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

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.