Characterization of the elemental composition of polish banknotes by X-ray fluorescence and laser-induced breakdown spectroscopy

In this study, two very promising techniques, micro X-ray fluorescence (mu XRF) and laser-induced breakdown spectroscopy (LIBS) were applied to the examination of Polish banknotes - Polish zloty (zl). Several areas on each banknote were selected and analysed. Different elemental compositions were identified after comparing the spectra recorded from various measurement locations. It was possible to identify characteristic atomic emissions from one or several elements such as Ca, Ti, Fe, Ba, Co, Cr, Cu, Mg, Mn, Ni, V, and Zr, depending on the banknote denomination, issue date, and evaluated spot. Potentially good discriminators with unique elemental composition were identified: black serial number (C) and microlettering (A). A comparison of brand-new banknotes with used banknotes (which have been in circulation) was also performed. The middle horizontal section of the banknotes shows higher exposure to contamination and consequently constitutes the most difficult part to analyse. Counterfeit banknotes were also analysed and were clearly distinguished from authentic notes in all cases. It was demonstrated that a comparison of the elemental composition is a useful way to detect counterfeit banknotes (10, 20, 50 and 100 zl) in 'real-world' cases. This study shows the potential of LIBS and mu XRF as effective and practical techniques to analyse Polish banknotes. Their many advantages provide a good alternative to the analytical methods routinely used for the examination of these objects.