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

Hou Chun Liu, Chen Feng You, Wei Jun Cai, Chuan Hsiung Huang, Kuo Fang You, Bao Shan Chen, Yen Li

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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 μL aliquot of seawater was spiked with an appropriate 43Ca enriched solution for 44Ca/43Ca 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 μL 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.

Original languageEnglish
Pages (from-to)734-741
Number of pages8
JournalAnalyst
Volume139
Issue number4
DOIs
Publication statusPublished - 2014 Jan 20

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biochemistry
  • Environmental Chemistry
  • Spectroscopy
  • Electrochemistry

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