Here we report the development and
optimization of a mass spectrometry
imaging (MSI) platform that combines an atmospheric-pressure matrix-assisted
laser desorption/ionization platform with plasma postionization (AP-MALDI-PPI)
and trapped ion mobility spectrometry (TIMS). We discuss optimal parameters
for operating the source, characterize the behavior of a variety of
lipid classes in positive- and negative-ion modes, and explore the
capabilities for lipid imaging using murine brain tissue. The instrument
generates high signal-to-noise for numerous lipid species, with mass
spectra sharing many similarities to those obtained using laser postionization
(MALDI-2). The system is especially well suited for detecting lipids
such as phosphatidylethanolamine (PE), as well as numerous sphingolipid
classes and glycerolipids. For the first time, the coupling of plasma-based
postionization with ion mobility is presented, and we show the value
of ion mobility for the resolution and identification of species within
rich spectra that contain numerous isobaric/isomeric signals that
are not resolved in the m/z dimension
alone, including isomeric PE and demethylated phosphatidylcholine
lipids produced by in-source fragmentation. The reported instrument
provides a powerful and user-friendly approach for MSI of lipids.
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