δ13C of free and macromolecular aromatic structures in the murchison meteorite
δ13C of free and macromolecular aromatic structures in the murchison meteorite
复制标题
默奇森陨石中游离芳香族结构和大分子芳香族结构的 δ13C
DOI：
10.1016/s0016-7037(98)00108-2
复制
发表时间：
1998
影响因子：
5
通讯作者：
I. Gilmour
中科院分区：
文献类型：
--
作者：
M. Sephton;C. Pillinger;I. Gilmour
对墨尔奇森陨石中有机化合物的分析使人们对外星有机物质的性质有了更多的了解。然而，低分子和高分子物质之间的关系仍然知之甚少。为了研究这种关系，对未经处理的Murchison进行了超临界流体萃取(SFE)，以获得陨石中的游离有机成分。萃取物中以甲苯等挥发性芳香烃为主，用气相色谱-同位素比质联用(GCIRMS)测定了这些分子的碳同位素组成。芳香烃的δ~(13)C值在−28.8~−5.8‰之间。随着碳数的增加，这些化合物表现出13C的富集性，这表明它们的来源是裂解。分离出陨石中的高相对分子质量有机物，并进行水合热解。这一过程产生了许多芳香族产品，其中大部分是挥发性芳香烃，特别是甲苯。采用超临界流体萃取法成功地提取并保留了它们。这使得GCIRMS能够在分子水平上对这种鲜为人知的材料进行第一次碳同位素分析。芳香族裂解产物的δ~(13)C值在−24.6~−5.6‰之间。在游离化合物中观察到的~(13)C-随着碳数的增加而富集的趋势在大分子碎片中也很明显。此外，与结构相同的自由分子相比，大分子材料的有机碎片具有一致的13C富集性。这表明Murchison中的游离芳香烃是由有机大分子物质的陆外降解产生的。水合热解实验延长了这一自然降解事件。
Analyses of the organic compounds in the Murchison meteorite have led to a greater understanding of the nature of extraterrestrial organic materials. However, the relationship between low and high molecular weight material remains poorly understood. To investigate this relationship, untreated Murchison was subjected to supercritical fluid extraction (SFE) to obtain the free organic components in the meteorite. Toluene and other volatile aromatic hydrocarbons dominated the extract, and the carbon isotopic composition of these molecules was determined by gas chromatography-isotope ratio-mass spectrometry (GCIRMS). δ13C values of the aromatic hydrocarbons ranged from −28.8 to −5.8‰. These compounds displayed a13C-enrichment with increasing carbon number suggesting an origin by cracking. The high molecular weight organic material in the meteorite was isolated and subjected to hydrous pyrolysis. This procedure produced a number of aromatic products, the majority of which were volatile aromatic hydrocarbons, particularly toluene. SFE was used to extract and successfully retain them. This enabled the first carbon isotopic analysis of this poorly understood material to be performed at the molecular level by GCIRMS. δ13C values for aromatic pyrolysis products occupied a range from −24.6 to −5.6‰. The trend of13C-enrichment with increasing carbon number, observed in the free compounds, was also evident in the macromolecular fragments. Furthermore, the organic fragments of the macromolecular material were consistently13C-enriched when compared to structurally identical free molecules. This suggested that the free aromatic hydrocarbons in Murchison were produced by the preterrestrial degradation of the organic macromolecular material. This natural degradation event was extended by the hydrous pyrolysis experiment.