Electrooxidation of sulfide by cobalt pentacyanonitrosylferrate film on glassy carbon electrode by cyclic voltammetry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dissociation and electrooxidation of primaquine diphosphate as an approach to the study of anti-chagas prodrugs mechanism of action

This paper describes the voltammetric behavior of primaquine as a previous support to the further understanding of the delivery and action mechanisms of its respective synthesized prodrugs. There are few papers describing the drug behavior and most of the time no correlation between oxidation process and pH is done. Our results showed that primaquine oxidation is a one-step reaction involving two electrons with the charge transfer process being strongly pH-dependent in acid medium and pH-independent in a weak basic medium, with the neutral form being easily oxidized.This leads to the conclusion that quinoline nitrogen ring neutralization is a determinant step to the formation of the oxidized primaquine form. The existence of a relationship between the primaquine dissociation equilibrium and its electrooxidation process is shown.This work points the importance of voltammetric methodology as a tool for further studies on quantitative relationship studies between chemical structure and biological activity (QSAR) for electroactive drugs. (C) 2000 Elsevier B.V. S.A. All rights reserved.

Electrooxidation and determination of dopamine using a Nafion (R)-cobalt hexacyanoferrate film modified electrode

The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 x 105 cm(3) mol(-1) s(-1) at a concentration of 5.0 x 10(-5) mol L-1. When a Nafion (R) film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 x 10(-5) to 5.0 x 10(-4) mol L-1 with a slope of 23.5 mA mol(-1) L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 x 10(-6) mol L-1 and the relative standard deviation for five measurements of 2.5 x 10(-4) mol L-1 dopamine was 0.58%.

Electrochemical behavior of ruthenium-hexacyanoferrate modified glassy carbon electrode and catalytic activity towards ethanol electrooxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sugars Electrooxidation at Glassy Carbon Electrode Decorate with Multi-Walled Carbon Nanotubes with Nickel Oxy-Hydroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of tartrate content on aging and deposition condition of copper-tin electrodeposits from a non-cyanide acid bath

The effect of the presence of tartrate additive on the chemical stability of a Cu-Sn acid bath was evaluated. It was observed that this additive hinders decomposition of the Cu/Sn deposition bath with storage time, since the decrease in electrochemical efficiency was attenuated. In addition, it was observed that optimal galvanostatic deposition with or without tartrate occurs at approximately 11 mA cm(-2). However, in the presence of tartrate the deposition charge was lower, leading to lower energy consumption. SEM analysis showed that the tartrate added to the plating bath caused a marked change in the morphology of the Cu/Sn films obtained gal vanostatic ally. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Electrochemical Oxidation of Hydroxylamine on Gold in Aqueous Acidic Electrolytes: An in Situ SERS Investigation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determination of free glycerol in biodiesel at a platinum oxide surface using potential cycling technique

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Fabrication and Characterization of a Nickel Nanoparticle Modified Boron Doped Diamond Electrode for Electrocatalysis of Primary Alcohol Oxidation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A disposaable electrochemical sensor for the rapid determination of levodopa

Levodopa (L-dopa), the biological precursor of catecholamines, is the most widely prescribed drug in the treatment of Parkinson's disease. The present work presents a proposal for the application of a gold screen-printed electrode an electrochemical sensor for monitoring L-dopa in stationary solution and a flow system. Using the electrooxidation of L-dopa at +0.63 V in acetate buffer pH 3.0 on a gold screen-printed electrode it is possible to obtain a linear calibration curve from 9.9 x 10(-5) to 1.2 x 10(-3) mol L-1 and a detection limit of 6.8 x 10(-5) mol L-1. Under amperometric conditions (E-app = 0.8 V; flow rate = 14.1 ml, min(-1); pH 3.0), an analytical calibration graph for L-dopa was obtained from 1.0 x 10(-6) mol L-1 6.6 x 10(-4) mol L-1 with a detection limit of 9.9 x 10(-7) mol L-1. The method was successfully applied to the determination of L-dopa in commercial dosage forms without any pre-treatment. (c) 2005 Elsevier B.V. All rights reserved.

Electrochemical oxidation and voltammetric determination of the antimalaria drug primaquine

Primaquine, an antimalarial drug, presents a well-defined oxidation peak around +0.6V vs SCE at a glassy carbon electrode that can be used for its determination. Calibration graphs were obtained for primaquine in B-R buffer pH 4.0 from 3.00 x 10(-5) mol L-1 to 1.00 x 10(-2) mol L-1 using linear-scan voltammetry and 3.00 x 10(-5) mol L-1 to 1.00 x 10(-2) mol L-1 using differential pulse or square-wave voltammetry. The correspondent detection limits was 9.4 mu g mL(-1); 4.2 and 1.8 mu g mL(-1), respectively. All the voltammetric methods were applied with success in direct determination of the primaquine in commercial tablets without separation or extraction procedures.

Electrochemical decomposition of cyanides on tin dioxide electrodes in alkaline media

The electrochemical oxidation of cyanide in alkaline media was studied at different pH levels on SnO2 doped with Sb supported on titanium, at 25 degrees C, the electrooxidation of CN- at constant current follows a first-order rate law with a half life of t(1/2) = 35 min on SnO2-SbOx electrodes and t(1/2) = 69 min on SnO2-SbOx-RuO2 electrodes, in K2SO4(aq), pH 12, the reaction rate increases with the applied current and tends to reach a plateau when j > 20 mA cm(-2), In the pH range 10-13.5 the reaction rate diminishes as pH is increased owing to an increasing competition between CN- and OH- ions for the electrode surface. Addition of chloride to the solution does not alter the rate law but increases the reaction rate, A mechanism is proposed to explain the observed behaviour.

Platinum surface modification with cerium species and the effect against the methanol anodic reaction

Spontaneous deposition and electrochemical deposition by potential perturbation programs were used to place cerium-containing species on platinum surfaces in acid solution. Cyclic voltammetric profiles of cerium-modified platinum surfaces obtained after potentiostatic or potentiodynamic procedures (applied in the true hydrogen evolution region) differ from those recorded after spontaneous methods. However, the catalytic effects are nearly the same on these cerium-modified platinum surfaces for methanol electrooxidation, i.e. lower onset potential values for the anodic reaction. Besides, a different electrocatalytic effect was observed at large positive potentials on methanol oxidation due to the cerium oxide capability of oxygen storage. This effect is observed on platinum modified by a drastic potentiostatic procedure (by applying -2.0 V) in cerium(IV) acid solution. (C) 2008 Elsevier B.V. All rights reserved.

Influence of the morphology and microstructure on the photocatalytic properties of titanium oxide films obtained by sparking anodization in H3PO4

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Voltammetric determination of dipyrone using a N,N′- ethylenebis(salicylideneaminato)oxovanadium(IV) modified carbon-paste electrode

The preparation and electrochemical characterization of a carbon paste electrode modified with N.N′-ethylenebis(salicylideneiminato) oxovanadium(IV) complex ([VO(Salen)]) as well as its behavior as electrocatalyst toward the oxidation of dipyrone were investigated. The electrochemical behavior of the modified electrode and the electrooxidation of dipyrone were explored using cyclic voltammetry. The voltammetric response of the modified electrode is based on two reactions. One electrochemical related to the oxidation of the metallic center of the [VO(Salen)] and the other involving the chemical redox process involving the oxidized form of the complex and the reduced form of dipyrone. The best voltammetric response was observed for a paste composition of 25% (m/m) [VO(Salen)], KCl solution pH from 5.5 to 8.0 as the electrolyte and potential scan rate of 10 mV s-1 in the presence of dipyrone. A linear voltammetric response for dipyrone was obtained in the concentration range from 9.9 × 106 to 2.8 × 10 -3 mol L-1, with a detection limit of 7.2 × 10 -6 mol L-1. Among of several compounds tested as potential interference, only ascorbic acid presented some interference. The proposed electrode is useful for the quality control and routine analysis of dipyrone in pharmaceutical formulations.