High-precision analysis of Pb isotope ratios using MC-ICP-MS and the Pb isotope compositions of rock standard samples

A method for high-precision analysis of Pb isotope using MC-ICP-MS(Neptune plus) was established in Wuhan Centre, China Geological Survey.This study has focused on the influence of Tl standard solution of various concentration on the test results of Pb isotope ratio, and the optimal concentration of Tl standard solution has been determined to be 25 ng/mL, and the Pb concentration in the sample solution should be higher than 25 ng/mL(i.e.the Pb/Tl concentration ratio should be higher than 1).The Pb isotope reference material SRM 981 has been tested with this method for 11 months(July 2020~June 2021).The isotope ratios for SRM 981 are ²⁰⁶Pb/²⁰⁴Pb=16.9415±0.0010, ²⁰⁷Pb/²⁰⁴Pb=15.4985±0.0009 and ²⁰⁸Pb/²⁰⁴Pb=36.7204±0.0023, which are identical to the published data.The blank of long-term monitoring is less than 0.25 ng, which can meet the needs of high-precision lead isotope ratio test of geological samples.Meanwhile, we determined the Pb isotope composition of four trace element standard samples(BCR-2、AGV-2、BHVO-2 and BIR-1a) by using the same procedure.The results are consistent with the published data, hence this method is accurate and reliable.