MALDI is an ionization technique in which a chemical matrix is mixed with a sample and allowed to dry into a co-crystalline structure. A laser is fired at spots of the co-crystal where the absorbed energy ionizes the sample components and releases them for detection. MALDI is used for ionization of larger molecular weight compounds especially peptides, proteins, and oligosaccharides.
Mass detection by time of flight is more accurate than that of other mass spectrometer detectors and has a large detection range, commonly 50-150,000 Da. For this reason, it is often paired with MALDI for the detection of complex bio-molecules. Time of flight determines mass by measuring the time it takes for the ionized molecule to travel from the sample plate through a vacuum tube to the detector.