COMPARISON OF FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY AND SIZE-EXCLUSION CHROMATOGRAPHY IN DEFINING HIGH-MOLECULAR MASSES IN COAL-DERIVED MATERIALS

The detection by fast atom bombardment mass spectrometry (f.a.b.-m.s.) of high molecular mass (greater than 1000 Da) material in coal-derived products was investigated. The pentane insoluble (PI) fractions of liquefaction extracts from maceral concentrates of two UK coals (Linby and Cortonwood), prepared in a low-residence time (less than 10s) flowing-solvent reactor and fractions of hydropyrolysis tar prepared in a hot-rod reactor at 500-degrees-C were examined. F.a.b.-m.s. spectra of the Cortonwood liptinite concentrate liquefaction extract PI-fraction mounted in a thiodiethanol matrix indicated ions up to molecular masses of about 4000 Da. This appears to be the highest reported molecular mass identified by fast atom bombardment in a coal-derived material. Other liquefaction extract PI-fractions showed somewhat lower molecular masses. The phenolic, basic nitrogen and aromatic fractions of the hydropyrolysis tar indicated ionization up to molecular mass limits between 1500 and 2000 Da. Comparison of these results with size exclusion chromatography (s.e.c.) showed agreement with results for the hydropyrolysis tar fractions; however, the presence of molecular masses in excess of 10 000 Da was indicated by s.e.c. for the liquefaction extract PI-fractions. Not all problems associated with vaporization, ionization and detection of high molecular mass materials in f.a.b.-m.s. appear to have been solved, with the choice (polarity) and preparation of matrices for sample mounting remaining an empirical procedure.