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dc.contributor.authorScarlett, Alan
dc.contributor.authorSpaak, G.
dc.contributor.authorMohamed, S.
dc.contributor.authorPlet, Chloe
dc.contributor.authorGrice, Kliti
dc.date.accessioned2019-02-19T04:17:55Z
dc.date.available2019-02-19T04:17:55Z
dc.date.created2019-02-19T03:58:32Z
dc.date.issued2019
dc.identifier.citationScarlett, A. and Spaak, G. and Mohamed, S. and Plet, C. and Grice, K. 2019. Comparison of tri-, tetra- and pentacyclic caged hydrocarbons in Australian crude oils and condensates. Organic Geochemistry. 127: pp. 115-123.
dc.identifier.urihttp://hdl.handle.net/20.500.11937/74719
dc.identifier.doi10.1016/j.orggeochem.2018.11.010
dc.description.abstract

Thermally stable and biodegradation resistant, the tricyclic and pentacyclic diamondoid caged hydrocarbons are commonly used as source and maturity indicators of oils and potential source-rocks, but similar tetracyclic structures appear to have received much less attention. Using two-dimensional (2D) gas chromatography – time of flight mass spectrometry (GC × GC-TOFMS), 29 Australian crude oils and condensates were analysed for the presence of caged C12H18 tetracyclics such as ethanoadamantane and iceane. The thermodynamically more stable 2,4-ethanoadamantane was identified by comparison with a synthesised authentic standard. Three of its bridgehead methyl-substituted isomers, 6-methylethanoadamantane (6-ME), 1-ME and 2-ME, were tentatively assigned based on mass spectral comparison and relative elution order. Further series of non-bridgehead methyl isomers, plus dimethyl isomers, were also inferred based on mass spectra and 2D elution positions. The tri-, tetra and pentacyclic caged hydrocarbons and their methyl-substituted homologues were semi-quantified in the Australian oils. The potential of a novel index, the methylethanoadamantane index (MEI), based on the ratio of the more stable bridgehead isomers divided by the sum of all the methyl substituted isomers (MEI = S(6-ME + 1-ME + 2-ME)/STotal methylethanoadamantanes), was explored. A significant positive association was found between the MEI and MAI (r2 = 0.203, p < 0.05) and a significant negative association was found between MEI and MDI (r2 = 0.246, p < 0.05). Stronger relationships were found for other commonly applied diamondoid ratio indices, including S Methyl Adamantanes/S Methyl Diamantanes (SMA/SMD) versus SMA/SME (r2 = 0.781, p < 0.0001, n = 26). The relatively low volatility of the ethanoadamantanes compared to the adamantanes and their likely greater resistance to microbial attack than the ethyladamantanes, may make analysis of these compounds a useful addition to the commonly measured diamondoids.

dc.publisherPergamon
dc.relation.sponsoredbyhttp://purl.org/au-research/grants/arc/LP150100341
dc.relation.sponsoredbyhttp://purl.org/au-research/grants/arc/DP13010057
dc.relation.sponsoredbyhttp://purl.org/au-research/grants/arc/LE130100145
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.titleComparison of tri-, tetra- and pentacyclic caged hydrocarbons in Australian crude oils and condensates
dc.typeJournal Article
dcterms.source.volume127
dcterms.source.startPage115
dcterms.source.endPage123
dcterms.source.issn0146-6380
dcterms.source.titleOrganic Geochemistry
curtin.accessStatusOpen access


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