Date: 16:00 – 18:00, Friday, April, 21, 2023
発表者：煙山優太
Speaker：Yuta Kemuyama
タイトル : 超音波霧化装置を用いたDBDイオン化法の開発
Title : Development of ultrasonic extraction system for DBD ion source
有機質量分析法は得られた質量スペクトルから化合物の分子量を決定し、フラグメントイオンのパターンから分子の構造推定をする手法として広く用いられている。従来はマトリックス支援レーザー脱離イオン化法（MALDI）、2次イオン質量分析法（SIMS）などが用いられてきた。しかし、これらの手法は真空下で作動することから分析できる試料形態が限定されるうえ、試料の分析前処理が複雑であり、分析に長時間を要する等の問題があった。こうした背景から新しいイオン化手法としてアンビエントイオン法が注目されている。アンビエントイオン化法では液体クロマトグラフィー(LC)やレーザーアブレーション装置(LA)など多様なアプリケーションと接続可能な上に（例えばKhoo et al., 2022）、少ない試料量で前処理なしに迅速に分析できるなどの特徴がある（Takats et al., 2004, Robert et al., 2005, Na et al., 2007)として有用である。
本研究では、アンビエントイオン源であるDielectric barrier discharge (DBD)イオン源と超音波加湿器で霧化した試料を質量分析計に導入する新たな分析法の開発を目指している。本実験では前段階として新たに導入された有機質量分析計（Hclass/Xevo-G2-XS）を用いた基礎データの収集（各試料のプロトン付加分子ピーク[M+H]+）の検出確認や繰り返し再現性の評価を行っている。本発表ではその結果を報告し、今後の実験計画についても簡潔に紹介する。
Title: O-H⋯F hydrogen-bonding configurations of fluorinated hydroxides under high pressure
Name: Xuejing He
Abstract:
Fluorine (F) is supposed to be the most abundant halogen in the mantle [1]. Hydrous minerals such as the serpentine group minerals, the mica group minerals, and the humite group minerals commonly contain F, and play a crucial role in transporting F into the mantle via subduction processes (e.g. [2,3]). Fluoride ion (F-) is incorporated into hydrous minerals by substituting hydroxyls in the crystal structure, which can lead to modifications of physicochemical properties such as the crystal structure, the compressional properties, the electric conductivity, and in particular the formation of the O-HF hydrogen bond. The stability of hydroxyls in the mineral structure under high pressure and high temperature is strongly related to large-scale geological processes, such as slab dehydration, rock melting, and subduction earthquakes (e.g. [4]). Therefore, the investigation on the O-HF hydrogen-bonding configuration under high pressure and high temperature is a fundamental issue in geochemistry.
Hydrogen bonds are a pervasive intermolecular interaction resulting from the directional attractive force between a hydrogen atom covalently bonded to an electronegative atom (e.g. O, F, N, or C), i.e., the proton donor, and a neighboring electronegative atom or group, i.e., the proton acceptor. Halogens (F, Cl, Br, and I) are commonly found as hydrogen-bond acceptors. In particular, F- is the strongest acceptor group second only to OH- [5], which can form strong hydrogen-bonding interactions such as [F-H-F]-. Pressure is a variable which can modify the hydrogen-bonding geometry, and would further affect the compound’s physicochemical properties. In previous studies, systematic investigations have been performed under varying pressure and/or temperature on the O-HO hydrogen-bonded systems. But there is limited knowledge about the pressure/temperature dependence of the properties of the O-HX halogen hydrogen bond (specifically O-HF).
Herein I focus on studying the O-H(D)⋯F hydrogen-bonding configuration in fluorinated hydroxides under high pressure. Magnesium hydroxyfluoride, Mg(OH)F and Mg(OD)F (Pnma, Z = 4), with the -AlOOH diaspore-type structure and F-doped brucite, Mg(OH,F)2 and Mg(OD,F)2 (P3m1, Z = 1), have been chosen as the subjects of research. Combined in-situ high-pressure experimental methods of structural analysis (synchrotron radiation X-ray diffraction and neutron diffraction) and spectroscopic measurements (FTIR and Raman spectroscopy) were utilized to characterize the O-H(D)⋯F hydrogen-bonding geometries and vibrational properties. The studies are aimed at providing knowledge about the high-pressure configuration of the O-H(D)⋯F hydrogen bond in solid hydroxides with archetype structures, which would pave the way for future investigations on F-bearing hydrous minerals and phases with more complex structures.
References: [1] McDonough W. F., Sun S.-s. (1995) Chem. Geol., 120: 223-253. [2] Gasparik T. (1993) J. Geophys. Res., 98(B3): 4287-4299. [3] Pagé L., Hattori K. (2019) Minerals., 9: 61. [4] Peacock S.M., Hyndman R.D. (1999) Geophys. Res. Lett., 26(16): 2517-2520. [5] Lutz H.D., et al. (1994) J. Mol. Struct., 322: 263-266.