Dispersive Solid-Phase Extraction Separation and Molecular Composition Characterization of Asphaltene-Occluded Saturated Hydrocarbons

In source rocks or crude oil systems, asphaltene-occluded hydrocarbons serve as important carriers for tracing the original composition of organic matter. The non-destructive (non-chemically disruptive) separation and characterization of these hydrocarbons are critical for understanding the source and evolution of sedimentary organic matter. This study employed dispersive solid-phase extraction (DSPE) combined with column chromatography to isolate asphaltene-occluded saturated hydrocarbons from various genetic types of sedimentary organic matter, including source rocks, coal, crude oil, and solid bitumen, and analyzed the compositional characteristics and implications of their normal chain hydrocarbons. The results indicate that: The DSPE method effectively separates asphaltene-occluded saturated hydrocarbons from samples of diverse geological origins; Signature even-carbon-numbered n-1-alkenes (C₁₆~C₂₈) were detected in source rocks, crude oil, and solid bitumen samples but not in coal samples; The distribution of n-alkanes in asphaltene-occluded hydrocarbons varies significantly among genetic types, with terrestrial sedimentary organic matter exhibiting relative enrichment of higher-molecular-weight n-alkanes, closely linked to source input; Even-carbon-numbered n-1-alkenes (C₁₆-C₂₈) are commonly occluded in asphaltenes formed in reducing depositional environments, with origins traceable to the diagenetic stage. This study confirms the applicability of DSPE for separating asphaltene-occluded saturated hydrocarbons across diverse geological samples, offering a reliable method for analyzing the original geochemical information of sedimentary organic matter. Furthermore, it highlights the potential of molecular composition characteristics in asphaltene-occluded hydrocarbons as indicators of sedimentary organic matter sources.