Development of a novel stigmatic imaging mass spectrometer using laser ionization and a multi-turn time-of-flight mass spectrometer

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 ma de 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 crysta l 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. Keywords: imaging mass spectrometry, matrix-assisted laser desorption/ionization, multi-turn time-of-flight mass spectrometer, delay-line detector, mid-infrared tunable laser