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Titel |
On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion-isotope ratio mass spectrometry |
VerfasserIn |
Jochen Schmitt, Barbara Seth, Michael Bock, Carina van der Veen, Lars Möller, Célia Sapart, Markella Prokopiou, Todd Sowers, Thomas Röckmann, Hubertus Fischer |
Konferenz |
EGU General Assembly 2014
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 16 (2014) |
Datensatznummer |
250100874
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Publikation (Nr.) |
EGU/EGU2014-16885.pdf |
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Zusammenfassung |
Stable carbon isotope analysis of methane (δ13C of CH4) on atmospheric samples is one key
method to constrain the current and past atmospheric CH4 budget. A frequently applied
measurement technique is gas chromatography isotope ratio mass spectrometry coupled to a
combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton
can severely interfere during the mass spectrometric measurement leading to significant
biases in δ13C of CH4 if krypton is not sufficiently separated during the analysis.
According to our experiments, the krypton interference is likely composed of two
individual effects with the lateral tailing of the doubly charged 86Kr peak affecting the
neighbouring m-z 44 and partially the m-z 45 Faraday cups. Additionally, a broad signal
affecting m-z 45 and especially m-z 46 is assumed to result from scattered ions
of singly charged krypton. The introduced bias in the measured isotope ratios is
dependent on the chromatographic separation, the Kr to CH4 mixing ratio in the sample,
the mass spectrometer source tuning as well as the detector configuration and can
amount to up to several permil in δ13C. Apart from technical solutions to avoid
this interference we present correction routines to a posteriori remove the bias. |
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