ELECTROCHEMICAL Analysis | Academic Articles

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Posts Tagged ‘ELECTROCHEMICAL analysis’

A tutorial on the application of ion-selective electrode potentiometry: an analytical method with unique qualities, unexplored opportunities and potential pitfalls; tutorial

Abstract: Ion-selective potentiometry enjoys practical utility as a simple analytical technique to measure ionic constituents in complex samples. Advances in the field have improved the selectivity and decreased the detection limit of ion-selective electrodes (ISEs) by orders of magnitude such that trace analysis in micro and nanomolar concentrations is now possible with potentiometric sensors. This tutorial reviews the fundamental principles of ion-selective potentiometry, describes the practical considerations involved in the use of these sensors to measure real samples, and discusses the statistical evaluation of experimental results compared with alternative analytical techniques. [Copyright &y& Elsevier]

October 30, 2012 Tags: ELECTROCHEMICAL analysis, ELECTROCHEMICAL sensors, ELECTRODES, Ion selective, POTENTIOMETRY, TECHNOLOGICAL innovations, TRACE analysis
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A review on determination of steroids in biological samples exploiting nanobio-electroanalytical methods

Abstract: The applications of nanomaterial modified sensors, molecularly imprinting polymer based, aptamer based, and immunosensors have been described in the determination of steroids using electroanalytical techniques. After a brief description of the steroids and assays in biological fluids, the principles of electrochemical detection with the advantages and the limitations of the various sensors are presented. The nanomaterial modified sensors catalyze the oxidation/reduction of steroids and are suitable for sensing them in environmental samples and biological fluids. The determination of steroids based on their reduction has been found more useful in comparison to oxidation as the common metabolites present in the biological fluids do not undergo reduction in the usual potential window and hence, do not interfere in the determination. The sensors based on immunosensors and aptamers were found more sensitive and selective for steroid determination. Conducting polymer modified bio-sensors and microchip devices are suggested as possible future prospects for the ultra sensitive and simultaneous determination of steroids and their metabolites in various samples. [Copyright &y& Elsevier]

October 30, 2012 Tags: APTAMERS, BIOELECTROCHEMISTRY, ELECTROCHEMICAL analysis, IMPRINTED polymers, MOLECULAR imprinting, NANOSENSORS, NANOSTRUCTURED materials, STEROIDS -- Analysis
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Voltammetric monitoring of electrochemical reduction of riboflavin using silver solid amalgam electrodes

Abstract: The voltammetric behavior of riboflavin (RF), an important compound belonging to the group of vitamins B, has been investigated using mercury meniscus modified electrode (m-AgSAE) and polished silver solid amalgam electrode (p-AgSAE). Obtained results were compared with those obtained using hanging mercury drop electrode (HMDE). Cyclic voltammetry (CV), direct current voltammetry (DCV) and differential pulse voltammetry (DPV) have been applied for investigation of electrochemical behavior of RF on the above mentioned electrodes. Optimum conditions for DPV determination of RF have been found in acetate buffer of pH 5 for m-AgSAE and HMDE, and in Britton–Robinson (BR) buffer of pH 3 for p-AgSAE. The limits of detection amounted to 8.2×10−10 molL−1 (m-AgSAE) and 1.3×10−9 molL−1 (p-AgSAE). DPV with optimized parameters was utilized for successful determination of RF in 2 vitamin preparations. [Copyright &y& Elsevier]

July 7, 2012 Tags: Amalgam, ELECTROCHEMICAL analysis, ELECTRODES, HYDROGEN-ion concentration, REDUCTION (Chemistry), SILVER, VITAMIN B2
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The electrochemical transfer reactions and the structure of the iron|oxide layer|electrolyte interface

Abstract: The thickness, barrier (protecting) and semiconducting properties of the potentiostatically formed oxide films on the pure iron electrode in an aqueous borate buffer solution were investigated by electrochemical quartz crystal nanobalance (EQCN), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (MS) analysis. The thicknesses of the prepassive Fe(II)hydroxide layer (up to monolayer) nucleated on the bare iron surface and the passive Fe(II)/Fe(III) layer (up to 2nm), deposited on the top of the first one, were determined using in situ gravimetry. Electronic properties of iron prepassive and passive films as well as ionic and electronic transfer reactions at the film|solution interface were discussed on the basis of a band structure model of the surface oxide film and the potential distribution at the interface. The anodic oxide film formation and cathodic decomposition are coupled processes and their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode|solution interface. The structure of the reversible double layer at the iron oxide|solution interface was discussed based on the concept of the specific adsorption of the imidazolium cation on the negatively charged electrode surface at pH>pHpzc. [Copyright &y& Elsevier]

July 7, 2012 Tags: CHEMICAL reactions, CHEMICAL structure, ELECTROCHEMICAL analysis, ELECTRODES, IRON, IRON oxides, SEMICONDUCTORS, THICKNESS measurement
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The effect of nickel on alloy microstructure and electrochemical behaviour of aa1050 aluminium alloy in acid and alkaline solutions

Abstract: The study investigates the influence of nickel and magnesium additions to AA1050 aluminium alloy on the alloy electrochemical behaviour in sodium hydroxide and hydrochloric solutions under conditions relevant to industries that use alkaline etching as a standard surface treatment procedure and to the lithographic and electronic industries where surface convolution is assisted by pitting in hydrochloric acid. Scanning and transmission electron microscopes were used to characterize the intermetallic particles, and scanning Kelvin probe microscopy was utilised in monitoring the surface potential. Nickel is shown to be incorporated into second phase particles, which mostly consisted of Al3Fe and α-(AlFeSi) phases, resulting in enhanced cathodic activity on the aluminium surface. Consequently, the dissolution rates of the superpure aluminium, alloys without nickel addition and alloy with nickel addition are increased respectively in sodium hydroxide, and increased pitting is respectively promoted in hydrochloric acid. In contrast, the addition of magnesium to the alloy had negligible influence on the etching and pitting behaviour. [Copyright &y& Elsevier]

July 7, 2012 Tags: ALKALINE solutions, ALUMINUM alloys, ELECTROCHEMICAL analysis, METALS -- Etching, MICROSTRUCTURE, NICKEL alloys, SODIUM hydroxide
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Synthesis and electrochemical performance of mno2/cnts–embedded carbon nanofibers nanocomposites for supercapacitors

Abstract: MnO2/carbon nanotubes (CNTs)–embedded carbon nanofibers (CNFs) nanocomposites (MnO2/CNTs–CNFs) have been prepared using electrospinning and in situ redox deposition technique. The as-prepared nanocomposites were directly employed as freestanding electrodes to evaluate the electrochemical properties. Results showed that the nanoscopic MnO2 deposits were incorporated uniformly into the CNTs–embedded CNFs network structure, which hold a great promise for high-performance supercapacitor applications. Compared to the pure CNFs substrate, the improved electric conductivity of CNTs–embedded CNFs substrate enabled a better utilization of MnO2 coating, thus resulting in higher specific capacitance (374F/g) and better rate capability (53.4%). Excellent capacitance retention of 94% of the initial capacitance after 1000cycles was achieved on the freestanding MnO2/CNTs–CNFs nanocomposites electrode. The specific capacitance was found to increase significantly with the increase in the electrolyte temperature, which offered an insight into the practical supercapacitor applications. [Copyright &y& Elsevier]

July 6, 2012 Tags: CARBON nanofibers, ELECTROCHEMICAL analysis, MANGANESE compounds -- Synthesis, NANOCOMPOSITES (Materials), OXIDATION-reduction reaction, SUPERCAPACITORS
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Study of a novel cathode tool structure for improving heat removal in electrochemical micro-machining

Abstract: In this paper, the effects of a hollow structure of cathode tool and radial flow of electrolyte on heat removal are studied using COMSOL software. A multi-physics (electrical field, flow field and heat transfer) model, which implement the bilateral interactions with customized PDE, is proposed to simulate the EMM process with a moving cathode tool. The ALE method is used to track the moving interface. The simulations show that the electrolyte flow rate and flushing time are the most important factors for the heat removal. A hollow structure of the cathode tool is proposed to improve the stability of flow rate, which will remove the heat generated during the EMM process effectively. [Copyright &y& Elsevier]

July 6, 2012 Tags: CATHODES, ELECTRIC fields, ELECTROCHEMICAL analysis, ELECTROLYTES, HEAT -- Transmission, MICROELECTROMECHANICAL systems
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Simultaneous determination of vitamins b2, b9 and c using a heterocyclic conducting polymer modified electrode

Abstract: This paper illustrates the simultaneous determination of riboflavin (RB), ascorbic acid (AA) and folic acid (FA) at physiological pH by electrochemical method for the first time using the electropolymerized film of 3-amino-5-mercapto-1,2,4-triazole modified glassy carbon (p-AMTa) electrode. Bare GC electrode fails to show stable voltammetric signals for AA, RB and FA in a mixture due to the surface fouling caused by the oxidation products of them. In contrary, the p-AMTa electrode shows stable voltammetric signals for RB, AA and FA in a mixture with potential differences of 670mV and 530mV between RB-AA and AA-FA, respectively. Further, the p-AMTa electrode was used to selectively determine either of the vitamins individually in the presence of high concentrations of other two vitamins. When the concentration of RB was increased from 10μM to 90μM, AA was increased from 30μM to 270μM and FA was increased from 20μM to 180μM, the oxidation currents of the respective compounds increased linearly. The detection limit was found to be 4.54×10−8 M for RB, 7.14×10−7 M for AA and 2.5×10−7 M for FA (S/N=3). The practical application of the present modified electrode was demonstrated by determining the concentrations of RB, AA and FA in human plasma samples. [Copyright &y& Elsevier]

July 6, 2012 Tags: ELECTROCHEMICAL analysis, ELECTRODES, ELECTROPOLYMERIZATION, HYDROGEN-ion concentration, SIGNAL detection, VITAMIN B2, VITAMIN C
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Pt-implanted indium tin oxide electrodes and their amperometric sensor applications for nitrite and hydrogen peroxide

Abstract: A facile ion implantation method was developed to prepare a novel Pt nanoparticles loaded ITO (PtNPs/ITO) electrode. The resulting nanoparticles were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods. From the result of electrochemical oxidation of nitrite, we observed that the PtNPs/ITO electrode exhibited excellent electrocatalytic activity, which might be useful in nitrite sensor. The oxidation current of nitrite was linear to its concentration in the range of 5–800μM and the detection limit (S/N=3) was down to 0.4μM. Upon immobilization of the surface of PtNPs/ITO with cytochrome c, Cyt c/PtNPs/ITO for H2O2 biosensor was developed. The characteristics of the biosensor were studied by UV–vis absorption spectra and electrochemical methods. The results revealed that the modified electrode could enhance electron transfer of Cyt c and retain electrochemical activity, good stability and reproducibility. The immobilized Cyt c exhibited a rapid response to H2O2, low detection limit of 0.1μM and high sensitivity of 37.20μAmM−1. [Copyright &y& Elsevier]

July 5, 2012 Tags: CHARGE exchange, CONDUCTOMETRIC analysis, ELECTROCHEMICAL analysis, ELECTRODES, HYDROGEN peroxide, INDIUM tin oxide, PLATINUM, PLATINUM nanoparticles
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Preparation of co3o4 nanowires grown on nickel foam with superior electrochemical capacitance

Abstract: Co3O4 nanowires have been successfully synthesized on nickel foam by a hydrothermal method. The morphology of Co3O4 is examined by scanning and transmission electron microscopy and the phase structure of Co3O4 nanowires is confirmed by X-ray diffraction. The electrochemical capacitance behavior of the Co3O4 nanowires electrode is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy in 6moldm−3 KOH solution. The results show that the Co3O4 nanowires have diameters of around 100nm and the lengths up to 1–2μm. The specific capacitance of Co3O4 nanowires is 1019.58Fg−1 at 3.38Ag−1 and 466.06Fg−1 at 33.80Ag−1. The capacitance loss is less than 5% after 1000 charge/discharge cycles at 3.38Ag−1 and with columbic efficiency higher than 98%. The enhancement of pseudocapacitive properties at a higher charging/discharging rate is due to the porous nanostructure and the high utilization of active material. [Copyright &y& Elsevier]

June 25, 2012 Tags: COBALT compounds, ELECTROCHEMICAL analysis, METAL foams, NANOSTRUCTURES, NANOWIRES -- Synthesis, NICKEL, X-rays -- Diffraction
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