ABSTRACT
Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has become an indispensable tool in macromolecule and small molecule analysis for solid and liquid samples.However, there were few studies focusing on the ionization mechanisms especially for the small molecules.In this work, the compounds of pyrene, coronene and rubrene which have similar molecular structures were used to investigate the ionization mechanism via SALDI-MS.Additionally the effect of the laser power on the product ions was also investigated.It was found that strong cluster ions peaks nM+(M=pyrene, coronene) were observed for pyrene and coronene, and daughter ions of coronene by loss of C2H2 were also observed.On the contrary, no cluster ion was obtained for rubrene, only daughter ions with the losses of nC6H5 (n=1, 2, 3) were acquired.Finally, the ionization mechanisms were discussed.The formation of clusters of pyrene and coronene was attributed to the interaction of π-π bands.For rubrene, the spatial barrier weakened the interaction of π-π bands because the four phenyl groups were not on the same plane of skeleton structure, thus impeding the formation of cluster ions.