New supplemental activator for lead isotope analysis using TIMS

Abstract

We have devised a new supplementary activator for lead isotope measurements performed using thermal ionization mass spectrometry (TIMS). The activator consisted of a mixture of 250 ppm Ge and 500 ppm Re and was used with normal colloidal silica. This new substance shows excellent performance in terms of enhancing the ion beam intensity. The supplementary activator yielded 3.5–4.5 × 10^–11 A ²⁰⁸Pb for 10 ng Pb, 1.5–2.5 × 10^–11 A for 5 ng Pb, and ~1.5 × 10^–11 A for 2.5 ng Pb samples, indicating that the new activator was superior to those currently in use. This improvement should be applicable to samples with low Pb content, for example, in environmental tracer studies and Pb–Pb chronology studies.