Ion Formation and Fragmentation of Sinapinic Acid in Electron Ionization, Liquid Secondary Ion and Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

The ion formation and fragmentation of sinapinic acid, which is a typical matrix material for matrix-assisted laser desorption/ionization (MALDI), have been investigated by using electron ionization (EI), liquid secondary ion (LSI) and MALDI methods. Collisionally activated dissociation (CAD) spectra of the molecular ions of sinapinic acid appearing in the EI and LSI mass spectra were acquired. Some differences regarding the ion formation and fragmentation of sinapinic acid between EI and LSI mass spectra were observed. It has been demonstrated that thermal decomposition of sinapinic acid occurred under EI conditions but not under LSI conditions. The ion formation and fragmentation behavior of sinapinic acid under MALDI conditions was similar to that under LSI conditions. Slight thermal decomposition of sinapinic acid under MALDI conditions was observed with higher laser power.