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.

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.

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.

Automatic ^(40)Ar/^(39)Ar Dating Techniques Using Multicollector ARGUS VI Noble Gas Mass Spectrometer with Self-Made Peripheral Apparatus

A new fully automatic ^40Ar/^39Ar laboratory with a Thermo Scientific ARGUS VI mass spectrometer has been established in China University of Geosciences （Wuhan）. We designed and developed a mini efficient preparation system （80 mL）, a CO2 laser for heating samples, a crusher for extracting fluid inclusions within K-poor minerals and an air reservoir （31 L） and pipette （0.1 mL） system. The ARGUS VI mass spectrometer is operated by the Qtegra Noble Gas software, which can control the peripheral accessories, such as pneumatic valves, CO2 laser and crusher through a PeriCon （peripheral controller）. The experimental procedures of atmospheric argon ana- lyses, ^40Ar/^39Ar dating by laser stepwise heating and by progressive crushing in vacuo, can be fully automatically performed. The weighted mean of atmospheric ^40Ar/^36Ar ratios is 302.22＋0.03 （1σ, MSWD=0.74, n=200）, indicating that air reservoir and pipette system and the whole instrument sys- tem are very stable. This laboratory is a successful pioneer example in China to establish a new no- ble gas laboratory with self-made peripheral accessories expect for the mass spectrometer.

Recent developments of miniature ion trap mass spectrometers

With outstanding analytical performance and portability, miniature mass spectrometer is one of the most powerful tools for in-situ analysis. The miniaturization of mass spectrometers has lasted for more than ten years, during which a number of miniature mass spectrometers employing different techniques have been developed. Small-in-size, working at relatively high pressure region and capable of performing tandem mass spectrometry, ion trap is the most widely used mass analyzer in miniature mass spectrometer systems. The recent development of miniature ion trap mass spectrometer systems in the last ten years was reviewed in this paper. These instruments adopt different atmospheric pressure interfaces （APIs）, which are membrane inlets （MIs）, discontinuous atmospheric pressure interface （DAPI） and continuous atmospheric pressure interface （CAPI）. This review emphasizes on the mini mass spectrometry （MS） system that can be handheld by one person, but not the field-able ones that are too large to be hand-portable.

Determining gaseous composition of fluid inclusions with quadrupole mass spectrometer

Quadrupole mass spectrometer (QMS) is an instrument for effectively determining gaseous composition of fluid inclusion. The gaseous component is extracted from inclusions with thermal decrepitation method and then determined with the sensitive QMS instrument. The method is characterized by high sensitivity and high accuracy with the relative standard deviation (RSD,n=6) of less than 3%. It has been successfully used for analyzing fluid inclusions. The analytical results meet the requirement of geological study.

Pollutants identification of ambient aerosols by two types of aerosol mass spectrometers over southeast coastal area, China

Two different aerosol mass spectrometers, Aerodyne Aerosol Mass Spectrometer（AMS） and Single Particle Aerosol Mass Spectrometer（SPAMS） were deployed to identify the aerosol pollutants over Xiamen, representing the coastal urban area. Five obvious processes were classified during the whole observation period. Organics and sulfate were the dominant components in ambient aerosols over Xiamen. Most of the particles were in the size range of 0.2–1.0 μm, accounting for over 97% of the total particles measured by both instruments.Organics, as well as sulfate, measured by AMS were in good correlation with measured by SPAMS. However, high concentration of NH4＋was obtained by AMS, while extremely low value of NH4＋was detected by SPAMS. Contrarily, high particle number counts of NO3-and Clwere given by SPAMS while low concentrations of NO3-and Cl-were measured by AMS. The variations of POA and SOA obtained from SPAMS during event 1 and event 2 were in accordance with the analysis of HOA and OOA given by AMS, suggesting that both of AMS and SPAMS can well identify the organic clusters of aerosol particles. Overestimate or underestimate of the aerosol sources and acidity would be present in some circumstances when the measurement results were used to analyze the aerosol properties, because of the detection loss of some species for both instruments.

Development of a Rapid and Simultaneous Detection Method for Buprenorphine, Norbuprenorphine and Naloxone in Human Plasma Using Ultra-high Performance Liquid Chromatography- tandem Mass Spectrometer with Solid-phase Extraction

A simultaneous method was successfully established and validated for the separation and determination of bu- prenorphine （BP）, its primary metabolite, nor-buprenorphine （NBP） and a proposed co-formulate, naloxone （NLX） in human plasma. The method used buprenorphine-d4 （BP-D4）, nor-buprenorphine-d3 （NBP-D3）, naltrexone （NTX） as internal standards （ISs）. 100 μL of plasma sample fortified with the ISs was cleaned up by solid-phase extraction （SPE）, and was then separated on a Waters AcquityTM BEH C18 column with gradient elution using methanol and water （containing 0.2% formic） at a flow rate of 0.25 mL·min^-1. The mass spectrometer was used for detection and was operated in the positive electrospray ionization with multiple reaction monitoring （MRM） mode. The three compounds were effectively separated in 5 min. The linear ranges of the compounds were 0.1--25, 0.25--25 and 0.05--25 ng·mL^-1 for BP, NBP and NLX, respectively, with r≥0.9935. The method had high sensitivity （the lim- its of detection were 0.02, 0.1 and 0.01 ng.mL-1 for BP, NBP and NLX, respectively） and high recoveries （≥97.6%）. The result was shown to be linear and satisfactorily met current acceptance criteria for validation of bio- analytical method： intra and inter assay precisions within the required limits of ≤25% RSD. The LOQs fulfilled the LOQ requirements： precision≤25% RSD, and was fully validated according to the State Food and Drug Administration （SFDA） regulations. The results demonstrated that ultra-high performance liquid chromatography- tandem mass spectrometer （UPLC-MS/MS） with SPE was a powerful detection tool and contributed to pharmaceutical analysis in biological matrices.

Ultra-High-Performance Liquid Chromatograph with Triple-Quadrupole Mass Spectrometer Quantitation of Twelve Phenolic Components in Different Parts of Sarcandra glabra

Objective:The study objective was to determine phenolic components for the quality control(QC)of cultivated Sarcandra glabra(Thunb.)Makino(S.glabra).Materials and Methods:A sensitive,ultra-high-performance liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 12 phenolic components has been developed.Six caffeoylquinic acids,two caffeoylshikimic acids,and four flavanonol glucosides were selected for the comprehensive analysis of distribution in different parts(root,stem,and leaf).Results:Twelve phenolic components were linear in the concentration range of 0.005–5.0μg/mL(R^(2)>0.995).The relative standard deviation of intra-day and inter-day precision across three validation runs over the entire concentration range was<5%.The recovery determined was within 5%in terms of relative error.Our results showed that the 12 phenolic compounds were mainly distributed in leaves and stems far more than those in roots.Conclusions:This study provided an ultra-high-performance liquid chromatograph with triple-quadrupole mass spectrometer quantitative method of 12 phenolic components for the QC of cultivated S.glabra.It was found that the phenolic components were significantly accumulated in the aerial parts(stems and leaves)of cultivated S.glabra.

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

It is difficult to rapidly and on-line detect trace volatile organic compounds for miniature massspectrometry due to its limited sampling volume at slow pumping speed. In this paper, we developed anew radiofrequency field enhanced chemical ionization source （RF-ECI） with vacuum ultraviolet （VUV）lamp by coupling radiofrequency electric field and direct-current field together. The experiment resultsshowed that the sensitivity of benzene, toluene, hydrogen sulfide and other compounds increased by 2-3orders of magnitude under the introduction of RF-ECI comparing to traditional single photon ionization（SPI）. At the same time, the reagent ion of O2＋ realized the charge transfer reaction chemical ionization,and the RF-ECI effectively expanded the detection range of the VUV lamp based SPI. The VUV lamp hasinherent advantages in the on-site analytical instrument for its small size and low power consumption,and the VUV lamp based RF-ECI miniature time-of-flight mass spectrometer （TOFMS） has a limit-of-detection for H2S as low as 0.0571 mg/m3, and it is expected to be used widely in the field of on-site rapidanalvsis.

Chemical composition of different size ultrafine particulate matter measured by nanoparticle chemical ionization mass spectrometer

New particle formation(NPF)is the primary source of nanoparticles and contributes a large number of concentrations of cloud condensation nuclei.In recent years,field campaigns and laboratory experiments have been conducted to promote cognition of the mechanism for NPF and its following growth processes.The chemical composition measurement of nanoparticles could help deepen understanding of the initial step of particulate matter formation.In this work,we developed a nanoparticle chemical ionization mass spectrometer to measure nanoparticles’chemical compositions during their initial growth stage.Meanwhile,a non-radioactive ion source was designed for aerosol charging and chemical ionization.Time of flight mass spectrometer coupled with integrated aerosol size selection and collection module would guarantee the picogram level detection limit and high-resolution ability to measure the matrix of ambient samples.The performance of this equipment was overall evaluated,including the transmission efficiency and collection efficiency of custombuilt nano differential mobility analyzer,chemical ionization efficiency,and mass resolution of the mass spectrometer.The high sensitivity measurement of ammonium sulfate and methylammonium sulfate aerosols with diameters ranging from 10 to 25 nm could guarantee the application of this instrument in the ambient measurement.

Improved identification of glycerophospholipids using a linear ion trap mass spectrometer(LTQ) with Pulsed Q Collision Induced Dissociation(PQD)

Phospholipids are the major building blocks of the biological membranes. Additionally, phospholipids modulate membrane trafficking and metabolites derived from their

A collinear tandem time-of-flight mass spectrometer for infrared photodissociation spectroscopy of mass-selected ions

An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.

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.

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.