony doped tin oxide yielded reproducible, linear calibration curves in the flow injection analysis mode as well as with differential pulse polarography.
TL;DR: In this article, eight new compounds of α- and β-MaHbSiW9Cr3(OH2)3O37·xH2O types (M = K+, Me4N+, Et4N+ or n-Bu4N+) were synthesized from trivacant heteropoly tungstate α and β-[SiW 9O34]10− precursors and products were character]zed by IR, UV, X-ray photoelectron spectroscopy, polarography, cyclic voltammetry and their magnetic moments.
TL;DR: The proposed method has been applied to the determination of uranium in uranium minerals and the interference of some concomitant ions were examined and EDTA was used as an effective masking agent to separate uranium from other metals.
TL;DR: The HPLC separation of heavy metal cations was studied with a column packed with Separon SGX silica gel and the results were compared with the theoretical model of ion-exchange separation.
TL;DR: In this paper, the stabilization of copper(I) by some amines was analyzed by voltammetric methods at the ionic strength of seawater (I = 0.7 M NaClO4).
Abstract: The stabilization of copper(I) by some amines was analyzed by voltammetric methods at the ionic strength of seawater (I = 0.7 M NaClO4). The amines studied were ethylamine, diethylamine, triethylamine, ethanolamine, and 5-aminopenthanol. Voltammetric methods were used because copper(I) can be produced electrochemically if the ligands in solution stabilize this oxidation state. Differential pulse polarography (DPP) and voltammetry with platinum rotating disk electrodes (RDE) were employed. Because some of the voltammograms were distorted as a result of adsorption problems, adsorption has been studied by ac polarography. For the experimental conditions of negligible adsorption, the stability constants of copper(II) and copper (1) complexes have been determined.
TL;DR: In this paper, the electroreduction of 8-, 5- and 2-hydroxyquinoline (8, 5-, and 2, QOH) was studied in DMF.
TL;DR: In this paper, the electrochemical behavior of a Cu(II)GGH solution with a mercury electrode has been investigated, and anomalous currentpotential and current-time characteristics in the electrode processes at the mercury electrode, which are described as follows.
TL;DR: A very sensitive electrochemical method for trace measurement of fluoride in water is discussed, where the complex of cerium(III) with alizarin complexone (ALC) and fluoride ion is adsorbed at the dropping mercury electrode.
TL;DR: In this paper, the same authors presented procedures for simultaneous determination of copper, cadmium, lead, and zinc in 0.05 M nitric acid (0.1 M CTRAc) and 0.2 M oxalic acid in the presence of 0.1 mM potassium chlorate.
Abstract: Information on the transition metals content in natural waters is of great environmental interest. The procedures presented in this paper deal with the simultaneous determination of copper, cadmium, lead, and zinc in 0.05 M nitric acid (0.05 M HNO3 + 0.1 M CTRAc) 0.1 M citric acid by differential pulse anodic stripping voltammetry or differential pulse polarography; manganese, nickel, and cobalt were determined in ammonia/ammonium acetate buffer at pH 9.1 by differential pulse anodic or cathodic stripping voltammetry, titanium and relevant iron concentrations by pulse polarography in 0.2 M oxalic acid in the presence of 0.1 M potassium chlorate. The voltammetric schemes and response are critically compared to Zeeman graphite furnace atomic absorption spectrometry.
TL;DR: In this article, the electrochemical reduction of benzenes and cyclic I(III) and I(V) compounds has been studied in aqueous neutral and acid solutions by employing polarography and rotating disk voltammetry.
TL;DR: In this paper, the results of a systematic investigation of anodic CH,O behavior on a dropping mercury electrode (DME) are presented in order to investigate the anodic oxidation of formaldehyde on Hg.