Showing papers on "Polarography published in 1997"
TL;DR: In this article, the detailed mechanism of anodic reactions of cysteine on mercury electrodes has been ascertained by means of electrocapillary measurements together with d.c. polarography and voltammetry, which consist of electro-oxidation of mercury in two separate steps to cystein mercurous and mercuric thiolates respectively which are both strongly adsorbed at the electrode.
91 citations
TL;DR: In this paper, it was shown that those writing tools are readily adapted to produce a "low-tech" renewable and minimal cost electrode which, when employed for anodic stripping voltammetry under mercury plated thin-film conditions, performs equally well as commercially available carbon electrodes.
88 citations
TL;DR: In this paper, a model for the complexation of Cd2+ by GSH involving the formation of cd(GSH)2 and cd2GSH2 complexes is proposed.
82 citations
TL;DR: In this article, a Nafion-coated mercury thin-film working electrode is placed in a specially designed small-volume sonovoltammetric cell, where the preparation and curing procedure for the Nafions film on a glassy carbon electrode substrate as well as ultrasound-enhanced mercury deposition through the nafion film are optimized.
Abstract: The high mass transport caused by ultrasonic radiation in the preconcentration of trace metal species in anodic stripping voltammetry (ASV), leads to an order of magnitude enhancement in sensitivity. A Nafion-coated mercury thin-film working electrode is placed in a specially designed small-volume sonovoltammetric cell. The preparation and curing procedure for the Nafion film on a glassy carbon electrode substrate as well as ultrasound-enhanced mercury deposition through the Nafion film are optimized. The resulting electrode assembly is stable under ultrasonic irradiation. Optical microscopy observations show the formation of closely spaced mercury droplets of micrometer dimensions under the Nafion film. The performance characteristics of ultrasound-enhanced ASV at the Nafion-coated mercury thin-film electrode are studied in detail. The detection limit obtained for lead and cadmium test species is 3 × 10-11 M (30 s preconcentration in the presence of ultrasound). A relative standard deviation of 1.2% is o...
69 citations
TL;DR: In this paper, a thin-layer anodic stripping voltammetry model was developed for anodization by a linear potential ramp, which assumes uniformity of the amalgam concentration, reversible electrode behavior, and planar diffusion of the stripped ions away from the anode.
Abstract: The principles of thin-layer anodic stripping voltammetry, are discussed and a model for the stripping stage is developed for anodization by a linear potential ramp. The model assumes uniformity of the amalgam concentration, reversible electrode behavior, and planar diffusion of the stripped ions away from the anode. The entire shape of the stripping peak is then predicted from the model. Several stringent tests are developed to assess how well the model accords with experimental reality. One of these tests is analogous to the “log plot” of classical polarography. Another relates the peak current of the stripping voltammogram to its area. Experiments were carried out on amalgams of cadmium and lead formed by cathodic codeposition with the mercury onto an array of carbon microdisks in an unstirred solution, and the results have been used to test the model exhaustively. The results for lead amalgam agree well with the model, but agreement is less satisfactory for cadmium amalgam. A comparison is made of thr...
45 citations
TL;DR: In this article, the voltammetric behavior of two sulfonamides, salazosulfapyridine (I) and sulfamethoxazol (II), and trimethoprim (III) was investigated in aqueous medium at various pH using classical and DC-polarography and fast scan differential pulse voltammetry (FSDPV) at a mercury dropping and a static drop electrode.
45 citations
TL;DR: The electron transfer at the interface between an aqueous solution (W) containing flavin mononucleotide (FMN) and an organic solution (Org) containing decamethylferrocene in the absence and presence of oxygen was studied by polarography as discussed by the authors.
32 citations
TL;DR: In this article, the anodic electrolytic reaction of cysteine on mercury electrodes proceeds differently in acetate and borate buffer solutions, even though in both solutions the product of its electrode reaction is adsorbed at the electrode.
30 citations
TL;DR: In this article, a very well resolved diffusion controlled differential pulse polarographic peak obtained at pH 7 was used to develop a new method for the determination of nimesulide in pharmaceutical dosage forms and the recovery study (104.8% with a RSD of 1.3%) showed that the method is sufficiently accurate and precise to be applied in the individual tablet assay of commercial samples.
Abstract: Nimesulide, N-(4-nitro-2-phenoxyphenyl)methanesulfonamide is an antiinflamatory analgesic agent that is both reducible at the mercury electrode and oxidizable at the glassy carbon electrode. Nimesulide in hydroalcoholic solution, presents cathodic response in a wide range of pH (2–12), both, by differential pulse and tast polarography techniques. The obtained results show only one main well-defined peak or wave in all the pH range studied. This peak (or wave) corresponds to the nitro group reduction in position 4. The voltammetric oxidation shows one well-resolved signal in all the pH range studied. This anodic signal could be attributed to the methylsulfonamide group oxidation. For analytical purposes, a very well resolved diffusion controlled differential pulse polarographic peak obtained at pH 7 was selected. This peak was used to develop a new method for the determination of nimesulide in pharmaceutical dosage forms. The recovery study (104.8% with a RSD of 1.3%) shows that the method is sufficiently accurate and precise to be applied in the individual tablet assay of commercial samples.
29 citations
TL;DR: In this article, the amount of mercury, deposited on a glassy carbon electrode at various potentials during the first 200 ms of electrolysis, has been determined by constant current coulometric stripping potentiometry.
25 citations
TL;DR: Polarography has been used in investigations of equilibria between carbonyl compounds and Schiff bases as mentioned in this paper, which can be used in mechanistic studies and in choice of representative model compounds.
TL;DR: In this article, the application of square-wave polarography (SWP) to the determination of sulfide in water is reported, in comparison with other pulse techniques, cathodic stripping SWP was found to be the most sensitive.
TL;DR: In this paper, the electrochemical reduction of secnidazole has been carried out in aqueous solution in the pH range of 2.0-12.0 by DC polarography, AC polarography and cyclic voltammetry.
Abstract: The electrochemical reduction of secnidazole has been carried out in aqueous solution in the pH range of 2.0–12.0 by DC polarography, AC polarography and cyclic voltammetry. Two well-defined reduction waves appear in acidic media, whereas at higher pHs the two waves overlap. The variation of E1/2 or Ep and Ilim or Ip with pH was studied. The diffusion-controlled nature of the waves was established and the irreversibility of the electrode process was verified by different criteria. The mechanism of reduction was discussed. A method for the detemination of secnidazole by DC polarography at pH 8.5 which allows quantitation over the 1 × 10−5 M-4 × 10−4 M range was proposed and applied to the determination of secnidazole in tablets. The mean recovery was 99.67% and the relative standard deviation was 0.89%. Excipients did not interfere in the determination.
TL;DR: In this paper, the mechanism of the oxidation of 3-mercaptopropionic acid (3-MPA) by hydrogen peroxide was studied in the acidic pH range, and the nucleophilic attack by sulphur on the peroxide bond controlled the rate.
Abstract: The mechanism of the oxidation of 3-mercaptopropionic acid (3-MPA) by hydrogen peroxide was studied in the acidic pH range. The nucleophilic attack by sulphur on the peroxide bond controls the rate. Extrapolation of the pH dependency suggests that the rate of attack by the deprotonated dianion is highest. Traces of Fe(III), at levels below 10−7 mol dm−3, do not catalyze efficiently the process through one-electron mechanisms; at higher concentrations, or on the surface of iron(III) oxides, this type of catalysis becomes important. The electrochemical oxidation of 3-MPA was also studied, using differential pulse polarography and cyclic voltammetry techniques. The mechanism is of the EC2E type, the second electron transfer step corresponding to the oxidation of the disulphide RS-SR. The rate constant for the dimerization of the RS• radicals was 1.8 × 103 mol−1 dm3 s−1; the slowness of this step agrees with the mechanisms observed in the course of one-electron oxidations by metal ions. Keywords: electrochemi...
TL;DR: In this paper, the maleic hydrazide (3,6-dihydroxypyridazine) was reduced to the dicarbonyl form I at the dropping mercury electrode in two-electron waves.
TL;DR: In this paper, a model was proposed for the voltammetric study of metal ions in mixtures of macromolecular and simple ligands, with the assumption that the complexes formed are totally labile or totally inert.
TL;DR: In this paper, differential pulse polarography was used to study the adsorption of atrazine on three tropical soils with different compositions regarding organic matter, clay, silt and sand.
Abstract: Differential pulse polarography was used to study the adsorption of atrazine on three tropical soils with different compositions regarding organic matter, clay, silt and sand. The corresponding Freundlich isotherms were determined and the calculated adsorption coefficients, KF, were 4.4, 9.9 and 5.2 mL g−1 for Pindorama, Monte Alegre and Ribeirao Preto soils, respectively. These values are in good agreement with previous reports. A comparison between the results obtained by differential pulse polarography and by gas chromatography was also performed showing that both techniques yield very similar isotherms.
Journal Article•
TL;DR: In this article, the standard reaction rate constants from a.c. polarography on the dropping and the hanging mercury electrode in a three-electrode system as well as from cyclic voltammetry in a two-electric system were measured in various concentrations of the supporting electrolyte tetrabutylammonium perchlorate in N,N-dimethylformamide.
TL;DR: In this article, a two-step reduction of Zn(II) ions at the dropping mercury electrode in 1 M NaClO4 + 0.001 M HClO 4 with the addition of 3,4-diaminotoluene using an impedance method in wide potential and frequency ranges was examined.
TL;DR: In this paper, phase sensitive ac polarography with DME was used to compare the behavior of Cephalexin (Cef), Cefaclor (Cfx), and 7-aminodesacetoxycephalosporanic acid (7-ADCA) molecules at a mercury electrode.
TL;DR: In this paper, the electrochemical reduction of three nitrotetralone derivatives by tast and differential pulse polarography and cyclic voltammetry in a wide pH range was studied.
TL;DR: In this article, the electrochemical behavior of copper complexed with phenazopyridine monohydrochloride (2.6-diamino 3-phenylazo-pyridine, pyridium) has been studied in 0.1 M phosphate buffer.
Abstract: The electrochemical behavior of copper complexed with phenazopyridine monohydrochloride (2.6-diamino 3-phenylazo-pyridine monohydrochloride, pyridium) has been studied in 0.1 M phosphate buffer (pH 6.0). It was observed that CuII ions in the presence of pyridium are reduced at the mercury electrode in two distinct stages; this is a consequence of the interaction of pyridium with CuI ions. Tests showed that pyridium forms stable complexes with CuI and CuII ions. However, it was found that pyridium formed a 1 : 1 complex with CuII and a 1 : 2 complex with CuII ions.
Patent•
07 Apr 1997TL;DR: A polarographic self-referencing probe uses an electrode that is oscillated between two positions to measure oxygen, nitric oxide, or other molecules or compounds as discussed by the authors, depending on the electrode used and the voltage applied.
Abstract: A polarographic self-referencing probe uses an electrode that is oscillated between two positions. Depending on the electrode used and the voltage applied, the probe can be used to measure oxygen, nitric oxide, or other molecules or compounds.
TL;DR: In this article, the complex formation of Zn 2+, Pb 2+ and Hg 2+ with polyacrylic acid (PAA) and polymethacrylacryllic acid(PMA) was studied by different polarographic techniques and differential pulse anodic stripping voltammetry (DPASV) on mercury drop and glassy carbon rotating disc electrodes ( rde ).
TL;DR: In this article, a detailed study of the CoII prewave induced by carbendazim is proposed and adequate conditions for the analytical determination of carbindazim by differential pulse voltammetry are established.
Abstract: Methyl 1H-benzimidazol-2-ylcarbamate (carbendazim or MBC) catalyzes the reduction of CoII at mercury electrodes in sodium barbital/nitric acid/sodium chloride media. On the basis of a detailed study of the CoII prewave induced by carbendazim, a mechanism for the electrode reaction is proposed and adequate conditions for the analytical determination of carbendazim by differential pulse voltammetry are established. Based on this finding, a voltammetric method for the indirect determination of methyl[1-(butylcarbamoyl)-1H-benzimidazol-2yl]carbamate (benomyl) is described, following the conversion of benomyl to carbendazim.
20 Sep 1997-Journal of Environmental Science and Health Part A-toxic\/hazardous Substances & Environmental Engineering
TL;DR: In this paper, the complexation of the pesticide Metamitron by copper was investigated by polarography, anodic stripping voltammetry and cathodic stripping voltage-ammetry, and the maximum value for the conditional stability constant of the copper-metamitram complex (log β'=3.8) was obtained at pH 5.6.
Abstract: Summary The complexation of the pesticide Metamitron by copper was investigated by polarography, anodic stripping voltammetry and cathodic stripping voltammetry. The influence of the pH on the complexation was determined and a maximum value for the conditional stability constant of the copper‐metamitron complex (log β'=3.8) was obtained at pH 5.6. An investigation into the photochemical degradation of the pesticide demonstrated that copper decreases the degradation rate of metamitron by 15% within the first 30 days, due to stabilisation by complexation.
TL;DR: In this article, the reduction mechanisms of a series of nickel(II) dithiocarboxylate complexes have been investigated in dimethyl sulphoxide at the mercury electrode, and various electrochemical techniques, including polarography, cyclic voltammetry, chronoamperometry, and controlled potential coulometry, were employed.
Abstract: The reduction mechanisms of a series of nickel(II) dithiocarboxylate complexes have been investigated in dimethyl sulphoxide at the mercury electrode. Various electrochemical techniques, including polarography, cyclic voltammetry, chronoamperometry, and controlled potential coulometry, were employed. The reduction of the complexes of the acid derivatives of 2-aminocyclopentene-1-dithiocarboxylate (ACD) proceeds initially by an ECE mechanism (electron transfer – chemical reaction – electron transfer) followed by a one-electron irreversible process. The nature of the complete electrode reaction suggests a metal-centered reduction. The nickel complexes of the ester derivatives of ACD underwent a one-electron reduction that was subject to a follow-up catalytic reaction (EC′ mechanism) and the original complex is regenerated through this regeneration reaction. Keywords: reduction, nickel(II) dithiocarboxylate, mercury electrode.
TL;DR: Theoretical equations of the current vs. potential curves are derived on the basis of the reaction layer theory in this paper, and theoretical predictions are in good agreement with experimental results obtained with procaine and 4-ethylaniline at nitrobenzene/water interface using a dropping electrolyte electrode.
Abstract: Theory of the voltammetric or polarographic ion transfer current of organic amines at the water/organic solvent interface is discussed. Theoretical equations of the current vs. potential curves are derived on the basis of the reaction layer theory. The theoretical predictions are in good agreement with experimental results obtained with procaine and 4-ethylaniline at nitrobenzene/water interface using a dropping electrolyte electrode. Ion-transfer voltammetry and polarography is useful for study of the partition of amines between water and an organic solvent phase in both neutral and protonated forms and of the protonation reaction in water phase as well.