Generation of ion-bound solvent clusters as reactant ions in dopant-assisted APPI and APLI.
Anal Bioanal Chem
; 405(22): 6933-51, 2013 Sep.
Article
em En
| MEDLINE
| ID: mdl-23828208
ABSTRACT
We provide experimental and theoretical evidence that the primary ionization process in the dopant-assisted varieties of the atmospheric pressure ionization methods atmospheric pressure photoionization and atmospheric pressure laser ionization in typical liquid chromatography-mass spectrometry settings is--as suggested in the literature--dopant radical cation formation. However, instead of direct dopant radical cation-analyte interaction--the broadly accepted subsequent step in the reaction cascade leading to protonated analyte molecules--rapid thermal equilibration with ion source background water or liquid chromatography solvents through dopant ion-molecule cluster formation occurs. Fast intracluster chemistry then leads to almost instantaneous proton-bound water/solvent cluster generation. These clusters interact either directly with analytes by ligand switching or association reactions, respectively, or further downstream in the intermediate-pressure regions in the ion transfer stages of the mass spectrometer via electrical-field-driven collisional decomposition reactions finally leading to the predominantly observed bare protonated analyte molecules [M + H](+).
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MEDLINE
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En
Ano de publicação:
2013
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Article