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The Matrix Suppression Effect and Ionization Mechanisms in Matrix‐assisted Laser Desorption/Ionization
Author(s) -
Knochenmuss Richard,
Dubois Frédéric,
Dale Michael J.,
Zenobi Renato
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19960610)10:8<871::aid-rcm559>3.0.co;2-r
Subject(s) - chemistry , ionization , soft laser desorption , excited state , desorption , matrix assisted laser desorption/ionization , ion , matrix (chemical analysis) , analyte , matrix assisted laser desorption electrospray ionization , mass spectrometry , adduct , mass spectrum , atmospheric pressure laser ionization , polyatomic ion , analytical chemistry (journal) , photoionization , atomic physics , electron ionization , chromatography , organic chemistry , physics , adsorption
At appropriate matrix:analyte mixing ratios, small to moderate sized analyte ions (1000–20 000 u) can fully suppress positively charged matrix ions in matrix‐assisted laser desorption/ionization (MALDI) mass spectra. This is true for all matrix species, including radical cations and adducts with protons or alkali‐metal ions. Full matrix suppression is also observed, regardless of the preferred analyte ion form, be it protonated or an alkali adduct. These facts lead us to propose a mechanism for prompt, primary (not secondary gas‐phase) MALDI ionization in which excited matrix molecules are the key species. At least two such excited molecules are believed to be necessary for free ion generation. This model is found to be consistent with the available data, as well as making several predictions which are confirmed by new observations. The model also predicts that the matrix suppression effect will not be observable with heavy analytes because their large excluded volume precludes desorption at the necessary mixing ratios.