Hiraoka Kenzo, Usmanov Dilshadbek T, Akhmedov Sherzod M, Rankin-Turner Stephanie, Ninomiya Satoshi
Clean Energy Research Center, University of Yamanashi, Kofu, Yamanashi, Japan.
Institute of ion-Plasma and Laser Technologies, Tashkent, Uzbekistan.
Rapid Commun Mass Spectrom. 2025 Apr 30;39(12):e10029. doi: 10.1002/rcm.10029.
The objective of the present study is to investigate the ionization mechanisms for atmospheric pressure surface ionization (APSI).
APSI of carbaryl, papaverine, cocaine, morphine, and triethylamine using heated surface-oxidized metal filaments of W, Re, Pd, Mo, Ti, and SUS304 were measured by mass spectrometry. Low-volatility analytes dissolved in methanol were desorbed by Leidenfrost phenomenon-assisted thermal desorption and introduced to the heated metal filament used as an emitter. Alkylamine benzene solutions were simply placed 10 mm below the filament.
Carbaryl, papaverine, cocaine, and morphine (M) gave protonated molecules [M+H] with little fragment ions. Triethylamine (TEA) gave both [TEA+H] and [TEA-H].
Because [M+H] was detected with little [M-H], which is usually detected as a major ion by vacuum surface ionization (VSI), it was concluded that [M+H] is formed by the proton transfer reaction between the protonated filament surface and the gas-phase analyte molecules approaching the solid surface. Namely, the heated metal filament acts as a Brønsted acid. This idea is supported by the APSI for TEA.
本研究的目的是探究大气压表面电离（APSI）的电离机制。
使用W、Re、Pd、Mo、Ti和SUS304的加热表面氧化金属丝对西维因、罂粟碱、可卡因、吗啡和三乙胺进行大气压表面电离，并通过质谱法进行测量。溶解在甲醇中的低挥发性分析物通过莱顿弗罗斯特现象辅助热脱附进行解吸，并引入用作发射器的加热金属丝。烷基胺苯溶液简单地放置在金属丝下方10毫米处。
西维因、罂粟碱、可卡因和吗啡（M）产生了带少量碎片离子的质子化分子[M+H]。三乙胺（TEA）产生了[TEA+H]和[TEA-H]。
由于检测到的[M+H]很少有[M-H]（在真空表面电离（VSI）中通常将[M-H]检测为主要离子），因此得出结论，[M+H]是由质子化的金属丝表面与接近固体表面的气相分析物分子之间的质子转移反应形成的。也就是说，加热的金属丝起到了布朗斯特酸的作用。三乙胺的大气压表面电离支持了这一观点。
