CEEPC/IPM/CMSC - Abstrakt prezentace

(CEEPC/IPM/CMSC 2022 - FrP-32)
Machine learning classification unveils secrets of natural indigo analyzed by ion mobility coupled to mass spectrometry

Volodymyr Pauk 1 *, Jana Michalčáková 1,2, Klára Jagošová 1, Karel Lemr 1

  1. Department of Analytical Chemistry, Faculty of Science, Palacky University Olomouc
  2. National Heritage Institute, Prague

Abstrakt

Identification of pigments and dyes is essential for characterization and restoration of cultural heritage. Besides confirmation of colorants, which is already challenging due to minute amount of available samples, their provenance or biological origin is often required. Indigo, the most prominent historical blue colorant was produced from four sources: European woad, Indian indigo, Central and South American anil and Eastern Asian knotweed. Regardless of the used instrumental technique, traditional analytical approaches based on detection of its main components, indigotin and indirubin, were insufficient for such a demanding task. We present the first systematic comprehensive untargeted strategy for discrimination of indigo colorants from different biological sources. The analysis was based on FIA-ESI-IMS-MS, which captured all ionizable analytes including trace components. The massive of data consisting of natural pigments from various biological sources as well as reference paint samples embedded in common binders was statistically processed to select the important features and subjected to classification based on machine learning algorithms using a multi-method screening scheme. Combinations of eight feature selection methods and five classification algorithms were assessed with a set of independent samples using a nested (double) cross-validation process. The best-performing model based on a random forest classifier (average classification accuracy 94%) was used to classify historical samples. Important features were further identified based on their fragmentation patterns and confirmed by comparison with available standards. Flavonoids diosmetin and chrysoeriol were proposed as markers of woad and an indole alkaloid 2,2′ -biindolyl was confirmed in true indigo.

* Korespondující autor: volodymyr.pauk@upol.cz

Literatura

  1. Pauk V., Michalčáková J., Jagošová K., Lemr K.: Dyes and Pigments 197, 109943 (2002).

Poděkování:

The authors gratefully acknowledge the financial support by the project Arteca [ERDF/ESF CZ.02.1.01/0.0/0.0/17_048/0007378] from Ministry of Education, Youth and Sports of the Czech Republic. The authors are thankful to Magdalena Marjaková, Eliška Randůšková (Sklenářová), Lenka Zamrazilová and Kateřina Cichrová for the provided historical samples.


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