Position-specific 13C distributions within propane from experiments and natural gas samples

Abstract

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Position-specific hydrogen isotope equilibrium in propane

“…We used two pure propane gas samples: (1) A reference propane, CITP-1, from a highpressure cylinder of high purity propane (>99%) purchased from Air Liquide (UN1978); this is the same propane used as a reference standard by Piasecki et al, (2016aPiasecki et al, ( , 2018. Its bulk D VSMOW is -179±3‰, measured independently by GC-pyrolysis-MS. And (2) 98+ % pure CH 3 -CD 2 -CH 3 ('PROPANE (2,2-D2, 98%)') purchased from Cambridge Isotope Laboratories, Inc.…”

“…Intramolecular isotope fractionations in propane (most simply, differences in 13 C or D content between the central methylene and terminal methyl groups) have potential to constrain mechanisms and conditions of its formation, the chemical and biological processes of its destruction, the conditions of its migration and storage in the sub surface, and to add forensic specificity to attempts to identify sources of fugitive atmospheric and aquatic emissions. (Gilbert et al, 2016;Gao et al, 2016;Piasecki et al, 2018). An additional motivation for this study is that recent theoretical models suggest the temperature dependence of site specific hydrogen isotope fractionation in propane has promising applications to geothermometry (Webb and Miller, 2014;Cheng and Ceriotti, 2016;Piasecki et al, 2016b).…”

Identifying apparent local stable isotope equilibrium in a complex non‐equilibrium system

“…Another important condition in applying the |Δα| matrix approach is to know the equilibrium state, from which the disequilibrium state can be evaluated. Some compound‐ and/or position‐specific 13 β values for organic molecules have been calculated . More 13 β values need to be estimated by ab initio calculations.…”

“…Some compound-and/or position-specific 13 β values for organic molecules have been calculated. 4,14,22,23 More 13 β values need to be estimated by ab initio calculations.…”

Computer-generated isotope model achieves experimental accuracy of filiation for position-specific isotope analysis

“…Isotopic analysis helps scientists explain the origin of compounds across a wide range of disciplines. (Gentile et al, 2015;Marcus, 2004;Piasecki et al, 2018) Methods for the analysis of isotopic enrichment vary by the information they provide: bulk isotope analysis methods give information about bulk properties of mixtures; compound-specific isotope analysis methods give information about the enrichment of individual molecules in a mixture; (Elsner et al, 2012) and position-specific isotope analysis (PSIA) methods give information about the enrichment at a specific position within a molecule. (Gauchotte-Lindsay and Turnbull, 2016;Eiler, 2013) PSIA is able to obtain information about the origin of specific atoms in a given compound, but often requires more separation steps and more sample mass for similar precision.…”