*2.3. Mobile X-ray Fluorescence Microspectrometry*

Portable XRF (pXRF) measurements were performed without any contact between the instrument and the artifact using an ELIO instrument (ELIO, XGLab/Bruker, Italy). This setup consisted of a miniature X-ray tube system with a Rh anode (max voltage of 50 kV, max current of 0.2 mA, a 1 mm collimator determining a rather similar surface) and a large-area silicon drift detector (SDD) (50 mm<sup>2</sup> active area). Details about the procedure have already been published; it should be noted the information thickness during the analysis of the enamel was estimated to be ~4 µm at Si Kα, 130 µm at Cu Kα, 220 µm at Au L<sup>α</sup> and ~2.5 mm at Sn K<sup>α</sup> [18].
