Otimização da metodologia de determinação voltamétrica dos isômeros do ácido butenodióico

• Ano de defesa: 2009
• Autor(a) principal: Pereira, Fernanda de Melo
• Orientador(a): Reis, Efraim Lázaro
• Banca de defesa: Bellato, Carlos Roberto , Teófilo, Reinaldo Francisco , Paiva, José Fernando de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Ácido fumárico; Ácido naleico; Otimização; Planejamento fatorial fracionário; Superfície de resposta; Suco de maçã
• Palavras-chave em Inglês: Fumaric acid; Maleic acid; Optimization; Fractional factorial design; Response surface
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2088

The butanedioic acid has two geometric isomers: the fumaric and maleic acids. The natural occurrence of these acids in apple juice at levels greater than 3 mg L-1 may be due to the metabolism of some fungi or bacteria present in the apple itself. The fumaric and maleic acids are electrochemically reduced in acid solutions in the same potential value, and they are determined in the form of butanedioic acid. In solution whose pH is 8.20, it is possible to differentiate the two acids as the reduction of both acids occurs in different potentials. This present work describes the optimization process of the fumaric and maleic acids determination in samples of apple juice using NH3/NH4Cl 1mol L-1 solution as supporting electrolyte (Method A), and the optimization of the butanedioic acid determination (Method B) using HCl 30% (v/v) solution as supporting electrolyte. The cathodic scans were performed by square wave voltammetry with hanging mercury drop electrode (HMDE). In both methods, a fractional factorial design and a complete factorial design were performed; also, the response surface of each method was determined using a central composite design. The results obtained at the optimized conditions showed linear response in the range of 4.0 to 50 mg.L-1 for fumaric acid, and limits of detection and quantification of 0.0689 mg L-1 and 0.100 mg L-1, respectively. For the maleic acid, linear response was obtained in the range of 2.5 to 25 mg L-1, with limits of detection and quantification of 0.0108 mg L-1 and 0.0209 mg L-1, respectively, using the Method A. Using the Method B, the linear response was obtained in the range of 2.15 to 15.0 mg L-1, with limits of detection and quantification of 1.04 mg L-1 and 1.32 mg L-1, respectively. The samples of apple juice were previously treated using the solid phase extraction process and in the voltammetric analysis they were spiked with solutions of fumaric and maleic acids, obtaining recovery of 99.39% and 98.77%, respectively, using the Method A. Using the Method B, the percentage of recovery of butanedioic acid was 99.51%. The optimization of the voltammetric parameters for the determination of butanedioic acid and its isomers was planned considering factors such as execution time of the experiment, sensitivity, selectivity and low limits of quantification.