A TUTORIAL, PART IV. The aim of this manuscript is to present a didactic experiment based on the combination of Near Infrared chemical imaging and Multivariate Curve Resolution for beginners, undergraduate and graduate students. In this tutorial, using MATLAB environment, the instrumental signals will be separated into two matrices, of spectral profiles and relative concentrations in the samples. Then, chemical images were generated to identify and verify the distribution of the components in the pellet samples. Chemical imaging was obtained from the mapping of predetermined area and the results for relative concentrations obtained in the ALS optimization for the analyzed area. This approach was successfully tested in chemistry undergraduate course at the Chemistry Institute of Campinas State University.
Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) was for the first time successfully used to evaluate an intricate photophysical behavior, where deprotonation on the electronic ground state (S0), intra and intermolecular proton transfer processes (ESPT and ESIPT) on the electronic excited state (S1) can simultaneously be presented. In this sense, the organic dye 2-(2′-hydroxyphenyl)benzothiazole (HBT) was used as a proof-of-concept model, where MCR-ALS showed to be a powerful tool for discriminate chemical reactions that occur concomitantly on different potential energy surfaces, which include photochemical reactions. As a result, the chemometric method showed to be a straightforward approach for the determination of the acidic strengths of those equilibria were estimated as 8.61 and 1.11 to hydroxyl deprotonation on electronic ground and excited states, respectively.
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