Enhancement of Lipid Signals in Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry with Ammonium Fluoride as a Matrix Additive

Lipids are essential macromolecules
that play a crucial
role in
numerous biological events. Lipids are structurally diverse which
allows them to fulfill multiple functional roles. Matrix-assisted
laser desorption/ionization mass spectrometry imaging (MALDI-MSI)
is a powerful tool to understand the spatial localization of lipids
within biological systems. Herein, we report the use of ammonium fluoride
(NH4F) as a comatrix additive to enhance lipid detection
in biological samples, with a signal increase of up to 200%. Emphasis
was placed on anionic lipid enhancement with negative polarity measurements,
with some preliminary work on cationic lipids detailed. We observed
lipid signal enhancement of [M–H]− ions with
the addition of NH4F additive attributed to a proton transfer
reaction in several different lipid classes. Overall, our study demonstrates
that the use of the NH4F comatrix additive substantially
improves sensitivity for lipid detection in a MALDI system and is
capable of being applied to a variety of different applications.