Interlaboratory test for stable carbon isotope analysis of dissolved inorganic carbon in geothermal fluids

Verma MP, van Geldern R, Carvalho MC, Grassa F, Delgado-Huertas A, Monvoisin G, Carrizo D (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Rapid Communications in Mass Spectrometry Wiley

Book Volume: 34

Article Number: e8685

Journal Issue: 9

DOI: 10.1002/rcm.8685

Abstract

Rationale: Stable carbon isotope ratios have many applications in natural sciences. In the first worldwide interlaboratory proficiency test, the discrepancies in measured δ13CDIC values of natural waters were up to σ = ±3‰. Therefore, we continued the investigation on the analytical data quality assurance of individual laboratories and internal consistency among laboratories worldwide. Methods: We designed and performed an interlaboratory comparison exercise for δ13C analyses of ten water and two solid samples (Na2CO3, CaCO3), including two synthetic samples prepared by dissolving the carbonates individually. Three laboratories analyzed an additional sample set to assess solution stability, at least one month after the first set analysis period. The δ13C values were measured using dual inlet isotope ratio mass spectrometry (DI-IRMS) or continuous flow (CF)-IRMS. Results: The δ13C values of solid Na2CO3 and its aqueous solution were −5.06 ± 0.21‰ and 5.32 ± 0.24‰, respectively, while the δ13C value of solid CaCO3 was −4.49 ± 0.93‰. Similarly, the lake water has a consistent value (2.45 ± 0.19‰). The δ13C values of geothermal water have a wide dispersion among individual laboratory measurements and among those of different laboratories; however, a trend exists in the δ13C values measured at the three sampling points of each well. Conclusions: The δ13C values of solid Na2CO3 and its solution, and lake water (i.e. DIC concentration samples >100 mg/L carbon) are consistent among all the participating laboratories. The dispersion in the δ13C values of solid CaCO3 is associated with its lower chemical affinity than that of Na2CO3. The poor reproducibility in the δ13C values of geothermal fluids, collected at three points of a geothermal well, despite overall consistent trends regarding their collection points suggests inadequate sample handling (atmospheric CO2 exchange) and/or inappropriate analytical approaches (incomplete H3PO4 acid reaction).

Authors with CRIS profile

Robert van Geldern Lehrstuhl für Angewandte Geologie

Involved external institutions

Southern Cross University (SCU) AU Australia (AU) Istituto Nazionale di Geofisica e Vulcanologia (INGV) IT Italy (IT) Instituto Andaluz de Ciencias de la Tierra IACT ES Spain (ES) Université Paris-Sud FR France (FR) Centro de Astrobiología (CSIC/INTA) ES Spain (ES) National Institute of Electricity and Clean Energies / Instituto Nacional de Electricidad y Energías Limpias (INEEL) MX Mexico (MX)

How to cite

APA:

Verma, M.P., van Geldern, R., Carvalho, M.C., Grassa, F., Delgado-Huertas, A., Monvoisin, G., & Carrizo, D. (2020). Interlaboratory test for stable carbon isotope analysis of dissolved inorganic carbon in geothermal fluids. Rapid Communications in Mass Spectrometry, 34(9). https://dx.doi.org/10.1002/rcm.8685

MLA:

Verma, Mahendra P., et al. "Interlaboratory test for stable carbon isotope analysis of dissolved inorganic carbon in geothermal fluids." Rapid Communications in Mass Spectrometry 34.9 (2020).

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