Direct measurement of Cu and Pb isotopic ratios without column chemistry for bronzes using MC-ICP-MS

This study presents a practical method for high-precision Cu and Pb isotope determination without column chemistry for bronzes using MC-ICP-MS. The standard-sample bracketing method combined with Ga internal normalization (SSBIN) is used to correct the instrumental mass bias during Cu isotopic analysis. The effects of acidity mismatch, concentration mismatch and matrix effect were rigorously evaluated using Nu Plasma II MC-ICP-MS in a wet plasma mode. The precision and accuracy of this method were verified by measurements of the Chinese bronze standard material GBW02137 over four months. The δ65Cu of GBW02137 is 0.04 ± 0.02 ‰ (2s (standard deviation), n = 44) relative to NIST SRM 976, well consistent with the recommended value (0.04 ± 0.02 ‰). GBW02137 could serve as a potential bracketing standard and quality control sample for in-situ Cu isotope measurement of ancient bronze artifacts. The 205Tl/203Tl ratio of 2.3889 and an exponential law were used to correct the instrumental mass discrimination during Pb isotopic analysis. The Pb isotopic ratios determined without column chemistry were within 0.04 % of the reference values. Therefore, the method for direct determination of Cu and Pb isotope presented here constitutes a promising tool for bronze materials research since it involves non-column-chemistry, high precision and accuracy, and rapidity.