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Mercury Electrode (mercury + electrode)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Polylysine-Catalyzed Hydrogen Evolution at Mercury Electrodes

ELECTROANALYSIS, Issue 17-18 2010
Marko, ivanovi
Abstract It has been shown that peptides and proteins produce at nanomolar concentrations a structure-sensitive chronopotentiometric peak H at mercury electrodes, which is due to the catalytic hydrogen evolution reaction (HER). Herein, we use for the first time poly(amino acids) to obtain information about the role of individual amino acid residues in the HER. At pH,6 polylysine (polyLys) and polyarginine,tryptophan yield a peak H, in agreement with their ionization state, while polyglutamic acid gives no catalytic response. PolyLys catalyzes hydrogen evolution in its adsorbed state. Even at potentials negative to the potential of zero charge, hydrophobic interactions could be involved in polyLys adsorption. [source]

Bismuth Film Electrode as an Alternative for Mercury Electrodes: Determination of Azo Dyes and Application for Detection in Food Stuffs

ELECTROANALYSIS, Issue 21 2007
Benoît Claux
Abstract Bismuth electrodes were investigated and exhibit electrochemical properties similar to mercury electrodes but with much lower toxicity. An electrochemical application of bismuth film modified glassy carbon electrode for azo dyes determination was investigated. The plating step was optimized in order to achieve its analytical efficiency. A plating potential of ,0.9,V in a solution of 200,mg/L Bi(NO3)3, 0.5,M HNO3 for 100,s yields to a suitable electrode (in terms of stability and detection). Azo dyes such as azorubine (i.e., carmoisine, E122), amaranth (E123), ponceau 4R (i.e., new coccine, E124) and allura red (E129) were determined by differential pulse voltammetry in a NaCl solution in the concentration range of few ppm to 100 ppm. The reproducibility of the signal, characterized by the relative standard deviation, was found to be less than 5%, the detection and quantification limits were few mg/L. The influence of other food components on the signal was studied and the applicability was tested on real beverages samples. [source]

Electrochemical Determination of Manganese Solubility in Mercury via Amalgamation and Stripping in the Room Temperature Ionic Liquid n -Hexyltriethylammonium Bis(trifluoromethanesulfonyl)imide, [N6,2,2,2][NTf2]

ELECTROANALYSIS, Issue 24 2008

Abstract The solubility of manganese in mercury was determined electrochemically via amalgamation and stripping in the room temperature ionic liquid n -hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, [N6,2,2,2][NTf2]. A hemispherical mercury electrode was made by electrodepositing mercury onto a planar platinum microelectrode. Cyclic voltammetry of Mn2+ in [N6,2,2,2][NTf2] at the mercury microhemisphere electrode was investigated at temperatures of 298, 303 and 313,K. The solubility of Mn in Hg was determined on the basis of the charge under the reduction peak (Mn2+,Mn0) and the corresponding reoxidation. [source]

Rainwater Dissolved Organic Carbon: Characterization of Surface Active Substances by Electrochemical Method

ELECTROANALYSIS, Issue 19-20 2007
osovi
Abstract Surface active substances as organic constituents of bulk precipitation were studied by AC voltammetric method. Adsorption characteristics at the mercury electrode of real rainwater samples are compared with aqueous solutions of a number model substances suggested to be representative of water soluble organic compounds (WSOC) in atmospheric aerosols and droplets: monocarboxylic, dicarboxylic, and polyacidic compounds, levoglucosan, polyaromatic hydrocarbon naphtalene and anionic surfactant sodium dodecylbenzene sulfonate. On the basis of the capacitance vs. potential curves and the surfactant activity normalized to the organic carbon content it is concluded that humic like substances, monocarboxylic acids and polyaromatic hydrocarbons may play an important role in atmospheric aquatic system because of their surface active potential. [source]

DNA Determination in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

ELECTROANALYSIS, Issue 11 2007
Augusto, Mardini Farias, Percio
Abstract A stripping method for the determination of single-stranded DNA in presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of adenine (from acid-treated DNA) at thin-film mercury electrode followed by linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0×10,3,M NaOH solution, an accumulation potential of ,0.40,V and a scan rate of 200,mV s,1. The response of adenine,copper is linear over the concentration range 50,250,ppb. For an accumulation time of 15,minutes, the detection limit was found to be 4,ppb. The more convenient relation to measuring the ssDNA in presence of metals and nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of adenosine-triphosphate (ATP) and amino acids. [source]

Utilization of a Copper Solid Amalgam Electrode for the Analytical Determination of Atrazine

ELECTROANALYSIS, Issue 22 2005
Djenaine De, Souza
Abstract A copper solid amalgam electrode was prepared and used for the voltammetric determination of atrazine in natural water samples by square wave voltammetry. This electrode is a convenient substitute for the hanging mercury electrode since it is selective, sensitive, reliable and inexpensive and presents low toxicity characteristic. The detection limit of atrazine obtained in pure water (laboratory samples) was shown to be lower than the maximum limit of residue established for natural water by the Brazilian Environmental Agency. The relative standard deviation for 10 different measurements was found to be only 3.98% in solutions containing 8.16×10,6,mol L,1 of atrazine. In polluted stream water samples, the recovery measurements were approximately 70.00%, sustaining the applicability of the proposed methodology to the analysis of atrazine in such matrices. [source]

Tensammetric Analysis of Nonionic Surfactant Mixtures by Artificial Neural Network

ELECTROANALYSIS, Issue 12 2005
A. Safavi
Abstract An artificial neural network (ANN) model has been developed for tensammetric determination of a series of Brijes (Brij 30, Brij 35, Brij 56, Brij 96) as nonionic surfactants. The tensammetric method is based on the measurement of the capacitive current of the mercury electrode after adsorption of surfactants. All Brijes were analyzed in the concentration range of 1.0,100.0,,g mL,1. The proposed method shows good sensitivity and applicability to the simultaneous determination of mixtures of four Brijes in aqueous solutions. [source]

Early Polarographic Studies on Proteins

ELECTROANALYSIS, Issue 13-14 2004
Michael Heyrovsky
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. [source]

Study of the Complexation, Adsorption and Electrode Reaction Mechanisms of Chromium(VI) and (III) with DTPA Under Adsorptive Stripping Voltammetric Conditions

ELECTROANALYSIS, Issue 19 2003
Sylvia Sander
Abstract The complexation of Cr(III) and Cr(VI) with diethylenetriaminepentaacetic acid (DTPA), the redox behavior of these complexes and their adsorption on the mercury electrode surface were investigated by a combination of electrochemical techniques and UV/vis spectroscopy. A homogenous two-step reaction was observed when mixing Cr(III), present as hexaquo complex, with DTPA. The first reaction product, the electroactive 1,:,1 complex, turns into an electroinactive form in the second step. The results indicate that the second reaction product is presumably a 1,:,2 Cr(III)/DTPA complex. The electroreduction of the DTPA-Cr(III) complex to Cr(II) was found to be diffusion rather than adsorption controlled. The Cr(III) ion, generated in-situ from Cr(VI) at the mercury electrode at about ,50,mV (vs. Ag|AgCl) (3,mol,L,1 KCl), was found to form instantly an electroactive and adsorbable complex with DTPA. By means of electrocapillary measurements its surface activity was shown to be 30 times higher than that of the complex built by homogenous reaction of DTPA with the hydrated Cr(III). Both components, DTPA and the in-situ built complex Cr(III) ion were found to adsorb on the mercury electrode. The effect of nitrate, used as catalytic oxidant in the voltammetric determination method, on the complexation reaction and on the adsorption processes was found to be negligible. The proposed complex structures and an overall reaction scheme are shown. [source]

Redox Properties of the Iron Complexes of Orally Active Iron Chelators CP20, CP502, CP509, and ICL670

HELVETICA CHIMICA ACTA, Issue 12 2004
Martin Merkofer
Redox cycling of iron is a critical aspect of iron toxicity. Reduction of a low-molecular-weight iron(III)-complex followed by oxidation of the iron(II)-complex by hydrogen peroxide may yield the reactive hydroxyl radical (OH.) or an oxoiron(IV) species (the Fenton reaction). Complexation of iron by a ligand that shifts the electrode potential of the complex to either to far below ,350,mV (dioxygen/superoxide, pH=7) or to far above +320,mV (H2O2/HO., H2O pH=7) is essential for limitting Fenton reactivity. The oral chelating agents CP20, CP502, CP509, and ICL670 effectively remove iron from patients suffering from iron overload. We measured the electrode potentials of the iron(III) complexes of these drugs by cyclic voltammetry with a mercury electrode and determined the dependence on concentration, pH, and stoichiometry. The standard electrode potentials measured are ,620,mV, ,600,mV, ,535,mV, and ,535,mV with iron bound to CP20, ICL670, CP502, and CP509, respectively, but, at lower chelator concentrations, electrode potentials are significantly higher. [source]

Polylysine-Catalyzed Hydrogen Evolution at Mercury Electrodes

Directly Heated Bismuth Film Electrodes Based on Gold Microwires

ELECTROANALYSIS, Issue 13 2010
Martin Jacobsen
Abstract As a nontoxic substitute for mercury electrodes, bismuth electrodes attained a lot of attention during the last years. In this report we describe for the first time the preparation of two different directly heatable bismuth-modified microwire electrodes. We characterized the electrochemical behaviour using cyclic voltammetry in acetate buffer and alkaline tartrate solution. The bismuth electrodes show a significantly wider potential window compared with bare gold wires. In the presence of picric acid as one example for the detection of explosives, the bismuth electrodes deliver higher signals. By applying heat during the measurements, the signals can be enhanced further. We used the temperature pulse amperometry (TPA) technique to improve the electrochemical response at the different types of electrodes. In this preliminary study, we were able to detect 3,ppm traces of picric acid. [source]

Electroactivity of Nonconjugated Proteins and Peptides.

ELECTROANALYSIS, Issue 23 2007
Towards Electroanalysis of All Proteins
Abstract Present proteomics and biomedicine require sensitive analytical methods for all proteins. Recent progress in electrochemical analysis of peptides and proteins based on their intrinsic electroactivity is reviewed. Tyrosine and/or tryptophan-containing proteins are oxidizable at carbon electrodes. At mercury electrodes all peptides and proteins (about 13 peptides and >25 proteins were tested) produce chronopotentiometric peak H at nanomolar concentrations. This peak is sensitive to changes in protein structure. Microliter sample volumes are sufficient for the analysis. Electrochemical methods can be used in studies of nucleic acid-protein interactions and can be applied in biomedicine. Examples of such applications in neurogenerative diseases and cancer are presented. [source]

Bismuth Film Electrode as an Alternative for Mercury Electrodes: Determination of Azo Dyes and Application for Detection in Food Stuffs

Stripping Analysis at Bismuth Electrodes: A Review

ELECTROANALYSIS, Issue 15-16 2005
Joseph Wang
Abstract For many years mercury electrodes were the transducer of choice in stripping voltammetry of trace metals owing to their high sensitivity, reproducibility, and renewability. However, because of the toxicity of mercury, alternative (,environmentally friendly') electrode materials are highly desired for both centralized and field applications. Recently introduced bismuth electrodes offer a very attractive alternative to commonly used mercury electrodes. Such electrodes display well-defined, undistorted and highly reproducible response, favorable resolution of neighboring peaks, high hydrogen evolution, with good signal-to-background characteristics comparable to those of common mercury electrodes. The attractive stripping behavior of bismuth electrodes reflects the ability of bismuth to form ,fused' multicomponent alloys with heavy metals. Bismuth stripping electrodes thus hold great promise for decentralized metal testing, with applications ranging from continuous remote sensing to single-use measurements. Fundamental studies aimed at understanding the behavior of bismuth film electrodes should lead to rational preparation and operation of reliable alternative (,non,mercury') stripping electrodes that would have a major impact upon electroanalysis of trace metals. This article reviews the development, behavior, scope and prospects of bismuth electrodes for stripping-based electrochemical measurements of trace metals. [source]

Amalgam Electrodes for Electroanalysis

ELECTROANALYSIS, Issue 8 2003
Øyvind Mikkelsen
Abstract Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising. [source]

In situ micro Raman investigation of electrochemically formed halide and pseudohalide films on mercury electrodes,

JOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2002
Alexandre G. Brolo
Oxidation of pure mercury electrodes was followed by in situ surface-unenhanced Raman spectroscopy. A special spectroelectrochemical cell allowed the observation of spectral features of the oxidation products using a Raman microprobe. The electrochemical behaviour of mercury in basic solution, halide (F,, Cl,, Br, and I,) and pseudohalide (SCN,) media was investigated. Insoluble films were formed during the anodic processes in all these systems. The identities of the electrochemically generated films were clearly determined from the Raman spectra. The main product of the electrochemical oxidation of mercury in basic solutions was solid HgO. The anodic behaviour of mercury in the presence of halide yielded insoluble Hg2X2 compounds (where X is the halide). The time dependence of the Raman signals indicated a diffusion-controlled growth of the halide films. The oxidation of mercury in SCN, solutions also produced a solid precipitate [Hg2(SCN)2]. Raman bands due to soluble mercury(II) thiocyanate complexes [Hg(SCN)x2,x], present in the electrochemical diffusion layer, were also observed. Copyright © 2002 John Wiley & Sons, Ltd. [source]