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.

Screening and Identifying of Nephrotoxic Compounds in Lithospermum erythrorhizon Using Live-cell Fluorescence Imaging and Liquid Chromatography Coupled with Tandem Mass Spectrometry

In order to identify the potential nephrotoxic compounds in traditional Chinese medicine Lithospermum erythrorhizon,it was separated into serial fractions according to their polarities.An in vitro method was utilized to determine the nephrotoxicity of these fractions with the help of fluorescence image analysis.As a result,the primary fraction A05 and its secondary fractions C06 ＂C09 and C12 ＂C14 were found to have significant toxicity to LLC-PK1 cell line,as determined by the survive rate less than 20% after they were treated with these fractions.These potential nephrotoxic fractions were further analyzed by multistage and high resolution mass spectrometry.The main compounds in these fractions were tentatively identified to be acetylshikonin,isobutyrylshikonin,β,β＇-dimethyla-cryloylshikonin,and isovalerylshikonin,which may bring nephrotoxicity.

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.

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.

Determination of persistent organic pollutants by gas chromatography/laser multiphoton ionization/time-of-flight mass spectrometry

An authentic mixture of polychlorinated biphenyls was measured using a short wide-bore capillary column for the group separation of major components present in an actual sample of Kanechlor. The limits of detection were improved by ca. 2 fold in comparison with those obtained using a conventional capillary column, since the retention time was reduced and the amount of analytes introduced into the mass spectrometer per unit time could be increased. On the other hand, surface-water and sediment samples containing polycyclic aromatic hydrocarbons （PAHs） were collected from the river located in the vicinity of a waste water treatment plant. Even acenaphthylene, a minor component of the mixture could be measured for the sediment sample, and the concentra- tions were determined for several heavy PAHs. As demonstrated, a technique involving laser multiphoton ionization/time-of-flight mass spectrometry was useful as a sensitive and selective analytical tool for the trace analysis of persistent organic pollutants in an environmental sample.

Mass spectrometric study of Ag's clustering ability with O,S and Se

Samples Ag/O/S, Ag/O/Se and Ag/S/Se were ablated directly by laser to produce clusters. The detection was performed with a time-of-flight mass spectrometer (TOF MS). The cluster ions produced had the following distribution: Ag/S binary cluster ions for sample Ag/O/S, Ag/Se binary cluster ions for sample Ag/O/Se, and Ag/Se binary cluster ions and Ag/S/Se ternary cluster ions as the main products for sample Ag/S/Se. Laser double ablation reactor was used to study the reaction between Ag/S(Se, O) binary clusters and Se(S) homoclusters. The experiments show that Se clusters can replace S and O in Ag/S and Ag/O clusters while S clusters can replace O in Ag/O clusters. This fact indicates the sequence of the clustering ability of Ag presented as follows: Ag/Se 】 Ag/S 】 Ag/O, which was also proved by theoretical calculation. The reason of this tendency was considered to be the different abilities of the elements’ polarization, which acts on the stability of clusters.

Optimization of multi-reflection time-of-flight mass analyzer operating in in-trap-lift mode

Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating in in-trap-lift mode have to be optimized to achieve a very high mass resolving power.Methods Our method to design and optimize an MRTOF mass analyzer has been updated to introduce constraints on the potentials,and this method now can be used to optimize the parameters of MRTOF-MS both operating in mirror-switching mode and in in-trap-lift mode.By using this method,the optimal potential parameters of the electrodes have been obtained for our MRTOF mass analyzer operating in the in-trap-lift mode.Results and conclusion With a beam size of 2.8 mm diameter and an initial average ion kinetic energy of 1500 eV,the maximal mass resolving power has been achieved to be 3.2×10^(4) with a total TOF of 7.0 ms for an ion species of ^(40)Ar^(1+).It can reach up to 5.6×10^(4) for a beam size of 0.3 mm diameter.The simulation shows that the inaccuracy of the potentials applied on the outermost mirror electrodes M1–M2 must be less than 50 ppm or preferably 20 ppm.

Characterization of submicron aerosols in the urban outflow of the central Pearl River Delta region of China

Submicron aerosol particles （with aerody- namic diameters less than 1 pm, PM1） were sampled and measured in Heshan, an urban outflow site of Guangzhou megacity in Pearl River Delta in South China, using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer （HR-ToF-AMS） in November 2010 during 2010 Guangzhou Asian Games. The mean PM~ mass concentration measured was 47.9 ± 17.0 μg.m3 during the campaign, with organic aerosol （OA） and sulfate being the two dominant species, accounting for 36.3% and 20.9% of the total mass, respectively, followed by black carbon （17.1%, measured by an aethalometer）, nitrate （12.9%）, ammonium （9.6%） and chloride （3.1%）. The average size distributions of the species （except black carbon） were dominated by an accumulation mode peaking at -550 nm. Calculations based on high-resolution organic mass spectrum showed that, C, H, O and N on average contributed 58.1%, 7.3%, 30.7%, and 3.9% to the total organic mass, respectively. The average ratio of organic mass over organic carbon mass （OM/OC） was 1.73 ± 0.08. Four components of OA were identified by the Positive Matrix Factorization （PMF） analysis, including a hydro- carbon-like （HOA）, a biomass burning （BBOA） and two oxygenated （SV-OOA and LV-OOA） organic aerosol components, which on average accounted for 18.0%, 14.3%, 28.8% and 38.9% of the total organic mass, respectively.

Single particle analysis of ambient aerosols in Shanghai during the World Exposition,2010:two case studies

ATSI Model 3800 aerosol time-of-flight mass spectrometer(ATOFMS)was deployed for single-particle analysis in Shanghai during theWorld Exposition(EXPO),2010.Measurements on two extreme cases:polluted day(1st May)and clean day(25th September)were compared to show how meteorological conditions affected the concentration and composition of ambient aerosols.Mass spectra of 90496 and 50407 particles were analyzed respectively during the two sampling periods.The ART-2a neural network algorithm was applied to sort the collected particles.Seven major classes of particles were obtained:dust,sea salt,industrial,biomass burning,organic carbon(OC),elementary carbon(EC),and NH4-rich particles.Number concentration of ambient aerosols showed a strong anti-correlation with the boundary layer height variation.The external mixing states of aerosols were quite different during two sampling periods because of different air parcel trajectories.Number fraction of biomass burning particles(43.3%)during polluted episode was much higher than that(21.6%)of clean time.Air parcels from the East China Sea on clean day diluted local pollutant concentration and increased the portion of sea salt particle dramatically(13.3%).The large contribution of biomass burning particles in both cases might be an indication of a constant regional background of biomass burning emission.Mass spectrum analysis showed that chemical compositions and internal mixing states of almost all the particle types were more complicate during polluted episode compared with those observed in clean time.Strong nitrate signals in the mass spectra suggested that most of the particles collected on polluted day had gone through some aging processes before reaching the sampling site.