磷脂液相二次离子质谱分析中的分子离子簇

对3种极性头不同的磷脂DMPG、DMPC、DMPE的液相二次离子质谱分析中出现 的分子离子簇现象进行了系统的研究。结果表明，虽然分子离子簇的形成与许多因素有关， 如PH值、离子强度等，但起决定作用的是样品在底物中的浓度，浓度增大有利于分子离子簇 的形成。研究还发现，由不同种类磷脂分子形成的分子离子簇峰明显高于由同种磷脂分子所 形成的分子离子簇峰，指出异种磷脂分子间的簇离子形成能力高于同种磷脂分子。此外还讨 论了磷脂分子在离子源条件下的稳定性、裂解规律及相互作用等。结果表明，本实验所选用 的磷脂分子在LSIMS条件下是稳定的，均能得到较强的分子离子峰，其主要碎片峰是磷酰键断裂而产生的碎片离子峰。

Molecule-ion Cluster Formed in the Liquid Secondary Ion Mass Spectrometric Analysis of Phospholipids

In this paper the formation of molecule-ion clusters in the liquid secondary ion mass spectrometric analysis of phospholipids DMPG, DMPC and DMPE has been studied systematically. The results showed that although this formation is related with many fac- tors, such as pH, ionic strength, etc, but it depends mainly upon the concentration of phos- pholipids in the matrix. The extent of the molecule-ion cluster formation increases with the increase of the concentration of phospholipid. It has also been found that the peaks corre- sponding to the clusters formed by different kinds of phospholipid molecules are more intense than those formed by the same kind of phospholipid molecules, implying that the molecular cohesive force between different molecular species is stronger than that between the same molecular species. Beside this, the stability in the ion source conditions, fragmentation and interaction of the phospholipids have also been studied. The phospholipids examined in this paper are stable in the LSIMS conditions and all give intense molecular ion'peaks. The domi- nant fragment peak is the peak resulting from the cleavages around the phosphate groups.