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1.
To address the critical need for improving the chemical characterization of the organic composition of ambient particulate matter, we introduce a combined thermal desorption aerosol gas chromatograph—aerosol mass spectrometer (TAG-AMS). The TAG system provides in-situ speciation of organic chemicals in ambient aerosol particles with hourly time resolution for marker compounds indicative of sources and transformation processes. However, by itself the TAG cannot separate by particle size and it typically speciates and quantifies only a fraction of the organic aerosol (OA) mass. The AMS is a real-time, in-situ instrument that provides quantitative size distributions and mass loadings for ambient fine OA and major inorganic fractions; however, by itself the AMS has limited ability for identification of individual organic compounds due to the electron impact ionization detection scheme used without prior molecular separation. The combined TAG-AMS system provides real-time detection by AMS followed by semicontinuous analysis of the TAG sample that was acquired during AMS operation, achieving simultaneous and complementary measurements of quantitative organic mass loading and detailed organic speciation. We have employed a high-resolution time-of-flight mass spectrometer (HR-ToF-MS) to enable elemental-level determination of OA oxidation state as measured on the AMS, and to allow improved compound identification and separation of unresolved complex mixtures (UCM) measured on the TAG. The TAG-AMS interface has been developed as an upgrade for existing AMS systems. Such measurements will improve the identification of organic constituents of ambient aerosol and contribute to the ability of atmospheric chemistry models to predict ambient aerosol composition and loadings. Copyright 2014 American Association for Aerosol Research 相似文献
2.
A new aerodynamic lens system for an online aerosol time-of-flight mass spectrometer (ATOFMS) has been designed and constructed to transmit and allow the analysis of individual particles in the 4–10-μm-size range. Modeling was used to help design the lens within the bounds of ATOFMS instrumental constraints. The aerodynamic lens operates at a high inlet pressure, 3066 Pa (23 Torr), with a unique tapered relaxation region to improve large particle transmission. Every stage of the lens was tested empirically using a combination of particle deposition and light scattering experiments. The critical orifice was found to significantly impact large particle transmission, with orifices <200 μm in diameter completely suppressing large particle transmission. The addition of a virtual impactor allowed for the use of large orifices without any loss of functionality in the ATOFMS. The detection efficiency of the ATOFMS was >10% for particles from 4–10 μm with a peak efficiency of 74 ± 9% for 6-μm particles. With the extended size range provided by this inlet, the ATOFMS can now be extended to investigate single cell metabolomics. Copyright 2014 American Association for Aerosol Research 相似文献
3.
Copyright 2015 American Association for Aerosol Research 相似文献
4.
Copyright 2015 American Association for Aerosol Research 相似文献
5.
The Aerodyne aerosol mass spectrometer (AMS) employs flash vaporization (600°C) followed by 70-eV electron impact ionization (EI) to detect organic and inorganic aerosols. The signal at mass-to-charge ratio ( m/z) 44 (mainly CO 2 + ) is considered the most reliable marker of oxygenated organic aerosol. This study is the first to evaluate the contribution of selected low molecular weight dicarboxylic acids (diacids) and ω-oxocarboxylic acids (ω-oxoacids) to the particle-phase m/z 44 signal of the AMS mass spectrum. Ambient measurements were conducted at a surface site in Tokyo (35°39 ′ N, 139°40 ′ E) during August 3–8, 2003. Diacids and ω-oxoacids were measured using a filter sampling followed by extraction, derivation, and gas chromatograph-flame ionization detector (GC-FID) analysis. The mass concentrations of diacids and ω-oxoacids show tight correlation with the m/z 44 signal ( r 2 = 0.85–0.94) during the measurement period. Laboratory experiments were also performed to determine the fragment patterns of selected diacids (C 2–C 6 diacids and phthalic acids) and ω-oxoacid (glyoxylic acid) in ambient aerosols. Here, we report for the first time that the selected organic acids could account for 14 ± 5% of the observed m/z 44 signal on average during the measurement period. Oxalic acid (C 2) is the largest contributor, accounting for 10 ± 4% of the observed m/z 44 signal. These results would be useful for interpreting the m/z 44 signals obtained from ambient measurements in various locations. 相似文献
6.
A particle into liquid sampler (PILS) has been directly coupled to an accurate mass atmospheric ionization time-of-flight mass spectrometer (ToF) for use in the speciation of secondary organic aerosol (SOA) formed in the University of California—Riverside, College of Engineering–Center for Environmental Research and Technology (CE-CERT) atmospheric chambers. To this end, the PILS has been optimized for direct continuous injection into the ToF and the PILS-ToF system has been used to obtain real-time mass spectral traces of the particle phase products of atmospheric chamber reactions. The PILS-ToF system has been initially applied to SOA formed from α-pinene dark ozonolysis and isoprene photooxidation. The characterization of the PILS-ToF system includes experiments on the well understood α-pinene/O 3 system, which verifies the performance of the tool. The PILS-ToF tool is then used to provide new insight into the chemical composition of the SOA formed from isoprene photooxidation. For the first time, time resolved traces of oligomer formation during isoprene photooxidation are observed using the PILS-ToF. The unique subunits of oligomer series are reported. The PILS-ToF system is demonstrated to be a powerful tool for obtaining real-time electro spray ionization and chemical ionization mass spectral speciation of aerosols.Copyright 2013 American Association for Aerosol Research 相似文献
7.
We developed a laser induced incandescence–mass spectrometric analyzer (LII-MS) for online measurements quantifying the aerosol chemical compositions with respect to the mixing state of black carbon (BC). The LII-MS is developed as a tandem series comprising an LII chamber to detect and vaporize BC-containing particles and a particle trap laser desorption mass spectrometer (PT-LDMS: Takegawa et al. 2012). The PT-LDMS collects aerosol particles transferred from the LII chamber and quantifies the chemical compositions. A newly designed collection probe, coupled with the sheath-air inlet nozzle of the LII chamber, enables a high throughput of aerosol particles without significant dilution. Total aerosol particles can be analyzed in the PT-LDMS by turning off the laser (MS mode), and the aerosol particles externally mixed with BC can be analyzed by turning on the laser (LII-MS mode). The difference in the PT-LDMS signals between the MS and LII-MS modes yields the chemical composition of materials internally mixed with BC. Performance of the developed instrument was evaluated in the laboratory by generating BC particles internally-mixed with oleic acid (OL) and BC particles externally mixed with ammonium sulfate particles. Preliminary results from ambient measurements are also presented and discussed. Copyright 2014 American Association for Aerosol Research 相似文献
8.
Abstract This article examines the state-of-the art on aerodynamic separation and drying of leaves and stems. Relevant aerodynamic and drying characteristics of alfalfa leaves and stems, important in the design and functional performance evaluation of appropriate drying and separation systems, are presented. General features and design parameters of rotary drum dryers are discussed. A new efficient approach to combined drying and separation in a rotary drum dryer is described in which fresh or pre-wilted alfalfa mixture is dried at a moderate temperature, and in the same operation the dry leaf fraction is aerodynamically separated from the stem fraction. Preliminary test data obtained from the dryer indicated that the separated product stream had comparatively high leaf purity, confirming the feasibility of the new approach. 相似文献
9.
A new method for accurate mass and size measurement of monodisperse particles is proposed. In this method, charged aerosol particles are introduced into parallel plate electrodes similar to the Millikan cell, and the number of particles left suspended after a certainty holding time has elapsed is measured. The particle survival rate as a function of the voltage applied to the electrodes is used to determine the particle mass. The particle size is deduced by using the particle density which is determined in a separate experiment. The expression of the particle survival function, which is defined as the survival rate as a function of the mass, for particles with and without Brownian diffusion is derived. The sensitivity of this method to the number average diameter, as well as other size distribution parameters, is analyzed on the basis of the survival function. 相似文献
10.
In the framework of nuclear waste reprocessing, the separation processes of minor actinides from fission products are developed using liquid‐liquid extraction. To gain an understanding of the mechanism involved in the extraction process, a complex formation of actinides and lanthanides with BTBPs (6,6′‐bis(5,6‐dialkyl‐1,2,4‐triazin‐3‐yl)‐2,2′‐bipyridines) was characterized using the Electrospray Ionization Mass Spectrometry (ESI‐MS) technique. This study was carried out to compare the influence of diluents and side groups of the extractants on complex formation. Three different diluents, nitrobenzene, octanol and cyclohexanone, and two extractants, C5‐BTBP and CyMe 4‐BTBP, were selected for this experiment. It was found that the change of the diluent and of the substituent on the BTBP moiety does not modify the stoichiometry of the complexes which is L 2M(NO 3) 3. It is proposed that one nitrate is directly coordinated to the metal ion, the two other anions probably remaining in the outer coordination sphere. The difference observed in extracting properties is probably due to the solvation of the complexes by the diluent. The noncovalent force that holds complexes together are likely to be largely governed by electrostatic interactions even if the hydrophobic exterior of the complexes plays an important role in the complexation/extraction mechanism. The study of the stability of the ions in the gas phase shows that the C5‐BTBP ligand has a labile hydrogen atom, which is a fragility point of C5‐BTBP. 相似文献
11.
大家对“玩具总动员”中精美的三维动画人物尚未淡忘,河南先博公司便在这席卷全球的三维动画热潮中又添了一把火,推出本年度特别奉献"3D New Show"(三维新视野)。 该光碟是继一年前先博公司推出销售火爆的“三维视野”的超值续集。内容除包含有百余种以3DS格式的模型之外,还有千余种各种背景贴图文件,是三维动画设计人员之必备佳品。 相似文献
12.
卫丝兰竺些宣呈)经丝下啤,想曲碱凡移,l ——一—一减索未乡舀时护一口节仁公 叱十乙Or~一-~斗一户~一卜_~斗一一、一‘-一一斗十一{一~一仁土一上,一 仁l一一r书一下卜一件一十一中一斗一卜一l月 一一丁--一卜一__牛一十一!一一一卜一一4一上-一仁一一!l一!嘴臀管资望断贯瞥」怜1拐司侍净妒胃舟甲l‘Ieel|llwees‘11!1..|es|eses.|esesO少2J呼左锌一~-一一一一一廷铸拜或F{行一4且韵瑕社触啤低教切曲绒护凤依、l.~一~一-一一口日尸一‘一一一一———一—一-一不辛升渗道李司鸯拜不于兰吞会}0%‘司%、—一一丫一一~,一.一一一产一‘一下-… 相似文献
13.
Polyolefins are chemically inert and do not adhere well to metals, polymers or inorganics. To overcome this problem, polyolefin surfaces were modified thermally, plasmachemically, or by flame treatment with different oxygen-containing groups, however, unfortunately, such treatments were accompanied by undesired, adhesion lowering polymer degradation. To solve this dilemma, solutions of synthetic polymers and copolymers were prepared, sprayed into the barrier discharge or electrosprayed without discharge and deposited as thin adhesion-promoting layers. The deposited polymer layers from poly(vinylamine), poly(ethylene glycol)–poly(vinyl alcohol) copolymers and poly(acrylic acid) were endowed with monotype functional groups. Using the aerosol — dielectric barrier discharge only a fraction of functional groups survived the deposition process in contrast to the electrospray in which all functional groups were retained. 相似文献
14.
The α(1A)-adrenergic receptor (α(1A)-AR) antagonist is useful in treating benign prostatic hyperplasia, lower urinary tract symptoms, and cardiac arrhythmia. Three-dimensional quantitative structure-activity relationship (3D-QSAR) studies were performed on a set of α(1A)-AR antagonists of N-aryl and N-nitrogen class. Statistically significant models constructed from comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were established based on a training set of 32 ligands using pharmacophore-based molecular alignment. The leave-oneout cross-validation correlation coefficients were q(2) (CoMFA) = 0.840 and q(2) (CoMSIA) = 0.840. The high correlation between the cross-validated/predicted and experimental activities of a test set of 12 ligands revealed that the CoMFA and CoMSIA models were robust (r(2) (pred) (/CoMFA) = 0.694; r(2) (pred) (/CoMSIA) = 0.671). The generated models suggested that electrostatic, hydrophobic, and hydrogen bonding interactions play important roles between ligands and receptors in the active site. Our study serves as a guide for further experimental investigations on the synthesis of new compounds. Structural modifications based on the present 3D-QSAR results may lead to the discovery of other α(1A)-AR antagonists. 相似文献
15.
This work examines the unipolar charging of aerosol particles smaller than 100 nm by ions (at STP) both theoretically (Part I) and experimentally (Part II). Among numerous well-known models for particle charging by ions a gap has been identified for the case of diffusion charging with superimposed external electric field in the transition regime. A two dimensional extension of the classical Fuchs-model Fuchs, 1963 Fuchs, N. A. 1963. On the Stationary Charge Distribution on Aerosol Particles in a Bipolar Ionic Atmosphere. Geofisica Pura e Applicata, 56: 185–193. [Crossref] , [Google Scholar]) has been developed in order to bridge this gap in the knowledge. For the first time the complete expression for the electrostatic potential between a particle and an ion has been included. By using FEM-simulations, the quantitative influence of an external electric field on the charging process has been predicted. It is shown that an external electric field increases the average particle charge linearly. Compared to pure diffusion charging, an electric field of 10 kV/cm increases the charge on metallic particles up to 28% (30 nm particles), 55% (60 nm), and 95% (100 nm), respectively. When compared to the Fuchs-model, the assumptions of the new model introduce additional uncertainty of less than 3%. Comparison with the simpler, but physically less reasonable continuum model by Lawless (1996) Lawless, P. A. 1996. Particle Charging Bounds, Symmetry Relations and an Analytic Rate Model for the Continuum Regime. J. Aerosol Sci., 27: 191–215. [Crossref] , [Google Scholar] shows similar charge predictions (deviations < 20% for n·t-products 10 13 s/m 3), even for 30 nm particles. So, that continuum charging model can serve as simple approximation of the more accurate charging model for the transition regime. 相似文献
17.
Despite being geographically dispersed, abundant, and accounting for almost half of the world's coal reserves, low-rank coals (LRCs) find limited use due to their high moisture content and high propensity for spontaneous combustion. Reducing the moisture content of low-rank coal enhances its heating value and reduces transportation costs, thus increasing its economic value. In addition, dried low-rank coals have been proven to improve plant efficiency, enhance safety, and reduce greenhouse gas emissions. Although numerous technologies for coal drying already exist, it is often challenging, if not impossible, to find one that is cost-effective in all aspects. When selecting a dryer for coal upgrading applications, factors such as particle size/size distribution, throughput, energy consumption, material handling capabilities, safety, carbon footprint, capital and operating costs, return on investment, etc., are important considerations. This article provides an overview of the patent literature along with the archival literature that deals with drying of coal as well as biomass, which is relevant to coal drying. 相似文献
18.
Pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD) technique was examined as an alternative to solvent extraction for simultaneous separation and concentration of cobalt(II)–nickel(II) mixture using Cyanex-272 as the extractant. Experiments were carried out by continuous recirculation of the feed and pseudo-emulsion phases through a hollow-fiber module. The separation factor increased rapidly after 60 min of operation. The maximum value after 120 min of operation was ~128 (pH = 6.5) for the operating conditions studied. The mass transfer resistance from the extraction reaction appeared to be dominant. The results of mathematical modeling of the mass transfer process indicated that higher separation factor and extraction rate can be achieved using PEHFSD in comparison to solvent extraction. Mixing of the stripping and the feed solution was observed at high dispersed phase volume fraction in the pseudo-emulsion and low flow rate of this phase. The maximum value of backtransport flux from the stripping phase due to mixing was estimated to be approximately two orders lower than the initial extraction rates. 相似文献
19.
Dimethyl sulfate (DMS) is a potential carcinogen that may be formed during the production of α-sulfonated methyl ester (α-SME). To date, there have been no published analytical methods for quantification of DMS in palm oil-based α-SME. The objective of the method development was to establish a simple and reliable method for quantifying and monitoring DMS from palm oil-based α-SME. The sample preparation prior to analysis involved extracting DMS from α-SME using hexane. The gas chromatography–mass spectrometry (GC–MS) separation was performed on an Agilent MS-HP5 column (30 m × 320 μm × 0.25 μm). The MS signal was obtained in the selected ion monitoring (SIM) mode. The method was validated according to the International Conference on Harmonization (ICH) guidelines. The accuracy of the method was measured via percentage recoveries of DMS from spiked α-SME samples at spiking levels of (25, 125, 250, and 500) μg mL −1. The percentage recoveries for all spiking levels were found to be in the range of 88.6–97.4%. The repeatability and interday reproducibility were found to be satisfactory as the relative standard deviations (RSD) were within 11%. The method also has a good linear relationship as indicated by the coefficient of determination of 0.9996 over the range of 1.0–30 μg mL −1. The limits of detection (LOD) and quantification (LOQ) corresponded to 0.8 and 2.3 μg mL −1, respectively. The developed method demonstrated sufficient linearity, intraday and interday precision, sensitivity, and accuracy for determination of DMS in palm oil-based α-SME. 相似文献
20.
A previous article in this journal reported the results of an FTIR analysis of the ambient aerosol collected during a field study in Houston, Texas during August and September of 2000. The emphasis of that article was on the organonitrates collected during the study. In the discussion of their research, the authors noted some discrepancies between the organonitrate absorbances observed in Houston compared to those seen in a previous study conducted in Los Angeles, California. They offer several explanations for the observed differences. In these comments, an alternative explanation is offered for these differences. 相似文献
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