On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry

Schmitt, Jochen; Seth, Barbara; Bock, Michael; van der Veen, C.; Möller, L.; Sapart, C. J.; Prokopiou, M.; Sowers, T.; Röckmann, T.; Fischer, Hubertus (2013). On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry. Atmospheric Measurement Techniques (AMT), 6(5), pp. 1425-1445. Copernicus Publications 10.5194/amt-6-1425-2013

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Stable carbon isotope analysis of methane (delta C-13 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 (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton (Kr) can severely interfere during the mass spectrometric measurement, leading to significant biases in delta C-13 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 Kr-86 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 krypton-to-CH4 mixing ratio in the sample, the focusing of the mass spectrometer as well as the detector configuration and can amount to up to several per mil in delta C-13. Apart from technical solutions to avoid this interference, we present correction routines to a posteriori remove the bias.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics

UniBE Contributor:

Schmitt, Jochen; Seth, Barbara; Bock, Michael and Fischer, Hubertus

Subjects:

500 Science > 530 Physics

ISSN:

1867-1381

Publisher:

Copernicus Publications

Language:

English

Submitter:

Andrea Stettler

Date Deposited:

29 Sep 2014 17:14

Last Modified:

03 Jan 2015 21:13

Publisher DOI:

10.5194/amt-6-1425-2013

Web of Science ID:

000321679200022

BORIS DOI:

10.7892/boris.58938

URI:

https://boris.unibe.ch/id/eprint/58938

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