Matrix-Assisted Laser Desorption/Ionization (MALDI) is a soft ionization technique used in Mass Spectrometry to analyze larger molecules, which are either non-volatile or thermally unstable. This technique allows for identification and spatial distribution studies of biomolecules (e.g. DNA, proteins, peptides and sugars) and large synthetic organic molecules (e.g. polymers, dendrimers and other macromolecules).

MALDI is a unique technique allowing for desorption and ionization of entire molecules, unlike more conventional ionization techniques, which often lead to substantial fragmentation of the species of interest. Initially, the sample is mixed with a selected matrix, such α-cyano-4-hydroxycinnamic acid, and deposited on a target plate. This plate is bombarded by photons from a pulsed laser, resulting in the desorption and ionization of the matrix. Subsequently, the energy is transferred from the matrix to the sample molecules. This gentle energy transfer process leaves the sample molecules intact, but now in the gas phase, yielding protonated/ cationized or deprotonated/anionized molecular ions.