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.     

一种面向低真空环境的质量分析方法仿真研究

在低真空环境进行质谱分析可以大幅降低仪器的成本、体积和功耗,实现质谱仪的便携化。在四极杆质量分析器中,增大压强会导致离子轴向运动能量不足,无法到达检测器。为解决这一问题,提出了一种使用顺向气流作为离子出射动力,适用于低真空环境的质量分析方法,并在COMSOL Multiphysics中搭建仿真模型进行验证。仿真结果表明,利用该方法得到的谱峰强度和谱峰宽度明显优于无气流条件下的分析结果。该研究成果为低真空质谱仪的研发奠定了理论基础,促进质谱仪便携化和传感器化、降低使用门槛、扩展应用领域。     

Determination of dioxins/furans and PCBs by quadrupole ion-trap gas chromatography-mass spectrometry

The versatility and sensitivity of the quadrupole ion trap tandem mass spectrometer has been applied to the determination of polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs), and of polychlorinated biphenyls (PCBs). A brief introduction to the theory of ion confinement in a quadrupole ion trap permits discussion of ion trajectory stability, mass-selective ion ejection, the frequencies of ion motion, and the role of resonant excitation of ion motion. The tandem mass spectrometric examination of PCDDs and PCDFs eluting and co-eluting from a gas chromatographic column is described. Illustrative examples are given of the analysis of field samples containing PCDDs and PCDFs. A comparison is presented of the performance of each of a quadrupole ion trap tandem mass spectrometer, a triple stage quadrupole mass spectrometer, and a sector instrument of relatively high mass resolution for the determination of PCDDs and PCDFs. This comparison is made with respect to instrument tuning, calibration plots, detection limits, ion signals at low concentration, relative response factors, ionization cross-sections, and the examination of field samples. The application of quadrupole ion trap tandem mass spectrometry to the examination of PCBs is focused upon those PCB congeners that have the greatest toxicity. 39 congeners of the total of 209 PCB congeners have been identified as having the greatest toxicities. Chemical ionization has been used for the determination of co-eluting congeners #77 and #110 where the toxicity of the former is much greater than that of the latter. An analytical protocol, based on the variation of molecular ion fragmentation according to the degree (or absence) of chlorine ortho-substitution, has been proposed for distinguishing between toxic and nontoxic PCB congeners.     

美国应用生物系统公司串联液质系统--食品安全的卫士

高效液相色谱-串联质谱联用技术在近几年发展迅猛，已成为在复杂体系中进行微量组分的筛选、定性和定量极其可靠、快速和准确的分析手段。受到了学术界和分析测试行业的普遍青睐，并在生命科学、药学、医学、环境与健康等领域得到广泛应用。本文论述了美国应用生物系统公司串联液质系统用于食品安全领域关键的技术要点，比如三级四极杆质谱技术擅长快速定量分析，就好比是“长了眼睛的分析检测技术”，不需要液相色谱的完全分离，提高了方法建立与分析检测的速度，并拓展了分析测试的检测下限；同时。线性离子阱技术可提供高质量的化合物碎片离子全扫描图谱以及多级串联质谱功能，大大增强了系统的定性功能。而两种技术的完美组合即“串联四极杆-线性离子阱融合质谱技术”不仅出色地完成高灵敏度、高选择性的定量分析，同时可以获得增强性化和物结构碎片图谱，使定性、定量工作一次完成，大大提高了食品安全中分析检测的通量．本文介绍了这种新技术的基本原理及其在食品安全中的经典应用。     

瞬短脉冲辉光放电飞行时间质谱仪

本文介绍了本实验室研制的瞬短脉冲辉光放电飞行时间质谱仪。其中，辉光放电离子源具有离子产额高、工作稳定可靠等特点，可用于对金属（合金）样品的直接分析。该仪器为国内首台自制的常压（低真空）等离子体飞行时间质谱仪，亦为国际上首台瞬短脉冲辉光放电质谱仪，为研究瞬短脉冲辉光放电及其应用这一新兴领域打下了基础，仪器的分辨本领优于５００。     

WGA1000软件系统设计及定量分析方法优化研究

介绍了国内第一款用于录井系统的快速气相色谱-四极杆质谱联用气测仪WGA1000软件系统,说明了其设计原理和用户界面实现方法。该软件系统实现了对仪器的运行状态和参数的精确控制,以及对数据的快速采集与处理,可得到各组分的实时浓度值,并将该结果传送给终端服务系统,最终获得钻井过程中各组分浓度的变化趋势图;通过改进和优化线性校正方法与离子扫描方式,显著提高了气体组分定量计算结果的准确性和重复性。经过长期现场应用及模拟实验证明,WGA1000软件系统结合硬件及数据解析软件系统,能够满足目前气测录井系统在线气体分析仪器的实时监测要求。     

Rapid Isothermal Gas Chromatography‐Mass Spectrometry Method for Validating a Small Ion Mobility Spectrometer Sensor

Abstract

A fast and reproducible isothermal gas chromatographic‐mass spectrometric method for validating a small ion mobility spectrometer (IMS) sensor for detection of gaseous volatile organic compounds (VOCs) is presented. This method utilizes an automated cyclic valving (CV) sampling technique coupled to a gas chromatograph‐mass spectrometer (GC/MS) in selected ion monitoring (SIM) mode (CV/GC/MS/SIM). The sampling time is considerably reduced by operating the GC isothermally at 300°C. This approach provides rapid measurements with 15 times more data points than the conventional GC/MS methods in which the column temperature is ramped, then cooled before the next sample can be injected. With the mass spectrometer operated in SIM mode, pre‐selected ions that represent the primary quantitation and secondary ions of toluene and a BTX (benzene, toluene, o‐, m‐, and p‐xylene) mixture were monitored and their corresponding breakthrough curves for flow through partially saturated soil columns were generated. The small variation in measured steady state mean concentrations (SSMC) from run to run demonstrates the reproducibility of this new method. A comparison of the transient concentration profiles of toluene from a BTX mixture and toluene alone obtained under identical test conditions shows a linear correlation with R²=0.997. This result suggests that the new method can be used to analyze and quantify some mixtures of co‐eluting gaseous analytes.     

敞开式小型线-筒电极负电晕放电离子源(英文)

针对目前商用质谱仪的离子源都为封闭式且工作在真空或者低气压环境中,应用范围十分受限这一问题,提出了一种新型的可在大气环境下工作的离子源.该离子源通过电晕放电产生离子,呈线-筒结构,由内电极和外筒电极组成,电极直径分别为0.16 mm和4 mm.外筒电极上开有对称的4个槽,用于通入样品和牵引离子.实验结果表明,在大气环境下,当载气为N2,内电极电压达到-3 800 V时,内电极和外筒电极之间发生电晕放电,可以很好地电离乙酸等负电性的化学物质.质谱图显示,大气中的N2和O2可能也参与电离,生成了NO-2 (m/z:46)、 NO-3 (m/z:62)和[M+NO-H]- (m/z: 89).结合COMSOL仿真软件,对该离子源的放电起始电压进行了理论分析,分析结果与实验结果相符.此外,该离子源接口简单,可广泛应用于敞开式质谱仪、离子迁移质谱仪(IMS)和高场非对称波形离子迁移质谱仪(FAIMS)中.     

Note: Integration of trapped ion mobility spectrometry with mass spectrometry

The integration of a trapped ion mobility spectrometer (TIMS) with a mass spectrometer (MS) for complementary fast, gas-phase mobility separation prior to mass analysis (TIMS-MS) is described. The ion transmission and mobility separation are discussed as a function of the ion source condition, bath gas velocity, analysis scan speed, RF ion confinement, and downstream ion optical conditions. TIMS mobility resolution depends on the analysis scan speed and the bath gas velocity, with the unique advantage that the IMS separation can be easily tuned from high speed (~25 ms) for rapid analysis to slower scans for higher mobility resolution (R > 80).     

Structures,energetics, and dynamics of gas phase ions studied by FTICR and HPMS

Both Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS) and high‐pressure mass spectrometry (HPMS) are very powerful tools in the field of gas phase ion chemistry. Many experimental method developments based on FTICR‐MS and HPMS are summarized, including the coupling of a high‐pressure external ion source to a FTICR mass spectrometer, blackbody infrared radiative dissociation (BIRD), coupling laser desorption ionization with HPMS, infrared multiple photon dissociation (IRMPD), radiative association and bimolecular routes to gas phase cluster ion formation. An abundance of thermochemical data, such as proton affinities, gas phase acidities, methyl cation affinities and metal cation affinities, have been obtained. Some of these data are the basis of the standard data listed in the NIST thermochemical databases. Ion–molecule interactions, energetics, reactivities, and structures of molecules have been extensively investigated using the methods developed based on HPMS and FTICR mass spectrometric techniques. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:546–585, 2009     

High mass resolution time of flight mass spectrometer for measuring products in heterogeneous catalysis in highly sensitive microreactors

We demonstrate a combined microreactor and time of flight system for testing and characterization of heterogeneous catalysts with high resolution mass spectrometry and high sensitivity. Catalyst testing is performed in silicon-based microreactors which have high sensitivity and fast thermal response. Gas analysis is performed with a time of flight mass spectrometer with a modified nude Bayard-Alpert ionization gauge as gas ionization source. The mass resolution of the time of flight mass spectrometer using the ion gauge as ionization source is estimated to m∕Δm > 2500. The system design is superior to conventional batch and flow reactors with accompanying product detection by quadrupole mass spectrometry or gas chromatography not only due to the high sensitivity, fast temperature response, high mass resolution, and fast acquisition time of mass spectra but it also allows wide mass range (0-5000 amu in the current configuration). As a demonstration of the system performance we present data from ammonia oxidation on a Pt thin film showing resolved spectra of OH and NH(3).     

低真空环境下四极杆质量分析器灵敏度仿真研究

为了实现低真空环境下质谱仪的质量分析,提出了利用Langevin碰撞理论模拟低真空环境下离子运动轨迹的方法,该方法可以更准确地反映离子的运动状态。针对四极杆质量分析器,在COMSOL Multiphysics中搭建了适用于低真空环境的离子运动仿真平台。利用该平台仿真得到了低真空条件下,背景气体压强、离子质荷比、背景气体质量、离子初始能量、四极杆半径以及温度对四极杆质谱仪灵敏度的影响。仿真结果表明,随着压强升高,质谱仪灵敏度降低,通过改变离子操作模式,可以削弱由压强变化引起的灵敏度降低,这为低真空质谱仪的设计提供参考。     

HPR20PLUS在线气体分析质谱仪低压测试性能观察

To obtain data for experiments and applications of HPR20^PLUS on-line mass spectrometer in low pressure. The gas, standard gas, and breath gas of low pressure cabin were analyzed respectively in unman and manned experiments under different low pressure. The accuracy and stability of HPR20^PLUS On-line Mass Spectrometer in unman experiments under different low pressure were conformed to the requirements of HPR20^PLUS on-line mass spectrometer, and the changes of breath gas in manned experiments were accorded with the laws of human experiments . Performance tests of HPR20^PLUS on-line mass spectrometer in low pressure is excellent , and HPR20 ^PLUS on-line mass spectrometer can be used for human experiments under low pressure .     

监控软件对小型流程质谱分析系统的性能优化

小型流程质谱计是一种以四极质谱计为分析器、对工业过程中的气体成分进行监控和分析的仪器。其广泛应用于现代化工、制药、建材、食品等工业,对生产流程、质量进行精确控制,小型流程质谱计分析系统性能的高低直接影响这些产品的生产和质量,其性能指标主要指分析系统的稳定性和精度。本文从监控软件设计的数学建模、分析方法等方面探讨如何提高分析系统的性能。     

基于离子阱原理的空间小型质谱仪理论模拟研究

当前空间探测活动日益频繁,其中对空间有机分子的探测是空间探测的一项重要任务。由于太空中特殊的工作条件,一般商品质谱仪的体积、功耗和分析能力等都不能满足要求,因此需要研发小体积、低功耗、高稳定性的质谱仪。本研究基于离子阱原理,提出了由多个环形电极构成的新型平方离子阱,这种多环高压结构能有效减小离子阱的体积,从而实现质谱仪器的小型化。通过采用成比例的直流电压分时段供电,成功扩展了该质谱仪的离子检测范围。经仿真计算,拟合出了离子振荡频率与其质量数的关系。该质谱仪对质量数在1~2000 u 范围内的分子,质量分辨大于1400,能够满足空间大分子质量分辨的基本要求。     

基于傅里叶变换离子回旋共振质谱仪(FT ICR MS)的超宽波段光解离光谱系统的研制及应用

基于质谱技术的光解离光谱方法具有灵敏度高和可行性好的优势,近年来在气相离子化学和分析化学研究领域得到了快速发展和广泛应用。本工作基于一台7 T的傅里叶变换离子回旋共振质谱仪(FT ICR MS),搭建了超宽波段的可调谐激光光路系统,获得了气相离子超宽波段的光解离光谱。该系统的光谱可调谐范围为192~3 700 nm,是目前已知在单台质谱仪上可获得最宽波段的光解离光谱系统。超宽波段的波长覆盖范围使用两台宽波段可调谐OPO激光器实现,光路可以在真空传输,提高了紫外和红外激光的传输效率。该系统结合了电喷雾(ESI)电离源和FT ICR MS的高分辨能力以及超强的离子操控能力,可以获得目标离子的紫外-可见光以及中红外区域的光解离光谱,分别对应于分子的电子和振动能级,实现了分子结构信息的互补。以罗丹明110和色胺为例,获得了相应的离子在不同波段中的光解离光谱,初步证明了该仪器实现相关功能的可行性。     

基于质谱技术的二硫键定位分析方法研究进展

蛋白质中的二硫键是一种常见的重要翻译后修饰,对稳定蛋白质的三维空间结构、维持正确的折叠构象、保持和调节生物活性具有重要意义。因此,分析蛋白质中的二硫键对理解生命过程和药物研发至关重要。质谱既可断裂二硫键和肽键,又可作为检测终端,在二硫键定位分析中发挥了重要作用。本文根据断裂二硫键所处介质以及断裂机理进行分类整理,综述了基于质谱技术的主流二硫键定位方法,通过对比各方法的优缺点,为选择合适的质谱分析方式提供参考。最后,提出了二硫键分析领域面临的挑战和方法学研究的发展方向,以促进方法学相关研究者开发更有效的质谱方法。     

GC-MS-SIM检测糕点中的防腐剂和抗氧化剂

利用气相色谱-离子阱质谱联用仪和选择离子监测（SIM）技术建立了同时检测糕点制品面包、蛋糕、月饼中7种防腐剂（山梨酸、苯甲酸、脱氢乙酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯）和3种抗氧化剂（叔丁基对苯二酚、叔丁基羟基茴香醚、2,6-二叔丁基对甲酚）的方法。优化了色谱、质谱仪器参数。根据10种添加剂的特征离子峰进行定性定量,方法学数据良好。10种添加剂的检出限分别为0.10、0.050、0.015、0.038、0.025、0.019、0.036、0.060、0.050、0.060mg/kg;精密度为2.2%～5.5%;回收率为81%～98%。将本法应用于糕点中食品添加剂的检测,效果良好,检测效率大大提高。     

Modification of an AEI/GEC MS9 High-Resolution Mass Spectrometer for Electron Impact/Chemical Ionization Studies

ABSTRACT

A double-focusing MS9 mass spectrometer has been modified to permit operation in both chemical ionization (CI) and electron impact (EI) modes. The modifications consist mainly of a closed ion chamber, a high capacity pumping system, a reactant gas inlet system, a new solid sample probe, and a source pressure measuring device. Changes have also been made in the electronic system and a new ion source power supply has been incorporated. The new ion source can be operated in the CI mode at pressures up to 1 Torr while the pressure in the analyzer is better than 10^?7 Torr. The new set-up has the ability to analyze solid, liquid, and gas samples in both CI and EI mode. It has also the ability to do GC/MS without a Separator.

The sensitivity in the CI mode is comparable to the sensitivity in the EI mode, and the maximum resolution obtained with the CI/EI source is similar to that obtained with the original EI source.