Comprehensive Analysis of Oil Sands Processed Water by Direct-Infusion Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry with and without Offline UHPLC Sample Prefractionation

Abstract

Oil sands processed water (OSPW) is the main byproduct of the large-scale bitumen extraction activity in the Athabasca oil sands region (Alberta, Canada). We have investigated the acid-extractable fraction (AEF) of OSPW by extraction-only (EO) direct infusion (DI) negative-ion mode electrospray ionization (ESI) on a 12T-Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS), as well as by offline ultrahigh performance liquid chromatography (UHPLC) followed by DI-FTICR-MS. A preliminary offline UHPLC separation into 8 fractions using a reversed-phase C4 column led to approximately twice as many detected peaks and identified compounds (973 peaks versus 2231 peaks, of which 856 and 1734 peaks, respectively, could be assigned to chemical formulas based on accurate mass measurements). Conversion of these masses to the Kendrick mass scale allowed the straightforward recognition of homologues. Naphthenic (CnH2n+zO2) and oxy-naphthenic (CnH2n+zOx) acids represented the largest group of molecules with assigned formulas (64%), followed by sulfur-containing compounds (23%) and nitrogen-containing compounds (8%). Pooling of corresponding fractions from two consecutive offline UHPLC runs prior to MS analysis resulted in ~50% more assignments than a single injection, resulting in 3-fold increase of identifications compared to EO-DI-FTICR-MS using the same volume of starting material. Liquid-liquid extraction followed by offline UHPLC fractionation thus holds enormous potential for a more comprehensive profiling of OSPW, which may provide a deeper understanding of its chemical nature and environmental impact.

Sunlight creates oxygenated species in water-soluble fractions of Deepwater horizon oil

“…The current study was carried out in controlled laboratory conditions so that direct observation of photochemical transformations of oil composition could be observed. Previous studies have targeted oil molecules that partition into water (water soluble organics, WSO) [22][23][24]. Stanford et al identified molecular formulas of water-soluble species present in South American and Medium Arabian crude oils by FT-ICR MS [24].…”

Mass spectral characterisation of a polar, esterified fraction of an organic extract of an oil sands process water

“…considered that the distributions of SO x compounds in OSPW might allow different industrial sources to be distinguished. Nyakas et al . investigated the effects of several pre‐fractionation steps on monitoring of SO x (3–9 DBE) and NO x distributions in OSPW samples by negative ion ESI‐FTICRMS.…”

“…Such knowledge is important because the mixtures of organic and inorganic chemicals in undiluted OSPW are associated with a variety of toxic responses in many higher organisms. Thus, reclamation of some storage lagoons is difficult and can take many years unless treated (e.g . and references cited therein).…”

“…The extraordinary complexity of the mixtures of organic compounds in polar petroleum and petroleum‐related fractions, stated in some cases to comprise more than a million‐but at least tens of thousands, of compounds, has hindered attempts to identify the individual constituents. This applies even to the aqueous‐soluble fractions, where only a few thousand components are present (e.g …”

Combining UHPLC and high-resolution MS: A viable approach for the analysis of complex samples?

“…Highly complex issues, such as the distribution and mobilization of process water from oil sands, require extreme mass-resolving power. Such work was attempted using a 12-T FT-ICR instrument [86]. Many typical environmental monitoring tasks require the sequential analysis of samples in order to monitor the emergence and the disappearance of contaminants, such as chemical spills in rivers.…”