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Isotope analysis of hydrocarbons: trapping, recovering and archiving hydrocarbons and halocarbons separated from ambient air
Author(s) -
Pupek M.,
Assonov S. S.,
Mühle J.,
Rhee T. S.,
Oram D.,
Koeppel C.,
Slemr F.,
Brenninkmeijer C. A. M.
Publication year - 2005
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.1812
Subject(s) - chemistry , trace gas , isotope analysis , deuterium , hydrocarbon , isotope , methane , environmental chemistry , isotope ratio mass spectrometry , analytical chemistry (journal) , troposphere , boiling point , yield (engineering) , ozone , gas chromatography , chromatography , organic chemistry , atmospheric sciences , thermodynamics , ecology , physics , quantum mechanics , biology , geology
It is argued that isotope analysis of atmospheric non‐methane hydrocarbons (NMHCs) and, in particular, the analysis of the deuterium/hydrogen (D/H) ratio is valuable because the dominant self‐cleansing property of the troposphere is based on the OH radical which removes, e.g., CH 4 and other alkanes by H‐atom abstraction, which induces large kinetic isotope effects. The major obstacle in applying D/H isotope analysis to atmospheric NMHCs is not only the low abundance of D itself but, in particular, the low concentrations of NMHCs in the parts per trillion range. We show how a selection of NMHCs can be quantitatively separated from 300 L air samples together with CO 2 as carrier gas matrix, by using high efficiency cryogenic traps. After diluting the extracted NMHC mixtures with hydrocarbon free air, and determining the mixing ratios, good agreement with original whole air sample analysis exists for alkanes and several halocarbons. For unsaturated hydrocarbons and some other halocarbons the extraction and recovery yield under the given conditions fell considerably, as a function of boiling point. Furthermore, the mixture of NMHCs in the CO 2 matrix is proven to remain unchanged over several years when conveniently stored in glass ampoules. The ‘extracts’ or ‘concentrates’ of condensables extracted from larger air samples will enable the D/H isotope analysis of ultra trace gases in the atmosphere. Copyright © 2005 John Wiley & Sons, Ltd.