DETERMINAÇÃO DE HIDRAZINA POR VOLTAMETRIA DE ONDA QUADRADA SOBRE ELETRODO DE GRAFITE MODIFICADO COM FeTPyPz

• Ano de defesa: 2007
• Autor(a) principal: Dantas, Luiza Maria Ferreira
• Orientador(a): TAKANA, Auro Atsushi
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Maranhão
• Programa de Pós-Graduação: PROGRAMA DE PÓS-GRADUAÇÃO EM QUÍMICA/CCET
• Departamento: QUIMICA
• País: BR
• Palavras-chave em Português: hidrazina; grafite pirolítico; tetrapiridinoporfirazina de ferro
• Palavras-chave em Inglês: hydrazine; pyrolytic graphite; iron tetrapyridinoporphyrazine
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://tedebc.ufma.br:8080/jspui/handle/tede/888

In this work, the determination of hydrazine (N2H4) in aqueous solutions was investigated by voltammetric techniques on pyrolytic graphite electrodes (GP) before and after modification with iron tetra-pyridinoporphyrazine (FeTPyPz). The modified electrode GP/FeTPyPz presented higher oxidation currents and better voltammetric profiles in comparison with the unmodified electrodes. This modified electrode exhibited two reversible peaks attributed to the redox processes: Fe(I)TPyPz/Fe(II)TPyPz and Fe(II)TPyPz/Fe(III)TPyPz. The pH optimization conditions were performed in solutions prepared by the mixture of different proportions of 0.1 mol L-1 sodium hydroxide (NaOH) and 0.1 mol L-1 phosphate buffer solutions in order to obtain solutions with pH varying from 7 to 13. In order to increase the sensitivity for hydrazine oxidation, three voltammetric techniques were tested: cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The best results were provided by the latter one and the optimized conditions for hydrazine determinations were: i) electrolyte: 0,1 mol L-1 NaOH solution; ii) frequency: 30 s-1; pulse amplitude: 50 mV and scan increment: 8 mV. Under such conditions, the modified electrodes provided linear responses ranging from 5 up to 111 μmol L-1, with detection and quantification limits of 0.82 μmol L-1 and 2.7 μmol L-1, respectively. The investigated sensor presented relative standard deviation values for repeatability and reproducibility lower from 5%. The sensor was applied to analyze boiler water samples and a recovery average of 116 % was found.