Showing papers on "Polarography published in 2004"
TL;DR: In this article, a review of the applications of dropping mercury electrodes is presented, which is limited to applications of the dropping mercury electrode for protein adsorption on the electrode surface, anodic reaction with mercury at positive potentials, reduction of disulfidic bonds of their components, in their complexation with metallic ions in the solution, in electrode reactions of their prosthetic groups and in antigen-antibody interactions.
Abstract: The first effects of proteins observed with the dropping mercury electrode were catalytic, due to evolution of hydrogen in weakly alkaline solutions. Catalytic lowering of hydrogen overvoltage in presence of cobalt ions, the so-called Brdicka reaction, became the main means for polarographic study of proteins. Apart from that, polarography has been used for following proteins in their adsorption on the electrode surface, in their anodic reaction with mercury at positive potentials, in reduction of the disulfidic bonds of their components, in their complexation with metallic ions in the solution, in electrode reactions of their prosthetic groups and in antigen-antibody interactions. Our review is limited to applications of the dropping mercury electrode.
67 citations
TL;DR: A validated direct square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure has been described for the trace determination of the drug in bulk form, tablets and human serum, compared to previously reported methods.
54 citations
TL;DR: It was found that at neutral pH DNA-Os,bipy produces three redox couples in the potential range between 0 and -1 V (peaks I-III) and a cathodic peak at about -1.3 V (peak IV), which corresponds to the known differential pulse voltammetric (polarographic) peak of DNA- Os,L adducts for which catalytic hydrogen evolution is responsible.
39 citations
TL;DR: A novel method has been developed for the determination of telmisartan by linear sweep polarography based on the catalytic hydrogen wave and is applied to the rapid determination of the tel Misartan in capsule forms and biological sample without pre-separation.
38 citations
TL;DR: In this article, the constants of complexation of extracellular polymers (ECPs) extracted from sludges for three metals, Cu, Ni and Zn at pH 7, were determined using a polarographic method (stripping mercury dropping electrode mode).
34 citations
TL;DR: In this article, the theoretical and experimental pseudopolarographic curves of reversible, quasireversible and irreversible electrochemical reactions were compared and evaluated using differential pulse anodic stripping voltammetry (DPASV).
27 citations
TL;DR: In this article, the polarographic and voltammetric properties of 3allyl-4-hydroxyazobenzene were studied at room temperature using various electrochemical techniques.
26 citations
TL;DR: In this paper, the electroreduction of picolinic acid (2-pyridinecarboxylic acid) on mercury electrodes was performed in the acidity range 2.25 m H 2 SO 4 to pH 11.3.
20 citations
TL;DR: It is demonstrated that the lipid-transfer protein isolated from a domestic cultivar of brewer’s barley grain has an affinity to bind Co ( II) and Pb (II) and has no affinity towards Cd, Cu, Cu (II), Zn, Zn and Cr (III).
Abstract: A lipid-transfer protein was isolated from a domestic cultivar of brewer’s barley grain, Hordeum vulgare. The presence of Cu (II), Pb (II), Cd (II) and Zn (II) ions in its structure and its ability to bind Hg (II) and Ni (II) ions is known. We investigated its ability to bind other metal ions by differential pulse polarography. Here we demonstrate that the lipid-transfer protein has an affinity to bind Co (II) and Pb (II) and has no affinity towards Cd (II), Cu (II), Zn (II) and Cr (III). These results suggest a new possible role of barley lipid-transfer protein for phytoextraction.
19 citations
TL;DR: In this article, the interaction between Cu(II) and pectin extracted from citrus fruit was studied using ion selective electrode potentiometry and voltammetry, namely differential pulse polarography and square-wave voltammetrical.
Abstract: The interaction between Cu(II) and pectin extracted from citrus fruit was studied in KNO3 0.10 mol dm−3 at 25 °C and pH 5.5, using ion selective electrode potentiometry and voltammetry, namely differential pulse polarography and square-wave voltammetry. Although many independent variables may affect Cu(II)-polymer interactions such as charge density, polymer concentration and copper to polymer concentration ratio, a good fitting was observed for the model with ML and ML2 complex species, when M:L total concentration (mol dm−3) ratio varies from 0.2 to 2.7 and the ligand concentration is in the range (0.2 to 1) g dm−3, i.e., (0.4 to 2)×10−3 mol COO− dm−3. The complex parameters found in these conditions were log βCuL=3.5±0.1 and log βCuL2= 8.0±0.2. For lower total ligand and total metal ion concentrations, used in voltammetry, the interaction Cu(II)-pectin is affected by a cooperative mode (increase of metal ion-ligand affinity) when the total metal ion concentration increases and by an anti-cooperative mode when the total ligand concentration increases, possibly due to different conformations of the polymer.
18 citations
TL;DR: In this article, a method for simultaneous determination of sulfite and thiosulfate at sub-ppm levels in petroleum and its distillates was investigated using a convenient, accurate and sensitive procedure.
TL;DR: In this article, the stability constants of the metal ions with aza and tosylated-aza macrocycles using TBAP as supporting electrolyte in 75% DMF+water and 90% DMSO+water media were investigated.
Abstract: Complexation of Cu(II), Zn(II), Ni(II), Co(II), Pb(II), Cd(II), Cr(III) and Fe(III) ions with 15-crown-5, benzo-15-crown-5, 18-crown-6, dibenzo-18-crown-6, dicyclohexano-18-crown-6, dibenzo-24-crown-8, 5,6,14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadeca-5,14-diene, 1,4,10-trioxa-7,13-diazacyclopentadecane and cyclam has been investigated in 75% (v/v) DMF+water using the silver(I) ion as an auxiliary cation at 0.05 M ionic strength adjusted with tetrabutylammonium perchlorate (TBAP) by competitive potentiometry. Stability constant values obtained for the metal ion–aza macrocyclic complexes are higher than those for the oxa crowns. Shifts in the peak potential and reduction in the peak current in the differential pulse polarography (DPP) method were also used to determine the stability constants of some of the metal ions with aza and tosylated-aza macrocycles using TBAP as supporting electrolyte in 75% (v/v) DMF+water and 90% (v/v) DMSO+water media. Stability constant values determined both by shifts in th...
TL;DR: In this paper, the results of detailed studies aimed at optimizing the analytical parameters for simultaneous catalytic adsorptive stripping voltammetric determination of Co and Ni in the form of complexes with α-furil dioxime in the presence of Zn matrix are presented.
Abstract: The exploitation of the catalytic-adsorptive effect in the Co(II)-dioxime-nitrite systems provides a significant increase of the Co adsorptive stripping voltammetric response and subsequently the influence of the interfering elements such as Ni and Zn is strongly diminished The purpose of the present paper was to study voltammetric properties of Co and Ni in a supporting electrolyte containing ammonia buffer, α-furil dioxime in the absence and in the presence of nitrite, by differential pulse polarography and adsorptive stripping voltammetry Results of detailed studies aimed at optimizing the analytical parameters for simultaneous catalytic adsorptive stripping voltammetric determination of Co and Ni in the form of complexes with α-furil dioxime in the presence of Zn matrix are presented In the supporting electrolyte of composition 01 M NH4Cl, 05 M NH3, 4×10−5 M αFD, 05 M NaNO2 the linearity range amounts from 003 to 24 μg/L for Co and from 03 to 9 μg/L for Ni for 20 s of accumulation The method enables the determination of Co and Ni in the presence of a great excess of Zn with the detection limit equal to 002 μg/L Co and 02 μg/L Ni obtained for a 20 s accumulation time
TL;DR: In this article, the influence of the concentration of the sodium perchlorate supporting electrolyte on the standard electrode reaction rate constants for the one-electron reduction of Eu(CF 3 SO 3 ) 3 on mercury in dimethylsulfoxide has been studied.
TL;DR: In this paper, four models were chosen to assess the performance of such flow adaptors, which are directly fitted to the glass capillary of any MDE, light enough not to impair the mechanical drop knocker and can be easily built in the laboratory.
Abstract: Electrochemical batch cells with mercury drop electrodes, MDEs, are readily available from a number of producers and widely used in electroanalysis for polarography, voltammetry and stripping voltammetry. To increase sample throughput and reduce reagent and sample consumption, the tendency is to couple the MDE with flow analysis systems (e.g., FIA, SIA or BIA). Many special flow cells for MDEs are described in the literature, but it is easier to convert existing commercial batch cells to flow operation. To assess the performance of such flow adaptors, four models were chosen because they are directly fitted to the glass capillary of any MDE, light enough not to impair the mechanical drop knocker and can be effortlessly built in the laboratory. They were all found adequate for flow amperometry and stripping voltammetry, with differences in sensitivity, flow rate dependence, response time, drop stability, tolerance to bubbles, uncompensated resistance and recontamination of disposed analyte from the electrolytic bath. Two of them, a simple L-shaped PTFE tube and an upstream nozzle holder made from a disposable pipette tip, gather a larger set of desirable features.
TL;DR: A mathematical conversion of data from nonequilibrium and dynamic voltammetric techniques (direct-current-sampled (DC) and differential-pulse (DP) polarography) into potentiometric, free-metal ion sensor-type data is described and employed in the study of BiIII complexes with the ligand picolinic acid as mentioned in this paper.
Abstract: A mathematical conversion of data from nonequilibrium and dynamic voltammetric techniques (direct-current-sampled (DC) and differential-pulse (DP) polarography) into potentiometric, free-metal-ion sensor-type data is described and employed in the study of BiIII complexes with the ligand picolinic acid (=pyridine-2-carboxylic acid) (labile and dynamic metal/ligand system). A novel procedure that allows evaluation of experimental data collected at very low pH values (acid-base titration) is proposed. Software ESTA dedicated to potentiometry was successfully employed in the refinement operations performed with virtual potentiometric (VP) data obtained from DC and DP polarography, the latter being performed at fixed pH (ligand titration) as well as at fixed [LT]/[MT] ratio (acid-base titration). It was possible to refine stability constants either separately from VP-DC or VP-DP, or simultaneously from any combination of VP-DC and VP-DP obtained from ligand and/or acid-base titrations. The concept of VP-DC or VP-DP is employed for the first time in the study of an unknown BiIII/picolinic acid/OH system, and numerous documented and possible advantages are discussed. Five complexes of bismuth, ML, ML2, ML3, ML4, and ML3(OH) and their stability constants (as log β) 7.48±0.01, 13.94±0.01, 18.10±0.04, 20.47±0.25, and 26.65±0.03, respectively, are reported at 0.5M (Na,H)NO3 ionic strength and T 298 K. The proposed procedure can be easily utilized also by non-electrochemists who are interested in, e.g., ligand-design strategies.
TL;DR: In this article, a mathematical conversion of data coming from nonequilibrium and dynamic voltammetric techniques (a direct current sampled (DC) and differential pulse (DP) polarography) into potentiometric sensor type of data is described and tested on a dynamic metal-ligand system.
Abstract: A mathematical conversion of data coming from nonequilibrium and dynamic voltammetric techniques (a direct current sampled (DC) and differential pulse (DP) polarography) into potentiometric sensor type of data is described and tested on a dynamic metal-ligand system. A combined experiment involving DCP, DPP and glass electrode potentiometry (GEP) was performed on a single solution sample containing a fixed [LT] : [MT] ratio (acid-base titration). Dedicated potentiometric software ESTA was successfully employed in the refinement operations performed on virtual potentiometric (VP) data obtained from DC and DP polarography. It was possible to refine stability constants either separately, from VP-DC or VP-DP, or simultaneously from any combination of VP-DC, VP-DP and GEP. The concept of VP-DC or VP-DP is reported for the first time and numerous documented and possible advantages are discussed. The proposed procedure can be easily utilized also by nonelectrochemists who are interested in, e.g., the ligand design strategies.
TL;DR: In this article, a simple experiment is described that exposes students to two important aspects of electrochemistry: its potential use in industrial technologies and its application for solving analytical problems, and the electrolytic elimination of metal ions (Cd2+, Cu2+, Zn2+) from an aqueous solution.
Abstract: A simple experiment is described that exposes students to two important aspects of electrochemistry: its potential use in industrial technologies and its application for solving analytical problems. To illustrate these two points we have chosen to examine the electrolytic elimination of metal ions (Cd2+, Cu2+, Zn2+) from an aqueous solution. The metal ion concentrations are monitored by differential pulse polarography. This experiment is well suited to explain the connection between thermodynamics and kinetics based on the quantitative evolution of the different metal concentrations.
TL;DR: A preparative method of synthesis of the new methyl 3-iodo-1-benzothiophene-2-carboxylate was elaborated in this article, where the reduction in divided cells follows the ECE mechanism, where the primary radical anion is split into a halide anion and neutral heterocyclic radical, which is immediately reduced by the second electron and protonated.
Abstract: A preparative method of synthesis of the new methyl 3-iodo-1-benzothiophene-2-carboxylate was elaborated. Electrochemical behavior of methyl 3-chloro-, bromo- and iodo-1-benzothiophene-2-carboxylates 1-3, and of their reduction and dimer products 4, 5 in anhydrous dimethylformamide has been investigated at mercury and platinum electrodes using polarography, cyclic voltammetry and voltammetry on a rotating platinum disk electrode. The reduction in divided cells follows the ECE mechanism (electron - chemical step - electron), where the primary radical anion is split into a halide anion and neutral heterocyclic radical, which is immediately reduced by the second electron and protonated. The only reduction product is the methyl 1-benzothiophene-2-carboxylate (5); whereas the EDim mechanism (electron - dimer formation) leading to the dimeric species 4 was not observed under the above conditions. Reduction of 1-3 on platinum causes formation of a blocking film on the electrode. Sonication during electrolysis successfully reactivates the electrode.
01 Jan 2004
TL;DR: In this article, a new sensitive adsorptive voltammetric method was described for the determination of zirconium at a carbon paste electrode (CPE) in the presence of alizarin complexone.
Abstract: A new sensitive adsorptive voltammetric method was described for the determination ofzirconium at a carbon paste electrode (CPE) in the presence of alizarin complexone (ALC).Optimal analytical conditions are: 1.0~ l0"6 or 5.0x l0"7 mol/L ALC, 0.20 mol/L HAC-NaAc (pH4.3), accumulation for 60 s at 0 V (vs. SCE), and linear scanning from 0 V to 1.0 V at 250 mV/s.The peak potential of the complex is at 0.81 V. By using a model JP-303 polarographic analyzer,2.0~ l0l~ mol/L (S/N=3) zirconium can be detected with a 90 s accumulation, when the 2nd-orderderivative linear sweep technique is used, and the linear range is 6.0~ 10l~-2.0~ l0s mol/L (5.0~ l07mol/L ALC) and 2.0~108-2.0~ l07 mol/L (1.0~ 10.6 mol/L ALC), respectively. The developedmethod was applied to the determination of trace zirconium in the ore samples with satisfactoryresults.
TL;DR: In this article, the electroreduction of a binuclear complex of copper with a macrocyclic Schiff base of the Robson type on the basis of 4-tert-butyl-2,6-diformylphenol and 1,3-diaminopropane on the dropping-mercury, gold, amalgamated-gold, and glassy-carbon electrodes is studied in an aqueous environment.
Abstract: The electroreduction of a binuclear complex of copper(II) with a macrocyclic Schiff base of the Robson type on the basis of 4-tert-butyl-2,6-diformylphenol and 1,3-diaminopropane on the dropping-mercury, gold, amalgamated-gold, and glassy-carbon electrodes is studied in an aqueous environment. The data of experiments on preparative electrolysis and the results of measurements by a method of cyclic voltammetry and classic polarography suggest that the complex under study undergoes reduction in an aqueous environment with the transfer of four electrons with formation of copper(0) and a free Schiff base, which in conditions under investigation experiences hydrolytic decomposition.
TL;DR: In this article, the quasi-reversible electroreduction process of the Zn2+ in absence and in presence of N,N′-dimethylthiourea (DMTU) were quantitatively compared.
TL;DR: In this article, an electrochemical investigation of free thiamin and its phosphate esters was performed in acidic solutions at an unmodified platinum electrode by means of cyclic voltammetry.
TL;DR: Differential pulse voltammetry (DPV) and DC tast polarography (DCTP) at a static mercury drop electrode (SMDE) were used for the determination of trace amounts of carcinogenic nitrobiphenyls as mentioned in this paper.
Abstract: A number of environmentally important substances exhibit genotoxic or ecotoxic properties leading to the need for sensitive and selective methods for their determination Differential pulse polarography (DPP) and DC tast polarography (DCTP) at a static mercury drop electrode (SMDE) were used for the determination of trace amounts of carcinogenic nitrobiphenyls, namely 2‐nitrobiphenyl (2‐NBP), 3‐nitrobiphenyl (3‐NBP), and 4‐nitrobiphenyl (4‐NBP) within the concentration range from 2 · 10−7 to 1 · 10−4 mol · l−1 for DC tast polarography and from 2 · 10−8 to 1 · 10−4 mol · l−1 for DPP using a Britton‐Robinson buffer—methanol (1:1) mixture with resulting pH 12 as a base electrolyte Differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE) is applicable within the concentration range from 2 · 10−8 to 1 · 10−5 mol · l−1 The above mentioned techniques were used for the analysis of mixtures of carcinogenic nitrobiphenyls
TL;DR: In this paper, the electroreduction of 2,6-dimethoxy-4-chloro-1,3,5-triazine on mercury electrodes in aqueous solutions and in the acidity range 2m H2SO4 to pH 7.5 was investigated.
Abstract: This paper presents polarographic and voltammetric studies on the electroreduction of 2,6-dimethoxy-4-chloro-1,3,5-triazine on mercury electrodes in aqueous solutions and in the acidity range 2 M H2SO4 to pH 7. Above pH 6.5 no signals were obtained. In both DC and DP polarography and voltammetry, one or two partially overlapped reduction waves were observed, depending on the pH of the medium. The overall process corresponded to a four-electron irreversible reduction. In strongly acidic media (pH<4.5) the protonated reactant was reduced through a two-electron process to give a dechlorinated molecule that is subsequentely reduced at the potentials of the second wave. It was concluded that the reduction of the chlorinated s-triazine rings seems to occur through the reductive cleavage of the chlorine irrespective of the nature of the groups bonded to the ring in positions 2, 6.
TL;DR: Polarographic and voltammetric behavior of 1,5-dinitronaphthalene was investigated using tast polarography and differential pulse polarography at a classic dropping mercury electrode and differential pulses voltammetry and ad-sorptive stripping voltageammetry at a hanging mercury drop electrode as discussed by the authors.
Abstract: Polarographic and voltammetric behavior of 1,5-dinitronaphthalene was investigated using tast polarography and differential pulse polarography at a classic dropping mercury electrode and differential pulse voltammetry andadsorptive stripping voltammetry at a hanging mercury drop electrode. Optimum conditions have been found for the determination of tested substance in the concentration range 2-10 μmol l - 1 in tast polarography, 0.2-1 μmol l - 1 in differential pulse polarography at a classic dropping mercury electrode or differential pulse voltammetry at a hanging mercury drop electrode, and 0.02-0.1 μmol l - 1 using adsorptive stripping voltammetry. A possible mechanism of the electrochemical reduction of 1,5-dinitronaphthalene at mercury electrodes is discussed.
TL;DR: By studying the characteristics of the wave and the electrode reaction mechanism, it is proved that the catalytic wave is an adsorption wave and that the peak current comes from the reduction of Fe(II).
Abstract: In the buffer solution of NH3-NH4Cl (pH = 8.5, 0.04 mol l(-1)), iron-Methylthymol Blue (MTB) can produce a sensitive polarographic wave at -1.10 V (vs. SCE) in the NaNO2. The peak current is linear with the concentration of the iron in the range of 3 x 10(-8)-5 x 10(-6) mol l(-1), and the detection limit is 1 x 10(-8) mol l(-1). By studying the characteristics of the wave and the electrode reaction mechanism, we can prove that the catalytic wave is an adsorption wave and that the peak current comes from the reduction of Fe(II). The molar ratio of iron to ligand was found to be 1:1. Adsorption particles are neutral molecules, the saturated adsorption quantity of the complex on the mercury electrode is 1.92 x 10(-9) mol cm(-2), according with the Frumkin isothermal formula. In the experiments, the adsorption coefficient (beta) is 4.05 x 10(5); the adsorption factor (gamma) is 0.70: the electron transfer number (n) is 2; the free energy (deltaG(o)) is 31.99 kJ mol(-1); the transfer coefficient of the irreversible adsorption is 0.42-0.45; and the reaction velocity constant (Ks) is 1.35 s(-1). This method, whose result is satisfying, can be applied to the detection of trace total iron contents in medicinal products.
TL;DR: In this paper, the electrochemical behavior of bovine erythrocyte superoxide dismutase (BESOD) on a hanging or dropping mercury electrode was studied by cyclic voltammetry (CV) and normal pulse polarography (NPP).
TL;DR: In this article, the experimental set up required and probe for the various products formed have been tried and the anodic process has been carried out at low cost and readily available stainless steel electrode undar aqueous conditions.
Abstract: The electro-organic technique is observed to be the modern tool in achieving the oxidation of organic acids to some other useful organic molecules. In the present study, the favourable experimental conditions for carrying out the electrochemical oxidation of cinnamic acid, the experimental set up required and probe for the various products formed have been tried. The anodic process has been carried out at low cost and readily available stainless steel electrode undar aqueous conditions. On identification of the products using chromatographic and spectroscopic techniques, the most probable mechanism has been proposed. To confirm the positive occurrence of the oxidative process under electrolytic conditions, the current — potential study was carried out. The product was analysed by TLC technique, UV and IR spectral studies and identified as 1,4-diphenylbut — 1,3-diene. This work paves a humble way of opening up a new area wherein other electro analytical parameters like polarography, cyclic voltammetry, electrode variation, temperature variation, solvent effects etc. can be studied, along with innumerable substituent effect studies.