Illustrated Glossary of Organic Chemistry

MALDI (Matrix-Assisted Laser-Desorption/Ionization): In mass spectrometry, an ionization method in which the analyte is first suspended in a suitable matrix, then the matrix is ablated (evaporated) with a UV laser, resulting in ionization (by protonation or deprotonation) of the analyte. This "soft ionization" method causes little to no fragmentation. MALDI is often used for molecules that are difficult to vaporize by other techniques, and/or molecules that fragment readily, such as DNA and proteins.

Analyte in matrix
Protonated analyte