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Characterization of the atmospheric pressure ionization mass spectrometric process obtained using a fused‐silica emitter with the high voltage applied upstream
Author(s) -
Sjöberg Per J. R.,
Nyholm Leif,
Markides Karin E.
Publication year - 2000
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(200003)35:3<330::aid-jms939>3.0.co;2-2
Subject(s) - chemistry , analytical chemistry (journal) , corona discharge , ionization , electrospray ionization , atmospheric pressure , ion source , atmospheric pressure chemical ionization , ion , chemical ionization , mass spectrometry , chromatography , organic chemistry , electrode , oceanography , geology
The atmospheric pressure ionization process obtained when a mixture of methanol and water (90 : 10, v/v) also containing 50 µ M sodium hydroxide is dispersed from a fused‐silica emitter was studied. A combination of a high electric field and a nebulizer gas with the high voltage applied upstream in the liquid flow was utilized to facilitate the spray process. By comparing the dependences of the spray current and ion signals on the spray potential, it was found that electrical corona discharges were obtained for potentials higher than about 2.6 k V, which resulted in a mixed electrospray and chemical ionization process. By introducing vapour from a solvent, such as benzene or toluene, with a low ionization energy into the nebulizing gas, it was found that the appearance of the corresponding molecular ion was correlated with a change in the slope of the spray current–potential curve. This indicates that the breakpoints in the spray current–potential curves observed were correlated with the onsets of corona discharges. It was shown that the mixed ionization process gives rise to increased amounts of protonated solvent molecules and assists in the formation of sodiated adduct ions from an uncharged fatty acid methyl ester. Copyright © 2000 John Wiley & Sons, Ltd.