Removal of optimal cutting temperature (O.C.T.) compound from embedded tissue for MALDI imaging of lipids

Matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) is a common molecular modality used to characterise the abundance and spatial distribution of lipids in situ. There are several technical challenges predominantly involving sample pre-treatment preparation which have complicated analysis clinical tissues by MALDI-MSI. Firstly, embedding samples optimal cutting temperature (O.C.T.), contains high concentrations polyethylene glycol (PEG) polymers, causes analyte signal suppression during (MS) competing for available ions ionisation. This suppressive effect has constrained application MALDI-MSI mapping tissues. Secondly, complexity spectra obtained formation multiple adduct ions. The process ion MALDI can generate m/z peaks from single lipid species due presence alkali salts tissues, resulting protonated generation near isobaric produce overlapping distributions. Presented method simultaneously remove O.C.T. endogenous salts. approach was applied order prevent suppression, simplify data interpretation, improve sensitivity promoting protonation reducing adducts.