Página 1 dos resultados de 3183 itens digitais encontrados em 0.007 segundos

Poly(ester sulphonic acid) coated mercury thin film electrodes: characterization and application in batch injection analysis stripping voltammetry of heavy metal ions

Brett, Christopher M. A.; Fungaro, Denise A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
36.89%
Mercury-thin film electrodes coated with a thin film of poly(ester sulphonic acid) (PESA) have been investigated for application in the analysis of trace heavy metals by square wave anodic stripping voltammetry using the batch injection analysis (BIA) technique. Different polymer dispersion concentrations in water/acetone mixed solvent are investigated and are characterised by electrochemical impedance measurements on glassy carbon and on mercury film electrodes. The influence of electrolyte anion, acetate or nitrate, on polymer film properties is demonstrated, acetate buffer being shown to be preferable for stripping voltammetry applications. Although stripping currents are between 30 and 70% less at the coated than at bare mercury thin film electrodes, the influence of model surfactants on stripping response is shown to be very small. The effect of the composition of the modifier film dispersion on calibration plots is shown; however, detection limits of around 5 nM are found for all modified electrodes tested. This coated electrode is an alternative to Nafion-coated mercury thin film electrodes for the analysis of trace metals in complex matrices, particularly useful when there is a high concentration of non-ionic detergents.; http://www.sciencedirect.com/science/article/B6THP-3XX691V-B/1/0b3158737a56f528080be266d91c0dcb

Electroanalytical determination of promethazine hydrochloride in pharmaceutical formulations on highly boron-doped diamond electrodes using square-wave adsorptive voltammetry

RIBEIRO, Francisco Wirley P.; CARDOSO, Amanda S.; PORTELA, Rafael R.; LIMA, Janete E. S.; MACHADO, Sergio A. S.; LIMA-NETO, Pedro de; SOUZA, Djenaine De; CORREIA, Adriana N.
Fonte: WILEY-V C H VERLAG GMBH Publicador: WILEY-V C H VERLAG GMBH
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.89%
The electrochemical oxidation of promethazine hydrochloride was made on highly boron-doped diamond electrodes. Cyclic voltammetry experiments showed that the oxidation mechanisms involved the formation of an adsorbed product that is more readily oxidized, producing a new peak with lower potential values whose intensity can be increased by applying the accumulation potential for given times. The parameters were optimized and the highest current intensities were obtained by applying +0.78 V for 30 seconds. The square-wave adsorptive voltammetry results obtained in BR buffer showed two well-defined peaks, dependent on the pH and on the voltammetric parameters. The best responses were obtained at pH 4.0, frequency of 50 s(-1), step of 2 mV, and amplitude of 50 mV. Under these conditions, linear responses were obtained for concentrations from 5.96 x 10(-7) to 4.76 x 10(-6) mol L-1, and calculated detection limits of 2.66 x 10(-8) mol L-1 (8.51 mu g L-1) for peak 1 and of 4.61 x 10(-8) mol L-1 (14.77 mu g L-1) for peak 2. The precision and accuracy were evaluated by repeatability and reproducibility experiments, which yielded values of less than 5.00% for both voltammetric peaks. ne applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability...

Determinação de manganês em amostras de cimento e clínquer por voltametria de redissolução catódica empregando eletrodos de ouro; Manganese determination in cement and clinker samples by cathodic stripping voltammetry using gold electrodes

Joca, Jhonny Frank Sousa
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/06/2011 PT
Relevância na Pesquisa
36.89%
Este trabalho apresenta o desenvolvimento e a aplicação de um método alternativo para determinação de manganês em amostras de cimento e clínquer por voltametria de redissolução catódica por onda quadrada empregando eletrodos de ouro. Após estudos exploratórios acerca do comportamento eletroquímico do manganês no eletrólito suporte H3BO3 0,20 mol L-1 / KCl 0,10 mol L-1 com pH 6,5 e a otimização dos parâmetros operacionais para a voltametria de onda quadrada, foram obtidos excelentes resultados na determinação de manganês nas amostras analisadas. Destacam-se a ótima linearidade, verificada em duas faixas distintas de concentração, e os baixos limites de detecção e quantificação obtidos (3,1 x 10-8 mol L-1 e 9,8 x 10-8 mol L-1, respectivamente), além da concordância entre os resultados obtidos pela técnica eletroanalítica quando comparados aos resultados fornecidos pela espectrometria de absorção atômica de chama (FAAS). Para o tratamento das amostras foi avaliada a eficiência da extração ácida assistida por ultrassom. Foram avaliados ácidos minerais individualmente (HCl, H2SO4 e HClO4 em diferentes concentrações), em mistura ou ainda associados a H2O2. Os melhores resultados foram obtidos utilizando uma solução de HCl 3 mol L-1...

Stripping voltammetry of mercury(II) with a chemically modified carbon paste electrode containing silica gel functionalized with 2,5-dimercapto-1,3,4-thiadiazole

Dias, N. L.; do Carmo, D. R.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 1540-1546
ENG
Relevância na Pesquisa
36.89%
The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2,5-dimercapto-1,3,4-thiadiazole (DTTPSG-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to +0.8 V (vs. Ag/AgCl), (0.02 mol L-1 KNO3; nu=20 mV s(-1)) show two peaks one at about 0.0 V and other at 0.31 V. However, the cathodic wave peak, around 0.0 V, is irregular and changes its form in each cycle. This peak at about 0.0 V is the reduction current for mercury(II) accumulated in the DTTPSG-CPE. The anodic wave peak at 0.31 V is well-defined and does not change during the cycles. The resultant material was characterized by cyclic and differential pulse anodic stripping voltammetry performed with the electrode in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n=6) of 0.05 and 0.20 mg (L)-(1) Hg(II) was 2.8 and 2.2% (relative standard deviation), respectively. The method was satisfactory and used to determine the concentration of mercury(II) in natural waters contaminated by this metal.

Determination of sulfur compounds in gasoline using mercury film electrode by square wave voltammetry

Serafim, Diana Maria; Stradiotto, Nelson Ramos
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 1007-1013
ENG
Relevância na Pesquisa
36.89%
A sensitive method based on square wave voltammetry is described for the quantitative determination of elemental sulfur, disulfide and mercaptan in gasoline using a mercury film electrode. These sulfur compounds can be quantified by direct dissolution of gasoline in a supporting electrolyte followed by subsequent voltammetric measurement. The supporting electrolyte is 1.4 mol L-1 sodium acetate and No acetic acid in methanol. Chemical and optimum operational conditions for the formation of the mercury film were analyzed in this study. The values obtained were a 4.3 mu m thickness for the mercury film, a 1000 rpm rotation frequency, -0.9 V applied potential and 600 s depositing time. Voltammetric measurements were obtained using square wave voltammetry with detection limits of the 3.0 x 10(-9), 1.6 x 10(-7) and 4.9 x 10(-7) mol L-1 for elemental sulfur, disulfide and mercaptan, respectively. (C) 2007 Elsevier Ltd. All rights reserved.

Direct simultaneous determination of Pb(II) and Cu(II) in biodiesel by anodic stripping voltammetry at a mercury-film electrode using microemulsions

Martiniano, Lorena C.; Abrantes, Vivia R.; Neto, Sakae Y.; Marques, Edmar P.; Fonseca, Teresa C.O.; Paim, Leonardo L.; Souza, Antônio G.; Stradiotto, Nelson R.; Aucélio, Ricardo Q.; Cavalcante, Glene H.R.; Marques, Aldaléa L.B.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 1164-1167
ENG
Relevância na Pesquisa
36.89%
A mercury film electrode was used to determine direct and simultaneously Pb(II) (at -410 mV) and Cu(II) (at -100 mV) in biodiesel by anodic stripping voltammetry. A linear response was obtained for Pb(II) and Cu(II) in the 2.00 × 10-8-1.00 × 10-7 mol L-1 concentration range and detection limits were 2.91 × 10-9 mol L-1 and 4.69 × 10-9 mol L-1 for Pb(II) and Cu(II), respectively, with recovery around of 100.0%. © 2012 Elsevier Ltd. All rights reserved.

Estudo da capacidade antioxidante total em tecidos e fluidos biologicos usando a voltametria de pulso diferencial; Total antioxidant capacity in tissues and body fluids: a differential pulse voltammetry study

Paulo Guimarães Gandra
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/07/2006 PT
Relevância na Pesquisa
36.89%
O objetivo central deste trabalho foi analisar a variação da capacidade antioxidante total, conferida por antioxidantes de baixo peso molecular (ABPM) em fluidos biológicos e tecidos, através do uso da voltametria de pulso diferencial (VPO). O capítulo 1 corresponde a um artigo de revisão sobre as possíveis fontes de geração de espécies reativas de oxigênio no músculo esquelético durante o exercício físico. O capítulo 2 é um artigo de divulgação, cujo objetivo é fornecer subsídios para a análise da capacidade antioxidante total de amostras biológicas conferida por ABPM para acompanhar a modulação do sistema de defesa antioxidante em função do treinamento físico. Para tanto, são discutidos o uso da voltametria cíclica e a possibilidade do uso de outras técnicas voltamétricas, como a VPO. O artigo contido no capítulo 3 apresenta dados da concentração de ABPM no plasma e na saliva de atletas submetidos a um período de treinamento físico. Observou-se, nesse estudo, uma diminuição da capacidade antioxidante total do plasma após 6 semanas de treinamento (879.28 :t 197.92 j..Imol Trolox equiv. L-1 na segunda semana versus 787.82 :t 154.71 j..Imol Trolox equiv. L-1 na sétima semana). Essa diminuição foi associada a um aumento no desempenho em testes físicos específicos e à manutenção das concentrações de marcadores de lesão muscular e de processo inflamatório...

Medida da capacidade antioxidante de fluidos biologicos por voltametria de pulso diferencial associada ao uso de surfactante como resposta as adaptações geradas pelo exercicio; Antioxidant capacity measurement of biological fluids by differential pulse voltammetry associated to surfactant as respose to generated adaptations by the exercise

Madla Adami Passos
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/02/2009 PT
Relevância na Pesquisa
36.89%
Aumento na formação de espécies reativas de oxigênio como conseqüência do aumento na demanda energética pode aumentar o estado de oxidação celular, contribuindo para um estado redox celular ótimo e o desenvolvimento máximo de força. O poder redutor de amostras biológicas reflete sua capacidade antioxidante, mantida em grande parte pelos antioxidantes de baixo peso molecular (ABPM). Os ABPM agem como agentes redutores, doando elétrons para as espécies radicalares. Podem, dessa forma, ser quantificados por técnicas eletroquímicas. Os ABPM incluem compostos tais como ácido úrico, vitamina C, vitamina E e ácido lipóico. O objetivo do presente estudo foi investigar a aplicabilidade do surfactante catiônico cloreto de cetilpiridina (CPC) como sistema micelar no aperfeiçoamento da técnica de voltametria de pulso diferencial (VPD) para análise de amostras de soro e saliva de humanos. Analisamos ainda a correlação dos dados obtidos com outras metodologias de análise da capacidade antioxidante total. O presente trabalho está dividido em três capítulos. O primeiro capítulo apresenta uma introdução geral sobre o tema, incluindo dentre outros tópicos os mecanismos moleculares envolvidos na adaptação ao treinamento...

The use of cyclic voltammetry to detect biofilms formed by Pseudomonas fluorescens on platinum electrodes

Vieira, M. J.; Espírito Santo, I. A. C. P.; Gião, M. S.; Montenegro, M. I.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em /08/2003 ENG
Relevância na Pesquisa
36.89%
The development of an electrochemical detector to monitor the in situ formation of biofilms is described. The detector consisted of an electrochemical cell containing three electrodes, whose response to the application of a potential profile to the working electrode was sensitive to the amount of biofilm present on the surface. The electrochemical technique used was repetitive cyclic voltammetry. Differences between the response of the uncolonised electrode and after Pseudomonas fluorescens biofilms of different ages were grown on its surface were determined. The results show that cyclic voltammetry applied to platinum electrodes can be used to detect young biofilms. The development of the shape of the voltammogram as the potential is cycled may constitute a means of providing information on the coverage of the surface. Observation of the platinum electrodes before and after the electrochemical measurements showed that even after 30 min of recycling, most of the cells were still adhered to the surface, although some may have lost viability.; Fundação para a Ciência e Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação (POCTI) - POCTI/34945/EQU/2000.

Staining of wool using the reaction products of ABTS oxidation by Laccase : synergetic effects of ultrasound and cyclic voltammetry

Munteanu, Florentina-Daniela; Basto, Carlos; Gübitz, Georg M.; Paulo, Artur Cavaco
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /03/2007 ENG
Relevância na Pesquisa
37.05%
The effects of ultrasound on 2,2′-Azinobis(3-ethylbenzothiazoline-6-sulfonate) enzymatic oxidation by laccase (Trametes villosa) has been studied by means of cyclic voltammetry. The reaction was allowed to proceed in the presence of a piece of wool and the coloration depth of the wool fabric was measured by means of K/S. It was observed that cyclic voltammetry is influenced the dyeing process and higher K/S values were obtained when the cyclic voltammetry was combined with the ultrasonic irradiation. Moreover, the K/S value is the sum of the values obtained when the wool staining is done in just the presence of cyclic voltammetry or in just the presence of ultrasound. The results obtained on the indigo carmine decolourization gives information on the importance of controlling the amount of ABTS+ formed during the ultrasonication process.

Evaluation of the Antioxidant Activity of New Coumarin Derivatives by Cyclic Voltammetry

Teixeira, Jorge; Martins, Sérgio; Palmeiro, Gonçalo; Pereira, António
Fonte: The 61st Annual Meeting of the International Society of Electrochemistry, Electrochemistry from Biology to Physics, Nice, France. Publicador: The 61st Annual Meeting of the International Society of Electrochemistry, Electrochemistry from Biology to Physics, Nice, France.
Tipo: Aula
ENG
Relevância na Pesquisa
36.89%
Free radicals, species with one or more unpaired electrons are produced in normal or pathological cell metabolism, from xenobiotics, or trough ionizing radiation. Electron acceptors such as molecular oxygen react easily with free radicals, to become radicals themselves. Oxygen free radicals or reactive oxygen species (ROS) such as superoxide anion radicals (O2 .-), hydrogen peroxide (H2O2), hydroxy radicals (.OH), and singlet oxygen (1O2) are continuously generated in cells exposed to an aerobic environment, and have been associated with the genesis of tumors as well as age-dependent diseases such atherosclerosis, arthritis, and neurodegenerative disorders. In this context, the chemopreventive role of antioxidants present in consumable fruits, vegetables, and beverages has received considerable attention and has been a growing interest in finding novel antioxidants in order to meet the requirements of pharmaceutical industries [1]. Several analytical methods have been used to evaluate the activity of antioxidant compounds, such as the cyclic voltammetry[2] and the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay[3]. In this work the antioxidant activity of two new synthetic coumarin derivatives, 3-bromo-6,7-dihydroxycoumarin and 6...

Electroanalytical determination of 4-nitrophenol by square wave voltammetry on diamond electrodes

Pedrosa,Valber de A.; Codognoto,Lúcia; Avaca,Luis Alberto
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2003 EN
Relevância na Pesquisa
36.89%
The anodic voltammetric behavior of 4-Nitrophenol on a Boron-doped diamond electrode in aqueous solution has been studied using square wave voltammetry. After optimization of the experimental conditions, that model molecule was analyzed in pure water solutions using a Britton-Robinson buffer with pH 6.0 as the supporting electrolyte. Oxidation occurs at 1.0 V vs. Ag/AgCl in an irreversible two-electron process controlled by adsorption of the species. The detection limit (DL) obtained was 2.8 mug L-1. This result was comparable to that obtained from reduction of the molecule at -0.8 V vs. Ag/AgCl under the same experimental conditions (DL = 4.2 mug L-1). Both DL values are within the limits required by the legislation for drinking water (30 mug L-1). The combination of square wave voltammetry and diamond electrodes has proved to be an interesting and desirable alternative for the analytical determination of organic molecules.

Micelle-mediated method for simultaneous determination of ascorbic acid and uric acid by differential pulse voltammetry

Reis,Alaécio P. dos; Tarley,César R. T.; Kubota,Lauro T.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
36.89%
The present work describes an analytical methodology for simultaneous determination of ascorbic acid (AA) and uric acid (UA) by differential pulse voltammetry employing the cationic surfactant, cetylpyridinium chloride. Differential pulse voltammetry measurements revealed that the cationic micellar media may separate the oxidation peak potentials of AA and UA present in the same solution by about 282 mV, which is enough to determine both species simultaneously. As in pH 7.0 the AA is more ionized than UA, its electrostatic attraction towards the cationic micelles formed onto the surface of glassy carbon electrode is higher, therefore, promoting a decrease in the overpotential and increasing the electron transfer rate. Calibration curves to AA and UA in the concentration range from 4.70 up to 220 µmol L-1 and 0.50 up to 110 µmol L-1 were built. The proposed methodology was applied for the simultaneous determination of AA and UA in human urine samples.

Electrochemical behavior of metribuzin on a glassy carbon electrode in an aqueous medium including quantitative studies by anodic stripping voltammetry

Lima,Augusto César de Andrade; Silva,Emanuella Gomes da; Goulart,Marília Oliveira Fonseca; Tonholo,Josealdo; Silva,Tiago Terto da; Abreu,Fabiane Caxico de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
37.05%
The electrochemical behavior of the herbicide metribuzin was studied in an aqueous solution on glassy carbon, carbon paste/Nujol oil and carbon paste/castor oil using cyclic voltammetry, square-wave voltammetry, differential pulse voltammetry, controlled-potential coulometry and electrolysis, for quantification and decontamination purposes. The main electrolytic products obtained from the reduction of metribuzin, after consumption of 8.26 mol electron mol-1, were deaminometribuzin and diketometribuzin. The anodic wave observed after electroreduction is associated with the oxidation of the methylthiolate generated in the electrolytic process. This wave was used to quantitatively determine metribuzin in a commercial sample by anodic stripping voltammetry. The electro-Fenton method was employed to promote decontamination by eliminating the herbicide, resulting in 80% of mineralization of the metribuzin.

Determination of propylthiouracil in pharmaceuticals by differential pulse voltammetry using a cathodically pretreated boron-doped diamond electrode

Sartori,Elen Romão; Trench,Aline Barrios; Rocha-Filho,Romeu C.; Fatibello-Filho,Orlando
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2013 EN
Relevância na Pesquisa
36.89%
A simple procedure is described for the determination of propylthiouracil (PTU) by differential pulse voltammetry (DPV) using a cathodically pretreated boron-doped diamond (BDD) electrode. Cyclic voltammetry studies indicate that the oxidation of PTU is irreversible at a peak potential of 1.42 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a Britton-Robinson (BR) buffer solution (pH 2.0). Under optimized conditions, the obtained analytical curve was linear (r = 0.9985) for the PTU concentration range of 1.0 to 29.1 mmol L-1 in a BR buffer solution (pH 2.0), with a detection limit of 0.90 mmol L-1. The proposed method was successfully applied in the determination of PTU in pharmaceutical samples, with results in agreement at a 95% confidence level with those obtained using an official titration method.

Comparative Sensibility Study of WO3 ph Sensor Using EGFET and Ciclic Voltammetry

Campos,Renata de Castro; Cestarolli,Dane Tadeu; Mulato,Marcelo; Guerra,Elidia Maria
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
36.89%
In this present study, the investigation about pH sensorial properties of WO3, via sol-gel, was evaluated by Voltammetry and Extended Gate Field Effect Transistor techniques. The X-ray diffractogram indicates the presence of a lamellar structure, d = 0.69 nm, resulting in WO3.2H2O. From Scanning Electron Microscopy of WO3.2H2O was observed a process corresponding to the delamination which consists of irregular stacking with rounded platelets. The WO3.2H2O was investigated as a pH sensor in the pH range 2–12, by the EGFET and Voltametry techniques presenting a sensitivity of 52 mV/pH and 60 mV/pH, respectively. These results can indicate that both Voltammetry and EGFET techniques present values close to the theoretical limit (59.2 mV/pH) as well as the material is a promising candidate for applications as a pH sensor and as disposable biosensor in the future.

New and Sensitive Electroquantification of Sulfentrazone in Soil by Differential-Pulse Voltammetry

Catrinck,Mariana N.; Okumura,Leonardo L.; Silva,Antonio A.; Saczk,Adelir A.; Oliveira,Marcelo F.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2015 EN
Relevância na Pesquisa
36.98%
In this work, a new and sensitive electroanalytical methodology was developed and validated to quantify sulfentrazone in soil samples. Sulfentrazone was initially characterized qualitatively using cyclic voltammetry (CV). Its oxidation occurred by diffusion (mass transport) on a glassy carbon electrode (GCE) via irreversible transfer of one electron close to a peak potential of +0.936 V vs. Ag|AgCl, 3.0 mol L-1 KCl, in 0.10 mol L-1 KOH. Differential-pulse voltammetry (DPV) was the most sensitive and selective technique, with limits of detection (LOD) of 1.94 and 2.19 mmol L-1 and limits of quantification (LOQ) of 6.46 and 7.31 mmol L-1, in the absence and presence of soil matrix, respectively. The reproducibility of the method ranged between 2.65 and 4.2%, with intermediate precision between 5.32 and 10.9%. The recovery rate ranged between 88.5 and 103%. Additionally, the accuracy of the electroanalytical method was validated by comparing the results with data from a standard analytical methodology of high-performance liquid chromatography (HPLC/UV-Vis).

Design and testing of a computer-controlled square wave voltammetry instrument

Wengenack, Nancy L.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
37.1%
Square Wave Voltammetry is rapidly becoming the most popular and versatile electrochemical technique used in research laboratories today. A discussion of electroanalytical techniques, which are the forerunners to square wave voltammetry, provides a basis for understanding the theoretical and experimental aspects of SWV which are presented. A computer-controlled square wave voltammetry system was designed and built using an IBM PC computer, a Tecmar data acquisition board, an EG&G PARC Model 264A Polarographic Analyzer/Stripping Voltammeter, an EG&G PARC Model 303A Static Mercury Drop Electrode, and the scientific software package, ASYST. The system was tested by performing computer-controlled square wave voltammetry on a Zn^2+ system, popular for standardization of square wave analysis systems. The major problem encountered with the system was a large amount of noise in the collected data. The noise was substantially reduced by various data smoothing techniques which included signal averaging. The universality of the system was successfully 2A tested by using an IBM EC/225^2A Voltammetric Analyzer and a homemade electrolytic cell for the analysis. Finally, the control programs were written in BASIC as well as FORTH, the language of ASYST. FORTH proved to be the superior language for the interfacing application in terms of speed and accuracy of data collection.

Modeling of Catalytic Reaction in Protein-Film Linear Scan Voltammetry at Rotating Disk Electrode

Lovri,Milivoj
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
36.98%
The numerical method for the simulation of linear scan voltammetry on the rotating disk electrode is adjusted to the problem of irreversible redox reaction between the adsorbed catalyst and the dissolved reactant under transient conditions. The response consists of the wave and the maximum. The peak current depends on the scan rate in linear scan voltammetry, while the limiting current of the wave depends on the rate of rotation of the working electrode. The rate constant of catalytic reaction is determined from the kinetic current under steady-state conditions

Around voltammetry: from colouring matters to beer

Barros,A.A.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
Relevância na Pesquisa
36.98%
This paper is based on the plenary lecture that I was invited to present in the VIII Encontro Ibérico de Electroquímica and XIII Encontro da Sociedade Portuguesa de Electroquímica, a meeting which was "a tribute to the late Prof. João Cabral".The best way I found to honour his memory was to present the highlights of an investigation of 25 years in voltammetry, which would never happen without the enthusiasm and the guidance of Prof. João Cabral. After a first publication, in 1986, on the adsorptive stripping voltammetry of synthetic colouring matters, our investigation was soon directed towards the new analytical possibilities opened by the appearance of new voltammetric instrumentation capable of very fast potential scans. The instrumental elimination of oxygen interference obtained in the fast adsorptive stripping of some species reversibly reducible on the hanging mercury drop electrode (HMDE) was a first achievement, immediately followed by the development of a HMDE flow detector for the determination of those species. This detector is being applied in the flow determination of several compounds, with the determination of diacetyl deserving a special reference. In fact the determination of this compound it is very important for the brewing industry and it was possible to develop an equipment capable of its determination in flow: diacetyl is extracted from beer by pervaporation...