Multivariate analysis of pyrolysis-GC/MS data for identification of polysaccharide binding media

Abstract

The method of Thermally assisted Hydrolysis and Methylation (THM) was applied to the analysis of plant gums that can be found in artistic and archaeological objects. The main products obtained by THM of gums arabic, cherry, tragacanth, ghatti and karaya are permethylated and partially methylated 3-deoxyaldonic acids, characteristic products obtained from alkaline hydrolysis of monosaccharides.These markers allowed only a preliminary distinction between the different gums because they are not representative of the entire monosaccharides profile. As classification on the basis of sugars quantification is impossible, multivariate data analysis was employed, using the peak areas of THM products as variables. Calculations were performed on several different sets of data, enhancing the capability of the method to differentiate gums, also when submitted to accelerated ageing treatments. A case study on samples coming from ancient Egyptian cartonnage funerary masks is presented.

An Ancient Egyptian Multilayered Polychrome Wooden Sculpture Belonging to the Museo Egizio of Torino: Characterization of Painting Materials and Design of Cleaning Processes by Means of Highly Retentive Hydrogels

“…As for saccharides, markers derived from arabinose (n. 6, 7), rhamnose (n. 8, 10) and galactose (n. 14, 15) have been detected, as expected for gum Arabic [28]. Gum Arabic was extensively used as binding medium in ancient Egypt, therefore its finding on the surface of the sculpture is consistent with the presence of a paint layer [23,29]. Furthermore, yellowing of gum Arabic due to aging has been associated with the darkening of paints containing Egyptian blue, which in many ancient artefacts appear brownish green or almost black [30].…”

“…The two most intense signals are attributed to palmitic (peak n. 24) and stearic acid (n. 26), detected in the form of methyl esters. Longer chain saturated fatty acids have also been identified, with a number of carbon atoms from C 20 to C 28 (n. 27,28,29,31,35,38), and some unsaturated fatty acids (n. 23,25). These compounds, together with C 27 -C 30 linear alkanes (n. 30,32,34,36), are markers of lipidic substances such as natural waxes.…”

Tree gum-based renewable materials: Sustainable applications in nanotechnology, biomedical and environmental fields

“…KG has been extensively applied for the synthesis of various NPs with the typical dual advantages of KG as a reducing and stabilizing agent (Kora et al, 2010; Kora and Sashidhar, 2014;Rastogi et al, 2017Rastogi et al, , 2015Rastogi et al, , 2014Saravanan et al, 2012;Vinod et al, 2011a). Although the literature on tree gums-assisted nanoparticle synthesis is sparse relative to other biopolymers of a natural origin such as chitosan, alginate, hyaluronan, starch, cellulose, dextran, pectin, carrageenan, guar gum, pullulan, agar, and xanthan gum etc., recent studies have started to exploit the use of tree gums in view of their availability as an economic commodity and their distinctive structural-functional properties (Deshmukh et al, 2012;Fan et al, 2012;Riedo et al, 2013;Sanchez et al, 2017;Kashma Sharma et al, 2014;Xhanari et al, 2017).…”

Plant gum identification in historic artworks

“…In the field of conservation science, gum identification in art materials provides important information on how the artwork was made, but it is also crucial in addressing questions of authenticity and in the development of appropriate conservation and preservation strategies. The most conventional approach employed for the discrimination of plant sources is based on the monosaccharide composition using GC-MS 33 or pyrolysis coupled to GC-MS (Py-GC-MS) 34 following gum hydrolysis. For example the GC-MS profile of gum arabic is characterized by a high percentage (∼40%) of both Ara and Gal (Rha ~ 10%, GlcA < 10%, no Fuc, no GalA, no Man) while karaya gum does not contain Ara.…”