Rapid characterization of lipids by MALDI MS. Part 2: Artifacts, ion suppression, and TLC MALDI imaging

by Lay, Jackson O., Jr.; Gidden, Jennifer; Liyanage, Rohana; Emerson, Beth; Durham, Bill

A review. Several new methods have been developed recently that allow the direct detection of lipids without resorting to derivatization or chromatog. sepn. The simplest of these is direct MALDI (matrix-assisted laser desorption/ionization) mass spectrometry. This approach is most useful for mixts. that contain minimal amts. of ion-suppressing interfering components. However, when such components are present, their effects can often be minimized by using simple sepn. techniques beforehand, such as solid phase extn. or thin layer chromatog. For example, direct MALDI has been used for rapid screening of lipids and taxonomic identification of the source organisms with no sample pretreatment. Collecting fractions from solid phase extn. cartridges have also been used to avoid the most extreme effects of ion suppression from more complex lipid mixts. More recently, direct MALDI has been applied to the anal. of TLC plates allowing the detection of TLC-sepd. lipids from the complex lipidome. Herein, we briefly describe the application of rapid MALDI MS to some typical research problems involving the characterization of lipids. In Part 1 [1] we covered bacterial taxonomy by direct anal. of intact lipids and the anal. of food oil triacylglycerols . Part 2 will address ion suppression, spontaneous fragmentation, and coupling MALDI with chromatog. The spontaneous fragmentation of protonated lipids in oils by direct MALDI produces artifactual diacylglycerol-like ions. An understanding of this process and its minimization facilitates monitoring the decompn. of lipids by direct anal. Suppression also has an impact on direct anal. of lipids, esp. when mixts. contain both polar and non-polar lipids. We demonstrate the use of solid phase extn. and thin layer chromatog. to produce fractions or substrates from complex biol. samples in which lipids can be detected by direct and rapid MALDI MS anal.

Lipid Technology
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