乙胺分子的多光子电离过程质谱研究

报道了乙胺分子在４４０～４７５ｎｍ波长范围内多光子电离（ＭＰＩ）质谱（ＭＳ）研究结果。碎片离子主要由母体离子碎裂模式产生。母体离子ＣＨ３ＣＨ２Ｎ＋·Ｈ２由经３ｓ里德堡态的（２＋２）共振多光子电离产生后，大部分发生β键断裂，形成ＣＨ２＝Ｎ＋Ｈ２离子，还有一部分再吸收一个光子，通过Ｃ－Ｈ（ＣＨ２）键的断裂产生了ＣＨ３ＣＨ＝Ｎ＋Ｈ２离子。ＣＨ３ＣＨ＝Ｎ＋Ｈ２和ＣＨ２＝Ｎ＋Ｈ２离子最容易发生的碎裂过程是脱去氢分子，分别产生Ｃ２Ｈ４Ｎ＋（分子式）离子和ＣＨ≡Ｎ＋Ｈ离子。     

Mass Spectrometry,Review of the Basics: Ionization

Abstract: Mass spectrometry (MS) has become an integral tool in life sciences. The first step in MS analysis is ion formation (ionization). Many ionization methods currently exist; electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) are the most commonly used. ESI relies on the formation of charged droplets releasing ions from the surface (ion evaporation model) or via complete solvent evaporation (charge residual model). MALDI ionization, however, is facilitated via laser energy and the use of a matrix. Despite wide use, ESI cannot efficiently ionize nonpolar compounds. Atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization (APPI) are better suited for such tasks. APPI requires photon energy and a dopant, whereas APCI is similar to chemical ionization. In 2004, ambient MS was introduced in which ionization occurs at the sample in its native form. Desorption electrospray ionization (DESI) and direct analysis in real time (DART) are the most widely used methods. In this mini-review, we provide an overview of the main ionization methods and the mechanisms of ion formation. This article is educational and intended for students/researchers who are not very familiar with MS and would like to learn the basics; it is not for MS experts.     

355nm下乙胺的多光子电离质谱研究

利用多光子电离与飞行时间质谱相结合的方法,分析了乙胺分子在355nm激光作用下的电离信号随激光强度的变化。在355nm激光作用下,随着激光强度的增加,母体离子和大质量离子的信号逐渐减弱,小质量的离子信号逐渐增强,分析了乙胺分子在355nm激光作用下的解离过程。     

大气压基体辅助激光解析离子源发展及其应用

介绍了国际上新出现的一种离子源——大气压基体辅助激光解析离子源(atmospheric pressure matrix-assisted laser desorption/ionization,AP-MALDI)。该离子源是在真空MALDI的基础上研究发展起来的,广泛应用于生物大分子及其相关领域的研究。该离子源较真空MALDI电离更加柔和,产生的碎片离子更少,又由于其工作在大气压下,可作为外接离子源方便地与各类质谱分析器联用,大大扩展了基体辅助激光解析离子源的应用范围。文章详细介绍了AP-MALDI的基本原理、结构及技术进展。此外,还对该离子源在生物高聚物分析方面的最新应用进行了介绍。     

锌掺杂半导体材料的共振电离质谱分析

本文简要地描述了激光共振电离质谱的实验装置和测量方法,给出了用共振电离质谱方法对锌掺杂化合物半导体材料进行分析的光谱和质谱图,并估计了用这种方法进行痕量分析可能达到的检测限.     

共振离子化质谱在高纯材料表面杂质分析中的应用

用激光熔出－共振离子化质谱法测定纯铁中及高纯硅片表面的铬。测定含有１０１２原子／ｃｍ２Ｃｒ的信号强度表明本方法可测定低至１０９原子／ｃｍ２的样品，其空间分辨率为０．２ｍｍ，还可进行二维杂质元素分析。     

Resonance Ionization Mass Spectrometry (RIMS) with Pulsed and CW-Lasers on Plutonium

The detection of long-lived plutonium isotopes in ultra-trace amounts by resonance ionization mass spectrometry (RIMS) is a well-established routine method. Detection limits of 10⁶ to 10⁷ atoms and precise measurements of the isotopic composition have been achieved. In this work multi-step resonance ionization of plutonium atoms has been performed with tunable lasers having very different output intensities and spectral properties. In order to compare different ways for the resonance ionization of plutonium broadband pulsed dye and titanium:sapphire lasers as well as narrow-band cw-diode and titanium:sapphire lasers have been applied for a number of efficient excitation schemes. It has been shown, that for identical excitation schemes the optical isotope selectivity can be improved by using cw-lasers (bandwidths < 10 MHz) instead of pulsed lasers (bandwidths > 2 GHz). Pulsed and cw-laser systems have been used simultaneously for resonance ionization enabling direct comparisons of pulsed and continuous ionization processes. So far, a three-step, three-color laser excitation scheme has been proven to be most practical in terms of efficiency, selectivity and laser wavelengths. Alternatively a newly discovered three-step, two-color excitation scheme which includes a strong two-photon transition from an excited state into a high-lying autoionizing state yields similar ionization efficiencies. This two-photon transition was characterized with respect to saturation behavior and line width.     

锌掺杂产导体材料的共振电离质谱分析

本文简要地描述了激光共振电离质谱的实验装置的测量方法,给出了用共振电离质谱方法对锌掺杂化合物半导体材料进行分析的光谱和质谱图,并估计了用这种方法进行奶量分析可能达到的检测限     

Resonant Laser Excitation/Ionization and Mass Spectrometry in Isotope Geochemistry and Cosmochemistry

SCOPE OF REVIEW

This paper reviews the coupling of resonant laser ionization and laserexcited fluorescence with mass spectrometry to make difficult isotopic-ratio measurements. To keep this review focused and manageable in size, it covers only metal and noble-gas isotopic analyses that find applications in isotope geochemistry and cosmochemisty. Many research groups are applying lasers and mass spectrometry to atomic, molecular, and isotopic analyses that address problems in nuclear physics [1], materials science [2-4], biology [5,6], environmental science, and other areas of geochemistry and cosmochemistry [7,8]. Several previous reviews and monographs cover the basic principles and instrumentation of resonant laser processes and mass spectrometry in more breadth [9-12]. The latest Analytical Chemistry Fundamental Reviews [13] and the published proceedings of the biannual International Symposium on Resonance Ionization Spectroscopy and Its Applications provide updates of other recent work [8]. This review does not comprehensively encompass the use of lasers for analyte sampling by desoxption, ablation, sputtering, or melting. Several other specific reviews discuss laser sampling in elemental [14,15] and stable-isotope analyses [16,17]. This review does include applications in which pulsed ion sputtering and laser desoxption atomize analytes for ionization by resonance ionization mass spectrometry (RIMS). This review also does not include isotopic-analytical methcds that use solely optical spectroscopy. The continuing development of laser and plasma technology is leading to promising spectroscopic-only methods for stable-isotope analysis [18-21].     

用共振电离质谱测定铀原子奇宇称高激发态能级

对铀原子单色和双色多光子共振电离光谱开展了深入的研究。报道了用双色三步共振光电离技术测量位于３３００３￣３４２６４ｃｍ＾－１范围内的奇宇称高激发态能级的位置。利用总角动量选择定则指定了这些能级的总角动量Ｊ值。     

Laser Ionization and Penning Trap Mass Spectrometry – A Fruitful Combination for Isomer Separation and High-precision Mass Measurements

We have demonstrated for the first time that element-selective laser ionization in combination with ultra-high resolution mass spectrometry can be used to prepare isomerically pure ion ensembles. Together with β–γ coincidence studies this method allowed a determination of the low-energy structure and the unambiguous identification of triple β-decaying isomerism in ⁷⁰Cu. By selective resonant ionization and measurement of the masses of these three states using ISOLTRAP at ISOLDE/CERN with a relative uncertainty of δm/m ≈ 5 ⋅ 10⁻⁸ a clear state-to-mass assignment was possible which resolved the assignment puzzle in ⁷⁰Cu.     

Interaction Between Cytochrome c and the Hapten 2,4-Dinitro-fluorobenzene by Electrospray Ionization Mass Spectrometry

采用电喷雾质谱、H/D交换和紫外光谱测定了半抗原2,4-二硝基氟苯和模型蛋白细胞色素c的相互作用. 电喷雾质谱结果表明,随着2,4-二硝基氟苯体积比百分含量的增加,细胞色素c的构象可以由天然的折叠构象转变为部分非折叠构象,最后转变为完全非折叠构象.细胞色素c在平衡态的H/D交换结合电喷雾质谱实验结果进一步确认了上述构象变化. 紫外光谱结果表明半抗原的加入对辅基血红素上的亚铁离子和细胞色素c上His18和Met80的强场配位作用没有明显的影响.     

用激光解吸附电离飞行时间质谱法检测悬浮土壤颗粒物

在自行研制的气溶胶飞行时间激光质谱仪(ATOFLMS)上实时探测单个悬浮土壤颗粒的粒径和化学成分。利用双束连续激光对单个粒子的空气动力学粒径进行测量,并用266 nm的Nd∶YAG激光器对气溶胶单粒子进行解吸附电离作用,产物离子通过飞行时间质谱仪的无场漂移区后完成单粒子化学成分的检测。本实验中使用了4个不同地区的土壤样本,在实验室内对分析的样本进行预处理和再悬浮,通过导管引入ATOFLMS进行测量,得到大量单粒子的粒径和质谱数据。发现在众多的单粒子的阳离子质谱中,金属成分以地壳元素(Fe, K, Al, Ca)为主,在其他阳离子质谱中包含了Mg和Na等。对悬浮土壤粒子的粒径进行实时检测的结果表明这些粒子多以粗粒子为主, 粒径主要集中在1～2 μm。实验结果表明该仪器在大气气溶胶环境监测及相关研究领域具有重要的实用价值。     

Influence Factors on Particle Growth for On-line Aerosol Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

利用自行研制的蒸发/冷凝实验装置作为基质辅助激光解吸/电离飞行时间质谱仪的特种接口,通过冷凝方式在线添加基质,冷凝管出口处的最终粒子直接引入空气动力学粒径分析仪或自行研制的飞行时间质谱仪,可对实验室产生的生物气溶胶粒子进行实时检测. 同时研究了最终粒子粒径大小的决定因素：加热池温度、初始粒子大小及其粒子数浓度及基质种类,获得了探测分析物分子离子峰所需的实验条件.     

基于模糊聚类算法的大气粒子激光电离质谱数据分析

实验室自行研制了一台大气气溶胶飞行时间激光质谱仪(ATOFLMS),它可以在线地对气溶胶单粒子进行物理和化学特性分析,利用双束连续激光对单个粒子的空气动力学粒径进行测量,并通过飞行时间完成单粒子化学成分的检测。该仪器在运行过程中将产生海量的实验数据,对这些数据的快速、自动处理并提取有价值的信息是整机系统的关键之一。文章介绍模糊聚类算法FCM(fuzzy c-means)在大气气溶胶单粒子聚类分析中的成功运用。利用该算法对连续24 h采集的室内空气气溶胶单粒子质谱数据进行了聚类分析,在得到的5个聚类结果中包含了无机的海盐粒子、矿物质粒子以及其他的三种二次气溶胶成分粒子类型。在对室内空气气溶胶粒子的粒径进行实时检测的结果表明室内可吸入颗粒物以细粒子为主,其中大于1 μm的粒子所占比重较小。小于1 μm的粒子均占95％以上, 在0.4～0.8 μm之间的粒子占据主要部分。     

Imaging Mass Spectrometry

Abstract

Mass spectrometry has been a valuable resource in science for decades. The ability to know exact masses of analytes allows for a more precise knowledge of the composition of materials. The technique has evolved to allow analysis of increasing numbers compounds in increasingly complex environments. Selected examples of biological applications of mass spectrometry imaging are discussed, in addition to a variety of tissue imaging and other medical applications. A number of inorganic applications are also described. Finally, a conclusion regarding the prospects for the future of imaging mass spectrometry completes this brief review.     

Chemical Profiling of an Indian Herbal Formula Using Liquid Chromatography Coupled with Electro Spray Ionization Mass Spectrometry

Amruthotharam kashayam is an important Ayurvedic formulation prepared using specified plant parts of Tinospora cordifolia, Terminalia chebula, and Zingiber officinale. The current study developed a rapid liquid chromatographic method coupled with electro spray ionization mass spectrometry for the identification of major phytoconstituents present in the formulation. Reverse phase high-pressure liquid chromatogram was developed as chemical fingerprint. The mass spectrum along with the MS/MS fragmentation on collision-induced dissociation led to the structural identification of separated compounds. Phenolic acids such as quinic acid, protocatechuic acid, gallic acid, and chebulic acid were identified in the formulation along with some flavonoids.     

Pressure Ionization of Atoms in Plasmas

It is shown that the main physical reason leading to the ionization of the atoms in plasmas at high densities (pressures) is the Pauli exclusion principle for the electrons which is responsible for the big spatial extension of atoms. Especially for the example of hydrogen the theory is extended to include those effects. Spatial and energetic variants for the definition of the species atom are discussed. The quantum theory of bound states in plasmas is compared with the classical theory of ion association in electrolytes.     

Pressure Ionization in Nonideal Alkali Plasmas

A system of electrons (e) and ions (i) is considered in which beside the Coulomb interaction short range forces are taken into account, i.e. for the e-i interaction a pseudopotential is used, and for the (classical) ions crystallographic radii are used. For a Cesium plasma the thermodynamic properties are calculated quantumstatistically in a wide temperature-density region. Degeneration effects are taken into account approximately. In the region with bound states the ionization equilibrium is discussed, and the Mott-Transition is investigated critically. A phase transition occurs in the framework of the model chosen at T_c ≈ 4500 K and n^c ≈ 4.10²⁰ cm^?3.