MALDITOFmassaspectrometrie

MALDI-TOF mass spectrometry, or MALDI-TOF MS, is an analytical technique that combines matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry to determine the mass-to-charge ratios of molecules. The method is widely used for large biomolecules because the matrix absorbs laser energy and helps ionize the sample with minimal fragmentation, often producing predominantly singly charged ions and a broad, high mass range.

In a typical MALDI-TOF experiment, the analyte is co-crystallized with an ultraviolet-absorbing matrix on a metal plate. A pulsed laser desorbs and ionizes the sample; the resulting ions are accelerated in a near-vacuum tube, and their flight times to a detector are measured. The time of flight is proportional to the square root of the mass-to-charge ratio, producing a mass spectrum that serves as a molecular fingerprint. Instruments can operate in linear mode for broad mass ranges or reflectron mode for higher resolution. Tandem MS experiments can be added for structural information.

Applications of MALDI-TOF MS are diverse. In clinical microbiology, it enables rapid identification of bacteria and fungi by comparing spectral fingerprints to reference databases, often within minutes from a colony. In proteomics, it is used for analyzing intact proteins, peptides, and post-translational modifications, while MALDI is also employed in polymer, lipid, and metabolite analysis. The technique offers high throughput, minimal sample preparation, and robustness to some sample impurities, but performance depends on sample quality and database availability.

Limitations include reliance on comprehensive reference spectra, potential matrix-related artifacts, and challenges with small, highly polar, or isomeric compounds. Quantitation is less straightforward than with some other MS methods, and complex mixtures may require complementary techniques.