ABSTRACT

A MC-ICP-MS technique for precise isotope analysis of sub-nanogram sized Pb sample was developed. We found that combined uses of real-time on-line Tl doping, Tl-isotope-based mass discrimination correction, and desolvating nebulizer operated at relatively low temperature give the best analytical results. The 2SD reproducibility for the analyses with 0.4 ng Pb was better than ±0.0032 for 206Pb/204Pb and 207Pb/204Pb, and better than ±0.0069 for 208Pb/204Pb, which were about 2-3 times better than those obtained by standard bracketing technique without Tl normalization. Our method also enables rapid determination of Pb isotope ratios, 10-13 min per sample, which is about 3 times quicker than the bracketing analysis using an auto-sampler.