NIST 981 Pb. Neptune, Tl-corrected. 2-sigma SD uncertainties.
We routinely measure Pb isotopes using a static method on the Neptune MC-ICP-MS. Solutions with ~50-200 ppb Pb are spiked with NIST 997 Tl such that 208/205 ~2-10. Pb isotope ratios are corrected for instrumental bias with an exponential law relative to 203Tl/205Tl = 0.418911.