A simple calibration procedure of polycapillary based portable micro‐XRF spectrometers for reliable quantitative analysis of cultural heritage materials

Portable micro‐X‐ray fluorescence (micro‐XRF) spectrometers mostly utilize a polycapillary X‐ray lens along the excitation channel to collect, propagate and focus down to few tens of micrometers the X‐ray tube radiation. However, the polycapillary X‐ray lens increases the complexity of the quantification of micro‐XRF data because its transmission efficiency is strongly dependent on the lens specifications and the propagated X‐ray energy. This feature results to a significant and not easily predicted modification of the energy distribution of the primary X‐ray tube spectrum. In the present work, we propose a simple calibration procedure of the X‐ray lens transmission efficiency based on the fundamental parameters approach in XRF analysis. This analytical methodology is best suited for compact commercial and portable micro‐XRF spectrometers. The developed calibration procedure is validated through the quantitative analysis of a broad range of samples with archeological relevance such as glasses, historical copper alloys, silver and gold alloys offering an overall accuracy of less than 10%–15%.