MALDI: A Very Useful UV Light-Induced Process…That Still Remains Quite Obscure

Abstract

The matrix-assisted laser desorption ionization (MALDI) process constitutes a complex mixture of events, involving optical and mechanical phenomena, as well as thermodynamic and physicochemical processes of phase transition and ionization. The experiment is based on irradiation of the surface of a solid sample that is a mixture of a photosensitizer material (the matrix) and analyte(s) with a short-pulse UV laser. A successful MALDI analysis involves a number of crucial steps, namely, sample preparation, UV excitation of the matrix (photosensitizer)–analyte sample and disintegration of the condensed phase, generation and separation of charges and ionization of analyte and matrix molecules, and, finally, in the analysis step, ion separation according to the mass-to-charge ratio in the mass spectrometer, and detection (Fig. 9.1).