Negative Ion Mass Spectra of Organic Nitriles

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

Applied Spectroscopy ◽

10.1366/000370278774331125 ◽

1978 ◽

Vol 32 (4) ◽

pp. 388-399 ◽

Cited By ~ 38

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.

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Studies on the positive-ion mass spectra from atmospheric pressure chemical ionization of gases and solvents used in liquid chromatography and direct liquid injection

Journal of the American Society for Mass Spectrometry ◽

10.1016/s1044-0305(03)00786-4 ◽

2004 ◽

Author(s):

B Kolakowski

Keyword(s):

Liquid Chromatography ◽

Atmospheric Pressure ◽

Mass Spectra ◽

Chemical Ionization ◽

Atmospheric Pressure Chemical Ionization ◽

Liquid Injection ◽

Pressure Chemical Ionization ◽

Pressure Chemical ◽

Direct Liquid Injection ◽

Positive Ion

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Discrimination of structural isomers of amphetamine using carbon dioxide negative-ion chemical ionization mass spectrometry

Spectroscopy An International Journal ◽

10.1155/1997/521216 ◽

1997 ◽

Vol 13 (2) ◽

pp. 151-161 ◽

Cited By ~ 1

Author(s):

Kevin B. Thurbide ◽

C. M. Elson ◽

P. G. Sim

Keyword(s):

Carbon Dioxide ◽

Mass Spectra ◽

Chemical Ionization ◽

Negative Ion ◽

Ionization Mass ◽

Structural Isomers ◽

Mass Spectral ◽

Negative Ion Chemical Ionization ◽

Spectral Behaviour ◽

Carbon Dioxide Plasma

The negative‒ion chemical ionization mass spectra of a group of structural isomers of amphetamine have been studied using carbon dioxide as the reagent gas. Characteristic and reproducible differences are observed for each member of the set implying that this technique offers a means of distinguishing among groups of amphetamine isomers. Characteristic adducts to the molecular ion are observed in the form (M–[H]+[O]) and (M–[H]+[CO2]). Descriptions of some fragments are given based on the mass spectral behaviour of a set of analogue compounds and the results of oxygen-18 labelled carbon dioxide reagent gas experiments. Contents of the carbon dioxide plasma and their impact on various analytes is also discussed.

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