crude oil, oil, biomarkers, GC-MS, Thermo Scientific

Did anyone open this link only because it had Fossils in it? This is not fossils in the way you would normally think about them. This is not fossils as in dinosaurs but really interesting and more important as we discuss crude oil. These are steroid biomarkers in crude oil that indicate how and when the oil was formed, linking it to where it was pumped out of the ground. There are otherinstrument techniques used to determine origin of a sample. This GC-MS/MS techniquetargets the biomarkers that were originally from the organic material that eventually became the crude oil. There are a lot of reasons to study biomarkers in oil. They are economic, behavior of the crude as it is refined, political, and even environmental.

Due to the variety of geological conditions and ages under which oil was formed, every crude oil exhibits a unique biomarker fingerprint. Because of this, biological biomarkers are the most important hydrocarbon groups in petroleum because they can be used for chemical fingerprinting. Biomarkers reveal all or most of the original carbon skeleton of the original natural products. Relative to other hydrocarbon components petroleum biomarkers are more resistant to biodegradation but concentrations steadily decrease as petroleum matures. The information from biomarker analysis is used to determine the migration pathways from a source rock to the reservoir, for the correlation of oils in terms of oil-to-oil and oil-to-source rock, the source potential, ranking of the relative thermal maturity, as well as possible secondary alteration processes. Decisions for the commercial exploitation of a prospect are based on that analytical background. Economics ultimately determine if a petroleum reservoir is further developed and finally brought to the market. Refinery chemists are mostly interested in how oil behaves when feeding the processes into marketable products. Analyses of petrochemical biomarkers also have been proven useful in the determination of petroleum-derived environmental contaminations.

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Biomarkers found in crude oils, rocks and sediments, also referenced as “molecular fossils” in the literature, demonstrate few or even no changes from their former precursor compounds: terpenoids (isoprenoids) and steroids found in the cells of the originating living organisms. Biomarker concentrations in oils are low, typically in the low ppm and sub-ppm level in the presence of a highly complex petroleum hydrocarbon matrix. As the concentrations of biomarkers in petroleum decrease with thermal maturity, oils of high maturity exhibit particular analytical challenges with only low biomarker concentrations. Highly selective, fast and sensitive mass analyzers as high resolution or triple quadrupole GC/MS instruments are common and required for meaningful biomarker analysis.

The TSQ Quantum XLS was used to successfully analyze biomarkers in a native crude oil sample. Use of MS/MS offered excellent selectivity and sensitivity, allowing the biomarker information to be accurately determined despite the complex hydrocarbon matrix. The chromatograms in the application note demonstrate the desired hopane and sterane compound distribution with highest certainty even at the lowest levels. The individual peaks appear very well separated in remarkably intensity without interference from the intense background. Of the total GC runtime of about 120 min., the sterane and hopane elution window for the homologous series of C20 to C35 compounds is approximately 35 min. The compounds elute as homologous series with increasing carbon number within the typical distribution curve. Individual compounds are well separated with excellent peak shape. Extracted ion chromatograms are shown in figures in the application note, which depict steranes, tricyclic terpanes and pentacyclic terpanes in native crude oil. Sterane biomarkers are found in low abundance with increased concentration relative to the higher molecular weight compounds. Even at lower levels the tricyclic terpanes are found in the given sample. Hopane compounds in contrast are detected with high abundance over the complete molecular range.

Download application note here; Molecular Fossils in Crude Oil