Sequential thermal dissolution of two low-rank coals and characterization of their structures by high-performance liquid chromatography/time-of-flight mass spectrometry and gas chromatography/mass spectrometry.

Non-destructive methods were used to obtain soluble matter from coals, and different chromatographic and mass spectrometric techniques were used to separate and analyze the organic matter in coals. Detailed molecular structural information was obtained for the efficient and clean utilization of low-rank coals.