Effect of the number of substituents on the behavior of modified electrodes with cobalt porphyrins substituted with a different numbers of bis(methoxyphenyl) groups toward the oxidation of sulfite

William Cheuquepán Valenzuela; D. Villagra; M. I. Azocar; Galo Ramírez; Y-.y Chen; Betty Matsuhiro; Leonora Mendoza; Mauricio Isaacs; M.j Aguirre

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Effect of the number of substituents on the behavior of modified electrodes with cobalt porphyrins substituted with a different numbers of bis(methoxyphenyl) groups toward the oxidation of sulfite

W CHEUQUEPÁN ^[1] ; D VILLAGRA ^[2] ; M.I AZÓCAR ^[1] ; G RAMÍREZ ^[3] ; Y.Y CHEN ^[1] ; B MATSUHIRO ^[1] ; L MENDOZA ^[1] ; M ISAACS ^[3] ; M.J AGUIRRE ^[1]
1. [1] Universidad de Santiago de Chile
  
  Universidad de Santiago de Chile
  
  Santiago, Chile
2. [2] Universidad de Tarapacá
  
  Universidad de Tarapacá
  
  Arica, Chile
3. [3] Pontificia Universidad Católica de Chile
  
  Pontificia Universidad Católica de Chile
  
  Santiago, Chile
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Localización: Journal of the Chilean Chemical Society (Boletín de la Sociedad Chilena de Química), ISSN-e 0717-6309, ISSN 0366-1644, Vol. 55, Nº. 2, 2010, págs. 253-256
Idioma: inglés
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Resumen
- In this study, we compared four glassy carbon electrodes modified with adsorbed porphyrins of cobalt containing one, two, three, or four bis(methoxyphenyl) groups as substituents of the ligand. The aim of this work was to determine the effect of these donating groups on the electrocatalyst behavior of the modified electrodes for the reduction or oxidation of sulfite in water or in mixtures of 12% ethanol in water (v/v) at different pHs. The results showed that the modified electrodes are not catalytic toward the electro-reduction of sulfite in the whole range of pH studied (2-12). However, all the electrodes showed a catalytic toward the oxidation of sulfite at basic pHs. We found that the best catalytic system was the four-substituted porphyrin modified electrode at pH 9.8. This system performed well as an amperometric sensor for sulfite in ethanol-water mixtures and in aqueous solutions at the same pH. When the calibration curve was carried out by cyclic voltammetry, a detection limit of 0.10 mg L-1 for the four-substituted cobalt porphyrin modified electrode in water and in ethanol-water mixtures was found.