Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry

We describe a method for rapid, precise and accurate determination of calcium ion (Ca2+) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 mu L aliquot of seawater was spiked with an appropriate Ca-43 enriched solution for Ca-44/Ca-43 ID-...

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Bibliographic Details
Published in:The Analyst
Main Authors: Liu, Hou-Chun, You, Chen-Feng, Cai, Wei-Jun, Chung, Chuan-Hsiung, Huang, Kuo-Fang, Chen, Bao-Shan, Li, Yen
Other Authors: Department of Earth sciences
Format: Article in Journal/Newspaper
Language:English
Published: Royal Society of Chemistry 2014
Subjects:
Arctic
Arctic Ocean
Online Access:https://doi.org/10.1039/c3an01948a
http://ir.lib.ncku.edu.tw/handle/987654321/151960
http://ir.lib.ncku.edu.tw/bitstream/987654321/151960/-1/index.html
Description
Summary:We describe a method for rapid, precise and accurate determination of calcium ion (Ca2+) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 mu L aliquot of seawater was spiked with an appropriate Ca-43 enriched solution for Ca-44/Ca-43 ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 mu L solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca2+ values, possibly due to a contribution of interference from Mg2+ and Sr2+ in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca2+ determination with small sample size, high throughput, excellent internal precision and external reproducibility.

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