Rationale
Approximately 1 billion m3 of oil sands process‐affected water (OSPW) is currently stored in tailings ponds in Northern Alberta, Canada. The dissolved organic compounds in OSPW have been termed a supercomplex mixture of bitumen‐derived substances and continuing efforts to understand its underlying chemical composition are important for evaluating its environmental hazards.
Methods
Packed column supercritical fluid chromatography (SFC) was applied to OSPW analysis for the first time. By combining four columns in series (each 25 cm × 4.6 mm I.D., 5.0 µm bare silica) approximately 80,000 plates were achieved on a 1 m column. Using a simple fixed restrictor, the SFC eluent was coupled directly to ultrahigh‐resolution orbitrap mass spectrometry (SFC/Orbitrap‐MS).
Results
SFC/Orbitrap‐MS, with positive and negative atmospheric pressure chemical ionization (APCI +/–), revealed the partial or full chromatographic separation of isomers for a wide array of chemical species, including naphthenic acids (CnH2n + ZO2) and unknown sulfur‐ and nitrogen‐containing molecules. For smaller compounds (e.g. naphthenic acids where n ≤10), or for larger structurally constrained compounds (e.g. C16 naphthenic acid with 9 double‐bond equivalents), apparent baseline resolution of many isomers was possible. Isomer‐specific MS/MS experiments furthermore allowed characterization of functional groups in novel species. For example, in APCI+ mode, up to 16 isomers of C6H11ON were revealed to have amide and amino functionalities.
Conclusions
This combination of high efficiency chromatography and ultra‐high mass resolution detection resulted in a powerful method with capabilities for characterizing or 'fingerprinting' unknown species with little interference. The method has great promise for environmental monitoring and forensics in the oil sands region, as well as for further studies on the composition of dissolved organic compounds in OSPW. Copyright © 2015 John Wiley & Sons, Ltd.