Otimização da metodologia de determinação de boro empregando voltametria de pulso diferencial

• Ano de defesa: 2010
• Autor(a) principal: Cunha, Roselaine Calzavara da
• Orientador(a): Reis, Efraim Lázaro
• Banca de defesa: Teófilo, Reinaldo Francisco , Fidencio, Paulo Henrique
• 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: Otimização; Determinação de boro; Voltametria de pulso diferencial
• Palavras-chave em Inglês: Optimization; Determination of boron; Differential pulse voltammetry
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2096

The purpose of this study was to optimize, by means of experimental design, the technique of differential pulse voltammetry using electrode mercury drop (HMDE) in the determination of boron at trace level. Because it is electrochemically inactive, boron cannot be determined by voltammetric techniques. However, after the complexation reaction of boric acid and alizarin red S (VAS), an anodic voltammetric peak is obtained corresponding to oxidation of the group of anthraquinone at -0.473 V (vs. Ag/AgCl) using the supporting electrolyte acetic acid / ammonium hydroxide 0.1 mol L-1. Instrumental factors and pH were studied using the Plackett-Burman exploratory planning for screening of the relevant factors and then to analyze these factors a central composite design (CCD) was performed. The best voltammetric response was obtained when used pH 7.2, pulse time 10 ms, pulse amplitude of 50 mV and scan rate of 6.2 mV s-1. The accumulation potential and accumulation time parameters were set at -800 mV s-1 and 0 s, respectively. With optimized parameters, the voltammetric signal of the complex was linearly dependent on the concentration of boron in the range 0.05 -1.47 mg L-1 (n = 10). The detection and quantification limits were 9.72 and 32.4 μg L-1, respectively. The relative standard deviation (RSD) was 3.21% for five independent readings of a standard solution of boron of 40 μg L-1.