Analytical methodology for the analysis of terpan and steran biomarkers in crude samples by means of gaseous chromatography coupled to mass spectrometry

Abstract

Biomarkers are complex molecules derived from formerly living organisms such as bacteria, fungi, algae, plankton, lichens, mosses, ferns and other higher plants. Biomarker concentrations are relatively low in oil and due to the high stability of its chemical structures, they are archaeological witnesses to its formation and transformation process. Based on the qualitative and quantitative composition of the molecules, it is possible to know the degree of oil biodegradation, determination of depositional environmental conditions (such as marine, terrestrial, deltaic, or hypersaline environments) and the type of precursor organic matter in the source rock. In addition, it is possible to carry out environmental, forensic and behavioral studies of hydrocarbon reservoirs. The objective of the present work is to develop an analytical methodology to obtain the distribution of saturated terpanes and steranes biomarkers using combined gas chromatography–mass spectrometry. From the extracted ion chromatograms, the peaks of 37 compounds from the group of terpanes and 19 compounds from that of the steranes were identified and integrated. The distribution was determined with their characteristic fragment ions of m/z 191, m/z 217 and m/z 218. Repeatability, intermediate precision and relative standard deviations were lower than 5%, which shows that the results are in agreement with the quality criteria established for analogous chromatographic methods