Separation of Ions from Volatile Organic Compounds Using High-Field Asymmetric Waveform Ion Mobility Spectrometry-Mass Spectrometer

A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.

A Reflectron Time-of-Flight Mass Spectrometer with a Nano-Electrospray Ionization Source for Study of Metal Cluster Compounds

An experiment facility has been set up for the study of metal cluster compounds in our laboratory, which consists of a nano-electrospray ionization source, an ion transmission and focus system, and a reflectron time-of-fight mass spectrometer. Taking advantage of the nano-electrospray ionization source, polyvalent ions are usually produced in the ＂ionization＂ process and the obtained mass resolution of the equipment is over 8000. The molecular ion peaks of metal cluster compounds [Au20（PPhpy2）10Cl2]（SbF6）4, where PPhpy2=bis（2- pyridyl）phenylphosphine, and [AuaAg2（C）L6]（BF4）4, where L=2-（diphenylphosphino）-5- methylpyridine, are distinguished in the respective mass spectrum, accompanied by some fragment ion peaks. In addition, the mass-to-charge ratios of the parent ions are determi- nated. Preliminary results suggest that the device is a powerful tool for the study of metal cluster compounds. It turns out that the information obtained by the instrumentation serves as an essential supplement to single crystal X-ray diffraction for structure characterization of metal cluster compounds.

Characterization of Organic Aerosols in Beijing Using an Aerodyne High-Resolution Aerosol Mass Spectrometer

Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aerosol mass spectrometer （HR- ToF-AMS, Aerodyne Research Inc., USA） was deployed in urban Beijing in August and October 2012. The mean OA mass concentration in autumn was 30 4-30 μg m-3, which was higher than in summer （13 4-6.9 μg m-3）. The elemental anal- ysis found that OA was more aged in summer （oxygen-to-carbon （O/C） ratios were 0.41 and 0.32 for summer and autumn, respectively）. Positive matrix factorization （PMF） analysis identified three and five components in summer and autumn, re- spectively. In summer, an oxygenated OA （OOA）, a cooking-emission-related OA （COA）, and a hydrocarbon-like OA （HOA） were indentified. Meanwhile, the OOA was separated into LV-OOA （low-volatility OOA） and SV-OOA （semi-volatile OOA）; and in autumn, a nitrogen-containing OA （NOA） was also found. The SOA （secondary OA） was always the most important OA component, accounting for 55% of the OA in the two seasons. Back trajectory clustering analysis found that the origin of the air masses was more complex in summer. Southerly air masses in both seasons were associated with the highest OA loading, while northerly air masses were associated with the lowest OA loading. A preliminary study of OA components, especially the POA （primary OA）, in different periods found that the HOA and COA all decreased during the National Day holiday period, and HOA decreased at weekends compared with weekdays.

A Satellite-borne Miniature Ion Mass Spectrometer for Space Plasma

The miniature design technology is an important trend in space exploration.Mass spectrometer is used extensively in the space environment detection.The miniature ion mass spectrometer utilizes a 127° cylindrical electrostatic analyzer accompanied with a Time of Flight(TOF)unit based on ultrathin carbon foil to measure the energy spectra and composition of space plasma.The Time of Flight technique has been used broadly in space plasma measurement.A new type of miniature method for the ion mass spectrometer is introduced.The total mass of the instrument is1.8 kg and the total power consumption is 2.0 W.The calibration results show that the energy measurement range is 8.71~43550eV,the energy resolution is 1.86%and the ion mass from 1 amu(1 amu= 1.67 × 10^(-27)kg) to 58 amu can be resolved by the miniature mass spectrometer.The miniature ion mass spectrometer also has a potential to be increased in the field of view by an electrostatic deflecting system to extend its application in space plasma detection.The miniature ion mass spectrometer has been selected for pre-study of Chinese Strategic Priority Research Program on Space Science.

Modification of Reflectron Time-of-Flight Mass Spectrometer for Photodissociation of Mass-Selected Cluster lons

We introduce a modification of reflectron time-of-flight mass spectrometer for laser photodissociation of mass-selected ions. In our apparatus, the ions of interests were selected by a mass gate near the first space focus point and decelerated right after the mass gate, were then crossed by a laser beam for dissociation. The daughter ions and surviving parent ions were re-accelerated and analyzed by the reflectron time-of-flight mass spectrometer. Compared to the designs reported by other research groups, our selection-deceleration-dissociation-reacceleration approach has better daughter-parent-ions-separation, easier laser timing, and better overlapping between the ion beam and laser beam. We also conducted detailed cal- culations on the parent ion and daughter ion flight times, and provided a simplified formula for the calibration of daughter ion mass.

Laser-Ionization TOF Mass Spectrometer Characterization of Benzene Destruction in Atmospheric Pressure Pulsed Discharge

Benzene is a major industrial air pollutant and can cause serious human health disorders. In this paper an investigation on benzene destruction, in an atmospheric-pressure fast-flow pulsed DC-discharge by means of laser ionization combined with time-of-flight （TOF） mass spectrometry, is reported. Most by-products including transient reactive species from the benzene discharge were characterized by molecular beam sampling combined with TOF mass spectrometry. It is showed that, with a gas mixture of 0.5% C6H6 in Ar, benzene can be effectively destroyed by discharge plasma. The intermediate species consisted of small fragments of CnHm （n=3-5, m = 1-11）, cycle-chain species of CnHm （n =6-9, m = 7-10） and polycyclic species CnHm （n ≥9, m = 8-12）. The alternation of mass peaks （intensity） with even/odd electrons was observed in the measured mass spectra. The results indicated that the alternation is mainly due to the different ionization potentials of the open shell and close shell species. Based on the examination of the features of the species＇ composition, the primary reaction pathways are proposed and discussed.

A SUPER SENSITIVITY MINICYCLOTRON MASS SPECTROMETER SPECIALIZED FOR CARBON-14 DATING

The structure consideration of a minicyclotron as super- sensitivity mass spectrometer for carbon -14 dating being constructed at this Institute is described. Some new design ideas and techniques are presented.

GAS-PHASE ION-MOLECULE REACTIONS OF BUCKMINSTERFULLERENE(C_(60))WITH Si(CH_3)_n CL_(4-n)(n=2,3)IN MASS SPECTROMETER

Reactions of C60 with Si(CH_3)_nCl_(4-n) (n=2,3)in the ion source of the mass spectrometer have been studied.The corresponding adduct ions[C60Si(CH_3)_mCl3_(-m)]^+(m=1,2,3),[C60SiCl]^+ and[C60CH_3]^+ were observed and their possible structures were discussed.The results indicated that C60 is very reactive to electrophiles in the gas phase.

6-23 Design of Vacuum System for Magnetic Mass Spectrometer

Ions with different rigidity have different radius of deflection in the same magnetic field, based on this principle the magnetic mass spectrometer, which will be used to analyze the beam quality and the distribution, can separate mixed ion beams. In order to reduce the energy loss of beam in vacuum pipe, the vacuum pressure level must be less than 1x10?4 Pa.

Performance of Ionization Gauge and Quadrupole Mass Spectrometer with Bessel-Box Type Energy Analyzer:a Review of Progress

A novel energy analyzer with a simple structured Bessel box has been successfully developed and incorporated into ionization gauges and quadrupole mass spectrometers (QMS) to improve their measurement of the total and partial pressures,respectively.We found that the energy analyzer may not only effectively separate the gas phase ions and electron stimulated desorption (ESD) ions produced in the ionizer,but also screen the ion collector from irradiation of the soft X rays and VUVphotons generated in the ionizer.The screening effects considerably better the trace impurity detection limit of the QMS down to a few tens ppb in the pressure range of 10 -3 Pa.The modified ionization gauge is capable of measuring pressure ranging from 10 -11 to 10 -6 Pa in the pulse counting mode and its upper limit may extends to 10 -3 Pa in DC ion current mode with typical sensitivities factor of(6.7±0.2)×10 -3 Pa -1 for N 2 and (2.3±0.2)×10 -3 Pa -1 for H 2,respectively.No ESD ions was observed in the simple looking spectrum obtained with the modified QMS.We also found that the energy spectra of fragment ions depend strongly on species of parent ions.

Mass Spectrometric Studies of Selective Oxidation of n-Butane over a Vanadium Phosphorus Oxide Catalyst

The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.

Membrane Separator Interface for Mass-Spectrometric Analysis of Desflurane, Propofol and Fentanyl in Plasma and Cerebrospinal Fluid

Mass-spectrometric interface for the measurement of anaesthetic agent concentration in biological fluids (blood plasma and cerebrospinal fluid) is described. Sampling of biological fluids was performed during balanced inhalational (desflurane, fentanyl) anaesthesia and total intravenous (propofol, fentanyl) anaesthesia. The described method for drug concentration measurement in biologic fluids does not require long-term sample processing before injecting the sample into mass-spectrometer interface, in contrast to chromatographic methods. A hydrophobic membrane was used in the interface to separate anaesthetic agents from biological fluids: inhalational anaesthetic desflurane, hypnotic propofol, analgesic fentanyl. A possibility to use the interface for measurement of desflurane and propofol absolute concentration in blood plasma and cerebrospinal fluid was demonstrated for the study of blood-brain barrier (BBB) properties.

Mass Spectrometric Studies on Metal-hexafluorobenzene Anionic Complexes(M=Ag, Au, Pd, Pt, Pb and Bi)

The anionic products from the reactions between metal（M=Ag, Au, Pd, Pt, Pb and Bi） vapour produced by laser ablation and hexafluorobenzene seeded in carrier gas（Ar） were studied by means of a homemade reflectron time-of-flight mass spectrometry（RTOF-MS）. Experimental results show that the dominant products were [MmC6F6]^- complexes for the reactions ofAg, Au, Pd and Pt with C6F6, while the dominant products were [MmC6F5]^- complexes for the reactions of Pb and Bi with C6F6. The formation mechanisms of the products, including the adsorption of metal cluster anions on hexafluorobenzene and the C--F cleavage induced by metal cluster anions, were discussed.

Data-independent acquisition mass spectrometry quantitative proteomic analysis reveals that skin aging-related proteins differ between men and women

The skin is the largest organ of the human body,and its aging is visible to the naked eye.The aging rate of men and women is slightly different.This study compared the protein expression of skin samples on the curved forearms of 11 healthy women and 9 healthy men.Quantitative proteomics analysis found that the expression of epidermal proteins in men and women of the same age group was different.Compared with female skin,in male skin,20 proteins were upregulated,and 7 proteins were downregulated.These data suggest that men and women have differences in the speed of skin aging.For the first time in this experiment,a non-invasive mass spectrometer was used to detect 27 different-related epidermal proteins between men and women.Compared with women,among the 20 epidermal proteins upregulated in men,their functions can be classified into antioxidants,epidermal lipid metabolism,signal transduction,membrane transport,and cell biological processes;the 7 downregulated proteins are involved in a variety of biological processes and inflammatory reactions.Our experiments have discovered epidermal proteins related to the differences between men and women,enriching the library of epidermal differential proteins between men and women and enriching the mechanism of skin aging between men and women from the perspective of epidermal differential proteins.

Mass-Spectrometric Method of Measurement of Isotopic Content of Nitrogen in Organic Compounds

Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.

科学仪器自搭建实验的课程思政设计——以教学质谱仪的搭建、调试及应用为例

培养能够开展科学仪器原理创新、设计制造、应用开发的高端人才已成为建设人才强国、科技强国的必然要求。本案例在本科实验中引入我国科学家自主研制的教学质谱仪,采用学生亲自动手拆装、调试及应用的方式,深化学生对质谱仪工作原理、构造和相关分析方法的认识,破除对“高端仪器”的神秘感和畏难情绪,激发学生研制科学仪器的兴趣,培养敢于挑战自我、勇于自主创新的意志品质,坚定科技报国、服务国家的家国情怀。

一种空间微型质谱仪的芯片级离子源研究

设计了一种空间微型质谱仪用三电极场芯片级离子源结构,该离子源由5层电极板构成气体电离区和离子引出区。采用MEMS技术制备了芯片级离子源原理样机,测试了其电子流、离子流和稳定性。结果表明:该芯片级离子源能够产生0.357 mA以上的电子流,接收到的离子流可以达到527 pA,满足空间探测任务中微小型质谱仪离子源的功能要求。

质谱仪质量分析器的专利技术分析

【目的】重点分析质谱仪质量分析器的技术,对其技术发展脉络和研发路线进行剖析,以期为专利审查提供参考。【方法】通过专利分析,对质谱仪的质量分析器技术进行梳理,并对不同类型的质量分析器技术进行分析。【结果】从2012年起,我国针对质谱仪质量分析器的研究较多,主要包括飞行时间质量分析器、四极杆质量分析器、磁性质量分析器、离子阱质量分析器、傅里叶变换离子回旋共振质量分析器等方面,并在专利方面取得了一定成绩。【结论】我国在质谱仪质量分析器领域研究逐渐成熟,有助于我国物质分析和检测领域的发展。

不同干燥方式八角果实挥发性化合物代谢组分析

【目的】探明不同干燥方式对八角果实挥发性成分的影响,筛选出适宜八角果实干燥的处理方式,为八角后期深加工、保存及应用提供参考。【方法】以新鲜八角果实为材料,采用自然晾晒、40℃、50℃、60℃、70℃、80℃和90℃烘干7种处理方式进行干燥,通过液相色谱-质谱(LC-MS)技术检测分析八角果实代谢产物,阐明八角果实不同温度干燥与自然晾晒处理的代谢物差异。【结果】与自然晾晒相比,八角果实40℃干燥差异代谢产物有11类17种,其中,萜类、醇类和醛类3类代谢物上调;50℃干燥差异代谢物有10类25种,其中,上调代谢物6类(萜类、醇类、酯类、酮类、卤代烃类、酚类);60℃干燥差异代谢物有8类13种,其中,醇类和烃类代谢物上调;70℃干燥差异代谢物为13类40种,其中,醇类、萜类和酯类3类代谢物上调;80℃干燥差异代谢物有13类38种,仅醇类代谢物上调;90℃干燥差异代谢物有13类52种,其中,上调代谢物4类(萜类、醇类、酮类、卤代烃类)。40℃、50℃和60℃干燥的八角果实与自然晾晒差异代谢物较少,上调代谢物主要是苯甲醛、醋酸植物醇、茴香脑、6-异羟基樟脑、乙酸异丁香酚酯和甲基丁香酚等挥发性化合物,提升了八角浓厚的香味。70℃、80℃和90℃干燥的八角果实与自然晾晒差异代谢物较多,且与八角香味相关的许多代谢物下调表达,主要有香芹酮、茴香脑、E-氧化玫瑰、4-蒈烯、对薄荷脑1,5,8-三烯、苯甲醛、芳樟醇、3-甲基苯并噻吩、2-甲基-2-四氢呋喃和2-乙酰基-5-甲基呋喃等挥发性化合物,减弱了八角香味。【结论】不同干燥处理八角果实的挥发性化合物种类均存在一定差异。40℃、50℃和60℃干燥八角果实,苯甲醛、醋酸植物醇和茴香脑等上调表达的挥发性化合物提升了八角香味。八角果实经50℃干燥后,上调表达的代谢物有萜类、醇类、酯类、酮类、卤代烃类和酚类6类,果实独特香气保持最好,宜在生产上推广应用。

液液萃取-气相色谱质谱法测定水质中的环氧氯丙烷

比较了不同前处理方法进行水质中环氧氯丙烷的测试,其中液液萃取的前处理方法简单可靠,方便易行,适合复杂基质水样的测定。同时比较了气相色谱仪不同检测器对环氧氯丙烷(ECH)的响应值,其中质谱检测器对ECH的响应值最高。液液萃取-气相色谱质谱法测定水质中的环氧氯丙烷,该方法的检出限为0.6μg/L,测定下限为2.4μg/L。对海水、地表水、工业污水样品加标浓度为0.001 mg/L、0.02 mg/L、0.2 mg/L进行平行6次测定,结果的相对标准偏差分别为6.9%、2.7%和6.3%,加标回收率分别为93.5%、99.0%和99.6%,非常适合各类水质ECH的监测。