## 3 Results and Discussion
### Archaeological Samples  
Once the PLS-VIP model was calibrated and validated, it was applied to determine the concentration of 19 elements in the aforementioned archaeological samples (Figure 3) from the Archaeological Park of Tindari. These samples were selected as part of the SAMOTHRACE project, due to their silica-based matrix being compatible with that of the standard samples. The results are presented in Table 6. For samples with multiple replicates, the average concentration values are reported. From a methodological perspective, non-invasive or micro-destructive approaches are preferred when analyzing archaeological materials. In the case of h-LIBS devices, the laser leaves microscopic ablation marks on the sample surface. To minimize any visual or structural impact, measurements were taken on pre-existing fractures or in non-critical areas, following standard archaeometric practices. Visual inspection under magnification confirmed that the laser-induced marks were minimal and did not compromise the integrity or legibility of the artifacts. For fragile or particularly valuable samples, such as some of the glass fragments, measurements were performed on edges or undecorated surfaces to minimize any potential visual impact. When feasible, multiple replicates were collected from different areas of each sample to account for material heterogeneity and improve statistical robustness. However, in certain cases, such as very thin, uneven, or particularly fragile samples, only one representative measurement was acquired. It should be noted that even when a single replicate was reported, this does not correspond to a single laser shot, as already stated in Section 2.1.3. In the case of brick samples, for example, a single acquisition was considered sufficient due to the samples' uniformity at the analyzed scale. Currently, no comparative data are available to evaluate whether this experimental protocol provides superior performance compared to other analytical techniques (e.g., XRF or ICP-MS). \begin{table}
\begin{tabular}{l l l} \hline
**Element** & **This Work** & **[PERSON] et al. [47]** \\ \hline Si & 1.5\% & 1.7\% \\ Ti & 0.2\% & 0.2\% \\ Al & 1.2\% & 0.9\% \\ Fe & 2.5\% & 1.2\% \\ Mg & 1.2\% & 0.7\% \\ Ca & 1.0\% & 0.7\% \\ Na & 0.5\% & 0.4\% \\ K & 0.5\% & 0.6\% \\ P & 300 ppm & 350 ppm \\ Ba & 450 ppm & 232 ppm \\ Be & 9 ppm & 0.7 ppm \\ Cu & 400 ppm & 26 ppm \\ Mn & 400 ppm & 282 ppm \\ Mo & 20 ppm & 0.8 ppm \\ Pb & 65 ppm & 7 ppm \\ Rb & 50 ppm & 52 ppm \\ Sr & 120 ppm & 85 ppm \\ Y & 25 ppm & 10 ppm \\ Zn & 150 ppm & 26 ppm \\ \hline \end{tabular}
\end{table} 
Table 5: Comparison of prediction uncertainties obtained in this work and reported in the literature by [PERSON] et al. [47]. In detail, the glass samples TY_MA_7 and TY_MA_8 are green glass shards, while TY_MA_9, TY_MA_15, and TY_MA_20 appear slightly whitish, although they were likely originally transparent. All exhibit a thin, iridescent surface layer indicative of glass degradation [81]. Elemental analysis revealed a primary composition of Si (29-35%), Al (6-8%, except for TY_MA_20), and Ca (9-10%), with consistently low Na (2-3%) and undetectable Ti levels. K remained below 1%. Fe was only detected in TY_MA_15 (5.8%) and TY_MA_20 (9.8%), while Mg and Mn were exclusive to TY_MA_20 (1.3% and 0.1%, respectively). These findings contrast with typical silica-soda-line Roman glasses, which generally exhibit higher Na contents (ca. 15-17%). The significantly lower Na levels (ca. 2-3%) in these samples are consistent with degradation via alkali leaching, resulting in a hydrated, alkali-depleted surface [6; 82; 83]. Notably, TY_MA_20 differed from the other samples by showing high levels of Fe, Mn, K, Mg, Pb, and Ba, alongside reduced Al content. Although excavated from the same area as the others, TY_MA_20 was recovered in 2023, about 30 years after the others.