Characterization of aromatized biomarkers by GC/MS/MS with chemical ionization
- Exxon Research and Engineering Co., Annandale, NJ (United States)
- Exxon Production Research Co., Houston, TX (United States)
Although present in trace amounts, biomarkers are extensively studied by geochemists to understand paleotransformation processes that convert ancient living organisms into petroleum components and to assess age, maturity and source input of the petroleum. Most studied are saturated biomarkers that yield both molecular and characteristic fragment ions under high voltage (50-70 V) electron-impact ionization (HV/EI) conditions. Linking these molecular and fragment ions derived from saturated hydrocarbon compounds using GC/MS/MS resolves coeluting components and provides less ambiguous geochemical information than GC/MS. The same GC/MS/MS techniques cannot be applied to aromatized biomarkers because they yield trace or no molecular ions under HV/EI conditions. To overcome these difficulties, chemical ionization (CI) has been studied for producing ionic species more representative of molecules. Among the reagent gases evaluated, isobutane yields predominantly protonated molecular ions while methane and ammonia yield more than one type of pseudomolecular ions. Thus, isobutane is the gas of choice for the aromatic biomarkers using GC/MS/MS with CI. This analytical technique is particularly useful for resolving overlapping monoaromatic steranes (MAS). Characterization of aromatic biomarkers more accurately would help to explain better the maturation mechanism of petroleum molecules under thermal stress.
- OSTI ID:
- 210628
- Report Number(s):
- CONF-9505261--
- Country of Publication:
- United States
- Language:
- English
Similar Records
High temperature GC/MS of porphyrins and high MW polynuclears and saturated hydrocarbons
The effect of injection hold time on GC resolution and the effect of collision gas on mass spectra in geochemical biomarker research