title: Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water.
abstract: 'Naphthenic acids' (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted. The unfractionated OSPW acidic extract was characterized by elemental analysis, electrospray ionization-Orbitrap-mass spectrometry (ESI-MS), and an esterified extract by Fourier Transform infrared (FTIR) and ultraviolet-visible (UV) absorption spectroscopy and by comprehensive multidimensional gas chromatography-MS (GCxGC-MS). Methyl esters were fractionated by argentation solid phase extraction (Ag(+) SPE) and fractions eluting with: hexane; diethyl ether: hexane and diethyl ether, examined. Each was weighed, examined by elemental analysis, FTIR, UV, GC-MS and GCxGC-MS (both nominal and high resolution MS). The ether fraction, containing sulfur, was also examined by GCxGC-sulfur chemiluminescence detection (GCxGC-SCD). The major ions detected by ESI-MS in the OSPW extract were assigned to alicyclic and aromatic 'O2' acids; sulfur was also present. Components recovered by Ag(+) SPE were also methyl esters of alicyclic and aromatic acids; these contained little sulfur or nitrogen. FTIR spectra showed that hydroxy acids and sulfoxides were absent or minor. UV spectra, along with the C/H ratio, further confirmed the aromaticity of the hexane:ether eluate. The more minor ether eluate contained further aromatics and 1.5% sulfur. FTIR spectra indicated free carboxylic acids, in addition to esters. Four major sulfur compounds were detected by GCxGC-SCD. GCxGC-high resolution MS indicated these were methyl esters of C18 S-containing, diaromatics with ≥C3 carboxylic acid side chains.
authors.affiliation: Biogeochemistry Research Centre, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK.
authors.forename: D
authors.initials: D
authors.lastname: Jones
authors.forename: A G
authors.initials: AG
authors.lastname: Scarlett
authors.forename: C E
authors.initials: CE
authors.lastname: West
authors.forename: R A
authors.initials: RA
authors.lastname: Frank
authors.forename: R
authors.initials: R
authors.lastname: Gieleciak
authors.forename: D
authors.initials: D
authors.lastname: Hager
authors.forename: J
authors.initials: J
authors.lastname: Pureveen
authors.forename: E
authors.initials: E
authors.lastname: Tegelaar
authors.forename: S J
authors.initials: SJ
authors.lastname: Rowland
mesh_terms: D002264:Carboxylic Acids / Q000032:analysis* / Q000737:chemistry; D005591:Chemical Fractionation; D008401:Gas Chromatography-Mass Spectrometry; D061329:Oil and Gas Fields; D010578:Petroleum / Q000032:analysis*; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D002264:Carboxylic Acids; D010578:Petroleum; D014874:Water Pollutants, Chemical; C046170:naphthenic acid
keywords: Elemental analysis; FTIR; Naphthenic acids; Oil sands; Solid phase extraction; UV