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-derive d products was investigated. The pentane insoluble (PI) fractions of l iquefaction extracts from maceral concentrates of two UK coals (Linby and Cortonwood), prepared in a low-residence time (less than 10s) flow ing-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 mass es 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 molecula r masses. The phenolic, basic nitrogen and aromatic fractions of the h ydropyrolysis tar indicated ionization up to molecular mass limits bet ween 1500 and 2000 Da. Comparison of these results with size exclusion chromatography (s.e.c.) showed agreement with results for the hydropy rolysis tar fractions; however, the presence of molecular masses in ex cess of 10 000 Da was indicated by s.e.c. for the liquefaction extract PI-fractions. Not all problems associated with vaporization, ionizati on and detection of high molecular mass materials in f.a.b.-m.s. appea r to have been solved, with the choice (polarity) and preparation of m atrices for sample mounting remaining an empirical procedure.