Journal of the Mass Spectrometry Society of Japan
Online ISSN : 1880-4225
Print ISSN : 1340-8097
ISSN-L : 1340-8097
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Volume 62, Issue 3
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  • Formation of Ammonium Ion Adduct Molecules in Positive Direct Analysis in Real Time (DART) Ionization Mass Spectrometry
    Natsuhiko SUGIMURA, Asami FURUYA, Takahiro YATSU, Toshimichi SHIBUE
    2014 Volume 62 Issue 3 Pages 25-27
    Published: June 01, 2014
    Released on J-STAGE: June 24, 2014
    DOIhttps://doi.org/10.5702/massspec.14-56
    JOURNAL FREE ACCESS
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    Ammonium ion adduct molecules [M+NH4]+ that are produced in positive Direct Analysis in Real Time (DART) ionization mass spectrometry were examined using a selected set of compounds. The [M+NH4]+/[M+H]+ relative intensity ratio was dependent on the proton affinity (PA) of the compounds and ammonia (PA 846 kJ/mol). Ar-DART mass spectra of acetophenone (PA 850 kJ/mol) showed [M+D]+ and [M+ND4]+ ions. This observation suggests that hydrogen-bonded complexes between an ammonium ion ND4+ and an acetophenone molecule M initially formed an excited complex [M****D****ND3]+*, after which, some of the complexes then collapsed into [M+D]+. These results indicate that the mechanism responsible for the formation of [M+NH4]+ ion under ammonia chemical ionization and DART ionization is similar irrespectively of the compound under investigation.
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