Riebe Daniel, Erler Alexander, Ritschel Thomas, Beitz Toralf, Löhmannsröben Hans-Gerd, Beil Andreas, Blaschke Michael, Ludwig Thomas
Physical Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, Potsdam, Germany.
Bruker Daltonik, Permoserstrasse 15, Leipzig, Germany.
J Mass Spectrom. 2016 Aug;51(8):566-577. doi: 10.1002/jms.3784.
A promising replacement for the radioactive sources commonly encountered in ion mobility spectrometers is a miniaturized, energy-efficient photoionization source that produce the reactant ions via soft X-radiation (2.8 keV). In order to successfully apply the photoionization source, it is imperative to know the spectrum of reactant ions and the subsequent ionization reactions leading to the detection of analytes. To that end, an ionization chamber based on the photoionization source that reproduces the ionization processes in the ion mobility spectrometer and facilitates efficient transfer of the product ions into a mass spectrometer was developed. Photoionization of pure gasses and gas mixtures containing air, N , CO and N O and the dopant CH Cl is discussed. The main product ions of photoionization are identified and compared with the spectrum of reactant ions formed by radioactive and corona discharge sources on the basis of literature data. The results suggest that photoionization by soft X-radiation in the negative mode is more selective than the other sources. In air, adduct ions of O with H O and CO were exclusively detected. Traces of CO impact the formation of adduct ions of O and Cl (upon addition of dopant) and are capable of suppressing them almost completely at high CO concentrations. Additionally, the ionization products of four alkyl nitrates (ethylene glycol dinitrate, nitroglycerin, erythritol tetranitrate and pentaerythritol tetranitrate) formed by atmospheric pressure chemical ionization induced by X-ray photoionization in different gasses (air, N and N O) and dopants (CH Cl , C H Br and CH I) are investigated. The experimental studies are complemented by density functional theory calculations of the most important adduct ions of the alkyl nitrates (M) used for their spectrometric identification. In addition to the adduct ions [M + NO ] and [M + Cl] , adduct ions such as [M + N O ] , [M + Br] and [M + I] were detected, and their gas-phase structures and energetics are investigated by density functional theory calculations. Copyright © 2016 John Wiley & Sons, Ltd.
离子迁移谱仪中常见的放射性源有一个很有前景的替代物，即一种小型化、节能的光电离源，它通过软X射线（2.8 keV）产生反应离子。为了成功应用光电离源，必须了解反应离子的光谱以及导致分析物检测的后续电离反应。为此，开发了一种基于光电离源的电离室，该电离室可重现离子迁移谱仪中的电离过程，并有助于将产物离子高效转移到质谱仪中。文中讨论了纯气体以及含有空气、N₂、CO₂和N₂O以及掺杂剂CH₂Cl的气体混合物的光电离。根据文献数据，确定了光电离的主要产物离子，并与放射性和电晕放电源形成的反应离子光谱进行了比较。结果表明，负模式下软X射线的光电离比其他源更具选择性。在空气中，仅检测到O₂与H₂O和CO₂的加合离子。痕量的CO₂会影响O₂和Cl（加入掺杂剂后）加合离子的形成，并且在高CO₂浓度下几乎能完全抑制它们。此外，还研究了在不同气体（空气、N₂和N₂O）和掺杂剂（CH₂Cl₂、C₂H₅Br和CH₃I）中，由X射线光电离诱导的大气压化学电离形成的四种烷基硝酸盐（乙二醇二硝酸酯、硝化甘油、赤藓醇四硝酸酯和季戊四醇四硝酸酯）的电离产物。通过对用于烷基硝酸盐光谱鉴定的最重要加合离子（M）进行密度泛函理论计算，对实验研究进行了补充。除了加合离子[M + NO₂]和[M + Cl]外，还检测到了[M + N₂O₄]、[M + Br]和[M + I]等加合离子，并通过密度泛函理论计算研究了它们的气相结构和能量。版权所有© 2016约翰威立父子有限公司。
