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Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS)

Publication ,  Journal Article
Cassar, N; Barnett, B; Bender, ML; Kaiser, J; Hamme, RC; Tilbrook, B
Published in: Analytical Chemistry
February 4, 2009

The oxygen (O2) concentration in the surface ocean is influenced by biological and physical processes. With concurrent measurements of argon (Ar), which has similar solubility properties as oxygen, we can remove the physical contribution to O2 supersaturation and determine the biological oxygen supersaturation. Biological O2 supersaturation in the surface ocean reflects the net metabolic balance between photosynthesis and respiration, i.e., the net community productivity (NCP). We present a new method for continuous shipboard measurements of O2/Ar by equilibrator inlet mass spectrometry (EIMS). From these measurements and an appropriate gas exchange parametrization, NCP can be estimated at high spatial and temporal resolution. In the EIMS configuration, seawater from the ship’s continuous intake flows through a cartridge enclosing a gas-permeable microporous membrane contactor. Gases in the headspace of the cartridge equilibrate with dissolved gases in the flowing seawater. A fused-silica capillary continuously samples headspace gases, and the O2/Ar ratio is measured by mass spectrometry. The ion current measurements on the mass spectrometer reflect the partial pressures of dissolved gases in the water flowing through the equilibrator. Calibration of the O2/Ar ion current ratio (32/40) is performed automatically every 2 h by sampling ambient air through a second capillary. A conceptual model demonstrates that the ratio of gases reaching the mass spectrometer is dependent on several parameters, such as the differences in molecular diffusivities and solubilities of the gases. Laboratory experiments and field observations performed by EIMS are discussed. We also present preliminary evidence that other gas measurements, such as N2/Ar and pCO2 measurements, may potentially be performed with EIMS. Finally, we compare the characteristics of the EIMS with the previously described membrane inlet mass spectrometry (MIMS) approach.

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Published In

Analytical Chemistry

DOI

EISSN

1520-6882

ISSN

0003-2700

Publication Date

February 4, 2009

Volume

81

Issue

5

Start / End Page

1855 / 1864

Related Subject Headings

  • Oxygen Isotopes
  • Oxygen
  • Mass Spectrometry
  • Gases
  • Calibration
  • Argon
  • Analytical Chemistry
  • 4004 Chemical engineering
  • 3401 Analytical chemistry
  • 3205 Medical biochemistry and metabolomics
 

Citation

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Cassar, N., Barnett, B., Bender, M. L., Kaiser, J., Hamme, R. C., & Tilbrook, B. (2009). Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS). Analytical Chemistry, 81(5), 1855–1864. https://doi.org/10.1021/ac802300u
Cassar, N., B. Barnett, M. L. Bender, J. Kaiser, R. C. Hamme, and B. Tilbrook. “Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS).” Analytical Chemistry 81, no. 5 (February 4, 2009): 1855–64. https://doi.org/10.1021/ac802300u.
Cassar N, Barnett B, Bender ML, Kaiser J, Hamme RC, Tilbrook B. Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS). Analytical Chemistry. 2009 Feb 4;81(5):1855–64.
Cassar, N., et al. “Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS).” Analytical Chemistry, vol. 81, no. 5, Feb. 2009, pp. 1855–64. Manual, doi:10.1021/ac802300u.
Cassar N, Barnett B, Bender ML, Kaiser J, Hamme RC, Tilbrook B. Continuous high-frequency dissolved O2/Ar measurements by Equilibrator Inlet Mass Spectrometry (EIMS). Analytical Chemistry. 2009 Feb 4;81(5):1855–1864.
Journal cover image

Published In

Analytical Chemistry

DOI

EISSN

1520-6882

ISSN

0003-2700

Publication Date

February 4, 2009

Volume

81

Issue

5

Start / End Page

1855 / 1864

Related Subject Headings

  • Oxygen Isotopes
  • Oxygen
  • Mass Spectrometry
  • Gases
  • Calibration
  • Argon
  • Analytical Chemistry
  • 4004 Chemical engineering
  • 3401 Analytical chemistry
  • 3205 Medical biochemistry and metabolomics