Assuntos
Distúrbios Civis , Política , Pesquisadores , Ciência , Justiça Social , Animais , Conflitos Armados , Bolívia , Chile , Distúrbios Civis/economia , Equador , Hong Kong , Humanos , Irã (Geográfico) , Líbano , Ciência/economia , Espanha , Sudão , Síria , Incerteza , Universidades , VenezuelaAssuntos
Democracia , Governo Federal , Política , Pesquisadores/psicologia , Ciência/organização & administração , Bolsas de Estudo , Direitos Humanos , Motivação , Pesquisadores/economia , Ciência/economia , Ciência/tendências , Estudantes/psicologia , Universidades/economia , Universidades/organização & administração , Venezuela , Recursos HumanosRESUMO
We report about the use of carbon paste electrode modified with kaolinite for analytical detection of trace lead(II) in domestic water by differential pulse voltammetry. Kaolinite clay was modified with tripolyphosphate (TPP) by impregnation method. The results show that TPP in kaolinite clay plays an important role in the accumulation process of Pb(II) on the modified electrode surface. The electroanalytical procedure for determination of Pb(II) comprised two steps: chemical accumulation of the analyte under open-circuit conditions, followed by electrochemical detection of the pre-concentrated species using differential pulse voltammetry. The analytical performance of this system has been explored by studying the effects of preconcentration time, carbon paste composition, pH, supporting electrolyte concentration, as well as interferences due to other ions. The calculated detection limit based on the variability of a blank solution (3s(b) criterion) for 10 measurements was 8.4×10(-8) mol L(-1), and the sensitivity determined from the slope of the calibration graph was 0.910 mol L(-1). The reproducibility (RSD) for five replicate measurements at 1.0 mg L(-1) lead level was 1.6%. The results indicate that this electrode is sensitive and effective for the determination of Pb(2+).
Assuntos
Carbono/química , Caulim/química , Chumbo/análise , Polifosfatos/química , Silicatos de Alumínio , Calibragem , Argila , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Concentração de Íons de Hidrogênio , Chumbo/química , Oxirredução , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/análise , Difração de Raios XRESUMO
Dearomatization levels during electrochemical oxidation of p-methoxyphenol (PMP) and p-nitrophenol (PNP) have been determined through UV-Vis spectroscopy using solid phase extraction (UV-Vis/SPE). The results show that the method is satisfactory to determine the ratio between aromatic compounds and aliphatic acids and reaction kinetics parameters during treatment of wastewater, in agreement with results obtained from numerical deconvolution of UV-Vis spectra. Analysis of solutions obtained from electrolysis of substituted phenols on antimony-doped tin oxide (SnO(2)--Sb) showed that an electron acceptor substituting group favored the aromatic ring opening reaction, preventing formation of intermediate quinone during oxidation.
