All data were obtained using MC-ICP-MS (Multi-Collector Inductively Coupled Plasma Mass Spectrometry). Measurements were performed with a Nu Instruments Plasma 3 mass spectrometer. The sample introduction system consisted of a Cetac Aridus 3 desolvating nebulizer, operated at a flow rate of 50 or 100 μL/min.
The analyzed solutions included isotopic standard solutions of NIST SRM 981 with increasing concentrations of matrix elements (mainly Cu and Sn), as well as archaeological bronze samples with known Pb isotopic compositions reported in the literature.
Measurements were conducted using two approaches: the internal standard method, in which samples were spiked with thallium standard solution (NIST SRM 997), and the ORM (Optimised Regression Model) method, where the analytes were individual lead isotope pairs, and the calibrator was a pair of thallium isotopes (NIST SRM 997).
The file name corresponds to the name of the analyzed standard or sample. If an additional note in the format “XX ppb” appears in the name, it indicates the concentration of the analyte expressed in ng/mg. This makes it easy to distinguish files with the same base name but different applied concentrations (e.g., “nist981 20 ppb” vs. “nist981” – in the first case, it is a measurement of the NIST981 standard at a concentration of 20 ng/mg, while in the second, it is an analysis of the standard without an additional concentration note).
