著者

Ami Kageyama (Kaneshima) Akira Motoyama Mitsuo Takayama

出版者

The Mass Spectrometry Society of Japan

雑誌

Mass Spectrometry (ISSN:2187137X)

巻号頁・発行日

vol.8, no.1, pp.A0077, 2019-11-30 (Released:2019-11-30)

参考文献数

24

被引用文献数

7

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The influence of solvent composition and surface tension on the signal intensity of deprotonated molecules [M−H]− in electrospray ionization mass spectrometry (ESI MS) was evaluated using alanine (Ala), threonine (Thr) and phenylalanine (Phe), which have differing levels of hydrophobicity. The surface tension of the ESI solution was varied by changing the ratio of the organic solvents methanol (MeOH) and acetonitrile (MeCN) in water (H2O). In ESI MS, the signal intensity of all the amino acids was increased with decreasing surface tension for the two solutions, H2O/MeOH and H2O/MeCN. The use of H2O/MeCN was more favorable for achieving a strong signal for the analytes compared to H2O/MeOH. The smaller vaporization enthalpy of MeCN compared to MeOH was proposed as one of the most plausible explanation for this. The order of the signal intensity of amino acids was Phe>Thr>Ala, the same order as their hydrophobicity. It can be practically concluded that the use of solutions with lower surface tensions and lower vaporization enthalpies would result in higher signal intensities in ESI MS.

著者

Kanako Sekimoto Motoshi Sakakura Hiroshi Hike Takatomo Kawamukai Teruhisa Shiota Mitsuo Takayama

出版者

The Mass Spectrometry Society of Japan

雑誌

Mass Spectrometry (ISSN:2187137X)

巻号頁・発行日

vol.8, no.1, pp.A0075, 2019-10-25 (Released:2019-10-25)

参考文献数

36

被引用文献数

1

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Herein, a dark-current discharge state created by combining argon flow with a needle electrode in ambient air is described that has an ionization efficiency and mechanism comparable to those of conventional helium direct analysis in real time (DART), without requiring dopants and DART glow discharge. Using this method, polar compounds such as α-amino acids were ionized in the dark-current argon discharge via (de)protonation, molecular anion formation, fragmentation, (de)protonation with the attachment of oxygen, deprotonation with hydrogen loss and negative ion attachment. In contrast, nonpolar compounds (e.g., n-alkanes) were detected as positive ions via hydride abstraction and oxidation. Major background ions observed were H3O+(H2O)n, O2·+, O2·−(H2O)n and CO3·−. These results indicate that the present dark-current discharge efficiently generates resonance-state argon with an internal energy of ∼14.2 eV, higher than that of the well-known metastable state (∼11.6 eV). It is therefore suggested that ionization reactions occurring there can be attributed to the Penning ionization of atmospheric H2O and O2 by resonance-state argon, analogous to helium DART.