Measurement of position-specific 13C isotopic composition of propane at the nanomole level
Measurement of position-specific 13C isotopic composition of propane at the nanomole level
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DOI：
10.1016/j.gca.2016.01.017
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发表时间：
2016-03-15
影响因子：
5
通讯作者：
Yoshida, Naohiro
中科院分区：
文献类型：
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作者：
Gilbert, Alexis;Yamada, Keita;Yoshida, Naohiro
我们开发了一种分析丙烷分子内碳同位素分布的新方法，作为一种潜在的新的起源示踪剂。该方法基于丙烷的在线热解，然后分析热解产物甲烷、乙烯和乙烷的碳同位素比值。使用在末端甲基碳上添加了C-13的丙烷样品，我们表征了热解碎片的来源。结果表明，在热解过程中碳原子之间的交换可以忽略不计，从而可以计算相对分子内同位素组成。3个样品的初步数据表明，位置偏好(SP)值，定义为丙烷末端和亚末端C原子位置之间的增量C-13值的差异，范围在-1.8%到-12.9%之间。此外，对于热成因天然气样品，用我们的方法得到的SP值与热裂解理论模型的预期值一致，这表明与丙烷热解相关的同位素分馏可以忽略不计。该方法将为丙烷来源的表征提供新的见解，并将有助于更好地了解天然气矿床的生物地球化学。(C)2016爱思唯尔有限公司。保留所有权利。
We have developed a novel method for analyzing intramolecular carbon isotopic distribution of propane as a potential new tracer of its origin. The method is based on on-line pyrolysis of propane followed by analysis of carbon isotope ratios of the pyrolytic products methane, ethylene and ethane. Using propane samples spiked with C-13 at the terminal methyl carbon, we characterize the origin of the pyrolytic fragments. We show that the exchange between C-atoms during the pyrolytic process is negligible, and thus that relative intramolecular isotope composition can be calculated. Preliminary data from 3 samples show that site-preference (SP) values, defined as the difference of delta C-13 values between terminal and sub-terminal C-atom positions of propane, range from -1.8% to -12.9%. In addition, SP value obtained using our method for a thermogenic natural gas sample is consistent with that expected from theoretical models of thermal cracking, suggesting that the isotope fractionation associated with propane pyrolysis is negligible. The method will provide novel insights into the characterization of the origin of propane and will help better understand the biogeochemistry of natural gas deposits. (C) 2016 Elsevier Ltd. All rights reserved.