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. 2019 May 24;24(10):1997. doi: 10.3390/molecules24101997

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© 2019 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Spectra of samples with the highest and the lowest active pharmaceutical ingredient (API) concentrations measured by three instruments: (a) selected raw spectra based on the acetylsalicylic acid (ASA) concentration; (b) selected preprocessed spectra based on the ASA concentration by Savitzky-Golay 1st derivative (5 smoothing points and 2nd polynomial order) and SNV; (c) selected raw spectra based on the ascorbic acid (ASC) concentration; (d) selected preprocessed spectra based on the ASC concentration by Savitzky-Golay 2nd derivative (7 smoothing points and 3rd polynomial order) and SNV; (e) selected raw spectra based on the caffeine (CAF) concentration; (f) selected preprocessed spectra based on the CAF concentration by Savitzky-Golay 1st derivative (17 smoothing points and 3rd polynomial order) and SNV.

Spectra of samples with the highest and the lowest active pharmaceutical ingredient (API) concentrations measured by three instruments: (a) selected raw spectra based on the acetylsalicylic acid (ASA) concentration; (b) selected preprocessed spectra based on the ASA concentration by Savitzky-Golay 1st derivative (5 smoothing points and 2nd polynomial order) and SNV; (c) selected raw spectra based on the ascorbic acid (ASC) concentration; (d) selected preprocessed spectra based on the ASC concentration by Savitzky-Golay 2nd derivative (7 smoothing points and 3rd polynomial order) and SNV; (e) selected raw spectra based on the caffeine (CAF) concentration; (f) selected preprocessed spectra based on the CAF concentration by Savitzky-Golay 1st derivative (17 smoothing points and 3rd polynomial order) and SNV.