Shock tube/time-of-flight mass spectrometer for high temperature kinetic studies

A shock tube (ST) with online, time-of-flight mass spectrometric (TOF-MS) detection has been constructed for the study of elementary reactions at high temperature. The ST and TOF-MS are coupled by a differentially pumped molecular beam sampling interface, which ensures that the samples entering the TOF-MS are not contaminated by gases drawn from the cold end wall thermal boundary layer in the ST. Additionally, the interface allows a large range of postshock pressures to be used in the shock tube while maintaining high vacuum in the TOF-MS. The apparatus and the details of the sampling system are described along with an analysis in which cooling of the sampled gases and minimization of thermal boundary layer effects are discussed. The accuracy of kinetic measurements made with the apparatus has been tested by investigating the thermal unimolecular dissociation of cyclohexene to ethylene and 1,3-butadiene, a well characterized reaction for which considerable literature data that are in good agreement exist. The experiments were performed at nominal reflected shock wave pressures of 600 and 1300 Torr, and temperatures ranging from 1260 to 1430 K. The rate coefficients obtained are compared with the earlier shock tube studies and are found to be in very good agreement. As expected no significant difference is observed in the rate constant between pressures of 600 and 1300 Torr.     

Time-of-flight mass spectrometry for time-resolved measurements

A time-resolved time-of-flight mass spectrometer (TOF-MS) that can simultaneously monitor multiple species on the millisecond time scale has been constructed. A pulsed photolysis laser is used to initiate reaction, and then via a pinhole the reaction mixture is sampled by the TOF-MS. The ions are created by photoionization via either a discharge lamp or a pulsed laser. Comparison between the two ionization sources showed that the laser is at least an order of magnitude more efficient, based on the time to accumulate the data. Also, unlike the continuous lamp the pulsed laser is not mass limited. Frequency tripling the 355 nm output of a Nd:YAG laser provided a convenient laser ionization source. However, using a dye laser provided an equally intense laser ionization source with the ability to tune the vacuum ultraviolet (vuv) light. To show the versatility of the system the kinetics of the reaction of SO and ClSO radicals with NO(2) were simultaneously measured, and using the dye laser the vuv light was tuned to 114 nm in order to observe H(2)CO being formed from the reaction between CH(3)CO and O(2).     

小型飞行时间质谱装置的构建

飞行时间质谱仪（TOF MS）在准确度、分辨率、灵敏度、质量上限、分析速度等方面具有优势,在生命科学等领域发挥着重要作用。目前商用飞行时间质谱仪已经比较成熟,但仪器尺寸普遍较大,且价格昂贵,维护困难;而小型仪器则面临分辨率较低等问题。提高小型飞行时间质谱仪的分辨率,降低购置成本和维护成本,对于飞行时间质谱仪的大范围推广有着重要意义。本工作构建了一套分辨率较高的小型飞行时间质谱装置,包括真空系统、离子源、锥孔、引出加速及偏转模块、离子反射镜模块、探测器模块、电路系统等。该仪器主体尺寸较小（0.5 m×0.5 m×0.7 m）,飞行管长度仅0.25 m。由于采用了模块化设计思路,各个模块之间独立封装,仪器的维护、升级工作简单易行。该仪器的关键模块采用创新设计,使得在m/z 2 000处分辨率可达4 200。     

A New High-Resolution Tof Mass Spectrometer

ABSTRACT

UV laser-induced surface ionization with prism internal reflection is demonstrated to be a useful ion source for the Time-of-Flight mass spectrometer (TOF-MS). Spraying aniline (93 amu) on the prism surface and using 2 ns UV laser pulses, mass resolutions of 3,900 and 11,000 have been achieved in a linear TOF-MS and in a reflectron TOF-MS, respectively. Theoretical calculations indicate that mass resolution of over one million is possible, if a picosecond laser and appropriate electronics are employed.     

Shock tube coupled to the time-of-flight mass spectrometer via a molecular beam sampling system

A method for continuous mass spectrometric analysis of high-temperature reacting gas mixtures is described. The apparatus consists of a unique combination of three devices: the shock tube, the time-of-flight mass spectrometer, and the supersonic molecular beam. The driven section of the shock tube constitutes the reservoir of a supersonic molecular beam by which gas is continuously extracted from the reaction zone and introduced through a two-stage high-capacity vacuum system into the ionization region of the mass spectrometer. The shock tube and the mass spectrometer are coupled at right angles to one another. This configuration avoids excessive pressure buildup in the mass spectrometer system. The apparatus has an estimated mass resolution of 100 amu, a frequency range of 10-100 kHz, and can be operated over a wide range of shock conditions during the complete high-temperature pulse.     

Energy-sensitive cryogenic detectors for high-mass biomolecule mass spectrometry

Energy-sensitive calorimetric detectors that operate at low temperatures ("cryogenic detectors") have recently been applied for the first time as ion detectors in time-of-flight mass spectrometry. Compared to conventional, ionization-based detectors, which rely on secondary electron formation or the charge created in a semiconductor, cryogenic detectors measure low-energy solid state excitations created by a particle impact. This energy sensitivity of cryogenic detectors results in several potential advantages for TOF-MS. Cryogenic detectors are expected to have near 100% efficiency even for very large, slow-moving molecules, in contrast to microchannel plates whose efficiency drops considerably at large mass. Thus, cryogenic detectors could contribute to extending the mass range accessible by TOF-MS and help improving detection limits. In addition, the energy resolution provided by cryogenic detectors can be used for charge discrimination and studies of ion fragmentation, ion-detector interaction, and internal energies of large molecular ions. Cryogenic detectors could therefore prove to be a valuable diagnostic tool in TOF-MS. Here, we give a general introduction to the cryogenic detector types most applicable to TOF-MS including those types already used in several TOF-MS experiments. We review and compare the results of these experiments, discuss practical aspects of operating cryogenic detectors in TOF-MS systems, and describe potential near future improvements of cryogenic detectors for applications in mass spectrometry.     

质谱电喷雾电离源研究新进展

自1984年约翰芬恩(John Fenn)发明一种软电离离子源,即电喷雾电离源(ESI)以来,促进了质谱技术在大分子分析领域,特别是生物大分子领域的广泛使用。ESI源的低取样效率由ESI源的离子化效率和传输效率的构成,制约着ESI源质谱灵敏度的提高,因此研究者们一直努力改进ESI源的性能,以提高取样效率、改善ESI源质谱灵敏度。本研究介绍了ESI源的原理,并评述了近年来ESI源研究的新进展和应用。     

Quartz tube orifice leaks for local, fast-response gas sampling to mass spectrometers

Simple and versatile quartz tube orifice leaks, suitable for sampling of gas mixtures to mass spectrometers, have been made by heating the tip of a quartz tube in a hydrogen-oxygen flame. With these leaks the requirement of expensive and clumsy differential pumping stages is removed. The quartz probes have been used in gas sampling from catalytic reaction cells at 1 atm to a mass spectrometer. The sampling position can be located within 0.1 mm from the catalyst. Continuous recording of the local gas composition is then achieved with a response time of about 0.05 s, and with a minimum perturbation of the gas flow. The probes have been used in ambient air and at temperatures around 1000 K for extended periods of time without deterioration or plugging. The high stability at elevated temperatures and chemical resistance seem to make these probes useful for various applications, e.g., in sampling from combustion flames. The gas flow through the leak is determined by a very short and narrow constriction at the tube tip. In a leak with a throughput of 1x10(-4) Torr l/s at 1 atm inlet pressure, the constriction has a diameter of 5-7x10(-4) cm and a length of about 0.015. cm.     

峰形模拟在纳秒强激光电离碘甲烷团簇质谱中离子来源分析的应用

运用飞行时间质谱的峰形模拟程序，对纳秒强光场下CH₃I团簇电离过程中得到的离子峰进行模拟。根据模拟峰形与实验峰形的相似程度，直接反演出离子产生时的速度分布或空间分布，并根据速度或空间分布推测了离子产生的来源，其中C²⁺, I²⁺和I³⁺来源于库仑爆炸过程，C⁺, CH_x⁺⁽x=1,2,3), I⁺和CH₃I⁺来源于多光子电离过程，H⁺来源于上述两种过程，而少部分I⁺来源于电子碰撞电离。此外，通过峰形模拟，对离子的接收比例进行了研究。     

橡胶防老剂RD的GC/MS研究

采用气相色谱 (GC/ MS)法对橡胶防老剂 RD(2 ,2 ,4 -三甲基 -1 ,2 -二氢化喹啉多聚体 )进行了测试和分析。总离子色谱质谱图 (TIC)表明 :多聚体 RD中二聚体含量最高 ,热稳定性最好。质谱分析表明 :RD容易失去甲烷分子和甲基形成共轭体的离子 ,二聚体和三聚体容易形成二聚体的衍生物离子。采用气相色谱 -质谱(GC/ MS)可使不同分子量的所有多聚体的分子离子峰都出现。给出了 RD分子以及单体的质谱裂解途径     

光电子电离质谱在线监测SF_6气体分解物

电气设备内部放电故障的原因与其中SF6杂质气体的种类和含量相关。本工作设计了一套基于光电子电离飞行时间质谱的在线监测系统,通过对电气设备腔体内SF6气体组分的实时监测,实现电气设备放电故障的诊断。同时,结合实验室研制的SF6气体低压放电系统,研究了不同掺杂气的SF6气体放电产物谱图和动力学监测曲线,初步探讨了不同条件下SF6放电产物的产生机理。该技术有望实现在线质谱分析技术进入电力生产现场和及时监控SF6电气设备内部故障情况。     

Threshold photoionization in time-of-flight mass spectrometry

Multi-photon excitation in a time-of-flight mass spectrometer (TOF-MS) is shown to lead to threshold ions with defined internal energy. A powerful technique for the production of threshold ions is based on the excitation of high long-lived Rydberg states embedded in the ionization continuum. The Rydberg molecules are separated with suitable separation techniques from ions produced by a direct multi-photon ionization process. Finally, the ionization of the Rydberg molecules in a delayed pulsed electric field leads to threshold ions. This work reviews several separation techniques, and reports on applications of threshold ionization for investigation of the structure, energetics, and dynamics of neutral molecules, molecular cations, and cluster cations.     

激光烧蚀光谱-电感耦合等离子体质谱联用技术

激光烧蚀光谱（LAS）技术具有空间分辨率高,样品用量少,制样简单,分析速度快,可远程、实时、在线分析多相物质（气态、液态、固态）的特点,是近年来发展迅速的一种分析技术,具有广阔的应用前景,但它对痕量元素的分析能力不足。电感耦合等离子体质谱(ICP-MS)技术具有灵敏度高和多元素及同位素同时检测的能力,在微痕量元素精密分析方面具有很大的优势,但对基体元素分析存在困难。将LAS和ICP-MS技术相结合,形成LAS和LA-ICP-MS联用技术（LAS-ICP-MS）,可充分利用两种技术的优势,形成互补技术,为地质分析提供一种便捷、可靠的分析手段：利用LAS技术,可预先监测样品的大致含量与信号的稳定性等参数,筛选适用于LA-ICP-MS分析的样品,避免因元素含量过高引起的LA-ICP-MS采样锥锥口易堵塞,基体效应过大,以及因样品均匀性差或激光参数未优化等因素影响分析的准确性和精密度等问题;利用LA-ICP-MS技术,可对激光进样条件和原子化、离子化条件分开进行优化,从而改善仪器的分析性能。将LAS-ICP-MS用于岩石矿物分析,表现出其良好的应用前景     

热电离飞行时间质谱仪性能评价

本工作介绍了实验室自制的热电离飞行时间质谱仪（TI-TOF-MS）的基本结构、仪器运行参数和性能特点等。离子源产生的离子在推斥电压作用下进入聚焦透镜,然后进入垂直引入反射式的飞行时间质量分析器,最后到达检测器。信号通过数据采集卡处理后传输给计算机,采用编写的LabVIEW软件采集信号和处理数据。结果表明：仪器可测量的质量范围为m/z 6~320,在m/z 208位置的质量分辨率可达2000,2 h质量稳定性为7.76×10^-5,测量²⁰⁷Pb/²⁰⁶Pb、²⁰⁷Pb/²⁰⁶Pb和²⁰⁷Pb/²⁰⁶Pb同位素比值的精密度分别为0.85%、0.27%和0.55%。该仪器在研究热电离离子源电离行为、同位素比值测定和多原子离子信号监测等方面具有广泛的应用前景。     

Microchip technology in mass spectrometry

Microfabrication of analytical devices is currently of growing interest and many microfabricated instruments have also entered the field of mass spectrometry (MS). Various (atmospheric pressure) ion sources as well as mass analyzers have been developed exploiting microfabrication techniques. The most common approach thus far has been the miniaturization of the electrospray ion source and its integration with various separation and sampling units. Other ionization techniques, mainly atmospheric pressure chemical ionization and photoionization, have also been subject to miniaturization, though they have not attracted as much attention. Likewise, all common types of mass analyzers have been realized by microfabrication and, in most cases, successfully applied to MS analysis in conjunction with on‐chip ionization. This review summarizes the latest achievements in the field of microfabricated ion sources and mass analyzers. Representative applications are reviewed focusing on the development of fully microfabricated systems where ion sources or analyzers are integrated with microfluidic separation devices or microfabricated pums and detectors, respectively. Also the main microfabrication methods, with their possibilities and constraints, are briefly discussed together with the most commonly used materials. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:351‐391, 2010     

高效液相色谱检测器——高分辨飞行时间质谱仪的研制

本文研制的质谱仪是具有电喷雾离子源和射频四极杆接口的高分辨飞行时间质谱仪（ESI-QQQ-TOF-MS）。该仪器的特点如下：采用可三维调节、带有加热雾化气的电喷雾源液质联用接口；采用由三组四极杆组成、可有效调制离子束的离子光学系统；采用正负双脉冲推斥和垂直引入方式；采用经优化设计的二级有网反射器。该仪器分辨本领优于11 000（Full Width at Half Maximum, FWHM），质量测定精度优于10×10^-6，最低检测限低于3 fmol/μL。可作为高效液相色谱优良的质谱检测器。     

A theoretical study for the design of a new ballistic range

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.     

DART-MS在中国的应用研究现状

敞开式离子化质谱（ambient ionization mass spectrometry, AIMS）技术因其具有实时、原位分析等特点，已成为质谱学领域的一个研究热点。实时直接质谱分析（direct analysis in real-time mass spectrometry, DART-MS）作为一种典型的直接质谱分析技术，可在开放环境中实现样品的快速分析，具有性能稳定、操作简单、分析快速等优点，自2005年被报道以来，便引起了广泛的关注。本文从DART电离源的工作原理以及近2年DART-MS在环境分析、食品药品安全、生物医学分析以及公共安全等领域的应用研究进行了评述，并对其发展方向进行了展望。     

日本电子JMS-S3000的开发——具有螺旋状离子轨道的MALDI-TOF/TOF-MS

日本电子开发了一种具有螺旋状离子轨道的新型离子光学系统,它超越了现在市场上多数采用的反射式离子光学系统的基本性能;而且还开发了MALDI-TOF/TOF-MS（型号为JMS-S3000）,在第1个TOF MS中采用螺旋状轨道离子光学系统,第2个TOF MS中采用反射式离子光学系统,从而实现了以前的质谱仪器达不到的高质量分辨率和高母离子选择性。JMS-S3000质谱图显示：在m/z2093质量分辨率不仅超过60,000（FWHM）,而且在很宽的质量范围也能达到高质量分辨率。JMS-S3000具有高母离子选择性,只选择母离子的单一同位素离子,所以各个断裂途径的峰在子离子谱图上能够清晰地被看到其对应的信号峰,使得子离子谱图的解析变的更加简单明确。     

A numerical study of the gas and particle dynamics in a needle free drug delivery device

In recent times, a unique drug delivery system known as transdermal drug delivery has been developed which can deliver drug to the human skin without using any external needle. A shock tube system is used to generate a moving shock wave which flows through the tube. The idea is to accelerate particles behind the moving shock so that it can attain sufficient momentum to penetrate the outer layer of the skin (stratum corneum) and have a pharmaceutical effect. The important issue while delivering drug to the skin is to deliver it with uniform velocity and spatial distribution. Among different tried and tested systems the contoured shock tube (CST) seems to fulfill this requirement successfully. This paper focuses on numerically investigating the flow field and analyzing the gas and particle interaction through the contoured shock tube. Computational fluid dynamics (CFD) has been used to simulate and further analyze the flow field. The important issues regarding the flow field and the gas particle interaction are discussed in details.