Comparison of the Effects of Extraction Techniques on Mass Spectrometry Profiles of Dissolved Organic Compounds in Oil Sand Process-Affected Water

Abstract

Recent advances in mass spectrometry have facilitated chemical characterization and profiling of complex environmental mixtures such as oil sand process-affected water (OSPW) and identification of previously unresolved chemicals. However, because OSPW is a complex mixture of salts, metals, suspended particulate matter, and dissolved organics, extraction techniques are required to reduce the effects of signal suppression/enhancement. In this work, Orbitrap, ultrahigh resolution mass spectrometry was used to perform a comprehensive comparison of solid phase extraction (SPE) and liquid−liquid extraction (LLE) techniques on profiling of dissolved organic chemicals in OSPW. When operated in negative ion mode, extraction of naphthenic acid (NAs−O 2 ) was dependent on acidification of OSPW samples for C 18 and LLE techniques. However, when applying a hydrophilic lipophilic balance (HLB) sorbent (ABN) SPE technique, the extractability of NAs was independent of pH. When operated in positive ion mode, for all extraction methods, nitrogen-and sulfur-containing species were more abundant and diverse in basic extracts than in acidic extracts and ABN extracted the greatest number of chemical species including nitrogen-, sulfur-, and oxygen-containing species. Overall, this study supports the utility of HLB SPE techniques for profiling of species of dissolved organic chemicals in OSPW at environmentally relevant pH.

Effects of Oil Sands Process-Affected Water on Measured Concentrations of Polycyclic Aromatic Hydrocarbons

“…Therefore, concentrations of dissolved organic compounds in the final sample was 1000 times greater than in the original sample of OSPW. The profile of heteroatom classes of this fraction was reported previously …”

“…Organic compounds extracted from OSPW can vary at different pH values, , which might influence the desorption of PAHs from PDMS to the aqueous phase. It is not known whether the observed effect of OF-OSPW on the solubilities of PAHs was due to concentrations of anionic, cationic, or non-ionic surfactants.…”

“…OSPW was collected from Base Mine Lake in 2015, which is an end-pit lake constructed from the West-In-Pit settling basin that received input of tailings from the main extraction facility (Syncrude Canada, Ltd., Fort McMurray, AB). The preparation of OF-OSPW was described previously . Briefly, 500 mL of OSPW (pH ∼9) was passed through a glass microfiber filter (GF/D 0.47 mm, Whatman) to remove any suspended particulates.…”

“…Natural and industrial sources of bitumen can influence chemistries of surface waters and groundwaters in oil sands region, which might cause mobilization of polar water-soluble bitumen-derived chemicals into the Athabasca River watershed. − Water-soluble fraction (WSF) of bitumen contains NAs, which are surfactant-like, acyclic, monocyclic, and polycyclic acids that are defined by the molecular formula C n H 2 n + z O 2 . Organic acids are the most abundant, water-soluble compounds in bitumen, but their solubilities in water depend on pH. − In addition, bitumen and OSPW contain a suite of basic and neutral heterocyclic/aromatic NSO compounds that are soluble at ambient pH. ,, OSPW also consists of greater concentrations of inorganic ions such as Na + , Cl – , HCO 3 – , and SO 4 2– , which results in salinity of OSPW being greater than that of natural surface waters of the region . Because oil sands tailing ponds are a source of PAHs and heteroatomic PAHs, concentrations of salts and surfactants in tailings ponds might affect chemodynamics and kinetics of release of PAHs from tailings into the aqueous phase of OSPW.…”

Naphthenic Acids: Formation, Role in Emulsion Stability, and Recent Advances in Mass Spectrometry-Based Analytical Methods

“…SPE and LLE were also evaluated under acidic and basic conditions to profile OSPW samples by FT-Orbitrap MS [159]. Oxygen-containing compounds (i.e., O 1-6 ) were the most prevalent in acid extracts, especially O 4 .…”