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Interlaboratory test for stable carbon isotope analysis of dissolved inorganic carbon in geothermal fluids
Author(s)
Language
English
Obiettivo Specifico
2IT. Laboratori analitici e sperimentali
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
9/34 (2020)
Electronic ISSN
1097-0231
Pages (printed)
e8685
Issued date
2020
Subjects
Inter-Laboratory proficiency test
geothermal fluids
Keywords
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).
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).
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article
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