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The Scientific World Journal
Volume 2012, Article ID 168148, 6 pages
http://dx.doi.org/10.1100/2012/168148
Research Article

Critical Comparison between Modified Monier-Williams and Electrochemical Methods to Determine Sulfite in Aqueous Solutions

1Departamento de Química de Los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile (USACH), Avenida L.B. O'Higgins 3363, Estación Central, Santiago 9170022, Chile
2Departamento de Química Inorgánica, Facultad de Química, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago 7820536, Chile

Received 3 October 2011; Accepted 2 November 2011

Academic Editors: C. Mateo and I. Shibata

Copyright © 2012 C. Montes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.