IR-MALDI Mass Spectrometry Imaging with Plasma Post-Ionization of Nonpolar Metabolites.

Ambient mass spectrometry imaging (MSI) methods come with the advantage of visualizing biomolecules from tissues with no or minimal sample preparation and operation under atmospheric-pressure conditions. Similar to all other MSI methodologies, however, ambient MSI modalities suffer from a pronounced bias toward either polar or nonpolar analytes due to the underlying desorption and ionization mechanisms of the ion source. In this study, we present the design, construction, testing, and application of an in-capillary dielectric barrier discharge (DBD) module for post-ionization of neutrals desorbed by an ambient infrared matrix-assisted laser desorption/ionization (IR-MALDI) MSI source.