Abstract
Recently, MALDI (Matrix Assisted Laser Desorption/Ionization) imaging mass spectrometry has been a powerful tool to map spatial distribution of molecules on the surface of materials. In sample preparation in MALDI imaging mass spectrometry, in principle, sample is not purified prior to the analysis, so MALDI process generates mixture of various different molecular ions. To distinguish these ions to identify unknown molecular species exist on the sample surface, ultra-high resolution and ultra-high mass accuracy is required. To achieve high spacial resolution of MALDI imaging mass spectrometry, the LASER spot size should be smaller enough. However, smaller LASER spot size also decreases the ablated material amount, causing worse overall sensitivity. To overcome such problems, we developed new microscope MALDI ion source and built-in to the commercial Q-FTICR-MS. The combination of matrix compounds which absorb UV (Ultra-Violet) light and short pulsed UV-LASER is difficult to be applied simply to plant tissue slices, in some fundamental issues. We describe our approach towards identifying and locating unknown molecular species in plat tissue slices.
