Evaluation of optimized procedures for high-precision Pb isotope analyses of seawater by MC-ICP-MS
File(s)
Supporting information
Accepted version
Author(s)
Type
Journal Article
Abstract
The application of Pb isotopes to marine geochemistry is currently hindered by challenges associated with the analysis of Pb isotopes in seawater. The current study evaluates the performance of MC-ICP-MS measurements of seawater Pb isotope compositions following Pb separation by either solid-phase extraction with Nobias Chelate PA-1 resin or co-precipitation with Mg(OH)2, and using either a Pb double-spike or external normalization to Tl for mass bias correction. The four analytical combinations achieve results of similar quality when measuring 1–7 ng of seawater Pb, with reproducibilities (2SD) of 100–1200 ppm for 206Pb/207Pb, 208Pb/207Pb and 300–1700 ppm for ratios involving the minor 204Pb isotope. All four procedures enable significantly improved sample throughout compared to an established TIMS double-spike method and produce unbiased seawater Pb isotope compositions with similar or improved precision. Nobias extraction is preferable to co-precipitation due to its greater analytical throughput and suitability for analyses of large seawater samples with high Si(OH)4 contents. The most accurate Pb isotope data are produced following Nobias extraction and double-spike correction as such analyses are least susceptible to matrix effects. However, Nobias extraction with Tl-normalization constitutes an attractive alternative as, unlike the double-spike procedure, only a single mass spectrometric measurement is required, which improves analytical throughput and optimizes Pb consumption for analysis. Despite the advantages of solid-phase extraction, co-precipitation represents a useful Pb separation technique for samples with low to moderate Si contents as it is inexpensive, simple to implement and the data are only marginally less accurate, especially when combined with a Pb double-spike for mass bias correction.
Date Issued
2020-07-14
Date Acceptance
2020-07-01
Citation
Analytical Chemistry, 2020, 92 (16), pp.11232-11241
ISSN
0003-2700
Publisher
American Chemical Society (ACS)
Start Page
11232
End Page
11241
Journal / Book Title
Analytical Chemistry
Volume
92
Issue
16
Copyright Statement
© 2020 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.analchem.0c01780
Identifier
https://pubs.acs.org/doi/10.1021/acs.analchem.0c01780
Subjects
Analytical Chemistry
0301 Analytical Chemistry
0399 Other Chemical Sciences
Publication Status
Published
Article Number
acs.analchem.0c01780
Date Publish Online
2020-07-14