Abstract

Precision and accuracy have been quantified for the determination of lead isotope ratios using continuous leach–inductively coupled plasma–mass spectrometry (CL-ICP-MS) by optimizing acquisition parameters and minimizing the number of elements in the method. By analysing for only 204Pb, 206Pb, 207Pb, 208Pb, 200Hg, and 202Hg, counting times can be increased allowing improvements in isotope ratio precision over normal CL-ICP-MS determinations, which measure these elements as part of a much larger suite. At total Pb concentrations of 1 ppb in solution, results show that precisions of 6.7% to 8.3% and 7.8% to 21% can be achieved for 207Pb/206Pb and 207Pb/204Pb, respectively, over the 0% to 30% HNO3 concentrations used in CL-ICP-MS. Accuracy, as measured against the certified values for NIST 981, ranges from 0.5% to 1.4% and 1.4% to 21% for 207Pb/206Pb and 207Pb/204Pb, respectively. The improvement in precision and accuracy afforded by this technique allows greater differentiation of isotopically distinct reservoirs of Pb within natural samples collected for exploration and environmental geochemistry.

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