Laser energy is first absorbed by the matrix rather than hitting the sample directly, avoiding excessive analyte fragmentation; the matrix also disperses the sample evenly within the crystal.
Without matrix, the laser struggles to efficiently send biomacromolecules into the gas phase, which is also the fundamental reason why matrix is needed.
The matrix-analyte co-crystal volatilizes together under laser irradiation, and the analyte desorbs accordingly; the matrix supplies protons/electrons to form stable adduct ions (e.g., [M+H]+, [M+Na]+).
Different matrices give different adduct preferences, which is one basis for matrix selection.
MALDI imaging irradiates the sample surface point by point with a laser; each pixel yields a mass spectrum, from which a molecular spatial map is reconstructed; resolution is limited by the laser spot and step size.
Compared with LDPI (laser desorption + photoionization, matrix-free), MALDI has an extra matrix-mediation step.
MALDI shows outstanding ionization efficiency for proteins, peptides, lipids, and sugars; the trade-off is that matrix peaks occupy the low-mass region and interfere with small molecules.
Understanding the principle helps in making the right division of labor among ion source types.
To obtain detailed specifications, compatible models, or a quotation for the MSI LDPI / DPI full series imaging ion sources, visit the Neo-Source official website, or contact the official team for compatibility advice tailored to your mass spectrometer (Agilent / SCIEX / Thermo and other mainstream MS).