High-Precision Lead Isotope Ratio Measurement by Inductively Coupled Plasma Multiple Collector Mass Spectrometry

Abstract

An inductively coupled plasma (ICP) ion source coupled to a magnetic sector mass analyser equipped with seven Faraday detectors has been used to measure the lead isotope ratios in solutions of Sanshiro Pond sediment collected at the University of Tokyo, airborne particulates collected at Shinjuku in Tokyo and Merck multielement standard product number 97279494. A thallium correction technique was utilised to allow a simultaneous correction for mass bias. This work followed an earlier interlaboratory comparison study of the above-mentioned solutions using ICP quadrupole mass spectrometry, and has demonstrated a considerable improvement in analytical precision. The following isotope ratio measurements were recorded. Pond sediment solution containing 82ng ml^-1 lead: ²⁰⁶Pb/²⁰⁴Pb=17.762±0.014; ²⁰⁶Pb/ ²⁰⁷Pb=1.1424±0.0009; ²⁰⁸Pb/²⁰⁴Pb=37.678±0.034. Airborne particulate solution containing 45 ng ml^-1 lead: ²⁰⁶Pb/ ²⁰⁴Pb=17.969±0.006; ²⁰⁶Pb/²⁰⁷Pb=1.1528±0.0003; ²⁰⁸Pb/²⁰⁴Pb=37.915±0.021. Merck multielement standard solution containing 100ng ml^-1 lead: ²⁰⁶Pb/²⁰⁴Pb=19.255±0.015; ²⁰⁶Pb/²⁰⁷Pb=1.2238±0.0004; ²⁰⁸Pb/²⁰⁴Pb=38.476±0.021 (All errors are given as ±2 standard deviations).