Preparation of a clay-modified carbon paste electrode based on 2-thiazoline-2-thiol-hexadecylammonium sorption for the sensitive determination of mercury

A montmorillonite from Wyoming-USA was used to prepare an organo-clay complex, named 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay (TZT-HDTA-clay), for the purpose of the selective adsorption of the heavy metals ions and possible use as a chemically modified carbon paste electrode (CMCPE). Adsorption isotherms of Hg 2+, Pb 2+, Cd 2+, Cu 2+, and Zn 2+ from aqueous solutions as a function of the pH were studied at 298 K. Conditions for quantitative retention and elution were established for each metal by batch and column methods. The organo-clay complex was very selective to Hg(II) in aqueous solution in which other metals and ions were also present. The accumulation voltammetry of Hg(II) was studied at a carbon paste electrode chemically modified with this material. The mercury response was evaluated with respect to the pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. A carbon paste electrode modified by TZT-HDTA-clay showed two peaks: one cathodic peak at about 0.0 V and an anodic peak at 0.25 V, scanning the potential from -0.2 to 0.8 V (0.05 M KNO 3 vs. Ag/AgCl). The anodic peak at 0.25 V presents excellent selectivity for Hg(II) ions in the presence of foreign ions. The detection limit was estimated as 0.1 μg L -1. The precision of determination was satisfactory for the respective concentration level. 2005 © The Japan Society for Analytical Chemistry.

Toward the Optimization of an e-Tongue System Using Information Visualization: A Case Study with Perylene Tetracarboxylic Derivative Films in the Sensing Units

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

Stability of multistep second derivative methods for integro-differential equations

The stability of multistep second derivative methods for integro-differential equations is examined through a test equation which allows for the construction of the associated characteristic polynomial and its region of stability (roots in the unit circle) at a proper parameter space. (c) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A duplicated nitrotienyl derivative with antimycobacterial activity: synthesis, X-ray crystallography, biological and mutagenic activity tests

A duplicated nitrotienyl derivative was obtained as a by-product from the synthesis of a proposed molecular hybrid of a nitrotienyl derivative and isoniazid with an expected dual antimycobacteria mechanism. The structure was shown to be the 5,5'-dinitro-2(2,3-diaza-4-(2'-tienyl)buta-1,3-dienyl)tiophene by X-ray crystallography. The minimal inhibitory concentration (MIC) determination of this compound proved to be promising against Mycobacterium pathogenic strains such as M. avium and M. kansasei, although it had a high level of mutagenicity, as observed in mutagenic activity tests. (c) 2006 Elsevier Masson SAS. All rights reserved.

Synthesis, ex Vivo and in Vitro Hydrolysis Study of an Indoline Derivative Designed as an Anti-Inflammatory with Reduced Gastric Ulceration Properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Development and Validation of an UV-Derivative Spectrophotometric Method for Determination of Glimepiride in Tablets

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

Comparative study of analytical methods by direct and first-derivative UV spectrophotometry for evaluation of losartan potassium in capsules

O losartano potássico é um agente anti-hipertensivo não peptídico, que exerce sua ação por bloqueio específico dos receptores da angiotensina II. Este trabalho propôs a validação e aplicação de métodos analíticos orientados ao controle de qualidade de losartano potássico 50 mg na forma farmacêutica cápsula, utilizando a espectrofotometria direta e derivada de primeira ordem na região do UV. Baseado nas características espectrofotométricas de losartano potássico, um sinal a 205 nm do espectro de ordem zero e um sinal a 234 nm do espectro de primeira derivada foram adequados para a quantificação. Os resultados foram usados para comparar essas duas técnicas instrumentais. O coeficiente de correlação entre as respostas e as concentrações de losartano potássico na faixa de 3,0-7,0 mg L-1 e 6,0-14,0 mg L-1 para espectrofotometria direta e derivada de primeira ordem em solução aquosa, respectivamente, foi de (r) of 0,9999 para ambos os casos. Os métodos foram aplicados para quantificação de losartano potássico em cápsulas obtidas de farmácias de manipulação locais e demonstraram ser eficientes, fáceis de aplicar e de baixo custo. Além disso, não necessitam de reagentes poluentes e requerem equipamentos economicamente viáveis.

Performance characteristics of high performance liquid chromatography, first order derivative UV spectrophotometry and bioassay for fluconazole determination in capsules

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

Electrochemical evidence of sulfinic acid derivative as an intermediate in the reduction of aromatic sulfonyl chloride in an aprotic medium

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

Robust state-derivative pole placement LMI-based designs for linear systems

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Parameter-dependent Lyapunov functions for state-derivative feedback control in polytopic linear systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Robust State-Derivative Feedback LMI-Based Designs for Linear Descriptor Systems

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Stabilizability and Disturbance Rejection with State-Derivative Feedback

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Less Conservative Control Design for Linear Systems with Polytopic Uncertainties via State-Derivative Feedback

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morphology variation as a function of composition for blends of PVDF and a polyaniline derivative

Blends of poly(vinylidene fluoride), PVDF, and poly(o-methoxyaniline), POMA doped with toluene sulfonic acid, TSA, were prepared by casting at various compositions and studied by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The blend composition has a great influence on the morphology obtained. As the concentration of POMA-TSA is increased in the blend an interconnecting fibrillar-like morphology is formed and the spherulites characteristic of pure PVDF are destroyed. The variation of blend morphology is further discussed based on X-ray diffraction and differential scanning calorimetry analysis. (C) 1998 Elsevier B.V. Ltd. All rights reserved.