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ISSN: 1430-4171 (electronic version)

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Abstract Volume 9 Issue 4 (2004) pp 234-238

Chemometrics in the Teaching Laboratory. Quantification of a Ternary Mixture of Common Pharmaceuticals by First- and Second-Derivative IR Spectroscopy

Juan Ricardo Lucio-Gutiérrez, María de la Luz Salazar-Cavazos, and Noemí Waksman de Torres*

Department of Analytical Chemistry, Faculty of Medicine, U.A.N.L., P.O. Box 2316, Sucursal Tecnológico, 64841 Monterrey, N.L., México, nwaksman@fm.uanl.mx
Received December 17, 2003. Accepted April 13, 2004

Published online: 13 July 2004

Abstract. In this article, a quantification model using infrared is presented in which derivative spectroscopy is applied to a ternary mixture of substances commonly used in undergraduate laboratories, namely, acetylsalicylic acid (ASA), salicylic acid (SA), and caffeine (C). Optimal working conditions are as follows: for SA and ASA, first derivative, second-degree polynomial, 11 smoothing points at 1145 and 1707 cm^–1, respectively; for caffeine, second derivative, second-degree polynomial, 11 smoothing points at 1707 cm^–1. We consider that the procedure described here is useful for the teaching of chemometrics as it presents a series of theoretical and practical considerations that must be taken into account when using a technique such as derivative spectroscopy.

Key Words: Laboratories and Demonstrations; physical chemistry; analytical chemistry; instrumental analysis; IR

(*) Corresponding author. (E-mail: nwaksman@fm.uanl.mx)

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Issue date: August 1, 2004

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