Heteroatom-containing compounds in as-prepared and hydrotreated distillates produced from Tanito Harum coal were identified by the aid of gas chromatography with atomic emission detector (GC-AED) which can detect all the elements (C, H, N, S, O) contained in the molecules. Alkylated benzothiophenes and dibenzothiophenes were found to be the major sulfur compounds in the original fraction, all of them being completely removed by the hydrotreatment at 350 degreesC, 10 MPa, and 60 min. Alkylated anilines, quinoline, indoles, and carbazoles were found in the original oil as nitrogen compounds. Two specific nitrogen compounds survived through the hydrotreatment, being identified as C11H20N and C14H23N, respectively, according to the calibrated elemental ratios by GC-AED and molecular weights measured by GC-MS (mass spectrometry). Such empirical formulae were quite similar to C11H19N and C14H23N, respectively, which were detected by high MS and NMR after the concentration by extraction. Some sulfur compounds were observed in the non-aromatic fraction, while all the nitrogen compounds were completely concentrated in the aromatic fraction by the conventional column chromatographic separation. It is also noted that alkylated phenols, benzofurans and dibenzofurans were found as typical oxygen compounds in the distillate. Thus, GC-AED can identify the hetero-atom containing compounds based on the simultaneous multi-element analysis. (C) 2002 Elsevier Science Ltd. All rights reserved.