Mass spectrometric analyses of biomarkers and oxygen-containing species in petroleum ether-extractable portions from two Chinese coals

• Biomarkers, especially sterenes, were enriched into ESSBC and EML.
• OxN2 class species are predominant in ESSBC and EML.
• All the detected species have long alkyl side chains (LASCs).
• Twining actions play important role in extracting LASC-containing species with petroleum ether.
• Oxygen atoms exist in furan rings, R–O–R′, RCOOR′, and RCOR′ in the species detected in positive-ion mode.

Shaerhu subbituminous coal (SSBC) and Mengdong lignite (ML) were extracted with petroleum ether under ultrasonication at room temperature to obtain ESSBC and EML, respectively. The extracts were analyzed with a gas chromatograph/mass spectrometer and a positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer to characterize biomarkers and oxygen-containing species. The biomarkers consist of a homologous series of alkanes and sterenes. The biomarker distributions provide important information on the main origins and microorganism degradation of organic matter in SSBC and ML. Oxygen-containing species, including O2–O4, O2N2, and O1N2 class species, are predominant in the extracts with double bond equivalent (DBE) values of 2–28 and carbon numbers (CNs) of 15–50. The oxygen atoms exist in furan rings, R–O–R′, RCOOR′, and RCOR′ (R and R′ denote an alkyl or aryl group). The species in EML have more varied DBE values and CNs compared with those in ESSBC. Most of the OxN2 (x = 1–2) class species have larger DBE values and CNs than the Ox class species, which might be an evidence for more abundant intermolecular associations, such as hydrogen bonds, among the OxN2 class species than among the Ox class species.