## 4 Results
### Micro Destructive Investigations
#### 4.2.2 GC-MS Analysis  
Some selected samples (MY32, MY33, MY45e and MY46) were investigated by GC-MS. The samples MY32 and MY46 are composed both of plaster and a paint layer, while MY33 and MY45e consisted only of paint layers. The first survey was conducted with the aim of identifying polysaccharides. For this purpose, three vegetable gums (Table 1) as reference materials, such as two acacia gums (G1 and G2) and Neem gum (G3) were submitted to polysaccharide procedure for GC-MS analysis. Figure 4: ATR-FTIR-spectra of samples MY33 (**a**) and MY45 (**b**). The infrared bands are reported and the pattern of the OH stretching vibrations highlighted with an asterisk (*) is better illustrated in the detail of figure (**a**). The percentages of monosaccharides determined in the reference gums are shown in Table 2: in the acacia gums (G1 and G2) arabinose, galactose, mannose, fucose, xylose and glucuronic acid were detected. Conversely, in the chromatogram of Neem gum (Figure 5a) arabinose, galactose, mannose and glucuronic acid were revealed, whereas peaks related to fucose and xylose are missing. Weak chromatographic profiles of monosaccharides of all four samples were obtained. In fact, for all the samples examined, it was observed that the content of polysaccharide material is very diluted: the average of the polysaccharide content in the four samples is 0.08 mg/100 mg for each. The chromatograms of all paint samples show the only presence of monosaccharides such as arabinose, galactose and glucose, given the low content of polysaccharide material found, which would presumably be more abundant (Table 2). Figure 5b shows the chromatogram for monosaccharide analysis of the MY33 sample. Only two common analytes, arabinose and galactose, were considered to identify the organic material. As Figure 6a shows, the four samples of paint material are close to the G3 reference, i.e., the Neem gum, which could be used as a binder to apply the colour in all four painting samples, as also reported by [PERSON] et al. and reported in U Tin Lwin [41,42]. The absence of glucuronic acid and mannose could be due to the dilution of the sample or to the degradation of the rubber. A certain amount of glucose, found in all samples, could be due to the addition of honey [43]. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Gum** & **Arabinose** & **Fucose** & **Xylose** & **Mannose** & **Galactose** & **Glucuronic Acid** & **Glucose** \\ \hline G1 & 76.22 & 1.91 & 0.34 & 2.61 & 16.53 & 2.39 & \\ G2 & 76.45 & 1.06 & 0.28 & 1.72 & 19.81 & 0.55 & \\ G3 & 43.16 & & & 4.56 & 38.81 & 13.47 & \\ MY32 & 48.00 & & & & 35.80 & 16.20 & \\ MY33 & 48.08 & & & & 36.20 & 15.72 \\ MY45e & 47.90 & & & & 35.32 & 16.78 \\ MY46 & 43.80 & & & & 38.33 & 17.87 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Polysaccharide percentage content of reference gums and paint samples. Figure 5: (**a**) Chromatogram of polysaccharide content of Neem gum; (**b**) Chromatogram for monosaccharide analysis of the MY33 sample. _Azadirachta indica_, commonly known as Neem tree (_Tama_ in Burmese), is a tropical evergreen tree of the Meliaceae Family native to India, and it also grows in Asia, Africa and in central and South America. The Neem oil is isolated from its fruits and seeds; the juice from the sap and finally from the bark gum is obtained as the result of a certain metabolic mechanism of plants and trees [4]. All products derived from the tree contain pesticide components, whereas azadirachtin is best known for its antifungal properties. Most likely, this gum is used as a paint binder, as well as for its pesticide properties, determined by different compounds content in all parts of the tree including the most important azadirachtin [4]. A more recent study reports a high content of arsenic found in three different kinds of Azadirachta indica, whether from Sudan [44].