A stigmatic and microscopic imaging mass spectrometer has been developed using matrix-assisted laser
desorption/ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMG. Ion images of rhodamine 6G
masked by fine grids with pitches of 63.5, 25.4, and 12.7 μm were clearly observed in the linear mode. Separation of
stigmatic ion images according to the time-of-flight, i.e., the mass-to-charge ratio of ions was also successfully
demonstrated with a micro-dot pattern made with crystal violet and methylene blue. Stigmatic ion images of a micro-dot
pattern made with crystal violet was also observed and the ion image of the pattern was maintained after 10 cycles in
MULTUM-IMG. A section of a mouse brain stained with crystal violet and methylene blue was observed in the linear
mode, and the stigmatic total ion image of crystal violet and methylene blue was in good agreement with the optical
microphotograph of the hippocampus in the section.
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