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Diamondoid diacids ('O 4 ' species) in oil sands process‐affected water
Author(s) -
Lengger Sabine K.,
Scarlett Alan G.,
West Charles E.,
Rowland Steven J.
Publication year - 2013
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6729
Subject(s) - chemistry , diamondoid , mass spectrometry , fourier transform ion cyclotron resonance , naphthenic acid , oil sands , biodegradation , gas chromatography , fourier transform infrared spectroscopy , adamantane , mass spectrum , extraction (chemistry) , analytical chemistry (journal) , environmental chemistry , chromatography , organic chemistry , chemical engineering , molecule , corrosion , cartography , asphalt , engineering , geography
RATIONALE As a by‐product of oil sands extraction, large volumes of oil sands process water (OSPW) are generated, which are contaminated with a large range of water‐soluble organic compounds. The acids are thought to be derived from hydrocarbons via natural biodegradation pathways such as α‐ and β‐oxidation of alkyl substituents, which could produce mono‐ and diacids, for example. However, while several monoacids (‘O 2 ’ species) have been identified, the presence of diacids (i.e. 'O 4 ' species) has only been deduced from results obtained via Fourier transform infrared (FTIR) spectroscopy, Fourier transform ion cyclotron resonance high‐resolution mass spectrometry (FTICR‐HRMS) and nuclear magnetic resonance ( 1 H‐NMR) spectroscopy and the structures have never been confirmed. METHODS An extract of an OSPW from a Canadian tailings pond was analysed and the retention times and the electron ionization mass spectra of some analytes were compared with those of bis‐methyl esters of authentic diacids by gas chromatography × gas chromatography/time‐of‐flight mass spectrometry (GCxGC/TOFMS) in nominal and accurate mass configurations. RESULTS Two diamondoid diacids (3‐carboxymethyladamantane‐1‐carboxylic acid and adamantane‐1,3‐dicarboxylic acid) were firmly identified as their bis‐methyl esters by retention time and mass spectral matching and several other structural isomers were more tentatively assigned. Diacids have substantially increased polarity over the hydrocarbon and monoacid species from which they probably derive: as late members of biodegradation processes they may be useful indicators of weathering and ageing, not only of OSPW, but potentially of crude oil residues more generally. CONCLUSIONS Structures of O 4 species in OSPW have been identified. This confirms pathways of microbial biodegradation, which were only postulated previously, and may be a further indication that remediation of OSPW toxicity can occur by natural microbial action. The presence and abundance of these diacids might therefore be useful as a measure of biodegradation and weathering. Copyright © 2013 John Wiley & Sons, Ltd.