Comparing differentiation of xylene isomers by electronic ionization, chemical ionization and self-ion/molecule reactions and the first observation of methyne addition ions for xylene isomers in self-ion/molecule reactions for non-nitrogenated compounds

2003 ◽  
Vol 17 (21) ◽  
pp. 2399-2406 ◽  
Author(s):  
Hui-Fen Wu ◽  
Wen-Feng Wu
Keyword(s):  
Chemical Ionization ◽  
Ion Molecule Reactions ◽  
Xylene Isomers ◽  
Electronic Ionization

Comparison of Five Ionization Methods for Producing Mass Spectra of Typical Organophosphorus Pesticides

1978 ◽  
Vol 32 (4) ◽  
pp. 388-399 ◽  
Author(s):  
Kenneth L. Busch ◽  
Maurice M. Bursey ◽  
J. Ronald Hass ◽  
G. Wayne Sovocool
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Organophosphorus Pesticides ◽  
Large Fraction ◽  
Negative Ion ◽  
Oxygen Mixture ◽  
Ion Molecule Reactions ◽  
And Migration ◽  
Positive Chemical Ionization

Positive ion mass spectra obtained by conventional electron impact and by methane chemical ionization were compared with the negative ion mass spectra of 16 typical organophosphorus pesticides using methane, a methane-oxygen mixture, and oxygen as enhancement/reagent gases. In the negative ion spectra, phosphate and phenate anions typically carry a large fraction of the ion current. Displacement of chlorine by oxygen is noted in some cases, and migration of aryl groups from oxygen to sulfur is occasionally noted. Ion-molecule reactions between two species derived from sample molecules have been observed. The sensitivity of the negative ion techniques for the pesticides examined is greater than conventional electron impact or methane positive chemical ionization techniques, and can be up to 800 times more sensitive for some compounds.

Negative Ion Mass Spectra of Organic Nitriles

1981 ◽  
Vol 35 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Kenneth L. Bush ◽  
Carol E. Parker ◽  
Donald J. Harvan ◽  
Maurice M. Bursey ◽  
J. Ronald Hass
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Detection Limits ◽  
Negative Ion ◽  
Ionization Source ◽  
Ion Molecule Reactions ◽  
Residual Oxygen ◽  
Chemical Ionization Source ◽  
Positive Ion

Negative ion mass spectra organic nitriles have been determined using 1 Torr of methane moderator/reagent gas in a chemical ionization source. The spectra contain abundant (M – 1)− ions, and fragmentations are minimal. Ion/molecule reactions with residual oxygen, methane, and between sample molecules and ions form diverse products with low abundances relative to the ( M – 1)−. Detection limits are comparable with positive ion methods, and for selected compounds, can be several orders of magnitude lower.

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