Precise determination of 204Pb-based isotopic ratios in environmental samples by quadrupole inductively coupled plasma mass spectrometry

Abstract

The measurement of ²⁰⁴Pb-based isotopic ratios by quadrupole ICP-MS has been investigated. After multivariate optimization of the main operating conditions (sample uptake rate, spray chamber temperature, quadrupole voltages), the isotopic ratios were measured with an internal precision of ∼0.4% (% RSD, n = 12) at the Pb concentration of 1 μg L⁻¹ and ∼0.2% at 10 μg L⁻¹, close to the values usually reported for the measurement of major isotopes by quadrupole ICP-MS. The external precision was ∼0.3% (% RSD, n = 35) and the bias, after the correction of the isobaric overlapping of ²⁰⁴Hg on ²⁰⁴Pb, was lower than 2‰. The applicability of the developed method in the environmental field was demonstrated by the analysis of a time series of 84 atmospheric particulate samples collected from the Arctic and characterized by low Pb concentration, obtaining data in good agreement with the isotopic composition of airborne particulate deposited in central Greenland.