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  Home > JCE Print > Journal of Chemical Education > Issues > 2007  > July  >
In the Laboratory
An Introduction to Multivariate Curve Resolution-Alternating Least Squares: Spectrophotometric Study of the Acid–Base Equilibria of 8-Hydroxyquinoline-5-sulfonic Acid
Cristina Rodríguez-Rodríguez, José Manuel Amigo, Jordi Coello, and Santiago Maspoch
Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
Cover
July 2007
Vol. 84 No. 7
p. 1190
Abstract
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.
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Detailed students procedures, instructors' notes, a complete demo, equipment and reagent list, detailed procedures for preparing reagents, and hazards alerts are available.
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JCE2007p1190W.zip
Folder JCE2007p1190W containing JCE2007p1190W.doc (Microsoft Word) and JCE2007p1190W.mat (3D Studio)
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Citation
Rodríguez-Rodríguez, Cristina; Amigo, José Manuel; Coello, Jordi; Maspoch, Santiago. J. Chem. Educ. 2007, 84, 1190.
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Keywords
Acids / Bases; Analytical Chemistry; Aqueous Solution Chemistry; Calculator-Based Learning; Chemoinformatics; Chemometrics; Computer-Based Learning; Equilibrium; Graduate Education / Research; Hands-On Learning / Manipulatives; Laboratory Instruction; pH; Upper-Division Undergraduate; UV-Vis Spectroscopy
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History
Created:
Last Updated:
5/29/2007
6/7/2007
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