Characterization of Coal-Derived Materials by Laser Desorption Mass Spectrometry

Laser desorption time-of-flight mass spectrometry (LD/TOF MS) is used to characterize complex mixtures of large molecules derived from coals and separated coal macerals. Three groups of macerals, namely liptinite, vitrinite, and inertinite from Argonne Premium Coal Sample 7 were separated by a density gradient technique and subjected to small scale liquefaction. Samples of the maceral products were exposed to laser pulses from a XeCl-Excimer laser or the fourth harmonic output of a Nd:YAG laser. The general features of this method are the virtual absence of ion signal below m/z 100, a distribution of masses from m/z 200 to beyond m/z 1000 and reduced mass fragmentation in contrast to EI and FAB, where much fragmentation is present below m/z 200.