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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 9 Issue 5 (2004) pp 288-296

Precision in Two-Wavelength Spectroscopic Analysis of Binary Mixtures

Miguel A. Cabezón and Alejandro C. Olivieri*

Departamento de Química Analítica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, Rosario (S2002LRK), Argentina;
Received May 13, 2004. Accepted September 2, 2004.

Published online: 28 Sepember 2004

Abstract. The classical experiment where the concentrations of two analytes are determined in a mixture by measuring its absorbance at two different wavelengths is reviewed with specific emphasis on prediction uncertainty. It is shown that the standard prediction error on each concentration can be estimated by an equation that bears a strong resemblance to the well-known expression for the univariate case. Aqueous mixtures of potassium permanganate and potassium dichromate at an appropriately regulated pH are studied, and the concentrations are calculated along with the proper uncertainty estimates. Clues are given as to how the different experimental error sources propagate to the reported concentration values.

Key Words: Laboratories and Demonstrations; analytical chemistry; spectroscopy; binary mixtures; uncertainty estimation; error propagation

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Issue date: October 1, 2004

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