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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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Bush et al. (1981) studied this question.
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