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A gas chromatography/combustion/isotope ratio mass spectrometry system for high‐precision δ 13 C measurements of atmospheric methane extracted from ice core samples
Author(s) -
Behrens Melanie,
Schmitt Jochen,
Richter KlausUwe,
Bock Michael,
Richter Ulrike C.,
Levin Ingeborg,
Fischer Hubertus
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3720
Subject(s) - isotope ratio mass spectrometry , ice core , chemistry , methane , mass spectrometry , analytical chemistry (journal) , stable isotope ratio , isotopes of carbon , fractionation , gas chromatography , isotope analysis , isotope , isotope fractionation , environmental chemistry , chromatography , geology , climatology , oceanography , total organic carbon , physics , organic chemistry , quantum mechanics
Past atmospheric composition can be reconstructed by the analysis of air enclosures in polar ice cores which archive ancient air in decadal to centennial resolution. Due to the different carbon isotopic signatures of different methane sources high‐precision measurements of δ 13 CH 4 in ice cores provide clues about the global methane cycle in the past. We developed a highly automated (continuous‐flow) gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) technique for ice core samples of ∼200 g. The methane is melt‐extracted using a purge‐and‐trap method, then separated from the main air constituents, combusted and measured as CO 2 by a conventional isotope ratio mass spectrometer. One CO 2 working standard, one CH 4 and two air reference gases are used to identify potential sources of isotope fractionation within the entire sample preparation process and to enhance the stability, reproducibility and accuracy of the measurement. After correction for gravitational fractionation, pre‐industrial air samples from Greenland ice (1831 ± 40 years) show a δ 13 C VPDB of −49.54 ± 0.13‰ and Antarctic samples (1530 ± 25 years) show a δ 13 C VPDB of −48.00 ± 0.12‰ in good agreement with published data. Copyright © 2008 John Wiley & Sons, Ltd.