Gridless Ion Acceleration Systems for Time-of-Flight Mass Spectrometry

Pointlike ion sources allow the application of gridless acceleration systems in time-of-flight mass spectrometry (TOF/MS). When ions are extracted from large sample areas according to the applied ionization method and sample geometry, the application of electrostatic lenses for acceleration seems to be difficult. Inhomogeneous extraction fields are likely to induce acceleration time variations for ions emerging from different locations on the sample. We investigated gridless acceleration systems with the help of computer simulations. An appropriate solution for TOF/MS was found and experimentally tested, combining the features of compactness and a wide-acceptance aperture with simple principles of construction. nt]mis|Dedicated to Ronald D, Macfarlane on the occasion of his 60th birthday.     

Critical Moments in Time: Reflections on the Development of Orthogonal Acceleration Time-of-Flight Mass Spectrometry

This paper reflects on the historical development of orthogonal acceleration time-of-flight analyzers that have been used routinely for high sensitivity analyses of biological molecules for more than a decade. In particular, the role of the late Michael Guilhaus from the University of New South Wales in Australia is highlighted. This account shows that like most advances in science, successful commercialization of new technology is not straightforward and is often the result of critical contributions of different people and organizations at different points in time.     

Detection of Large Ions in Time-of-Flight Mass Spectrometry: Effects of Ion Mass and Acceleration Voltage on Microchannel Plate Detector Response

In time-of-flight mass spectrometry (TOF-MS), ion detection is typically accomplished by the generation and amplification of secondary electrons produced by ions colliding with a microchannel plate (MCP) detector. Here, the response of an MCP detector as a function of ion mass and acceleration voltage is characterized, for singly charged peptide/protein ions ranging from 1 to 290 kDa in mass, and for acceleration voltages from 5 to 25 kV. A nondestructive inductive charge detector (ICD) employed in parallel with MCP detection provides a reliable reference signal to allow accurate calibration of the MCP response. MCP detection efficiencies were very close to unity for smaller ions at high acceleration voltages (e.g., angiotensin, 1046.5 Da, at 25 kV acceleration voltage), but decreased to ~11% for the largest ions examined (immunoglobulin G (IgG) dimer, 290 kDa) even at the highest acceleration voltage employed (25 kV). The secondary electron yield γ (average number of electrons produced per ion collision) is found to be proportional to mv^3.1 (m: ion mass, v: ion velocity) over the entire mass range examined, and inversely proportional to the square root of m in TOF-MS analysis. The results indicate that although MCP detectors indeed offer superlative performance in the detection of smaller peptide/protein species, their performance does fall off substantially for larger proteins, particularly under conditions of low acceleration voltage.

Accurate Mass Determination of Amino Alcohols by Turboionspray／Time—of—Flight Mass Spectrometry

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High Energy Collisions on Tandem Time-of-Flight Mass Spectrometers

Long before the introduction of matrix-assisted laser desorption/ionization (MALDI), electrospray ionization (ESI), Orbitraps, and any of the other tools that are now used ubiquitously for proteomics and metabolomics, the highest performance mass spectrometers were sector instruments, providing high resolution mass measurements by combining an electrostatic energy analyzer (E) with a high field magnet (B). In its heyday, the four sector mass spectrometer (or EBEB) was the crown jewel, providing the highest performance tandem mass spectrometry using single, high energy collisions to induce fragmentation. During a time in which quadrupole and tandem triple quadrupole instruments were also enjoying increased usage and popularity, there were, nonetheless, some clear advantages for sectors over their low collision energy counterparts. Time-of-flight (TOF) mass spectrometers are high voltage, high vacuum instruments that have much in common with sectors and have inspired the development of tandem instruments exploiting single high energy collisions. In this retrospective, we recount our own journey to produce high performance TOFs and tandem TOFs, describing the basic theory, problems, and the advantages for such instruments. An experiment testing impulse collision theory (ICT) underscores the similarities with sector mass spectrometers where this concept was first developed. Applications provide examples of more extensive fragmentation, side chain cleavages, and charge-remote fragmentation, also characteristic of high energy sector mass spectrometers. Moreover, the so-called curved-field reflectron has enabled the design of instruments that are simpler, collect and focus all of the ions, and may provide the future technology for the clinic, for tissue imaging, and the characterization of microorganisms.      

富勒醇的直接激光解吸飞行时间质谱分析

采用激光解吸电离飞行时间质谱对富勒醇样品进行研究,并与富勒烯标准品的质谱特征比较,以正负离子模式联合检测方法考察其特征结构。结果显示,正离子模式下,富勒醇碳笼易为规律性的碎裂峰,负离子模式下,则保留碳笼主体结构的特征峰,而富勒烯的碳笼结构在两种模式下不发生变化。表明该方法可以方便、快速地鉴别富勒醇的结构。采用该方法对富勒醇在二甲基亚砜(DMSO)中的稳定性进行分析,结果发现富勒醇可稳定存在于DMSO溶剂中,用于碱式反应条件下合成富勒醇的鉴别与条件筛选,选择反应碱的最佳浓度为1.0 g/mL。     

Online Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with In situ Mixing

Online matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is reported with in situ matrix/analyte aerosol mixing. The analyte and matrix were dissolved in separate solvents and pneumatically atomized into particles. Continuous flows of analyte particles and matrix droplets in nitrogen were mixed in a tee. The resulting particles were sampled using a nozzle, focused into a beam with an aerodynamic lens system, and vertically deposited continuously on a movable target. The matrix/analyte mixture was desorbed/ionized using a 266 nanometers pulsed laser at an incident angle of 45°. The nascent ions were analyzed using reflectron TOF MS. The performance of online MALDI-TOF MS was evaluated by the analysis of palmityl palmitate with the lithium salt of 2, 4-dihydroxybenzoic acid as the matrix. Strong and stable MALDI signals of palmityl palmitate were obtained. The matrix solvent mixture and the analyte concentration were optimized and the results demonstrate the development of an alternative for online MALDI analysis.     

激光电离飞行时间质谱用于矿石表面元素成像

在自行研制的LI-TOF-MS[6]的基础上, 发展了新的LI-TOF-MS固体元素成像分析系统, 并在优化了的实验条件下, 对辉锑矿矿石样品(主要成分为Sb2S3)的表面进行了元素分析, 得到了Sb, S, Si, Al, K, Ca和Fe等元素的表面成像图. 矿石表面或截面的元素成像(或分布)对矿石乃至矿床的形成过程及分布特征等的研究具有很大的参考价值, 在地质学上具有重要意义.     

激光电离飞行时间质谱技术用于古代瓷片中元素的检测及元素成像分析

采用自制激光电离飞行时间质谱(LI-TOF-MS)及多元素成像体系,尝试分析了古瓷片中的多种元素.对一块北宋龙泉青瓷瓷片及一块仿古青瓷瓷片样品进行了表面元素分析,所得多元素半定量分析结果表明,这两种瓷片的胎体和釉面中所含元素的种类及含量存在差异;同时对一块明代青花瓷片进行表面多元素成像分析,获得Co,Mn,Fe,Ni,Ba,Ca,Mg,Na,Al,Si,P,K,Cu,Zn和Rb的元素成像图.     

宽离子能量检测范围垂直引入反射式飞行时间质谱仪的研制

本实验室研制了国内首台宽离子能量检测范围飞行时间质谱仪。仪器采用紧凑式电子轰击源设计,配合离子透镜系统有效的调制离子流,飞行时间质量分析器采用了离子垂直引入式,双场加速和双场反射以及大尺寸MCP检测装置设计。仪器单离子信号半峰宽约2 ns,仪器分辨率优于1600FWHM,检测实际样品质量范围为1~127 amu(仪器理论质量检测上限优于800 amu),可检测离子能量范围优于2个数量级(3~140 eV)。若该TOF质量分析器与短瞬高压脉冲放电离子源耦合联用,可广泛应用于高能离子束的快速检测,如真空阴极放电对制备薄膜、离子注入材料的表征,导电材料的离子电荷态分布以及离子扩散速度的测定等。     

Intensity Exaggeration of Endohedral Metallofullerenes in Laser Desorption-Ionization Time-of-Flight Mass Spectrometry

Massspectrometryhasplayedacriticalroleinthefullereneresearchesl-8.ItwillalsobeheIpfulinthestudyofendohedralmetallofullerenes6.Eventhoughtherehavebeenplentyofreportsonmet.ll.fullerenes'-",detailedstudiesabouttheirgas-phasebehaviorareverypoor.Inthisletter,wereportanunusualintensityexaggerationphenomenonofendohedralmetallofullerenesinLD-TOFmassspectrometry,whichisconsideredduetotheirpeculiarionizationenergiesandelectronaffinities.SootcontainingmetallofullereneswassynthesizedbyK-Hcarbonarcevap…     

高效液相色谱与飞行时间质谱联用技术研究

用青岛曹家汶河口沉积物中分离出的细菌L-10(希瓦氏菌属)进行了水体中甲基对硫磷的细菌降解研究.研究表明,该菌对甲基对硫磷具有显著的降解性.采用高效液相色谱/飞行时间质谱(HPLC-TOF-MS)联用技术对甲基对硫磷及其细菌降解产物进行了分析.样品经SPE-C18小柱富集分离后,进行液相色谱和在线电喷雾飞行时间质谱分析.采用C18反相色谱柱(15 cm×4.6 mm i.d. 5 μm), 线性梯度为0 min 乙腈/水(30/70),5 min 乙腈/水(30/70),20 min 乙腈/水(80/20),25 min 乙腈/水(80/20);流速0.8 ml/min,甲酸铵缓冲溶液浓度为0.1% (V/V);电喷雾正离子(ESI)模式,m/z扫描范围50～1000进行TOF-MS扫描、测定,测定结果用Analyst QS软件进行分析.结果表明,与甲基对硫磷光降解产生甲基对氧磷和对硝基酚不同,在降解菌L-10的存在下,甲基对硫磷发生了取代、氧化、还原等一系列反应,产生了相应的降解产物.降解过程的机理很复杂,从甲基对硫磷及其降解产物的分子结构式来分析,推断可能与细菌本身的代谢有关.     

Simultaneous Determination of 11 Elements in Fly Ash by Inductively Coupled Plasma Orthogonal Acceleration Time-of-Flight Mass Spectrometry After Closed-Vessel Microwave-Assisted Extraction with Ammonium Fluoride

A method for simultaneous multi-element analysis of fly ash samples by inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (oaTOF-ICP-MS) after closed-vessel microwave extraction with ammonium fluoride was introduced here. Corrosive and/or toxic acids like HF, HCl or HClO₄, as well as HNO₃, which are commonly used during sample preparation of the fly ash samples, are avoided in this method. The spectral effects due to the formation of different Cl, Na, K, Ca, Mg-containing polyatomic species interfering with the determination of a number of elements like As, Se or Ni during the oaTOF-ICP-MS analysis are negligible. Under the optimum experimental extraction conditions evaluated using a fractional factorial design (10 mg of the sample extracted with 5 mL of 140 g/L NH₄F for 10 min at 200°C), analysis of the resulting supernatant with Rh as an internal standard enabled precise and accurate simultaneous determination of 11 elements (Li, Be, Ni, As, Se, Rb, Sb, Cs, W, Tl and U) at trace and ultratrace levels. The accuracy was assessed by analysing two certified reference materials, namely Fine Fly Ash CTA-FFA-1 and Constituent Elements in Coal Fly Ash Standard Reference Material® 1633b. The precision of the reported method was better than 10%.     

高效液相色谱与飞行时间质谱联用技术研究甲基对硫磷的细菌降解产物

用青岛曹家汶河口沉积物中分离出的细菌L-10(希瓦氏菌属)进行了水体中甲基对硫磷的细菌降解研究。研究表明,该菌对甲基对硫磷具有显著的降解性。采用高效液相色谱/飞行时间质谱(HPLC-TOF-MS)联用技术对甲基对硫磷及其细菌降解产物进行了分析。样品经SPE-C18小柱富集分离后,进行液相色谱和在线电喷雾飞行时间质谱分析。采用C18反相色谱柱(15 cm×4.6 mm i.d.5μm),线性梯度为:0 m in乙腈/水(30/70),5 m in乙腈/水(30/70),20 m in乙腈/水(80/20),25 m in乙腈/水(80/20);流速0.8 m l/m in,甲酸铵缓冲溶液浓度为0.1%(V/V);电喷雾正离子(ESI)模式,m/z扫描范围50~1000进行TOF-MS扫描、测定,测定结果用AnalystQS软件进行分析。结果表明,与甲基对硫磷光降解产生甲基对氧磷和对硝基酚不同,在降解菌L-10的存在下,甲基对硫磷发生了取代、氧化、还原等一系列反应,产生了相应的降解产物。降解过程的机理很复杂,从甲基对硫磷及其降解产物的分子结构式来分析,推断可能与细菌本身的代谢有关。     

脉冲熔融-飞行时间质谱法测定Ti-Al合金中氩

以标准气体参考物质为依据绘制氩校准工作曲线,利用脉冲熔融-飞行时间质谱法建立了准确测定钛铝合金中氩的分析方法。通过程序升温法确定钛铝合金中氩可以在分析功率为2800W时完全释放。并对比了助熔剂和称样量等分析条件对实验结果的影响,结果表明,采用高纯镍篮,钛铝合金中氩释放完全。脉冲熔融-飞行时间质谱法测定的结果与传统脉冲熔融-热导法测定结果基本一致。     

基体辅助激光解吸电离飞行时间质谱及其在高分子量物质测定中的应用

对基体辅助激光解吸电离飞行时间质谱这种新兴的质谱技术的原理及其在蛋白质序列分析、免疫分析、蛋白质定量和聚合物分子量分布的测定等方面的应用做了评述。引用参数文献５９篇。     

Fragmentation of Moxifloxacin and Its Analogs by Electrospray Ionization Time-of-Flight Mass Spectrometry

The fragmentation of patterns of moxifloxacin, 2-N-methylated moxifloxacin (analog 1), and 1-cyclopropyl-6,7-difluoro-8-methoxy-4-oxo-3-quinolinecarboxylic acid (analog 2) were investigated by electrospray ionization quadrupole time-of-flight tandem mass spectrometry in the positive-ion mode. Many unusual ions were detected in the tandem mass spectra of moxifloxacin. Although the structures of moxifloxacin and analog 1 were similar, the relative abundances of products varied greatly. Comparison of the relative abundances of the product ions that lost CO₂ or H₂O and complementary product ions resulting from sequential four-membered hydrogen rearrangement showed that the differences were related to the protonation sites. The loss of HF, probably though the formation of an ion/neutral complex, is of scientific interest. The identities of the major product ions were confirmed by deuterium-labeling experiments that demonstrated an unusual loss of a deuterium atom. The major differences in fragmentation patterns were compared to previous reports in the literature.     

Identification of Nitro Explosives by Direct Analysis in Real-Time Time-of-Flight Mass Spectrometry

Nitro compounds such as 2,4,6-trinitrotoluene, cyclotrimethylene trinitramine, and pentaerythritol tetranitrate are common ingredients of high explosives found in homeland security threats, minefields, and industrial materials. This study aims at developing a convenient surface analysis method for rapid identification of these compounds by direct analysis in real time coupled with time-of-flight mass spectrometry. The possible ionization mechanisms and fragmentation pathways using the direct analysis in real-time ionization source were developed for each compound based on the ions produced by in-source collision-induced dissociation and acquired by a time-of-flight mass spectrometer. These compounds release nitro groups and form nitroless characteristic fragments with other nitro adducts during in-source collision-induced dissociation processes. The characteristic ion [M?+?C₂H₄N₃O₂]^? produced by cyclotrimethylene trinitramine was observed for the first time to our best knowledge. Direct analysis in real-time time-of-flight mass spectrometry has provided rapid identification of residues from various samples from explosion scenes and, therefore, is a potential powerful screening tool for criminal evidence.