Experimental An acrylic plate with a thickness of 1 mm was used as the nonconductive substrate. Polypropylene glycol (PPG, MW 1000) was used for SpiralTOF and TOF-TOF analyses. PPG 1000 was dissolved in water to 1 mg / mL. Matrix compound α-CHCA and cationization agent NaI were dissolved in methanol at concentrations of 10 mg / mL and 1 mg / mL, respectively. Equal amounts of PPG 1000 solution, matrix solution and cationization agent solution were mixed and then 1 μL was spotted on the acrylic plate and air-dried. For the MS imaging measurement, a red permanent ink was used as the sample, and the letters 'MS' were written on the acrylic plate. No matrix compound was applied because rhodamine, a major component of the red permanent ink, can be ionized without using a matrix. After the samples were applied, each surface of the acrylic plate was coated with gold by vapor deposition. Afterwards, the acrylic plate was affixed with conductive tape to a special stainless steel plate that was dug down 1 mm from the normal plate surface position. The target plate was then directly introduced into the JMS-S3000 'SpiralTOFTM” for MS analysis.