ASSESSMENT OF CHROMATOGRAPHIC SEPARATION TECHNIQUES FOR SATURATE AND AROMATIC BIOMARKERS USING GAS CHROMATOGRAPHY MASS SPECTROMETRY

Chromatography techniques are commonly used to obtain concentrations of saturate and aromatic biomarkers from source rock extracts. Extractable bitumen samples contain a complex hydrocarbon assemblage and are difficult to analyze using a gas chromatograph mass spectrometer (GCMS) instrument. The separation of the saturate and aromatic fractions from these samples is therefore necessary prior to analysis in a GCMS to reduce coelution of compounds. The scientific literature has a wide array of separation techniques, including traditional liquid column chromatography (LCC) and solid-phase extraction (SPE). The filters, sorbents, and solvents utilized vary based on the compounds of interest.

Presented is a study on the quality of chromatographic separations using both LCC and SPE techniques for saturate and aromatic biomarkers. Six SPE cartridges (SiOH, Si, Fl, Ag-ion, Al-N, and C18) are compared to LLC (activated silica) techniques to test the separation of the aromatic hydrocarbons from saturated hydrocarbons in three source rocks that are in the “early oil” maturity stage. Concentrations and isomer ratios of saturate biomarkers (hopanes, terpanes, and steranes) and aromatic biomarkers (triaromatic steroids and monoaromatic steroids) are analyzed in both the saturate and aromatic fractions to test the quality of the separations. Both a single quadrupole GCMS and a triple quadrupole GCMS are utilized to determine if full removal (or the percentage of removal) of the saturate fraction from the aromatic fraction has occurred with the various chromatographic techniques. Results from this study can increase the efficiency of source rock extract separations used to determine maturity parameters for hydrocarbon exploration initiatives.