Stable isotope analysis of saline water samples on a cavity ring-down spectroscopy instrument

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    Abstract

    The analysis of the stable hydrogen and oxygen isotope composition of water using cavity ring-down spectroscopy (CRDS) instruments utilizing infrared absorption spectroscopy have been comprehensively tested. However, potential limitations of infrared spectroscopy for the analysis of highly saline water have not yet been evaluated. In this study, we assessed uncertainty arising from elevated salt concentrations in water analyzed on a CRDS instrument and the necessity of a correction procedure. We prepared various solutions of mixed salts and separate solutions with individual salts (NaCl, KCl, MgCl2, and CaCl2) using deionized water with a known stable isotope composition. Most of the individual salt and salt mixture solutions (some up to 340 g L-1) had δ-values within the range usual for CRDS analytical uncertainty (0.1‰ for δ 18O and 1.0‰ for δ 2H). Results were not compromised even when the total load of salt in the vaporizer reached ∼38.5 mg (equivalent to build up after running ∼100 ocean water samples). Therefore, highly saline mixtures can be successfully analyzed using CRDS, except highly concentrated MgCl2 solutions, without the need for an additional correction if the vaporizer is frequently cleaned and MgCl2 concentration in water is relatively low. © 2014 American Chemical Society.
    Original languageEnglish
    Pages (from-to)2827-2834
    JournalEnvironmental Science and Technology
    Volume48
    Issue number5
    DOIs
    Publication statusPublished - 3 Feb 2014

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