Showing papers on "Polarography published in 1993"
TL;DR: In this article, the possibility for differential pulse polarography (DPP) determination of S-triazine has been shown and compared with gas-chromatographic (GC) measurements.
Abstract: The possibility for differential pulse polarography (DPP) determination of S-triazine has been shown and compared with gas-chromatographic (GC) measurements. Good agreement was found between GC and DPP measurements in analyzing 20 samples of industrial wastewater. It was found, using controlled potential coulometry (CPC), that four electrons take part in electrochemical reduction steps. On the basis of this and polarographic measurements, the mechanism of electrochemical reduction of S-triazine was postulated.
37 citations
TL;DR: In this article, two cephalosporin antibiotic derivatives, ceftriaxone (CFRX) and cefoperazone(CFPZ), have been studied by direct current, differential pulse polarography (DPP), and cyclic voltammetry.
Abstract: Two cephalosporin antibiotic derivatives, ceftriaxone (CFRX) and cefoperazone (CFPZ), have been studied by direct current, differential pulse polarography (DPP), and cyclic voltammetry. Both give rise to two irreversible two-electron reduction steps. The characteristics of the corresponding electrode reactions are discussed. The electrooxidation of both drugs was also studied at the carbon paste electrode (CPE). Both drugs give rise to one oxidation peak at about +1.05 V vs. SCE (pH 1.6, phosphate buffer solution). Optimum pH ranges for the determination of these drugs at the CPE are also given. Linear calibration plots were obtained over the concentration ranges 0.49 to 99 μg/mL and 0.66 to 534 μg/mL for CFRX and CFPZ, respectively. Detection limits of 2.5 ng/mL and 0.13 μg/mL for CFRX and CFPZ, respectively, were readily achieved.
36 citations
TL;DR: In this article, the direct current and differential pulse polarographic behavior of metal complexes, especially nickel(II), of Ampicillin and Amoxycillin at the dropping mercury electrode, is described.
35 citations
TL;DR: In this article, a carbon paste electrode modified with diphenyl carbazide has been prepared in order to improve the analytical determination of chromium (VI) and chromium(III) using voltammetric techniques.
Abstract: A carbon paste electrode modified with diphenylcarbazide has been prepared in order to improve the analytical determination of chromium(VI) and chromium(III) using voltammetric techniques. Several parameters, such as carbon/diphenylcarbazide ratio, carbon/Nujol ratio, scan rate, accumulation time, etc., have been explored. A voltammetric study of both chemical species and an explanation of the chemical and electrochemical mechanism are presented. When applied to assays of soil samples, the results compared favorably to those of a polarographic method.
35 citations
TL;DR: In this paper, an electrochemical study on the electronic interactions occurring between the two "CCo3(CO)9" redox cores in the dimers Co3( CO)9(CC)Co3 CO) 9 and Co3 CO 9(C ǫ cC�CCCCo3CO) 9 is reported.
34 citations
TL;DR: In this paper, a 0.1 M aqueous solution containing PF6 −, ClO4 −, C2O4 2-, SCN−, SO4 2- and F− anions has been studied by using an equation which takes account of the change in the cyclodextrin concentration due to the simultaneous complexation of the anion.
Abstract: Complexation of o-chloronitrobenzene with β-cyclodextrin has been studied in 0.1 M aqueous solutions containing PF6 −, ClO4 −, C2O4 2-, SCN−, SO4 2- and F− anions by a polarographic method. Using an equation which takes account of the change in the cyclodextrin concentration due to the simultaneous complexation of the anion, both stability constants have been calculated. Interaction of the ClO4 − anion with β-cyclodextrin has been confirmed by 1H NMR techniques. It has been found that the ClO4 − anion is trapped in the β-cyclodextrin cavity. The stability constant has been calculated. Results of polarographic and 1H NMR studies have been compared.
26 citations
TL;DR: In this article, it is proposed that the cations of the supporting electrolyte participate in the partial dehydration process which follows the first charge-transfer step, and the reduction of Bi(III) at a mercury electrode becomes fast and reversible.
Abstract: In highly concentrated HClO 4 (>8M) and acidic NaClO 4 (>7M) solutions the reduction of Bi(III) at a mercury electrode becomes fast and reversible. The redox kinetics depends on the electrolyte concentration and only indirectly on the water activity. It is proposed that the cations of the supporting electrolyte participate in the partial dehydration process which follows the first charge-transfer step. Hydration numbers of Bi 3+ are 8.2 in NaClO 4 and 6.9 in HClO 4 solutions
25 citations
TL;DR: In this article, the authors studied the multipeak phenomenon in the Cu peak during anodic stripping voltammetry (ASV) analysis, but the origin of this interference was not investigated and the experimental conditions were modified to make it disappear.
Abstract: In the presence of natural organic species, the electrochemical behavior of metals can be modified. Several authors have already noticed an extra peak or shoulder in the Cu peak during anodic stripping voltammetry (ASV) analysis, but the origin of this interference was generally not investigated and the experimental conditions were modified to make it disappear. In this article, this phenomenon alone was studied. The organic matter dissolved in interstitial waters of marine sediments was fractionated by ultrafiltration and gel permeation chromatography. The resulting fractions were qualitatively studied with respect to the complexity of the voltammograms they exhibit during an ASV analysis of Cu. Very similar electrochemical behaviors (multiple peaks) were found for interstitial waters and humic substances. The fractionation experiment suggests that particular families of molecules, which can be separated, are responsible for these extra peaks. Therefore, the “multipeak” phenomenon is related to the quality of the organic matter rather than to its quantity. This fact, supported by several experiments [DPASV, differential pulse polarography (DPP)], has led to a model which, although still somewhat speculative, describes well the usual observations: the extra peaks would originate from the oxidation of organic copper species [most likely as Cu(I)] adsorbed and stabilized on the mercury drop electrode.
24 citations
TL;DR: In this paper, the faradaic response of a slow electron transfer to a triple pulse of potentials was derived for the planar approximations of a static mercury drop electrode and the dropping mercury electrode.
Abstract: The faradaic response of a slow electron transfer to a triple pulse of potentials was derived for the planar approximations of a static mercury drop electrode and the dropping mercury electrode. The analytical solution obtained for a static mercury drop electrode is subject to no constraints in the time interval over which the different potentials are applied. The effects of the formation of the double layer have not been taken into account in the mathematical treatment
23 citations
TL;DR: In this article, a new method for analysis of current-potential curves in terms of their derivatives is suggested for studies of heterogeneous electron-transfer reactions and the Butler-Volmer theory on the shape of the derivatives are illustrated.
Abstract: New methods for analysis of current-potential curves in terms of their derivatives are suggested for studies of heterogeneous electron-transfer reactions. Consequences of the Butler-Volmer theory on the shape of the derivatives are illustrated. Comparisons are made between fast and slow electron-transfer reactions for various values of the standard heterogeneous rate constants (k o ) and the transfer coefficient (α) utilizing asymmetries found in the peak shapes of the derivatives' from a dc polarogram. Various parameters which characterize the peak asymmetry (such as ratios of peak-currents and ratios of peak-widths) are evaluated and analyzed
20 citations
TL;DR: In this article, a method for the determination of oxalic acid based on derivatization with o-phenylenediamine was developed, based on differential-pulse polarography and a linear calibration range was obtained, with a detection limit of 5 × 10−8 M.
TL;DR: In this paper, the voltammetric reduction of Cu(II) in the presence of polymethacrylic acid (PMA) was carried out by means of sampled direct current, normal pulse, differential pulse and reverse pulse polarography.
TL;DR: In this paper, the authors compared the performance of both direct and derivative PSA, square-wave voltammetry, d.c. polarography, and ASSWV with the non-ionic detergent Triton X-100.
TL;DR: In this paper, the authors used elimination polarography (EP) for the study of electrode processes and demonstrated the application of diffusion current elimination to the case of phenylglyoxylic acid (PGOA).
TL;DR: In this article, the electrochemical reduction of 1-[(2-hydroxyethyl)chloro-methyl]-2-methyl-5-nitro-1H-imidazole (ornidazoles) was studied by normal pulse polarography and reverse pulse polarograph.
Abstract: The electrochemical reduction of 1-[(2-hydroxyethyl)chloro-methyl]-2-methyl-5-nitro-1H-imidazole (ornidazole) was studied by normal pulse polarography and reverse pulse polarography. In aqueous solution with no surfactant, ornidazole gives rise to one wave (I) or two waves (I and II) depending on pH. The electrode reactions corresponding to these waves were characterized, and appropriate reaction mechanisms are hypothesized. In basic solutions containing DMF or sodium lauryl sulphate, wave I splits into two or three. When splitting is complete, the electrode reaction corresponding to the first daughter wave, I′, is the simple, reversible formation of the anion radical. This circumstance, and the analogous behaviour of metronidazole and tinidazole, was used to determine the formal potential of the nitroimidazole/anion radical system for ornidazole, metronidazole and tinidazole in aqueous media; the results agreed remarkably well with previously reported values obtained by pulse radiolysis. Optimal...
TL;DR: In this article, the electrochemical oxidation of niazid and isoniazid, at mercury electrodes, was studied by dc and differential pulse polarography and linear-sweep cyclic voltammetry in the pH range 6-13.
TL;DR: In this article, the electrochemical behavior of niazid and isoniazid on mercury electrodes was studied by dc and differential pulse polarography and, in the case of Niazid, by cyclic voltammetry in neutral and basic media.
TL;DR: In this paper, the electrochemical behavior of 1-[2-(ethylsulphonyl)ethyl]-2-methyl-5-nitro-1H-imidazole (tinidazoles) was studied by normal pulse and reverse pulse polarography.
TL;DR: In this article, the formation of ion pairs is used to greatly enhance the sensitivity of cathodic stripping measurements at the hanging mercury drop electrode (HMDE), illustrated for the trace determination of paraquat.
Abstract: The formation of ion pairs is used to greatly enhance the sensitivity of cathodic stripping measurements at the hanging mercury drop electrode (HMDE). Such a scheme is illustrated for the trace determination of paraquat. Factors affecting the response are explored.
TL;DR: In this paper, a method for the determination of furaltadone by differential-pulse polarography which allows 0.025 −2.0 μg ml−1 (7.7 × 10−8−6.2 × 10 −6 M) of this compound to be determined is proposed and was applied to the determination in its formulations, milk and urine.
TL;DR: The electrochemical properties of zopiclone, an anxiolytic and hypnotic drug, have been investigated by different techniques and the use of differential pulse and square-wave modes for quantitative measurements is more limited due to a slope modification in the current-concentration relationship.
TL;DR: In this article, the voltammetric behavior of Cu(II) in the presence of polyacrylic acid (PAA) was carried out by means of sampled direct current polarography (DCP), normal pulse polarography, differential pulse polarization (DPP), reverse pulse polarisation (RPP), cyclic voltammetry (CV), and differential pulse anodic stripping voltameters (DPASV).
Abstract: A systematic study of the voltammetric behavior of Cu(II) in the presence of polyacrylic acid (PAA) was carried out by means of sampled direct current polarography (DCP), normal pulse polarography (NPP), differential pulse polarography (DPP), reverse pulse polarography (RPP), cyclic voltammetry (CV), and differential pulse anodic stripping voltammetry (DPASV). Background currents due to PAA, and probably anodic oxidation of the Hg in this potential region, hinder the study of the Cu(II) reduction. Results obtained seem to indicate the lability of the Cu/PAA complex. Distorted DPASV signals are obtained for Cu(II) in the presence of PAA, which are explained on the basis of the change of the ligand-to-metal ratio during the different steps of the electrodic process. Titrations of Cu(II) with partially neutralized PAA allow the determination of the apparent formation constant K of the Cu/PAA complex system.
TL;DR: In this article, the temperature dependence of the transfer coefficient of bromate reduction at pH > 12 is studied in several supporting electrolytes (LiCl, NaCl, KCl, CsCl) in the temperature range 0-90° at the dropping mercury electrode.
TL;DR: In this article, photoelectron injection from mercury into aqueous electrolyte solution (PIMES) was used to determine the decay rates of polyfluorobenzoates and the redox potentials of radical anion decay products.
TL;DR: In this paper, the behavior of copper, lead, cadmium, and zinc in concentrated solutions of refined beetroot sugar was investigated by using differential pulse polarography (DPP).
Abstract: The behavior of copper, lead, cadmium, and zinc is investigated in concentrated solutions of refined beetroots sugar. The diffusion coefficients are found to decrease less than predicted by the Walden's rule, so trace determinations down to 10−7 M were measured by differential pulse polarography (DPP). Using anodic stripping voltammetry at a mercury film electrode, it was found that the refined sugar of alimentary grade contained: 57 (Cu), 34 (Zn), 1 (Cd), and 6 (Pb) μg/kg of dry sugar. For industrial syrups, resulting from a treatment by lime and water vapor of the raw material, some problems were encountered. Determination of copper and zinc was impossible, while that of lead and cadmium was possible after one liter of diluted syrup, at about 250 g l−1, had been treated with 20 g of activated carbon to absorb the major part of organic impurities. The lead and cadmium contents were found to be 20 (Pb) and 3.5 (Cd) μg kg−1.
TL;DR: In this paper, a differential pulse polarographic method for the identification and quantitative determination of enoxacin is described, which is based on the electrochemical reduction of the drug at the dropping mercury electrode.
Abstract: A differential pulse polarographic method for the identification and quantitative determination of enoxacin is described. The method is based on the electrochemical reduction of the drug at the dropping mercury electrode. It gives a well-developed polarographic response with a half-wave potential of -990 mV vs. SCE in 0.1 M HCl. The electroactive specie exhibits a diffusion-controlled polarographic wave and its limiting current shows a linear dependence with the enoxacin concentration in the range between 5.10−4 mM and 1 mM. This characteristic is applied for determination of enoxacin in commercial tablets. The recovery study shows a good accuracy and precision for the developed assay (average of 101.1% and standard deviation of 1.99). Furthermore, a comparative UV spectrophotometric assay also is developed.
TL;DR: In this paper, a new peak for the reduction of Solochrome Violet RS (SVRS) was found by using differential pulse polarography at temperatures below 10°C, and the most likely explanation for the appearance of the low temperature peak is the azo/hydrazone tautomeric equilibrium.
TL;DR: In this paper, arylhydroxylamine (II) condenses to form a nitrone, which is further reduced in two two-electron waves, corresponding to the cleavage of the N-O bond and reduction of the azomethine bond.
Abstract: In acidic media, at pH 7, the arylhydroxylamine (II) condenses to form a nitrone, which is further reduced in two two-electron waves, corresponding to the cleavage of the N-O bond and reduction of the azomethine bond. At pH 7, formation of anthranil (III) from II is a relatively slow process: in cyclic voltammetry (CV) and d.c. polarography, II is further reduced to IV; in controlled potential electrolysis at a mercury pool electrode, the same products are obtained at 0° C, but at 25° C, III is the predominant product.
TL;DR: In this paper, the electroanalytical behavior of 8-chlorotheophylline has been investigated by cyclic voltammetry on a hanging mercury drop electrode (HMDE) and by differential pulse polarography on a dropping mercury electrode (DME).
Abstract: The electroanalytical behavior of 8-chlorotheophylline has been investigated by cyclic voltammetry on a hanging mercury drop electrode (HMDE) and by differential pulse polarography on a dropping mercury electrode (DME). The differential pulse polarography approach offers a simple and yet reliable method for the determination of 8-chlorotheophylline in pharmaceutical preparations with good accuracy and precision.
TL;DR: The electrochemical behavior of the relatively new antibacterial antibiotic Pipril (Piperacillin) at the dropping mercury electrode is investigated using both direct current polarography (DCP) and differential pulse Polarography (DPP).