Analysis of Chemical Composition of Gases from Rock Samples by Pulsed Discharge Chromatography Combined Mass Spectrometry

Understanding the chemical composition of gases trapped in rocks is important in a wide variety of earth science studies and gases are often extracted from rock samples and analyzed. Gas chromatography (GC) and mass spectrometry (MS) are the most frequently used analytical techniques for measuring g...

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Bibliographic Details
Published in:Geochemistry international 2020-08, Vol.58 (8), p.968-979
Main Authors: Liwu Li, Liu, Yan, Cao, Chunhui, Li, Zhongping, Xing, Lantian, Zhang, Mingjie, Wang, Xianbin
Format: Article
Language:English
Subjects:
Analysis
Analytical methods
Carbon dioxide
Chemical composition
Chromatography
Continuous flow
Discharge
Earth and Environmental Science
Earth Sciences
Gas chromatography
Gases
Geochemistry
Hydrogen sulfide
Isotope ratios
Isotopes
Mass spectrometry
Mass spectroscopy
Rocks
Scientific imaging
Sediment samples
Sedimentary rocks
Sensitivity
Shale
Spectroscopy
Sulfur dioxide
Thermal conductivity
Trace gases
Vacuum
Volcanic ash, tuff, etc
Volcanic rocks
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Summary:Understanding the chemical composition of gases trapped in rocks is important in a wide variety of earth science studies and gases are often extracted from rock samples and analyzed. Gas chromatography (GC) and mass spectrometry (MS) are the most frequently used analytical techniques for measuring gases extracted from rock samples, but these techniques have rarely been coupled except for gas chromatography-mass spectrometry (GC-MS) or Continuous flow isotope ratio mass spectrometry (CF-IRMS). A thermal conductivity detector (TCD) is most frequently used in GC because of its ability to detect all gases, but has limited sensitivity and thus cannot accurately detect trace gases in some rock samples. To resolve this issue, we built a new device that tests gases extracted from rock samples by GC and MS together, and employs a pulsed discharge detector (PDD) with GC analyses rather than a TCD because PDD is capable of detecting most gases and exhibits higher sensitivity than that of TCD. In this device, a rock sample can be heated or crushed in vacuum to release gases. A diaphragm gauge is then used to measure the pressure of the gases released from the rock samples. Four kinds of samples were tested using this new device: serpentinized peridotites from Inner Mongolia, volcanic rocks from Wudalianchi, shale rocks from Sichuan basin and reservoir rocks from Songliao basin. The chemical contents of H 2 , CH 4 , H 2 O, CO, N 2 , C 2 H 4 , C 2 H 6 , O 2 , H 2 S, Ar, CO 2 , C 3 H 8 , COS and SO 2 could be measured simultaneously.
ISSN:0016-7029
1556-1968
DOI:10.1134/S0016702920080078