真空紫外灯单光子电离源飞行时间质谱仪的研制

研制了真空紫外灯单光子电离源飞行时间质谱仪(Vacuum ultraviolet single photon ionization time-offlight mass spectrometer,VUV-SPI-TOFMS),包括真空系统、毛细管进样系统、真空紫外灯电离源、垂直加速反射式飞行时间质量分析器和数据采集系统...     

Radiofrequency field enhanced chemical ionization with vacuum ultraviolet lamp for miniature time-of-flight mass spectrometer

Radiofrequency field enhanced chemical ionization enhances the sensitivity of benzene, toluene, hydrogen sulfide and other compounds by 2–3 orders of magnitude and expanded the detection range of the compounds with ionization energy from 10.6 eV to 12.0 eV.     

Mass spectrometry of natural organic phosphorus

This article provides a review of the use of modern mass spectrometry (MS) for quantitative and qualitative measurements of organic phosphorus compounds in nature. Included is a brief discussion of recent developments in large molecule mass spectrometry, focusing on time-of-flight (TOF) and ion cyclotron resonance (ICR) mass analysis techniques, as well as electrospray (ESI) and inductively coupled plasma (ICP) ionization. The use of ICP with high-resolution mass spectrometry for quantitative measurements of total phosphorus and as a detector coupled to HPLC and CE for defining organic phosphorus speciation is demonstrated using results from a study of phosphorus cycling in a treatment wetland. Qualitative identifications of individual phosphorus compounds by ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is demonstrated using dissolved organic phosphorus isolated from this same wetland.     

单光子电离飞行时间质谱仪对香烟新鲜主流烟气的在线检测

利用单光子电离飞行时间质谱仪对吸烟模拟装置中的新鲜主流烟气进行实时在线检测,共测得40多种挥发性有机化合物,获得不同物质在逐口吸烟过程中含量的变化情况以及不同通风率的香烟烟气中的化合物含量情况。与此同时,使用主成分分析法对不同通风率的香烟种类的新鲜烟气的谱图进行分析,结果表明,在PCA散点图中,PC1=94%,PC2=3%,PC2=1%,三者之和达到98%,不同通风率的香烟的差异显著。实现了对逐口吸烟产生的新鲜主流烟中的有机成分进行在线检测分析。     

Coupling two-step laser desorption/ionization with aerosol time-of-flight mass spectrometry for the analysis of individual organic particles

Analysis of organic compounds in aerosol particles using real-time single particle techniques is difficult because of extensive fragmentation that occurs in the laser desorption/ionization step. In an effort to avoid such fragmentation processes, we coupled a “soft” two-step laser desorption/ionization technique (L2MS) with aerosol time-of-flight mass spectrometry (ATOFMS). In these studies, we find this combination preserves intact organic molecules while providing the real-time mass spectra of suspended aerosol particles. Mass spectra of particles analyzed by one-step desorption mass spectrometry and L2MS are presented for comparison. These include 2,4-dihydroxybenzoic acid as a test case and wood and cigarette combustion particles as real world examples. This is the first published demonstration of L2MS performed on single particles not deposited on a substrate prior to analysis.     

The real-time analysis of gases by direct sampling–mass spectrometry: elemental and molecular applications

Real-time analysis of gases for volatile organic compounds or elements is required for a number of applications. Direct sampling-mass spectrometry (DS-MS) is one approach to solve these analytical problems. This article reviews various instrumental configurations and applications of DS-MS. Inlet systems employed for DS-MS include membranes, microtrap interfaces, atmospheric sampling glow discharge ionization, atmospheric pressure ionization, microwave plasma ionization, and capillary restrictors. The use of laser-based ionization methods for DS-MS is described, including resonance-enhanced multiphoton ionization and single photon ionization.     

Detection of volatile organic sulfur compounds in water by headspace gas chromatography and membrane inlet mass spectrometry

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in tlie analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethyl-methyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low (μg/1 levels with the two gas chromatographic methods and clearly below μg/1 level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.     

Selective Determination of Dimethyl Sulfide in Seawater Using Reactive Extractive Electrospray Ionization Mass Spectrometry

Reactive extractive electrospray ionization mass spectrometry was used for the rapid, sensitive determination of dimethyl sulfide in seawater without sample pretreatment. Using silver cations (Ag⁺) as the ionic reagent, the analyte was selectively extracted from seawater to form adduct ions of [CH₃SCH₃?+?Ag]⁺. The characteristic product ions of Ag⁺, generated from parent ions of [CH₃SCH₃?+?Ag]⁺ by tandem mass spectrometry, were used for quantitative analysis. A linear calibration curve was obtained from 1 to 10,000 pg/mL with acceptable relative standard deviations of 3.2–8.1%. This method provided a low limit of detection (0.3 pg/mL), reasonable recovery (82–111%), and acceptable precision (3.9 and 4.2% for intraday and interday measurements). Trace dimethyl sulfide was determined in seawater by this method. These results demonstrate that reactive electrospray ionization mass spectrometry is suitable for the rapid, reliable, and sensitive determination of dimethyl sulfide in seawater. Further investigations will improve our understanding on the relationship between global climate change and dimethyl sulfide concentrations in the ocean.     

Analysis of various organic and organometallic compounds using nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS)

Nanostructure-assisted laser desorption/ionization time-of-flight mass spectrometry (NALDI-TOFMS) has been developed recently as a matrix-free/surface-assisted alternative to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The NALDI surface of silicon nanowires is already very effective for the analysis of small to medium sized, polar organic molecules in positive ion mode. The current study examined this technology for the analysis of several nonpolar organic, organometallic, and ionic compounds in positive ion mode, as well as a fluorinated compound and various acids in negative ion mode. NALDI data are compared and contrasted with MALDI data for the same compounds, and the higher sensitivity of NALDI is highlighted by the successful characterization of two porphyrins for a sample amount of 10 amol per spot.     

气相色谱-单光子电离飞行时间质谱的联用及在柴油组分表征中的应用

建立了一种气相色谱(GC)与单光子电离-飞行时间质谱(SPI-TOF MS)联用(GC/SPI-TOF MS)的分析方法。首先,设计了一种双层套管的传输管用于连接GC与SPI-TOF MS,实现了GC与单光子电离离子源的无缝连接。在此基础上,以n-十五烷标准品和苯/甲苯/二甲苯的标准气为对象,对电离源的重要电压参数进行了优化,得到了纯净的分子离子峰,实现了对各类有机物的快速和准确定性。最后,将该方法用于分析柴油中的挥发性与半挥发性有机物,获得了柴油组分的二维GC×SPI-TOF MS谱图。不需要复杂的谱图解析和数据处理,根据谱图中离子的质荷比(m/z)归纳了柴油的主要成分,包括脂肪烃、芳香烃和含量很低的苯并吡咯等含氮化合物;根据色谱的保留时间将柴油中的同分异构体区分开来。结果表明GC/SPI-TOF MS法是一种简单、有效的分析方法,非常适于柴油及复杂环境样品等的分析表征。     

Comparison of electron ionization mass spectra of some organic compounds (MW < 200 Da) recorded on mass spectrometers of various types

Low-resolution electron ionization mass spectra recorded on various types of mass spectrometers (time-of-flight, quadrupole, and three-dimensional ion trap) were compared. A model mixture of 10 organic compounds (MW < 200 Da) was analyzed by gas chromatography-mass spectrometry. Pure mass spectra of analytes were extracted using the AMDIS software. The best repeatability was achieved for the time-of-flight mass spectrometer. The mass spectra recorded by a quadrupole and a time-of-flight mass spectrometer were quite similar. In the case of these instruments, library search using a commercial mass spectral data base (NIST’05) gave satisfactory result for each analyte (rank 1 or 2 in the “hit list”; Match > 900). In some cases, the mass spectra of model compounds recorded by the ion trap mass spectrometer differed in intensity of certain mass spectral peaks (but not in the set of peaks) from the mass spectra presented in the library and from the experimental mass spectra recorded by the time-of-flight and quadrupole instruments.     

Photoionization of atmospheric aerosol constituents and precursors in the 7-15 eV energy region: experimental and theoretical study

Photoionization mass spectrometry (PIMS) has been used to study the dissociative ionization of three anthropogenic atmospheric aerosol precursors (o-xylene, 2-methylstyrene, indene) and five of their main atmospheric degradation products (o-tolualdehyde, 2-methylphenol, o-toluic acid, phthalic acid, and phthaldialdehyde). Ionization and fragment appearance energies have been experimentally determined in the 7-15 eV photon energy regime. Moreover, intensive ab inito quantum chemical calculations have been performed to compute the first ionization energies and heats of formation of these compounds (including also phthalic anhydride). Several methods have been used, and the theoretical results are compared to the experimental values with the aim to find the best method to predict thermochemical data for similar molecules. The vacuum-UV fragmentation pathways following photoionization are discussed. The results of this work are important with respect to the analytical chemistry of these compounds since their basic gas phase ion energetics data are mostly unknown. They will help in interpreting real-time mass spectrometric measurements used for the study of organic aerosol formation in smog chambers and in the real atmosphere.     

Detection of organic products of polymer pyrolysis by thermogravimetry-supersonic jet-skimmer time-of-flight mass spectrometry (TG-Skimmer-SPI-TOFMS) using an electron beam pumped rare gas excimer VUV-light source (EBEL) for soft photo ionisation

A commercial thermogravimetry—supersonic jet-skimmer quadrupole mass spectrometer system (TG-Skimmer-QMS, Netzsch GmbH, Germany) was successfully converted for soft single photon ionisation time-of-flight mass spectrometric (SPI-TOFMS) detection of organic compounds. VUV light for SPI was generated by an electron beam pumped argon excimer light source (EBEL; E _photon = 9.8 eV). Furthermore, the versatility of the system was conserved, as high temperature TG and DSC measurements as well as electron ionisation mass spectrometry for the detection of inorganic compounds are still possible. The new system was tested with two polymers and a hydrocarbon mixture (diesel). It was demonstrated that aliphatic and aromatic organic compounds can be detected without fragmentation. Thus the system allows the recording of a readily interpretable organic signature of, e.g. thermal polymer decomposition. The thermal degradation of polystyrene shows a rich signature of the monomer, some oligomers and minor products of irregular cleavings of carbon chains. Polycarbonate exhibits a thermal decomposition fingerprint which is dominated by products of bisphenol A. The bisphenol A monomer, however, is also detectable.     

稠环齐聚物结构的激光解吸电离飞行时间质谱表征

应用激光解吸电离飞行时间质谱对几种不同结构的吡嗪稠环齐聚物进行了表征.样品溶解在二甲基亚砜中,以正离子方式记录谱图,结果发现除了产生目标化合物的质子化的分子离子峰外,还产生了少量的碎片分子离子峰.结果表明激光解吸电离飞行时间质谱能有效地、快速准确地给出这类化合物的分子离子峰,为吡嗪类稠环齐聚物的研究提供了有效的表征方法.     

The characterization of selected drugs with infrared laser desorption/tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

Some selected drugs including captopril, fudosteine and racecadotril have been analyzed by infrared (IR) laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The molecular ions of captopril and racecadotril are exclusively observed without any fragments at near threshold single-photon ionization (SPI). However, fudosteine easily forms fragments even at a photon energy near the ionization threshold, indicating the instability of its molecular ion. For these drugs, a number of fragments are yielded with the increase of photon energy. The structures of such fragments proposed by IR LD/VUV PIMS are supported by electron ionization time-of-flight mass spectrometry (EI-TOFMS) results. Fragmentation pathways are discussed in detail.     

Isotope determination of lead and bismuth by pulsed laser evaporation and resonance ionization time-of-flight mass spectrometry

Pulsed laser evaporation coupled with resonance ionization time-of-flight mass spectrometry has been used to measure the isotopic abundance of lead and bismuth. A pulsed Nd:YAG laser was used to evaporate the metal atoms, the evaporated atoms were then detected by one color two photon resonance ionization and time-of-flight mass spectrometry. The arrival time distributions of atoms evaporated by pulsed laser, and the isotopic abundances of Pb and Bi were measured. Our results show that this method is good enough for measuring the isotopic abundances of Pb and Bi with high sensitivity and selectivity.     

Selenium and sulfur trichalcogenides from the chalcogenide exchange reaction

Various selenium- and sulfur-containing volatiles have been detected and characterized as products of chalcogen exchange reactions. The formation of all possible selenium- and sulfur-containing trichalcogenide isomers (-SeSS-, -SSeS-, -SeSeS-, -SeSSe- and -SeSeSe-) was observed at room temperature in the solutions containing diselenide and trisulfide. Because of the low activation barrier of the selenium exchange reaction, these species are expected also to form in biological systems in the presence of diselenides and higher sulfides. Methyl and ethyl derivatives of these species were characterized using gas chromatography coupled to time-of-flight mass spectrometry with electron impact, chemical, and field ionization. Rearrangements of triselenides lead also to the formation of isomeric branched-structure triselenides, selanadiselenides. Because of the very similar structural properties, the behavior of these novel species was studied under various ionization modes (EI+, CI+, EI-, and CI-).     

Thermal analysis/mass spectrometry using soft photo-ionisation for the investigation of biomass and mineral oils

The combined analytical methods of thermal analysis and mass spectrometry have been applied in form of a newly developed prototype of a thermogravimetry — single photon ionisation time-of-flight mass spectrometer coupling (TG-SPI-TOFMS) to investigate the molecular patterns of evolved gases from several biomass samples as well as a crude oil sample. Single photon ionization (SPI) was conducted by means of a novel electron beam pumped argon excimer lamp (EBEL) as photon source. With SPI-TOFMS various lignin decomposition products such as guaiacol, syringol and coniferyl alcohol could be monitored. Furthermore, SPI allows the detection of aliphatic hydrocarbons, mainly alkenes, carbonylic compounds such as acetone, and furan derivatives such as furfuryl alcohol and hydroxymethylfurfural. More alkaline biomass such as coarse colza meal show intense signals from nitrogen containing substances such as (iso-)propylamine and pyrrole. Thermal degradation of crude oil takes place in two steps, evaporation of volatile components and pyrolysis of larger molecular structures at higher temperatures. Due to the soft ionisation, homologue rows of alkanes and alkenes could be detected on basis of their molecular ions. The obtained information from the thermal analysis/photo ionisation mass spectrometry experiments can be drawn on in comparison to the investigation of the primary products from flash pyrolysis of biomass for production of biofuels and chemicals.     

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants

Liquid chromatography–mass spectrometry using atmospheric pressure ionization (LC–API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC–MS application to transformation products.     

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.