Enrichment and analysis of long-chain normal alkanals from Zhundong subbituminous coal

Zhundong subbituminous coal was exhaustively extracted with isometric carbon disulfide (CDS) and acetone mixed solvent. The extract was fractionated with petroleum ether (PE) and CDS into PE-extractable portion (E₁) and CDS-extractable portion (E₂). E₂ was sequentially eluted with PE and 30% CDS/PE mixed solvent through a silica gel-packed column. A series of long-chain normal alkanals (LCNAs, C_18~27) were enriched from E₂ and identified with a gas chromatography/mass spectrometer. The fractional extraction and subsequent column chromatography provide an effective approach for enriching LCNAs from middle-and low-rank coals. LCNAs could be a class of important biomarkers.