离子阱颗粒物质谱

离子阱颗粒质谱装置结合了激光诱导声波脱附离子化方法、四极离子阱或圆柱型离子阱质量分析器及电荷感应探测器,能够对微米量级的颗粒进行快速质量分析。目前已成功地测定了聚苯乙烯球、色谱填料、红细胞等颗粒。本文综述了离子阱颗粒质谱仪的构造、工作原理及最近的研究成果,并对颗粒质谱仪的未来提出了展望。     

小型质谱双线形离子阱间离子传输

多级质谱串联在各个领域都有广泛应用。双线形离子阱的小型质谱可以实现类似传统三重四极杆质谱仪的串联质谱分析功能,而在此过程中,双阱间的离子传输为重要的仪器功能。在已发表的双线形离子阱工作中,对阱间离子传输,尤其是质量选择性传输鲜有系统的研究。本工作研究了离子阱q值、阱内气压、辅助性交流电（AC）的强度、辅助性AC的作用时长等因素对传输的目标离子强度的影响,优化了离子传输条件,如q1=q2=0.3,阱内气压为0.37 Pa,AC强度为350 mV,离子传输时长大于10 ms等。该结果对小型质谱双线形离子阱的自主研发和提升阱间离子传输效率具有指导作用。     

基于电喷雾电离源质谱仪系统的八电极线性离子阱性能研究

八电极线性离子阱在前期的理论模拟研究中取得了较好的质量分析性能,为验证理论模拟结果,选择其中最优的结构参数,设计、加工并组装了八电极线性离子阱实物,以此为基础搭建电喷雾电离源质谱测试系统。在传统射频电压施加模式下,测试八电极线性离子阱的分析性能。当扫描速度为765 u/s时,八电极线性离子阱获得离子峰的半峰宽可达0.3 u,对应利血平（m/z 609）的质量分辨率为2 030。当分析浓度为10 mg/m3的利血平样品时,对应的质谱峰信噪比可达45.8。本文进一步研究了扫描速度对质量分辨率和灵敏度的影响,实现了离子碰撞诱导解离,分析了不同浓度的25羟基维生素D2标准样品,线性动态范围可达4个数量级。结果表明,八电极线性离子阱具有良好的分析性能,可为结构简化线性离子阱的研究提供全新思路,推动小型化离子阱质谱仪的研究进展。     

静电轨道离子阱离子切向引入的新方式和模拟

静电轨道离子阱质谱仪的关键垄断技术是将离子引入静电轨道离子阱的C形离子阱。本工作提出一种新的离子引入方式,即设计了一种O形离子阱,用于将更多的离子以较少的损失引入到静电离子阱中进行分析。O形离子阱嵌套在静电轨道离子阱外轨道上,可以直接使离子从O形圆轨道下滑降轨内切至椭圆轨道,再沿椭圆轨道下滑降轨外切,最终射入静电轨道离子阱中的圆轨道。新的离子引入方式避免了C形离子阱远距离传输离子,离子流可连续进入O形圆轨,在脉冲电压作用下进入静电轨道离子阱;随着离子的引入面增大,离子的引入量有所增加。另外,还推导了离子运动轨迹方程及降轨脉冲的能量方程,对离子引入方式进行模拟,结果表明,多离子多位置同时引入对离子轨迹无明显影响,而离子是否切向引入则至关重要,偏离切向引入会大大降低离子寿命。     

离子阱质谱计的研究现状及其进展

离子阱质量分析器中离子的运动在数学上可用二阶线性微分方程——Mathieu方程的解来描述，利用离子在Mathieu方程解的稳定性图中所具有的特性，可实现离子的质谱扫描。离子阱质谱计的小型化主要集中在对离子阱质谱计各组成部分（离子源、质量分析器、离子检测、真空系统）的小型化上。随着科技的不断发展，离子阱质谱计体积的小型化，分析对象的不断扩大，仪器性能上实现大质量范围、高分辨率和高灵敏度，以及成本的有效降低等，将是离子阱质谱计相关研究的主要趋势。     

离子阱质谱中离子轨迹算法研究

高精度数值仿真算法是研究离子阱中离子的运动特征、仿真设计与优化离子阱质谱仪器的关键。本研究探讨了2种基于四阶、五阶龙格-库塔算法的数值方法,求解离子在离子阱内的运动方程--Mathieu方程。通过Matlab编程进行离子轨迹仿真实验,计算精度、初值、时间步长等因素对计算结果的影响。结果表明,五阶龙格-库塔算法可以满足离子阱的仿真要求,能实现高精度离子轨迹计算。     

蔬菜中41种农药的气相色谱-离子阱质谱多残留检测

建立了蔬菜中41种农药的气相色谱-离子阱质谱多残留检测方法,样品采用丙酮、二氯甲烷提取,经活性炭/celite/酸性氧化铝柱净化,用气相色谱-离子阱质谱在选择离子存储(SIS)模式下分析。以保留时间和特征离子定性,运用SIS技术定量。方法在0.1、0.5、1.0 mg/kg添加回收率为70%~110%,相对标准偏差<20%,最低检测限在0.02~0.1 mg/L,符合多残留分析要求。     

便携式快速色谱-质谱联用仪器的研制与应用

针对挥发性和半挥发性有机物的现场检测,基于快速色谱分析技术和三维离子阱质谱技术,研制了便携式快速色谱-质谱联用仪,仪器具有吸附热解吸进样和进样口直接进样两种分析模式,能实现气体、水体和固体中有机物的现场测试。本文详细描述了该仪器的主要组成结构,对该仪器进行性能测试,结果显示该仪器分析速度快（苯系物分析时间不超过2分钟）,灵敏度高（0．1ng甲苯总离子流色谱峰的峰／峰信噪比143）,便携性优（重量14kg）、性能稳定（峰面积RSD≤5％）。土壤、污染源和刑侦领域中挥发性有机物和半挥发性有机物（地西沣,沸点492℃）的现场分析结果表明,仪器具有分析速度快、进样方式多样和适用于半挥发性有机物分析等优点,能用于现场监测领域有机物快速定性定量分析。     

PCB分压离子阱性能优化的理论模拟研究

印刷线路板（Printed-Circuit-Board,以下简称PCB）分压离子阱是一种主要由印刷线路板围成的新型简单电极结构的质量分析器。PCB分压离子阱的尺寸小巧、加工装配容易且成本较低,适于用作小型化离子阱质谱仪的质量分析器。为进一步提高PCB分压离子阱的分析性能,本研究对原有的PCB分压离子阱的电压施加方式与几何结构进行改进。利用计算机模拟软件SIMION和AXSIM,分析了分压离子阱的内部电场、离子运动轨迹及模拟质谱峰图。模拟中分别采用m/z 4 000、4 001和4 002离子,结果显示在射频信号（RF）分压比不变的情况下,不同的共振激光信号（AC）分压比对质量分辨率有显著的影响。随着该分压比的减小,质量分辨率得到相应的提高。当仅在中央电极施加AC信号时,可将质量分辨率提高约25%。另一方面,撤除角接地电极的新型PCB分压离子阱结构的性能较原有PCB分压离子阱的性能更优,对于m/z 4 001离子,其质量分辨率可以达到10 325。该结果可为进一步的实验提供理论基础。     

三维离子阱内空间电荷效应的理论分析

离子阱内存储的大量离子之间会有强烈的库仑相互作用,导致所谓的空间电荷效应,它一直是质谱理论研究和应用领域内非常感兴趣的问题。本工作根据三维离子阱内的离子分布情况,假设离子在三维离子阱的中心区域呈近似于球对称的高斯分布, 通过求解阱内电场所对应的电势函数满足的泊松方程,得到这个球对称高斯分布的离子云所产生的电场解析表达式,在小振动近似下,得到离子运动的久期（secular）频率与阱内离子数目的理论关系。通过进一步应用Mathematica数学模拟软件,计算模拟了不同久期运动频率的离子在不同个数的离子所组成的离子云排斥作用下的久期主频率的移动。计算结果与小振动近似下的理论计算结果基本一致。由于离子阱的质量分析是通过改变离子偶极激发电压实现的,这种频率移动将对离子被激发逸出的电压值产生影响,最终影响离子阱质谱质量分析的准确度。因此,用离子阱质谱进行离子分析时,通过减少存储的离子数以减少空间电荷效应,或根据离子数对质谱测量结果进行校正是有意义的。     

Secondary ion imaging in the scanning ion microscope

The performance of a 60 keV prototype Ga⁺ scanning ion microscope has been improved in terms of resolution and secondary ion collection efficiency. High definition mass-unresolved secondary ion images are presented, of a variety of materials. The contrast due to the surface topography of conductors and insulators is discussed and illustrated. Previous observations of crystallographic contrast due to primary ion-channelling effects in metal samples are corroborated with better statistics of the secondary ion images.     

FT-ICR mass spectrometry: Superconducting magnet,external ion source,ion–molecule reactions,and ion–ion traps

The world of Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry has witnessed, especially in the last 30 years significant advances in many fields of science, such as electronics, magnets, new ICR cell designs, developed ICR event sequences, modern external ionization sources, and linear ion beam guides, as well as modern vacuum technology. In this review, a brief account is given focusing especially on the studies performed in Wanczek's group and ICR research laboratory at the University of Bremen. An FT-ICR mass spectrometer has been developed with a high magnetic field superconducting magnet, operating at 4.7 T. At this magnetic field, a trapping time of 13.5 h was obtained with 30% efficiency. For the tetrachloromethane molecular ion, m/z 166, a mass-resolving power m/Δm = 1.5 × 10⁶ was measured at a pressure of 2 × 10⁻⁸ Torr. The transition from magnet sweep to frequency sweep and the application of Fourier-transform has greatly enhanced the ICR technology. External ion sources were invented and differential pumping schemes were developed for enabling ultrahigh vacuum condition for ICR detection, while guiding ions at relatively higher pressures, during their flight to the ICR cell. With the external ion source, a time-of-flight ICR tandem instrument is built. A method to measure the ion flight time and to trap the ions in the ICR cell is described. Many ICR cell characteristics such as z-axis ion ejection and coupling of radial and axial ion motions in a superposed homogeneous magnetic and inhomogeneous trapping electric field were extensively studied. Gas-phase ion–molecule reactions of several reactive inorganic compounds with a focus on phosphorous and sulfur as well as silicon chemistry were also studied in great detail. The gas-phase ion chemistry of several trifluoromethyl-reagents such as trifluoromethyltrimethylsilane and tris(trifluoromethyl)phosphine were also investigated in ICR. Dual polarities multisegmented ICR cells were invented and deeply characterized. Sophisticated ICR pulse event programs were developed to enable long-range ion–ion interactions between simultaneously trapped positive and negative ions.     

New Cs sputter ion source with polyatomic ion beams for secondary ion mass spectrometry applications

A simple design for a cesium sputter ion source compatible with vacuum and ion-optical systems as well as with electronics of the commercially available Cameca IMS-4f instrument is reported. This ion source has been tested with the cluster primary ions of Si(n)(-) and Cu(n)(-). Our experiments with surface characterization and depth profiling conducted to date demonstrate improvements of the analytical capabilities of the secondary ion mass spectrometry instrument due to the nonadditive enhancement of secondary ion emission and shorter ion ranges of polyatomic projectiles compared to atomic ones with the same impact energy.     

小型化矩形离子阱捕获能力的仿真研究

基于SIMION 7.0离子光学仿真软件对设计的矩形离子阱（RIT）的离子捕获效率进行了仿真,研究了离子初始位置和射频电压、频率对离子捕获效率的影响。仿真结果表明,只有初始位置靠近RIT中心的离子才能被有效捕获到。针对常见毒品及爆炸物所在的质量范围,对于内建电场空间尺寸为10mm×8.4mm×44mm（x,y,z）的RIT,选择捕获射频电压为50V0-p～100V0-p、频率1MHz时,既能保证较高的离子捕获效率,同时也降低了对电路系统指标的要求。     

Upgraded vacuum arc ion source for metal ion implantation

Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed "Mevva," for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.     

Liquid metal alloy ion source based metal ion injection into a room-temperature electron beam ion source

We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au(60 +). The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.     

Lithium ion sources for investigations of fast ion transport in magnetized plasmas

In order to study the interaction of ions of intermediate energies with plasma fluctuations, two plasma immersible lithium ion sources, based on solid-state thermionic emitters (Li aluminosilicate) were developed. Compared to discharge based ion sources, they are compact, have zero gas load, small energy dispersion, and can be operated at any angle with respect to an ambient magnetic field of up to 4.0 kG. Beam energies range from 400 eV to 2.0 keV with typical beam current densities in the 1 mAcm(2) range. Because of the low ion mass, beam velocities of 100-300 kms are in the range of Alfven speeds in typical helium plasmas in the large plasma device.     

Evaluation of a liquid metal ion source for secondary ion mass spectrometry

Positive and negative secondary ion emission of 23 pure elements have been studied for 10 keV In⁺ and 10 keV O₂⁺ bombardment. In⁺ ions were produced in a liquid metal ion source. For most of the elements investigated positive and negative secondary ion yields under In⁺ impact are comparable to those obtained with O₂⁺ primary ions. Admission of oxygen into the sample chamber enhances positive and negative ion intensitities in a strongly element-specific manner. Depth profiles of a Ni/Cr multilayer (100 Å single-layer thickness) using 5 keV In⁺ primary ions show that these ions may also be applied successfully for secondary ion mass spectrometric depth profiling.     

Quadrupole ion traps

The extraordinary story of the three‐dimensional radiofrequency quadrupole ion trap, accompanied by a seemingly unintelligible theoretical treatment, is told in some detail because of the quite considerable degree of commercial success that quadrupole technology has achieved. The quadrupole ion trap, often used in conjunction with a quadrupole mass filter, remained a laboratory curiosity until 1979 when, at the American Society for Mass Spectrometry Conference in Seattle, George Stafford, Jr., of Finnigan Corp., learned of the Masters' study of Allison Armitage of a combined quadrupole ion trap/quadrupole mass filter instrument for the observation of electron impact and chemical ionization mass spectra of simple compounds eluting from a gas chromatograph. Stafford developed subsequently the mass‐selective axial instability method for obtaining mass spectra from the quadrupole ion trap alone and, in 1983, Finnigan Corp. announced the first commercial quadrupole ion trap instrument as a detector for a gas chromatograph. In 1987, confinement of ions generated externally to the ion trap was demonstrated and, soon after, the new technique of electrospray ionization was shown to be compatible with the ion trap. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:961–989, 2009