Characterization of Oil Sands Process-Affected Waters by Liquid Chromatography Orbitrap Mass Spectrometry

Abstract

Recovery of bitumen from oil sands in northern Alberta, Canada, occurs by surface mining or in situ thermal recovery, and both methods produce toxic oil sands process-affected water (OSPW). A new characterization strategy for surface mining OSPW (sm-OSPW) and in situ OSPW (is-OSPW) was achieved by combining liquid chromatography with orbitrap mass spectrometry (MS). In electrospray positive and negative ionization modes (ESI(+)/ESI(-)), mass spectral data were acquired with high resolving power (RP > 100,000-190,000) and mass accuracy (<2 ppm). The additional chromatographic resolution allowed for separation of various isomers and interference-free MS(n) experiments. Overall, ∼3000 elemental compositions were revealed in each OSPW sample, corresponding to a range of heteroatom-containing homologue classes: Ox (where x = 1-6), NOx (where x = 1-4), SOx (where x = 1-4), NO₂S, N, and S. Despite similarities between the OSPW samples at the level of heteroatom class, the two samples were very different when considering isomer patterns and double-bond equivalent profiles. The chromatographic separations also allowed for confirmation that, in both OSPW samples, the O₂ species detected in ESI(-) (i.e., naphthenic acids) were chemically distinct from the corresponding O₂ species detected in ESI(+). In comparison to model compounds, tandem MS spectra of these new O₂ species suggested a group of non-acidic compounds with dihydroxy, diketo, or ketohydroxy functionality. In light of the known endocrine-disrupting potential of sm-OSPW, the toxicity of these O₂ species deserves attention and the method should be further applied to environmental forensic analysis of water in the region.

Effects-Directed Analysis of Dissolved Organic Compounds in Oil Sands Process-Affected Water

“…Among the most abundant species in F1-NE was the O 2 + species (Figure 2) that were first described by Pereira et al as diketo, dihydroxyl, or keto/hydroxyl containing species, possibly similar in structure to sex steroids. 26 Monooxygenated species (i.e., the O + class) were also concentrated in F1-NE ( Figure 2). In contrast, the more oxygenated (and likely more hydrophilic) species (O 3 + , O 4 + , and O 5 + ) were primarily concentrated in F1-AE.…”

“…At the level of empirical formula class, however, there was little difference in the relative distribution of formula classes between F2-NE1 and F2-NE2, both being primarily composed of O 2 + > O + > SO + > NO + in descending order of intensity ( Figure 2). The mode of partitioning controlling the concentration of these presumed polar neutral substances into the alkaline water is not clear, but it is likely related to weakly acidic functional groups; for example, the neutral hydroxyl or phenoxy groups in the O 2 + species structures described by Pereira et al 26 would become negatively charged at highly alkaline pH.…”

A simple procedure for chromatographic analysis of bio-oils from pyrolysis

“…However several of these peaks were attributed to fragment having z of 2, thus compounds with molecular mass over 800 Da were identified. This insightful information provided an opportunity to improve the operating range and condition of the mass analyzer, which was employed in the analyses of several bio-oils having a m/z above 400 [61][62][63][64][65].…”

Estimates of Octanol–Water Partitioning for Thousands of Dissolved Organic Species in Oil Sands Process-Affected Water

“…Moreover, when Barrow et al switched from electrospray negative ionization mode (i.e., which is typically used to detect organic acids) to positive ionization mode (i.e., which can detect organic bases and neutral polar compounds) they showed an even greater number of organic species composed of C, H, O, S, and N. By analytical chromatographic separations, Pereira et al followed up on this work by demonstrating that O 2 species detected in electrospray negative mode (O 2 distinct from O 2 species detected in positive ionization mode (i.e., O 2 + species); which were tentatively identified as ketohydroxy, or dihydroxy compounds. 15 Thus, it is important to consider both modes of ionization when characterizing OSPW, and it has yet to be determined if other species that are detected in both negative and positive mode (e.g., SO 2 − and SO 2 + ) are distinct, overlapping, or the same chemical species which ionize in both modes of analysis.…”