Carbon isotope analysis of dissolved organic carbon in fresh and saline (NaCl) water via continuous flow cavity ring-down spectroscopy following wet chemical oxidation

Christopher H. Conaway; Randal B. Thomas; Nabil Saad; James J. Thordsen; Yousif K. Kharaka

doi:10.1080/10256016.2015.1009910

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Carbon isotope analysis of dissolved organic carbon in fresh and saline (NaCl) water via continuous flow cavity ring-down spectroscopy following wet chemical oxidation

Christopher H. Conaway·Randal B. Thomas·Nabil Saad·James J. Thordsen·Yousif K. Kharaka

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Abstract

This work examines the performance and limitations of a wet chemical oxidation carbon analyser interfaced with a cavity ring-down spectrometer (WCO-CRDS) in a continuous flow (CF) configuration for measuring δ 13 C of dissolved organic carbon ( δ 13 C-DOC) in natural water samples. Low-chloride matrix (<5 g Cl/L) DOC solutions were analysed with as little as 2.5 mg C/L in a 9 mL aliquot with a precision of 0.5 &permil;. In high-chloride matrix (10–100 g Cl/L) DOC solutions, bias towards lighter δ 13 C-DOC was observed because of incomplete oxidation despite using high-concentration oxidant, extended reaction time, or post-wet chemical oxidation gas-phase combustion. However, through a combination of dilution, chloride removal, and increasing the oxidant:sample ratio, high-salinity samples with sufficient DOC (>22.5 µg C/aliquot) may be analysed. The WCO-CRDS approach requires more total carbon (µg C/aliquot) than conventional CF-isotope ratio mass spectrometer, but is nonetheless applicable to a wide range of DOC concentration and water types, including brackish water, produced water, and basinal brines.

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BibTeX RIS

Christopher H. Conaway, Randal B. Thomas, Nabil Saad, James J. Thordsen, Yousif K. Kharaka. 2015-02-17. Carbon isotope analysis of dissolved organic carbon in fresh and saline (NaCl) water via continuous flow cavity ring-down spectroscopy following wet chemical oxidation. https://doi.org/10.1080/10256016.2015.1009910

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