Study of the potentiometric response of the doped spinel Li1.05Al0.02Mn1.98O4 for the optimization of a selective lithium ion sensor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Voltammetric performance and application of a sensor for sodium ions constructed with layered birnessite-type manganese oxide

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Selective sorption of mercury(II) from aqueous solution with an organically modified clay and its electroanalytical application

The organo-clay used in this work was prepared from a Na-montmorillonite (Wyoming-USA deposit) by treatment with water solution of hexadecyltrimethylammonium cations. As organo-clays exhibit strong sorptive capabilities for organic molecules, 2-mercapto-5-amino-1,3,4-thiadiazole organofunctional groups, with potential usefulness in chemical analysis, were incorporated on its solid surface. The physically adsorbed reagent did not present any restrictions in coordinating with several metal ions on the surface. The resultant organo-clay complex exhibited strong sorptive capability for removing mercury ions from water in which other metals and ions were also present. The purpose of this work is to study the selective separation of mercury(II) from aqueous solution using the organo-clay complex, measured by batch and chromatographic column techniques, and its application as preconcentration agent in a chemically modified carbon paste electrode for determination of mercury(II) in aqueous solution.

Electrochemical study of o-toluidine blue impregnated in mesoporous silica channels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determinação de chumbo em álcool combustível por voltametria de redissolução anódica utilizando um eletrodo de pasta de carbono modificado com resina de troca iônica Amberlite IR 120

Um método envolvendo a pré-concentração e redissolução anódica em condições de voltametria de pulso diferencial empregando um eletrodo de pasta de carbono modificado (EPCM) com uma resina de troca iônica Amberlite IR120 foi proposto para a determinação de íons chumbo em álcool combustível. O procedimento é baseado em um pico de oxidação do analito observado em -0,53 V(vs. Ag/AgCl) em solução de HCl. As melhores condições experimentais encontradas foram: 5% (m/m) da Amberlite IR120 para a construção do eletrodo, solução de HCl 0,1 mol L-1, velocidade de varredura de 10 mVs-1, tempo de pré-concentração de 15 min e amplitude de pulso de 100 mV. Utilizando essas condições, o EPCM apresentou uma resposta linear entre a corrente de pico anódica e a concentração de íons chumbo para o intervalo entre 9,9 x 10-9 e 1,2 x 10-6 mol L-1 e um limite de detecção de 7,2 x 10-9 mol L-1. Valores de recuperação entre 96 % e 102 % foram encontrados para amostras de álcool combustível enriquecidas com Pb2+ em níveis de 10-7 mol L-1. O efeito da presença de outros íons concomitantes sobre a resposta voltamétrica do eletrodo também foi avaliado.

Eletrodo de pasta de carbono em minicavidade de contato sólido

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Utilização de um eletrodo de grafite-epóxi recoberto com [Zn(FEN)3][tetratris(4-clorofenil) borato]2 sensível a zinco(II) em meio 1,10-fenantrolina como eletrodo indicador em titulações potenciométricas de precipitação

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

Electrochemical and theoretical evaluation of the interaction between dna and amodiaquine: evidence of the guanine adduct formation

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

Study of an organically modified clay: Selective adsorption of heavy metal ions and voltammetric determination of mercury(II)

In this work, a hydrophilic clay, Na-montmorillonite from Wyoming, USA, was rendered organophilic by exchanging the inorganic interlayer cations for hexaclecyltrimethylammonium ions (HDTA), with the formulae of [(CH3)(3)N(C16H33)](+) ion. Based on fact that organo-clay has high affinities for non-ionic organic molecules, 1,3,4-thiadiazole-2,5-dithiol was loaded oil the HDTA-montmorillonite surface, resulting in the 1,3,4-thiadiazole-2,5-dithiol-HDTA-montmorillonite complex (TDD-organo-clay).The following properties of TDD-organo-clay are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II).The main point of this paper is the construction of a selective sensor, a carbon paste electrode modified with TDD-organo-clay, its properties and its application to the determination of mercury(II) ions, as this element belongs to the most toxic metals. The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination. (c) 2005 Elsevier B.V. All rights reserved.

Manganese Phthalocyanine as a Biomimetic Electrocatalyst for Phenols in the Development of an Amperometric Sensor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Application of a Biomimetic Sensor Based on Iron Phthalocyanine Chloride: 4-Methylbenzylidene-Camphor Detection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Potentiometric study using chemically modified silica gel with pyridinium as membrane for ClO4 - ions

A potentiometric sensor for the perchlorate anion was developed by mixing chemically modified silicagel with pyridinium perchlorate, with an epoxy polymer and graphite. The electrode showed Nernstian response between 1.0 × 10-2 and 1.0 × 10-3M perchlorate concentrations. The electrode showed high selectivity to this ion at solutions pH between 5.5 and 8.0. The presence of IO4 -, NO3 -,Br-, IO3 -, Cl- and SO4 2- ions in the solutions, had only small interference in the electrode response in the range mentioned. © 1995 Springer-Verlag.

Preparation of a silica gel modified with 2-amino-1,3,4-thiadiazole for adsorption of metal ions and electroanalytical application

Silica gel with a specific area of 382 m2 g-1 and an average pore diameter of 60 Å was chemically modified with 2-amino-1,3,4-thiadiazole, for the purpose of selective adsorption of heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). The following properties of this functionalized silica gel are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II). The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination. ©2006 Sociedade Brasileira de Química.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Development and application of a highly selective biomimetic sensor for detection of captopril, an important ally in hypertension control

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