Simona Anna Rigantia, Elena L.C. Rigantea, Tommaso R.I. Cataldia,b, Cosima Damiana Calvanoa,b

aDipartimento di Chimica, and
bCentro SMART, Università degli Studi di Bari Aldo Moro, 70126 Bari, Italy

Natural gums have played a crucial role in the evolution of painting techniques throughout history, helping to mix and evenly apply pigments onto various surfaces such as wood panels, canvas, and parchment. In addition to polysaccharides, these binders can also contain proteins, lipids, and other organic compounds. Characterizing the binders used in artworks is essential for developing effective restoration and conservation strategies. Using advanced mass spectrometry (MS) techniques with soft ionization sources like MALDI [1] or electrospray ionization (ESI), it is possible to distinguish and identify these components, providing a detailed understanding of the binder’s chemical composition. In this study, we developed a rapid, non-invasive method for sampling and analyzing arabic, tragacanth, and cherry gums using highly retentive hydrogels [2]. These hydrogels act as intelligent micro-extractors directly on the artwork or, when loaded with enzymes, can enable in-situ digestion and capture of analyte molecules for further analysis. Previous studies demonstrated that loading the hydrogel with trypsin or a trypsin/chymotrypsin mixture allowed for the digestion and recovery of protein-based binders like egg, milk, or collagen [3]. 

In this work, to identify gums in artworks, the protocol was modified using exo- and endoglycosidases. The resulting oligosaccharides were then analyzed using MALDI-MS. The method was initially tested on gum solutions and fresh model samples to optimize the analytical process and ensure its effectiveness on complex, real-world samples.

Acknowledgements: This work was supported by Progetto di Ricerca di Interesse Nazionale-PRIN 2022CNNRWZ- REActive GEl for orgaNic bindERs recognition in Artworks (REAGENERA), financed by the Italian Ministero per l’Istruzione, l’Università e la Ricerca (MIUR).

Keywords: natural gum, arabic gum, MALDI MS, hydrogel.

References

1. Van Der Werf I., Calvano C.D., et al., Anal. Chim. Acta, 718, (2012), pp. 1–10, DOI: 10.1016/j.aca.2011.12.056.

2. Colombini M.P., Modugno F., Organic Mass Spectrometry in Art and Archaeology, (2009), DOI: 10.1002/9780470741917. 

3. Calvano C.D., Rigante E.C.:l, et al., Talanta, Volume 215 (2020) 120882, DOI: 10.1016/j.talanta.2020.120882.