Characterization of nitrogen- and oxygen-containing species in methanol-extractable portion from Xinghe lignite

Abstract Xinghe lignite was sequentially extracted with petroleum ether, carbon disulfide, methanol, acetone, and isometric carbon disulfide/acetone mixed solvent to afford extracts 1–5 (E 1 –E 5 ) and final residue. According to analysis with positive- and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), a series of nitrogen-containing species (NCSs) and oxygen-containing species (OCSs) were identified in E 3 . The ESI FT-ICR MS resolved ca. 3300 basic and 1300 non-basic compounds, which both have molecular mass distributions ranging from 100 to 700  u and dominate in 250–450  u . The predominant basic nitrogen compounds are N 1 O x and N 2 O x ( x  = 0–5) class species with double bond equivalent (DBE) values from 1 to 14 and carbon numbers (CNs) from 10 to 34. Acidic O x ( x  = 2–6) and non-basic N 1 O x ( x  = 0–2) classes are mainly detected in the negative-ion mode. According to DBE distributions and relative contents of different nitrogen/oxygen classes, pyridines and quinolines dominate the basic N 1 O x class species, while pyridines with an amino group and aliphatic amines share the characteristic core structures in basic N 2 O x class. For non-basic N 1 O x class, indoles and carbazoles may be the major nitrogen occurrences. In addition, all the NCSs in E 3 have up to 4 aromatic rings. Acidic O x class species with DBE = 1–17 and CN = 7–37 are assigned to alkanoic acids, arenepolyols, and arenoic acids, in which arenepolyols and arenoic acids are the main OCSs with up to 5 aromatic rings. Positive- and negative-ion ESI FT-ICR MS proved to be effective techniques for characterizing extractable NCSs and OCSs in coals.