表面辅助激光解吸电离-飞行时间质谱中多聚体离子产生规律的研究

表面辅助激光解吸电离质谱(SALDI-MS)已经成为固态、液态样品分析的重要手段,并且分析对象逐渐由生物大分子扩展到小分子.然而,对小分子电离微观反应机理的研究仍处于起步阶段.本研究选择3种分子结构相似的稠环芳烃化合物芘、六苯并苯、红荧烯作为研究对象,考察了这3种化合物激光电离产物的差异,并研究了激光能量对六苯并苯产物离子分布的影响.结果表明,观察到芘、六苯并苯多聚体离子产物,还观测到了六苯并苯失去C2H2的碎片离子峰;而没有观测到明显的红荧烯聚合物离子产物,只观测到了大量失去C6H5的碎片离子峰.最后,对3种不同化合物的激光电离微观机理进行了分析.由于芘、六苯并苯具有平面大π键,分子间的π-π键相互作用是产生多聚体离子的主要原因;而红荧烯的空间位阻削弱了分子间相互作用,从而阻碍了多聚体离子的形成.

Investigation on Production of Cluster Ions UsingSurface-Assisted Laser Desorption/Ionization Mass Spectrometry

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.