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

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). Th...

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Bibliographic Details
Published in:Journal of chemical education 2007-07, Vol.84 (7), p.1190
Main Authors: Rodríguez-Rodríguez, Cristina, Amigo, José Manuel, Coello, Jordi, Maspoch, Santiago
Format: Article
Language:English
Subjects:
Acids
Chemistry
Data Analysis
Evolution
Hydroxyquinoline
Least squares
Least Squares Statistics
Measurement Techniques
Multivariate analysis
Organic chemistry
Science education
Science Experiments
Science Instruction
Spectrophotometry
Spectroscopy
Spectrum analysis
Sulfonic acid
Teaching methods
Ultrasonic imaging
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Summary: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 pK a 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.
ISSN:0021-9584
1938-1328
DOI:10.1021/ed084p1190