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

Abstract

This study presents a practical method for high-precision Cu and Pb isotope determination without column chemistry for bronze materials using MC-ICP-MS. The standard-sample bracketing method combined with Ga internal normalization (SSBIN) was 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 a Nu Plasma II MC-ICP-MS in the 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 was 0.04 ± 0.02‰ (2s standard deviation, n = 44) relative to NIST SRM 976, which is 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 measurements 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 the direct determination of Cu and Pb isotope presented here is a promising tool for research on bronze materials owing to the chemistry without columns, high precision and accuracy, and rapidity.