Characterization of aromatic steroids and hopanoids in marine and lacustrine crude oils using comprehensive two dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS)

The distribution of the aromatic steroids and hopanoids in six crude oils was determined using comprehensive two dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) in order to improve their identification and application in geochemical studies. Co-elution between monoaromatic and triaromatic steroids and benzohopanes and their methylated homologues, which are commonly observed in 1D conventional GC, were resolved, with GCxGC facilitating recognition of the compounds. One important feature was that, despite the oils showing mid-oil window maturity characteristics, the distribution of long chain aromatic steroids decreased in lacustrine samples vs. marine samples. This difference in the distribution of long chain and short chain aromatic steroids may reflect the different origins of these oils although this aspect needs further evaluation.