Isotope analysis of hydrocarbons: trapping, recovering and archiving hydrocarbons and halocarbons separated from ambient air.
Isotope analysis of hydrocarbons: trapping, recovering and archiving hydrocarbons and halocarbons separated from ambient air.
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碳氢化合物的同位素分析：捕获、回收和归档从环境空气中分离的碳氢化合物和卤化碳。
DOI：
10.1002/rcm.1812
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
C. Brenninkmeijer
中科院分区：
文献类型：
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作者：
M. Pupek;S. Assonov;J. Mühle;T. Rhee;D. Oram;C. Koeppel;F. Slemr;C. Brenninkmeijer
有人认为，大气非甲烷碳氢化合物（NMHCs）的同位素分析，特别是氘/氢（D/H）比的分析是有价值的，因为对流层的主要自我清洁特性是基于OH自由基，它可以去除，例如，CH 4和其他烷烃的H-原子提取，这引起了大的动力学同位素效应。将D/H同位素分析应用于大气NMHCs的主要障碍不仅是D本身的低丰度，而且特别是NMHCs在万亿分之几范围内的低浓度。我们展示了如何选择的NMHCs可以从300 L的空气样品与CO2作为载气基质一起定量分离，通过使用高效的低温阱。在用无烃空气稀释提取的NMHC混合物并确定混合比后，对于烷烃和几种卤代烃，与原始的全空气样品分析存在良好的一致性。对于不饱和烃和某些其他卤烃，在给定条件下的萃取和回收率作为沸点的函数显著下降。此外，已证明CO2基质中的NMHC混合物在方便地储存于玻璃安瓿中时可保持数年不变。从较大的空气样品中提取的可冷凝物的“提取物”或“浓缩物”将使大气中超痕量气体的D/H同位素分析成为可能。
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., CH4 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 CO2 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 CO2 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.