title: Bicyclic naphthenic acids in oil sands process water: identification by comprehensive multidimensional gas chromatography-mass spectrometry.
abstract: Although bicyclic acids have been reported to be the major naphthenic acids in oil sands process-affected water (OSPW) and a well-accepted screening assay indicated that some bicyclics were the most acutely toxic acids tested, none have yet been identified. Here we show by comprehensive multidimensional gas chromatography-mass spectrometry (GC×GC-MS), that >100 C8-15 bicyclic acids are typically present in OSPW. Synthesis or purchase allowed us to establish the GC×GC retention times of methyl esters of numerous of these and the mass spectra and published spectra of some additional types, allowed us to identify bicyclo[2.2.1]heptane, bicyclo[3.2.1]octane, bicyclo[4.3.0]nonane, bicyclo[3.3.1]nonane and bicyclo[4.4.0]decane acids in OSPW and a bicyclo[2.2.2]octane acid in a commercial acid mixture. The retention positions of authentic bicyclo[3.3.0]octane and bicyclo[4.2.0]octane carboxylic acid methyl esters and published retention indices, showed these were also possibilities, as were bicyclo[3.1.1]heptane acids. Bicyclo[5.3.0]decane and cyclopentylcyclopentane carboxylic acids were ruled out in the samples analysed, on the basis that the corresponding alkanes eluted well after bicyclo[4.4.0]decane (latest eluting acids). Bicyclo[4.2.1]nonane, bicyclo[3.2.2]nonane, bicyclo[3.3.2]decane, bicyclo[4.2.2]decane and spiro[4.5]decane carboxylic acids could not be ruled out or in, as no authentic compounds or literature data were available. Mass spectra of the methyl esters of the higher bicyclic C12-15 acids suggested that many were simply analogues of the acids identified above, with longer alkanoate chains and/or alkyl substituents. Our hypothesis is that these acids represent the biotransformation products of the initially somewhat more bio-resistant bicyclanes of petroleum. Although remediation studies suggest that many bicyclic acids can be relatively quickly removed from suitably treated OSPW, examination by GC×GC-MS may show which isomers are affected most. Knowledge of the structures will allow the toxicity of any residual isomers to be calculated and measured.
authors.affiliation: Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wilde
authors.affiliation: Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: Charles E
authors.initials: CE
authors.lastname: West
authors.affiliation: Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: Alan G
authors.initials: AG
authors.lastname: Scarlett
authors.affiliation: Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: David
authors.initials: D
authors.lastname: Jones
authors.affiliation: Water Science and Technology Directorate, Environment Canada, 867 Lakeshore Road, Burlington, ON, Canada L7R 4A6.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Frank
authors.affiliation: Water Science and Technology Directorate, Environment Canada, 867 Lakeshore Road, Burlington, ON, Canada L7R 4A6.
authors.forename: L Mark
authors.initials: LM
authors.lastname: Hewitt
authors.affiliation: Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK. Electronic address: srowland@plym.ac.uk.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Rowland
mesh_terms: D000473:Alkanes / Q000032:analysis; D002264:Carboxylic Acids / Q000032:analysis* / Q000302:isolation & purification; D004952:Esters / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D061329:Oil and Gas Fields / Q000737:chemistry*; D010578:Petroleum / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D000473:Alkanes; D002264:Carboxylic Acids; D004952:Esters; D010578:Petroleum; D014874:Water Pollutants, Chemical; C012867:decane; C017573:nonane; C046170:naphthenic acid
keywords: Bicyclics; GC×GC–MS; Naphthenic acids