Ethanol-soluble portion (ESP) from Zhaotong lignite ethanolysis at 305 degrees C was analyzed with a positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). The range of molecular mass distribution is from m/z 100 to 600 with the center around m/z 330. Assignment of molecular formulae reveals that the main nitrogen-containing species with relative content of 86.4% are most probably basic nitrogen compounds (BNCs) ionized during ESI in positive-ion mode. The BNCs are N1Ox (x = 0-5) and N2Oy (y = 0-2) with 0-14 double bond equivalent (DBE) values and 9-39 carbon numbers. According to DBE distributions, pyridines and quinolines should be predominant BNCs in the ESP. In addition, amines (DBE < 4) were also identified in the ESP. The average DBE values are 6-8 for N1Ox class species and 7 and 8 for N2Ox class species, indicating that pyridines (or quinolones) and quinolines with an amino group are characteristic structures for N1Ox and N2Ox classes, respectively. Positive-ion ESI FT-ICR MS proved to be a powerful tool for identifying BNCs in coal-derived liquids. (C) 2014 Elsevier Ltd. All rights reserved.