Scheme 1.

Schematic representation of the workflow of SAII and typical LC-tandem MS methods. (I) Half of the brain tissue section from drug-treated mouse was scraped off from the glass slide, the other half was preserved for surface analysis. (II) From the preserved tissue section, surface SAII was performed in (A) discontinuous mode – extracting materials by solvent-droplet hanging at the pipet tip, and (B) continuous mode – extracting by liquid junction formed at the end of two pieces of silica tube. MS and MS/MS were performed in continuous mode. (C) Typical sample work-up was performed with the scraped tissue, the supernatant after vortex and centrifugation was analyzed by either LC-ESI-MS/MS²⁷ or SAII directly injection.