Determination of Naphthenic Acids in Oil Sand Processed Water by Two-Dimensional Gas Chromatography with Quadrupole Time-of-Flight Mass Spectrometry (2D GC-QTOFMS)

Abstract

Two-dimensional gas chromatography (2D GC)–quadrupole time-of-flight mass spectrometry (QTOFMS) combined with derivatization was applied to determine naphthenic acids (NAs) in oil sand processed water (OSPW). Using the excellent resolution of 2D GC and mass resolution of QTOFMS with derivatization, 8 cyclohexane carboxylic acid isomers, 18 methylcyclohexyl carboxylic acid isomers, and 18 methylcyclohexyl acetic acid isomers were identified. Linear relationships across wide concentration ranges were established with correlation coefficients (R²) of 0.9995, 0.9992, and 0.9990, for cyclohexanecarboxylic acid, 4-methylcyclohexanecarboxylic acid, and 4-methylcyclohexane acetic acid. The precision, expressed as the relative standard deviation (RSD, n = 5), was from 7. 7–9.5% with recoveries between 72.0% and 84.9%. This method was applied to analyze sewage and showed high concentrations of naphthenic acids in untreated samples.

KEYWORDS:

• Gas chromatography-mass spectrometry (GC-MS)
• naphthenic acids
• oil sand processed water
• quadrupole time-of-flight mass spectrometry (QTOFMS)
• Two-dimensional gas chromatography (2D GC)

Additional information

Funding

This work was supported by the GDAS' Project of Science and Technology Development (No. 2018GDASCX-0808 and 2019GDASYL-0105018).