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Does decarboxylation make 2,5‐dihydroxybenzoic acid special in matrix‐assisted laser desorption/ionization?
Author(s) -
Hsu Hsu Chen,
Lu IChung,
Lin PeiHsuan,
Dyakov Yuri A.,
Bagchi Arnab,
Lin ChihYuan,
Hung ShengWei,
Lee YuanTseh,
Ni ChiKung
Publication year - 2014
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/rcm.6885
Subject(s) - chemistry , decarboxylation , mass spectrometry , dissociation (chemistry) , photoionization , ion , ionization , electron ionization , analytical chemistry (journal) , photochemistry , mass spectrum , soft laser desorption , quadrupole mass analyzer , matrix assisted laser desorption/ionization , desorption , organic chemistry , chromatography , adsorption , catalysis
RATIONALE Among the six positional isomers of dihydroxybenzoic acid (DHB), 2,5‐DHB is a more favorable matrix for use in matrix‐assisted laser desorption/ionization (MALDI) than the other isomers because of its high ion‐generation efficiency at 337 and 355 nm. The generation of hydroquinone or p ‐benzoquinone through the decarboxylation of 2,5‐DHB has been suggested to play a crucial role in the ion‐generation efficiency of 2,5‐DHB. METHODS The mass spectra of desorbed neutrals generated from MALDI were measured using [Disp. Item 1. 2,5‐DHB+hv→2,5‐DHB+→HQ++CO2 ...] electron impact ionization (70 eV) and a quadrupole mass spectrometer and [Disp. Item 2. 2,5‐DHB→HQ+CO2 ...] vacuum ultraviolet (118 nm) photoionization and a time‐of‐flight mass spectrometer. The mass spectra of desorbed ions generated from MALDI were investigated using a time‐of‐flight mass spectrometer. The dissociation barrier height and dissociation rate of decarboxylation were calculated by an ab initio method and RRKM theory. RESULTS Decarboxylation of neutral 2,5‐DHB and 2,5‐DHB cations was not observed. Theoretical calculations indicated that decarboxylation of neutral 2,5‐DHB and 2,5‐DHB cations is too slow to occur. CONCLUSIONS The high ion‐generation efficiency of the 2,5‐DHB matrix at 337 and 355 nm is not related to decarboxylation. Copyright © 2014 John Wiley & Sons, Ltd.