An Introduction to Multivariate Curve Resolution-Alternating Least Squares: spectrophotometric Study of the Acid Base Equilibria of 8-Hydroxyquinoline-5-sulfonic Acid

• Autores: José Manuel Amigo Rubio, Cristina Rodríguez Rodríguez, Jordi Coello Bonilla, Santiago Maspoch Andrés
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 84, Nº 7, 2007, págs. 1190-1192
• Idioma: inglés
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• Resumen

  • We describe an experiment in which the UV�vis spectrum of 8-hydroxyquinoline-5-sulfonic acid (8HQS) is measured as a function of pH. This experiment introduces students to the chemometric treatments of evolving signals by means of multivariate curve resolution-alternating least squares (MCR-ALS). This is a well established decomposition method to obtain the concentration and spectral profiles of the absorbing components of an evolving system without using any previous assumptions about the chemical model. The student may estimate, by an additional simple graphical treatment, the acid�base constants of 8HQS. Since the spectra of the pure components can be obtained experimentally and the pKa values are well established in the literature, the student will be able to compare his or her results with the reference values and draw conclusions about the potential value of applying MCR-ALS to unknown systems.