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Issue 7, 2020
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An optimal separation method for high-precision K isotope analysis by using MC-ICP-MS with a dummy bucket

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Abstract

Previous studies have shown that significant K isotope fractionation is found in continental weathering, oceanic crust subduction, and plant growth, suggesting that K isotopes could be a potentially important tracer. However, the complicated separation method and analytical conditions limit the precise analysis of potassium isotopes via MC-ICP-MS under “cold” plasma conditions. Here, an improved separation method (single column) permits the complete purification of K from the matrix elements. This method is efficient and convenient and achieves a high yield (99.5 ± 0.6%) and low blank (<10 ng K) under complex matrix extraction conditions. The high-resolution mode with a desolvating nebulizer system was used to increase the signal intensity of 41K+ and 39K+ and reduce 38ArH+, 40ArH+, and some oxide/nitride interference. To eliminate scattered ions or secondary electrons, we used a new dummy bucket to collect high intensity 40Ar+ beams. Besides, potassium isotopes for the standard SRM 3141a and new geological, environmental and biological reference materials such as DNC-1a, JMS-2, and GSB-14 were determined on a Nu Plasma 3 MC-ICP-MS instrument. Overall, the reproducibility of K isotope analysis was better than ±0.06‰ (2SD) that reported in most laboratories around the world. The measured δ41K values of the rock samples are homogeneous, consistent with the previous published data. However, the K isotope composition in soils, sediments, and plants is inhomogeneous and varies greatly from −0.85‰ to −0.25‰. These results show that potassium isotopes have great application potential in the geological, environmental, and biological fields.

Graphical abstract: An optimal separation method for high-precision K isotope analysis by using MC-ICP-MS with a dummy bucket

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Supplementary files

Article information


Submitted
30 Mar 2020
Accepted
09 Jun 2020
First published
10 Jun 2020

J. Anal. At. Spectrom., 2020,35, 1330-1339
Article type
Paper

An optimal separation method for high-precision K isotope analysis by using MC-ICP-MS with a dummy bucket

X. Li, G. Han, Q. Zhang and Z. Miao, J. Anal. At. Spectrom., 2020, 35, 1330
DOI: 10.1039/D0JA00127A

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