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Obtaining structural information on perfluorocarbons by mass spectrometry II ‐charge‐exchange method
Author(s) -
Huang Sunkwei
Publication year - 1989
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210241206
Subject(s) - chemistry , mass spectrometry , ion , electron ionization , ionization , mass spectrum , analytical chemistry (journal) , dissociation (chemistry) , torr , polyatomic ion , atomic physics , chromatography , physics , organic chemistry , thermodynamics
Structural and molecular ion information on perfluorocarbons (PFCs) can be obtained by charge‐exchange reactions of nitrogen or oxygen radical cations with PFCs; such information usually cannot be obtained by the electron impact or negative ion chemical ionization methods. Charge‐exchange reactions occurred when 0.5‐1.0 Torr (1 Torr as 133.3 Pa) of nitrogen, air or other gases was introduced into the chemical ionization source of a mass spectrometer, with electron energies ranging from 55 to 230 eV. Changing the repeller voltages and electron energies had little effect on the appearance of charge‐exchange mass spectra of PFCs. However, when air or nitrogen was introduced in the direction opposite to sample flow, more intense molecular ions and/or higher mass fragment ions were obtained at the cost of a small loss of sensitivity. The charge‐exchange mass spectrum of perfluoro‐1,3‐dimethyladamantane is very similar to the high‐energy collisionally induced dissociation spectrum of its molecular radical cation. This technique provides an important validation tool without the use of tandem mass spectrometry for the structure determination of PFC isomers.