Matrix-Assisted Laser Desorption Ionization Imaging Mass Spectrometry of Drug Distribution in Mouse Brain Tissue by High-Resolution Time-of-Flight Mass Spectrometry

: Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry provides the opportunity to visualize the distributions of drugs and metabolites in tissue specimens without requiring radioisotopes, as are used for whole-body autoradiography. However, the analysis of low-molecular-weight compounds is often difficult using the common reflectron-type MALDI time-of-flight mass spectrometers. Insufficient mass resolving power causes overlapping of the target drug peak with matrix compound or surface contaminant peaks. To solve this issue, we describe the procedure for imaging mass spectrometry using a high-mass-resolution mass spectrometer that can separate isobaric peaks.