Maldi Mass Spectrometer (Maldi MS)

Matrix-assisted laser desorption/ionization (MALDI) is a so-called “soft” ionization technique that has found widespread use in biological mass spectrometry. Soft ionization techniques enable the ionization of large biological molecules (such as proteins) without fragmenting them, meaning they can be analyzed intact. In the case of MALDI MS, the molecules to be analyzed (for instance, a collection of tryptic peptides) are mixed with an organic compound called a matrix, spotted and dried (crystallized) on the surface of a metal target plate. Upon irradiation with laser light, the matrix absorbs the energy and converts it to heat, which then causes the sample to ionize and explode off the plate into the mass analyzer. Though most often associated with time-of-flight (TOF) mass analyzers, MALDI sources can be coupled to other types of analyzer as well, including triple quadrupoles. Whatever the configuration, MALDI mass spectrometers have the advantage that, because the sample is archived on a plate, it can be analyzed and reanalyzed at leisure.