Analytical methods for studying the composition of bronze age metal items: advantages and disadvantages

To obtain reliable information about the composition of ancient metal products, the correct choice of sampling and analysis methods is necessary. The article compares the results of studying the composition of 3 metal items by various analytical methods: optical emission spectral analysis, XRF, SEM-EDS and LA-ICP-MS. The methods showed good convergence of results in the determination of macroimpurities (Sn, Fe, Sb, Ni) in copper and bronze. The closest results at high sensitivity were obtained using spectral analysis and LA-ICP-MS. Using XRF and LA-ICP-MS, the composition of the patina and metal of 8 items is compared. In the patina of bronze artifacts, the content of Sn and Sb is 2-5 times higher than in metal; As - up to 10 times higher; Fe in the patina can either remain at the level of fractions of a percent, or significantly increase by several tens of times. High concentrations of S, as well as Se and Te, were recorded only in the metal of the item; in the patina, the S content is 0,3-0,8 wt %. Lithophilic elements such as Si, Ca, Mg, Al, Mn, P are practically not contained in the metal, however, their concentration in patina is higher by several orders of magnitude. Due to the significant differences in composition, the patinated parts of the item can only be used to a limited extent for interpreting the results of the analysis. The metal sample taken for bulk types of analysis (optical emission spectral, ICP-MS) should not be contaminated with patina particles.