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Effect of alcohol concentration and electrode composition on the ethanol electrochemical oxidation
Bergamaski, K.;Gomes, J. F.;Goi, B. E;Nart, F. C.;
Eclética Química , 2003, DOI: 10.1590/S0100-46702003000200011
Abstract: the electrochemical oxidation on platinum and platinum rhodium bimetallic electrodes was studied by differential electrochemical mass spectrometry for several ethanol concentrations in solution. it is found that increasing the ethanol concentration the production of the partially oxidized products (acetaldehyde) increases as the concentration increases. on the other hand, addition of 25% at. of rhodium increases the full oxidation to co2. another interesting result observed is a correlation between the intensity of the dehydrogenations peak at 0.3 v vs. rhe and the co2 yield for the different ethanol concentration studied.
Simultaneous Ultra Traces Voltammetric Determination of Platinum and Rhodium Using Adsorptive Preconcentration and Catalysis
Rojas,Carlos León;
Portugaliae Electrochimica Acta , 2005,
Abstract: it was evaluated a voltammetric method with adsorptive preconcentration and catalysis, using the hanging mercury drop electrode, for the simultaneous determination of ultra traces of platinum and rhodium. the optimized conditions were obtained after the sequential optimization, obtaining linearity until 6.00 ng/l for platinum and 0.7 ng/l for rhodium. the detection and quantification limits are 4.0 ng/l and 10 ng/l for platinum and 1.0 ng/l and 3.0 ng/l for rhodium.
Screen-Printed Carbon Electrodes Modified by Rhodium Dioxide and Glucose Dehydrogenase  [PDF]
Vojtěch Polan,Jan Soukup,Karel Vyt?as
Enzyme Research , 2010, DOI: 10.4061/2010/324184
Abstract: The described glucose biosensor is based on a screen-printed carbon electrode (SPCE) modified by rhodium dioxide, which functions as a mediator. The electrode is further modified by the enzyme glucose dehydrogenase, which is immobilized on the electrode's surface through electropolymerization with m-phenylenediamine. The enzyme biosensor was optimized and tested in model glucose samples. The biosensor showed a linear range of 500–5000?mg?L?1 of glucose with a detection limit of 210?mg?L?1 (established as 3σ) and response time of 39 s. When compared with similar glucose biosensors based on glucose oxidase, the main advantage is that neither ascorbic and uric acids nor paracetamol interfere measurements with this biosensor at selected potentials. 1. Introduction There exists today an ever-increasing demand for fast, selective, reliable, and, above all, inexpensive analytical methods. For food products, it is necessary to monitor whether or not microbial, or some other form of, contamination has occurred. Furthermore, it is necessary to monitor compliance with given technological procedures and whether the stated raw materials were used [1]. These requirements place very great demands on the analysis of given samples. The analysis itself should be very fast, sufficiently sensitive and accurate, but also inexpensive. To meet these criteria, an application of electrochemical biosensors seems to be a good alternative. Electrochemical biosensors combine two advantages: specificity of the enzyme to the given molecule and transfer of the biochemical signal to an electrochemical signal [2]. As a result, these biosensors are selective in establishing a specific substrate [3, 4]. By using these biosensors, it is possible to determine a large number of substances even in complex matrices. Electrochemical biosensors often use redox enzymes during catalysis of substrate splitting reactions. Most used redox enzyme’s are oxidases and dehydrogenases. There are several methods for establishing a substrates concentration. The most methods often used involve detecting hydrogen peroxide (a product of most oxidases) and nicotinamide adenine dinucleotide (NADH) (a product of dehydrogenases) resulting during the catalytic process. NADH oxidation on carbon electrodes requires high overvoltage (around 1.0?V). This is a highly unfavorable phenomenon, as the impact of interferents (e.g., uric acid, ascorbic acid, paracetamol) that are easily oxidized at a given overvoltage become most evident at such potentials. High overvoltage can be suppressed by using a so-called mediator [5–9]
Determination of rhodium and platinum by electrothermal atomic absorption spectrometry after preconcentration with a chelating resin
Sánchez Rojas, F.;Bosch Ojeda, C.;Cano Pavón, J.M.;
Journal of the Brazilian Chemical Society , 2007, DOI: 10.1590/S0103-50532007000600024
Abstract: the present publication describes a separation/preconcentration procedure for the subsequent trace analysis of rhodium and platinum in environmental samples. a chelating ion-exchange resin was employed for this purpose and an automatic on-line flow injection electrothermal atomic absorption spectrometry (fi-et-aas) method was used for the determination of trace amounts of rh and pt in different materials. the solutions are simultaneously treated and the ions determined sequentially. detection limits of rhodium and platinum are 0.8 and 1.0 ng ml-1, respectively. linearity was obtained in the range 0-50 ng ml-1 for rhodium and 0-100 ng ml-1 for platinum. the relative standard deviations were 1.8% for 10 ng ml-1 of rh and 1.6% for 10 ng ml-1 of pt. enrichment factors were 20 for rh and 14 for pt.
Cathodic Behaviour of Cysteine at a Platinum Electrode
Barroso,M. Fátima; Santos,Teresa; Sales,M. Goreti F.; Delerue-Matos,Cristina; Vaz,M. Carmo V. F.;
Portugaliae Electrochimica Acta , 2007,
Abstract: the electroreduction behaviour of cysteine was investigated using cyclic, square wave and differencial pulse voltammetric techniques at a platinum working electrode. the reduction of cysteine occurs at a potential of -0.36 v independent of ph. it is a reversible process, controlled mainly by diffusion and in the mechanism of reduction 1 electron per molecule is involved. using the voltammetric techniques: cyclic voltammetry, square wave voltammetry and differencial pulse voltammetry, different parameters (ph, frequency, step potential, pulse amplitude, scan rate) were optimized in order to develop an electrochemical procedure for determination of cysteine in pharmaceutical products. the repeatability, reproducibility, precision and accuracy of the methods were studied. no electroactive interferences from the excipient were found in the pharmaceutical compounds.
Cathodic Behaviour of Cysteine at a Platinum Electrode  [cached]
M. Fátima Barroso,Teresa Santos,M. Goreti F. Sales,Cristina Delerue-Matos
Portugaliae Electrochimica Acta , 2007,
Abstract: The electroreduction behaviour of cysteine was investigated using cyclic, square wave and differencial pulse voltammetric techniques at a platinum working electrode. The reduction of cysteine occurs at a potential of -0.36 V independent of pH. It is a reversible process, controlled mainly by diffusion and in the mechanism of reduction 1 electron per molecule is involved. Using the voltammetric techniques: Cyclic Voltammetry, Square Wave Voltammetry and Differencial Pulse Voltammetry, different parameters (pH, frequency, step potential, pulse amplitude, scan rate) were optimized in order to develop an electrochemical procedure for determination of cysteine in pharmaceutical products. The repeatability, reproducibility, precision and accuracy of the methods were studied. No electroactive interferences from the excipient were found in the pharmaceutical compounds.
Electrochemical and microstructural characterization of platinum supported on glassy carbon
Terzi? Sanja,Jovanovi? Vladislava M.,Tripkovi? Du?an,Kowal Andrzej
Hemijska Industrija , 2007, DOI: 10.2298/hemind0703135t
Abstract: The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE) for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE) for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment of the GC support leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GCox electrode for methanol oxidation is larger than that of polycrystalline Pt and by more than one order of magnitude larger than that of a Pt/GC electrode. This increase in activity indicates the pronounced role of the organic residues of the GC support on the properties of Pt particles deposited on glassy carbon.
Investigation of the electrochemical behaviour of thermally prepared Pt-IrO2 electrodes
Konan Honoré Kondro, Lassine Ouattara, Albert Trokourey, Yobou Bokra
Bulletin of the Chemical Society of Ethiopia , 2008,
Abstract: Different IrO2 electrodes in which the molar percentage of platinum (Pt) varies from 0 %mol Pt to 100 %mol Pt were prepared on titanium (Ti) substrate by thermal decomposition techniques. The electrodes were characterized physically (SEM, XPS) and electrochemically and then applied to methanol oxidation. The SEM micrographs indicated that the electrodes present different morphologies depending on the amount of platinum in the deposit and the cracks observed on the 0 %mol Pt electrode diminish in size tending to a compact and rough surface for 70 %mol Pt electrode. XPS results indicate good quality of the coating layer deposited on the titanium substrate. The voltammetric investigations in the supporting electrolyte indicate that the electrodes with low amount of platinum (less than 10 %mol Pt) behave as pure IrO2. But in the case of electrodes containing more than 40 %mol Pt, the voltammograms are like that of platinum. Electrocatalytic activity towards methanol oxidation was observed with the electrodes containing high amount of platinum. Its oxidation begins at a potential of about 210 mV lower on such electrodes than the pure platinum electrode (100 %mol Pt). But for electrode containing low quantity of Pt, the surface of the coating is essentially composed of IrO2 and methanol oxidation occurs in the domain of water decomposition solely. The increase of the electrocatalytic behaviour of the electrodes containing high amount of Pt towards methanol oxidation is due to the bifunctional behaviour of the electrodes. KEY WORDS: Iridium dioxide, Platinum, Methanol oxidation, Electrocatalytic activity Bull. Chem. Soc. Ethiop. 2008, 22(1), 125-134.
Mixed-valent Complexes of Rhodium with Acetylinic Ligands: Their Electrochemical Studies
Festus Agbo S. Fabiyi,Carlos Stempler Gonzalez,Gregory O. Adewuyi,Samuel Oluwole Aremu
International Journal of Chemistry , 2011, DOI: 10.5539/ijc.v3n3p62
Abstract: Two acetylinic mixed- valent rhodium(II, III) complexes: [cis-{Rh2(II,III)Cl(bpy)2(u-C=C-)}]2, (A) and cis-[Rh(II,III)Cl(bpy)2]-C=C-SiMe3, (B) (where bpy=bipyridine) have been prepared. (A) was accomplished through two pathways. The two complexes were characterized by 1H, 13C NMR, elemental, magnetic, electrochemical analyses and mass spectrophotometry. Cyclic voltametric analyses of the products from 0.00 -1.20 V display two one–electron quasi-reversible oxidation peaks which were attributed to the Rh(II), Rh(III) couple. The redox processes were separated by 528 mV, indicating a significant electronic communication between the two metallic centres. The yields of (A) and (B) were found to be 37 and 32 % respectively.
Electrochemical oxidation of sulfide ions on platinum electrodes  [cached]
Ibrahim Mohamed Ghayad,Faiza M Al Kharafi,Ayman Y Saad,Badr G Ateya
Modern Applied Science , 2010, DOI: 10.5539/mas.v4n3p2
Abstract: This paper treats the electrochemical oxidation of sulfide ions on platinum using cyclic voltametry. An electrolyte of 3.5% NaCl containing sulfide ions was used as the testing medium. The effects of scan rate, concentration of sulfide ions and temperature on the cyclic voltamograms were investigated. Cyclic voltamograms show small currents in the absence of sulfide ions. In the presence of sulfide ions, the magnitude of the anodic currents in the forward sweep is much more than these in the reverse sweep. Cyclic voltamograms show three features appear in the forward sweep at potentials of -0.1, 0.475 and 1.0 V vs Ag/AgCl, respectively. Peaks currents are increased upon the increase of either the scan rate or temperature. These peaks are explained to show the possible formed species and the possible electrochemical oxidation reactions at the electrode surface.
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