A gas chromatography/combustion/isotope ratio mass spectrometry system for high-precision delta C-13 measurements of atmospheric methane extracted from ice core samples

作者：Behrens Melanie^*; Schmitt Jochen; Richter Klaus Uwe; Bock Michael; Richter Ulrike C; Levin Ingeborg; Fischer Hubertus

来源：Rapid Communications in Mass Spectrometry, 2008, 22(20): 3261-3269.

DOI：10.1002/rcm.3720

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 delta(CH4)-C-13 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 similar to 200 g. The methane is melt-extracted using a purge-and-trap method, then separated from the main air constituents, combusted and measured as CO2 by a conventional isotope ratio mass spectrometer. One CO2 working standard, one CH4 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 delta C-13(VPDB) of -49.54 +/- 0.13 parts per thousand and Antarctic samples (1530 +/- 25 years) show a delta C-13(VPDB) of -48.00 +/- 0.12 parts per thousand in good agreement with published data.

• 出版日期2008-10