# FUXYA2020: A Low-Cost Homemade Portable EDXRF Spectrometer for Cultural Heritage Applications
## 3 FUXYA2020 Performance on Real Cases in Cultural Heritage Field
### Pigments
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Layer**} & \multirow{2}{*}{**Pigment**} & **Characterizing Elements** & **Detected** \\  & & **from Known Composition** & **Elements (Traces)** \\ \hline A1 & Natural Lapis Lazuli & S, Si & (Si, K, Fe) \\ A2 & Smalt Blue & Co, K, Si & Co, K, (Si, Fe) \\ A3 & Cobalt Blue & Co & Co, Zn \\ A4 & Azurite & Cu & Cu (Fe) \\ A5 & Verdigris & Cu & Cu \\ A6 & Green Earth & Fe, K & Fe, K (Mn, Ti) \\ A7 & Raw Earth Umber & Fe, Mn & Fe, Mn (Ti) \\ A8 & Tin-Lead Yellow & Pb, Sn & Pb, Sn, (Cu) \\ A9 & Minium & Pb & Pb \\ A10 & Cinnabar & S, Hg & Hg (S) \\ A11 & Red Ochre & Fe & Fe (K, Ti, V) \\ A12 & Burnt Sienna & Fe (Mn) & Fe (K, Ti, V) \\ B1 & Cerulean Blue & Co, Sn & Co, Sn, Zn, Ti \\ B2 & Naples Yellow & Pb, Sb & Pb, Sb, Zn (V, Mn) \\ B3 & Malachite & Cu & Cu (Fe) \\ B5 & Chromium Orange & Cr, Pb & Cr, Pb \\  & Mount Amiata & & \\ B6 & Cinnabar * & S, Hg & Ti, Ba, Zn, Sr \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Pigment layers considered and elements detected by FUXYA spectrometer. (*) Layer B6, labelled as Mount Amiata cinnabar, revealed to be a counterfeit pigment. Besides verifying the capability of our spectrometer to identify pigments, pigment spectra were also used to verify the ability to distinguish the signal with respect to fluctuations of the background. With this aim, peak areas were normalized to the acquisition time and anode current, and the instrumental limit of determination (ILD) was defined as: \(ILD=3\sqrt{cps(mA)}\), according to the definition usually given for the concentration MDL [50]. We did not normalize with respect to the irradiated surface on the sample, as we wanted to compare performance in standard working conditions for each spectrometer. We did not opt for the normally used MDL as, in this case, the passage to concentration values would be aleatory; anyway, ILD and MDL are proportional. Moreover, ILD depends on the instrument, the specimen matrix composition and the element considered and can thus be used for comparing the performance of different instruments used in the same analytical context. The results (see Table 3) were then compared with those obtained measuring the same samples with a commercial portable micro-XRF spectrometer (Bruker ARTAX 200) equipped with a Mo anode X-ray tube, collimated down to 0.65 mm in diameter (excited sample area of 0.33 mm\({}^{2}\)). The Artax 200 mounts an SDD detector and exploits the principle of optical triangulation for the adjustment of the distance between sample and measuring head, and a CCD camera to visualize the sample. The system has an exchangeable filter slide with three filter positions; in this work, no filter has been used. The working conditions were 40 kV and 0.6 mA with an acquisition time of 200 s for each measurement; the distance between the analyzed spot and both the source and the detector was 1.3 cm. Bruker Spectra 5.1 software was used to perform peak deconvolution. As evident from Table 3, even if the results are similar to those obtained in a former publication [51], they cannot be directly compared, as in that case the Artax source was filtered by a 12.5 \(\upmu\)m Mo transmission filter. It is worth noting that, in this same paper, the MDL for the Assing Lithos portable and Niton handheld spectrometers were also considered; in particular, our spectrometer can be compared with Lithos for dimensions, features and portability, showing a better performance when using non-filtered X-ray tube emission in standard working conditions. When dealing with qualitative XRF analysis, an obvious limit is the difficulty in detecting low energy signals, as for instance for Sb and Sn L lines, and Si K lines, because the probability of emission is lower for light elements and for L lines. To better visualize the different performances, in Figure 9, we report the comparison between FUXYA and Artax spectra for samples A8 and B2 in their standard operating conditions.