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1

Analysis and characterization of sophorolipids by liquid chromatography with atmospheric pressure chemical ionization  

Microsoft Academic Search

Summary  A reversed phase high performance liquid chromatographic method combined with atmospheric pressure chemical ionization mass\\u000a detection (LC\\/APCI-MS) has been developed for the separation and analysis of sophorolipids produced byC. bombicola when grown on fatty acid mixtures. Using this method it was found that the incorporation of palmitic, linoleic, and linolenic\\u000a acids into the sophorolipid structure was dependent on the initial

A. Nuñez; R. Ashby; T. A. Foglia; D. K. Y. Solaiman

2001-01-01

2

Evaluating the Utility of an Atmospheric Pressure Chemical Ionization Mass Spectrometer for Analyzing Organic Peroxides  

NASA Astrophysics Data System (ADS)

Secondary organic aerosols (SOA) are known to affect the earth's radiation budget through its ability to scatter and absorb radiation. Consequently, the mechanisms and factors that influence SOA composition and formation are poorly understood. However, recent modeling studies coupled with smog chamber experiments suggest that organic peroxides (organic hydroperoxides and peroxyhemiacetals) might be a major component of SOA composition under low NOx conditions. This study utilized an atmospheric pressure chemical ionization mass spectrometer (APCI-MS) in the positive mode to detect organic peroxides. Mass spectra of organic peroxides analyzed in this study show excessive fragmentation during ionization with protonated water clusters. It was believed that intact ions were not found due to decomposition in the ion source. Future work will explore new reagents for ionization to reduce fragmentation during analysis.

Jameer, A.; Hastie, D. R.

2013-12-01

3

Simultaneous LC/MS analysis of hexachlorobenzene and pentachlorophenol by atmospheric pressure chemical ionization (APCI) and photoionization (APPI) methods.  

PubMed

The simultaneous LC/MS analyses of hexachlorobenzene (HCB) and pentachlorophenol (PCP), two dioxin precursors were studied by both atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization mass spectrometry (APPI/MS). The optimum LC/MS conditions of the simultaneous analysis were determined for these two compounds with different polarity. Ionization by APPI was found to be more effective than by APCI, and is thus a better ionization method for analysis of the two compounds. Using LC/APPI/MS we can achieve the simultaneous analysis of HCB and PCP at ppb levels. PMID:19907098

Osaka, Issey; Yoshimoto, Arifumi; Nozaki, Kazuyoshi; Moriwaki, Hiroshi; Kawasaki, Hideya; Arakawa, Ryuichi

2009-11-01

4

Laser-Induced Acoustic Desorption/Atmospheric Pressure Chemical Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a commercial linear quadrupole ion trap mass spectrometer (LQIT). Model compounds representing a wide variety of different types, including basic nitrogen and oxygen compounds, aromatic and aliphatic compounds, as well as unsaturated and saturated hydrocarbons, were tested separately and as a mixture. These model compounds were successfully evaporated into the gas phase by using LIAD and then ionized by using APCI with different reagents. From the four APCI reagent systems tested, neat carbon disulfide provided the best results. The mixture of methanol and water produced primarily protonated molecules, as expected. However, only the most basic compounds yielded ions under these conditions. In sharp contrast, using APCI with either neat benzene or neat carbon disulfide as the reagent resulted in the ionization of all the analytes studied to predominantly yield stable molecular ions. Benzene yielded a larger fraction of protonated molecules than carbon disulfide, which is a disadvantage. A similar but minor amount of fragmentation was observed for these two reagents. When the experiment was performed without a liquid reagent (nitrogen gas was the reagent), more fragmentation was observed. Analysis of a known mixture as well as a petroleum cut was also carried out. In summary, the new experiment presented here allows the evaporation of thermally labile compounds, both polar and nonpolar, without dissociation or aggregation, and their ionization to predominantly form stable molecular ions.

Gao, Jinshan; Borton, David J.; Owen, Benjamin C.; Jin, Zhicheng; Hurt, Matt; Amundson, Lucas M.; Madden, Jeremy T.; Qian, Kuangnan; Kenttämaa, Hilkka I.

2011-03-01

5

Thin-layer chromatography and mass spectrometry coupled using proximal probe thermal desorption with electrospray or atmospheric pressure chemical ionization.  

PubMed

An atmospheric pressure proximal probe thermal desorption sampling method coupled with secondary ionization by electrospray or atmospheric pressure chemical ionization was demonstrated for the mass spectrometric analysis of a diverse set of compounds (dyestuffs, pharmaceuticals, explosives and pesticides) separated on various high-performance thin-layer chromatography plates. Line scans along or through development lanes on the plates were carried out by moving the plate relative to a stationary heated probe positioned close to or just touching the stationary phase surface. Vapors of the compounds thermally desorbed from the surface were drawn into the ionization region of a combined electrospray ionization/atmospheric pressure chemical ionization source where they merged with reagent ions and/or charged droplets from a corona discharge or an electrospray emitter and were ionized. The ionized components were then drawn through the atmospheric pressure sampling orifice into the vacuum region of a triple quadrupole mass spectrometer and detected using full scan, single ion monitoring, or selected reaction monitoring mode. Studies of variable parameters and performance metrics including the proximal probe temperature, gas flow rate into the ionization region, surface scan speed, read-out resolution, detection limits, and surface type are discussed. PMID:20499315

Ovchinnikova, Olga S; Van Berkel, Gary J

2010-06-30

6

Characterization of triacetone triperoxide by ion mobility spectrometry and mass spectrometry following atmospheric pressure chemical ionization.  

PubMed

The atmospheric pressure chemical ionization of triacetone triperoxide (TATP) with subsequent separation and detection by ion mobility spectrometry has been studied. Positive ionization with hydronium reactant ions produced only fragments of the TATP molecule, with m/z 91 ion being the most predominant species. Ionization with ammonium reactant ions produced a molecular adduct at m/z 240. The reduced mobility value of this ion was constant at 1.36 cm(2)V(-1)s(-1) across the temperature range from 60 to 140 °C. The stability of this ion was temperature dependent and did not exist at temperatures above 140 °C, where only fragment ions were observed. The introduction of ammonia vapors with TATP resulted in the formation of m/z 58 ion. As the concentration of ammonia increased, this smaller ion appeared to dominate the spectra and the TATP-ammonium adduct decreased in intensity. The ion at m/z 58 has been noted by several research groups upon using ammonia reagents in chemical ionization, but the identity was unknown. Evidence presented here supports the formation of protonated 2-propanimine. A proposed mechanism involves the addition of ammonia to the TATP-ammonium adduct followed by an elimination reaction. A similar mechanism involving the chemical ionization of acetone with excess ammonia also showed the formation of m/z 58 ion. TATP vapors from a solid sample were detected with a hand-held ion mobility spectrometer operated at room temperature. The TATP-ammonium molecular adduct was observed in the presence of ammonia and TATP vapors with this spectrometer. PMID:21524145

Ewing, Robert G; Waltman, Melanie J; Atkinson, David A

2011-06-15

7

Laser Microdissection and Atmospheric Pressure Chemical Ionization Mass Spectrometry Coupled for Multimodal Imaging  

SciTech Connect

This paper describes the coupling of ambient laser ablation surface sampling, accomplished using a laser capture microdissection system, with atmospheric pressure chemical ionization mass spectrometry for high spatial resolution multimodal imaging. A commercial laser capture microdissection system was placed in close proximity to a modified ion source of a mass spectrometer designed to allow for sampling of laser ablated material via a transfer tube directly into the ionization region. Rhodamine 6G dye of red sharpie ink in a laser etched pattern as well as cholesterol and phosphatidylcholine in a cerebellum mouse brain thin tissue section were identified and imaged from full scan mass spectra. A minimal spot diameter of 8 m was achieved using the 10X microscope cutting objective with a lateral oversampling pixel resolution of about 3.7 m. Distinguishing between features approximately 13 m apart in a cerebellum mouse brain thin tissue section was demonstrated in a multimodal fashion including co-registered optical and mass spectral chemical images.

Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

2013-01-01

8

Kinetic and Thermodynamic Control of Protonation in Atmospheric Pressure Chemical Ionization  

NASA Astrophysics Data System (ADS)

For p-(dimethylamino)chalcone ( p-DMAC), the N atom is the most basic site in the liquid phase, whereas the O atom possesses the highest proton affinity in the gas phase. A novel and interesting observation is reported that the N- and O-protonated p-DMAC can be competitively produced in atmospheric pressure chemical ionization (APCI) with the change of solvents and ionization conditions. In neat methanol or acetonitrile, the protonation is always under thermodynamic control to form the O-protonated ion. When methanol/water or acetonitrile/water was used as the solvent, the protonation is kinetically controlled to form the N-protonated ion under conditions of relatively high infusion rate and high concentration of water in the mixed solvent. The regioselectivity of protonation of p-DMAC in APCI is probably attributed to the bulky solvent cluster reagent ions (SnH+) and the analyte having different preferred protonation sites in the liquid phase and gas phase.

Chai, Yunfeng; Hu, Nan; Pan, Yuanjiang

2013-07-01

9

Document authentication at molecular levels using desorption atmospheric pressure chemical ionization mass spectrometry imaging.  

PubMed

Molecular images of documents were obtained by sequentially scanning the surface of the document using desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS), which was operated in either a gasless, solvent-free or methanol vapor-assisted mode. The decay process of the ink used for handwriting was monitored by following the signal intensities recorded by DAPCI-MS. Handwritings made using four types of inks on four kinds of paper surfaces were tested. By studying the dynamic decay of the inks, DAPCI-MS imaging differentiated a 10-min old from two 4 h old samples. Non-destructive forensic analysis of forged signatures either handwritten or computer-assisted was achieved according to the difference of the contour in DAPCI images, which was attributed to the strength personalized by different writers. Distinction of the order of writing/stamping on documents and detection of illegal printings were accomplished with a spatial resolution of about 140 µm. A Matlab® written program was developed to facilitate the visualization of the similarity between signature images obtained by DAPCI-MS. The experimental results show that DAPCI-MS imaging provides rich information at the molecular level and thus can be used for the reliable document analysis in forensic applications. PMID:24078245

Li, Ming; Jia, Bin; Ding, Liying; Hong, Feng; Ouyang, Yongzhong; Chen, Rui; Zhou, Shumin; Chen, Huanwen; Fang, Xiang

2013-09-01

10

Direct probe atmospheric pressure photoionization/atmospheric pressure chemical ionization high-resolution mass spectrometry for fast screening of flame retardants and plasticizers in products and waste.  

PubMed

In this study, we develop fast screening methods for flame retardants and plasticizers in products and waste based on direct probe (DP) atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization (APCI) coupled to a high-resolution (HR) time-of-flight mass spectrometer. DP-APPI is reported for the first time in this study, and DP-APCI that has been scarcely exploited is optimized for comparison. DP-APPI was more selective than DP-APCI and also more sensitive for the most hydrophobic compounds. No sample treatment was necessary, and only a minimal amount of sample (few milligrams) was used for analysis that was performed within a few minutes. Both methods were applied to the analysis of plastic products, electronic waste, and car interiors. Polybrominated diphenylethers, new brominated flame retardants, and organophosphorus flame retardants were present in most of the samples. The combination of DP with HR mass spectra and data processing based on mass accuracy and isotopic patterns allowed the unambiguous identification of chemicals at low levels of about 0.025 % (w/w). Under untargeted screening, resorcinol bis(biphenylphosphate) and bisphenol A bis(bisphenylphosphate) were identified in many of the consumer products of which literature data are still very limited. PMID:24493336

Ballesteros-Gómez, A; Brandsma, S H; de Boer, J; Leonards, P E G

2014-04-01

11

Determination of Organic Acids in Ground Water by Liquid Chromatography\\/Atmospheric Pressure Chemical Ionization\\/Mass Spectrometry  

Microsoft Academic Search

Current methods of determining organic acids in ground water are labor-intensive, time-consuming and require a large volume of sample (100 milliliter to 1.0 liter). This paper reports a new method developed to determine aliphatic, alicyclic, and aromatic acids in ground water using liquid chromatography\\/atmospheric pressure chemical ionization\\/mass spectrometry (LC\\/APCI\\/MS). This method was shown to be fast (less than 1 hour),

Jiasong Fang; Michael J. Barcelona

1999-01-01

12

Mass spectrometric behavior of anabolic androgenic steroids using gas chromatography coupled to atmospheric pressure chemical ionization source. Part I: ionization.  

PubMed

The detection of anabolic androgenic steroids (AAS) is one of the most important topics in doping control analysis. Gas chromatography coupled to (tandem) mass spectrometry (GC-MS(/MS)) with electron ionization and liquid chromatography coupled to tandem mass spectrometry have been traditionally applied for this purpose. However, both approaches still have important limitations, and, therefore, detection of all AAS is currently afforded by the combination of these strategies. Alternative ionization techniques can minimize these drawbacks and help in the implementation of a single method for the detection of AAS. In the present work, a new atmospheric pressure chemical ionization (APCI) source commercialized for gas chromatography coupled to a quadrupole time-of-flight analyzer has been tested to evaluate the ionization of 60 model AAS. Underivatized and trimethylsylil (TMS)-derivatized compounds have been investigated. The use of GC-APCI-MS allowed for the ionization of all AAS assayed irrespective of their structure. The presence of water in the source as modifier promoted the formation of protonated molecules ([M+H](+)), becoming the base peak of the spectrum for the majority of studied compounds. Under these conditions, [M+H](+), [M+H-H2O](+) and [M+H-2·H2O](+) for underivatized AAS and [M+H](+), [M+H-TMSOH](+) and [M+H-2·TMSOH](+) for TMS-derivatized AAS were observed as main ions in the spectra. The formed ions preserve the intact steroid skeleton, and, therefore, they might be used as specific precursors in MS/MS-based methods. Additionally, a relationship between the relative abundance of these ions and the AAS structure has been established. This relationship might be useful in the structural elucidation of unknown metabolites. PMID:24913403

Raro, M; Portolés, T; Sancho, J V; Pitarch, E; Hernández, F; Marcos, J; Ventura, R; Gómez, C; Segura, J; Pozo, O J

2014-06-01

13

Production and Utilization of CO3- Produced by a Corona Discharge in Air for Atmospheric Pressure Chemical Ionization  

SciTech Connect

Atmospheric pressure chemical ionization is a multistep ionization process used in mass spectrometry and ion mobility spectrometry. The formation of product ions depends upon interactions with the analyte and the reactant ion species formed in the ionization source. The predominant reactant ion observed in a point-to-plane corona discharge in air occurs at m/z 60. There have been multiple references in the literature to the identity of this ion with some disagreement. It was postulated to be either CO3- or N2O2-. The identity of this ion is important as it is a key to the ionization of analytes. It was determined here to be CO3- through the use of 18O labeled oxygen. Further confirmation was provided through MS/MS studies. The ionization of nitroglycerine (NG) with CO3- produced the adduct NG•CO3-. This was compared to ionization with NO3- and Cl- reactant ions that also formed adducts with NG. The fragmentation patterns of these three adducts provides insight into the charge distribution and indicates that CO3- has a relatively high electron affinity similar to that of nitrate.

Ewing, Robert G.; Waltman, Melanie J.

2010-12-14

14

Mass spectral behavior of the hydrolysis products of sesqui- and oxy-mustard type chemical warfare agents in atmospheric pressure chemical ionization  

Microsoft Academic Search

Bis(2-hydroxyethylthio)alkanes and bis(2-hydroxyethylthioalkyl)ethers are important biological and environmental degradation\\u000a products of sulfur mustard analogs known as sesqui- and oxy-mustards. We used atmospheric pressure chemical ionization mass\\u000a spectrometry (APCI MS) to acquire characteristic spectra of these compounds in positive and negative ionization modes. Positive\\u000a APCI mass spectra exhibited [M + H]+; negative APCI MS generated [M + O2]?, [M ? H]?,

Sharon W. Lemire; Doris H. Ash; Rudolph C. Johnson; John R. Barr

2007-01-01

15

Analysis of toxic norditerpenoid alkaloids in Delphinium species by electrospray, atmospheric pressure chemical ionization, and sequential tandem mass spectrometry.  

PubMed

A rapid electrospray mass spectrometry method was developed for screening larkspur (Delphinium spp.) plant material for toxic norditerpenoid alkaloids. The method was calibrated using two standard alkaloids, methyllycaconitine (1) and deltaline (2), with a recovery of 92% from spiked samples and relative standard deviations of 6.0% and 8.1% for the two alkaloids, respectively. Thirty-three samples of plains larkspur, Delphinium geyeri, were analyzed. Methyllycaconitine (1) concentration was 0.27% +/- 0.08% during a 1-month period in 1997 establishing the relative risk of poisoning from the plant to be low. The method was also applied to the trace analysis (<1 ppm) of 1 in serum samples from sheep dosed different levels of the alkaloid. Electrospray ionization combined with sequential tandem mass spectrometry and HPLC coupled to atmospheric pressure chemical ionization (APCI) mass spectrometry were used to detect and tentatively identify three new norditerpenoid alkaloids from Delphinium nuttallianum [bearline (6), 14-acetylbearline (7), 16-deacetylgeyerline (8)]. The tentative structure of the new alkaloids was predicted from the tandem mass spectra fragmentation patterns and assigning the substitution pattern for methoxy and acetyl groups at the C-14 and C-16 carbons. PMID:10606571

Gardner, D R; Panter, K E; Pfister, J A; Knight, A P

1999-12-01

16

Accurate quantitation of pentaerythritol tetranitrate and its degradation products using liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.  

PubMed

After an explosion of pentaerythritol tetranitrate (PETN), its degradation products pentaerythritol trinitrate (PETriN), dinitrate (PEDiN) and mononitrate (PEMN) were detected using liquid chromatography-atmospheric-pressure chemical-ionization-mass spectrometry (LC-APCI-MS). Discrimination between post-explosion and naturally degraded PETN could be achieved based on the relative amounts of the degradation products. This information can be used as evidence when investigating a possible relationship between a suspect and a post-explosion crime scene. The present work focuses on accurate quantitation of PETN and its degradation products, using PETriN, PEDiN and PEMN standards specifically synthesized for this purpose. With the use of these standards, the ionization behavior of these compounds was studied, and a quantitative method was developed. Quantitation of PETN and trace levels of its degradation products was shown to be possible with accuracy between 85.7% and 103.7% and a precision ranging from 1.3% to 11.5%. The custom-made standards resulted in a more robust and reliable method to discriminate between post-explosion and naturally-degraded PETN. PMID:24656542

Brust, Hanneke; van Asten, Arian; Koeberg, Mattijs; Dalmolen, Jan; van der Heijden, Antoine; Schoenmakers, Peter

2014-04-18

17

Determination and characterization of organic explosives using porous graphitic carbon and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.  

PubMed

A new LC-MS method for the determination and characterization of three groups of commonly used organic explosives (nitroaromatic compounds, cyclic nitroamines and nitrate esters) was developed using a porous graphitic carbon (PGC) (Hypercarb) column. Twenty-one different explosive-related compounds--including 2,4,6-trinitrotoluene, its by-products and its degradation products--were chromatographically separated in a single analysis. This efficient separation facilitates the identification of the manufacturer of the explosive using the identified analytes as a fingerprint. A final, conclusive identification of the analytes can be obtained using LC-MS equipped with an atmospheric pressure chemical ionization (APCI) interface. Solvent effects on chromatographic behaviour were investigated, as were the effects of solvent mixtures and mobile phase additives. The number and the relative positions of the nitro groups within analyte molecules influence their order of elution; these effects were investigated. The data thus generated can be interpreted to support a hypothesis concerning the retention mechanism of nitro-containing compounds when using PGC. Limits of detection ranged from 0.5 to 41.2 ng. The new methodology described herein improves the sensitivity and selectivity of explosive detection. The effectiveness of the method is demonstrated by the analysis of soil samples containing explosives residue from test fields in Sweden and Afghanistan. PMID:16213509

Holmgren, Erik; Carlsson, Håkan; Goede, Patrick; Crescenzi, Carlo

2005-12-16

18

Thermal desorption counter-flow introduction atmospheric pressure chemical ionization for direct mass spectrometry of ecstasy tablets.  

PubMed

A novel approach to the analysis of ecstasy tablets by direct mass spectrometry coupled with thermal desorption (TD) and counter-flow introduction atmospheric pressure chemical ionization (CFI-APCI) is described. Analytes were thermally desorbed with a metal block heater and introduced to a CFI-APCI source with ambient air by a diaphragm pump. Water in the air was sufficient to act as the reactive reagent responsible for the generation of ions in the positive corona discharge. TD-CFI-APCI required neither a nebulizing gas nor solvent flow and the accompanying laborious optimizations. Ions generated were sent in the direction opposite to the air flow by an electric field and introduced into an ion trap mass spectrometer. The major ions corresponding to the protonated molecules ([M + H](+)) were observed with several fragment ions in full scan mass spectrometry (MS) mode. Collision-induced dissociation of protonated molecules gave characteristic product-ion mass spectra and provided identification of the analytes within 5 s. The method required neither sample pretreatment nor a chromatographic separation step. The effectiveness of the combination of TD and CFI-APCI was demonstrated by application to the direct mass spectrometric analysis of ecstasy tablets and legal pharmaceutical products. PMID:19565470

Inoue, Hiroyuki; Hashimoto, Hiroaki; Watanabe, Susumu; Iwata, Yuko T; Kanamori, Tatsuyuki; Miyaguchi, Hajime; Tsujikawa, Kenji; Kuwayama, Kenji; Tachi, Noriyuki; Uetake, Naohito

2009-09-01

19

Analyses of polycyclic aromatic hydrocarbons in seafood by capillary electrochromatography-atmospheric pressure chemical ionization/mass spectrometry.  

PubMed

In this work, an on-line preconcentration capillary electrochromatographic (CEC) separation coupled with atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) was used for 16 PAHs analyses, in which poly(stearyl methacrylate-divinylbenzene) (poly(SMA-DVB)) monolith was used as the separation column. With variations in the effective length of poly(SMA-DVB) monolith as well as the volume fraction of acetonitrile (ACN) in the mobile phase, both separation and resolution were improved. A poly(SMA-DVB) monolith of 50-cm effective length (i.e. 50-cm column length filled with polymer) and a two-step step-gradient elution (by changing the ACN levels of the mobile phase starting with an initial of 70% up to 80% with 30-min time interval), which provided baseline separation for PAHs solutes (except for chrysene and benzo[a]anthracene) within 50 min, were employed as the optimal chromatographic conditions. In contrast to the other mass spectrometer parameters (nebulizer gas pressure, vaporizer temperature, corona current) as well as on-line preconcentration parameter (the ACN level in the sample matrix), the sheath liquid composition (methanol/water in the ratio of 3:1) and the sample injection time (40 min) were found as the predominant factors that control the sensitivity of PAHs determination. Finally, this on-line preconcentration CEC-APCI-MS method determined PAH residues in seafood samples successfully with as low as 10 ng/g level. PMID:23992841

Cheng, Yi-Jie; Huang, Sing-Hao; Chiu, Ju-Yin; Liu, Wan-Ling; Huang, Hsi-Ya

2013-10-25

20

Qualitative analysis of some carboxylic acids by ion-exclusion chromatography with atmospheric pressure chemical ionization mass spectrometric detection.  

PubMed

A simple, selective and sensitive method for the determination of carboxylic acids has been developed. A mixture of formic, acetic, propionic, valeric, isovaleric, isobutyric, and isocaproic acids has been separated on a polymethacrylate-based weak acidic cation-exchange resin (TSK gel OA pak-A) based on an ion-exclusion chromatographic mechanism with detection using UV-photodiode array, conductivity and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). A mobile phase consisting of 0.85 mM benzoic acid in 10% aqueous methanol (pH 3.89) was used to separate the above carboxylic acids in about 40 min. For LC-MS, the APCI interface was used in the negative ionization mode. Linear plots of peak area versus concentration were obtained over the range 1-30 mM (r2=0.9982) and 1-30 mM (r2=0.9958) for conductimetric and MS detection, respectively. The detection limits of the target carboxylic acids calculated at S/N=3 ranged from 0.078 to 2.3 microM for conductimetric and photometric detection and from 0.66 to 3.82 microM for ion-exclusion chromatography-APCI-MS. The reproducibility of retention times was 0.12-0.16% relative standard deviation for ion-exclusion chromatography and 1.21-2.5% for ion-exclusion chromatography-APCI-MS. The method was applied to the determination of carboxylic acids in red wine, white wine, apple vinegar, and Japanese rice wine. PMID:12108651

Helale, Murad I H; Tanaka, Kazuhiko; Taoda, Hiroshi; Hu, Wenzhi; Hasebe, Kiyoshi; Haddad, Paul R

2002-05-17

21

Analysis of malachite green and metabolites in fish using liquid chromatography atmospheric pressure chemical ionization mass spectrometry.  

PubMed

Malachite green (MG), a traditional agent used in aquaculture, is structurally related to other carcinogenic triphenylmethane dyes. Although MG is not approved for use in aquaculture, its low cost and high efficacy make illicit use likely. We developed sensitive and specific methods for determination of MG and its principal metabolite, leucoMG (LMG), in edible fish tissues using isotope dilution liquid chromatography atmosphere pressure chemical ionization mass spectrometry. MG and LMG concentrations were measured in filets from catfish treated with MG under putative use conditions (ca. 250 and 1000 ppb, respectively) and from commercial trout samples (0-3 and 0-96 ppb, respectively). Concentrations of LMG in edible fish tissues always exceeded those of MG. A rapid cone voltage switching acquisition procedure was used to simultaneously produce molecular ions for quantification and diagnostic fragment ions for confirmation of MG and metabolites. The accurate and precise agreement between diagnostic ion intensity ratios produced by LMG in authentic standards and incurred fish samples was used to unambiguously confirm the presence of LMG in edible fish tissue. This suggested the validity of using LMG as a marker residue for regulatory determination of MG misuse. Additional metabolites derived from oxidative metabolism of MG or LMG (demethylation and N-oxygenation) were identified in catfish and trout filets, including a primary arylamine which is structurally related to known carcinogens. The ability to simultaneously quantify residues of MG and LMG, and to confirm the chemical structure of a marker residue by using LC/MS, suggests that this procedure may be useful in monitoring the food supply for the unauthorized use of MG in aquaculture. PMID:9807836

Doerge, D R; Churchwell, M I; Gehring, T A; Pu, Y M; Plakas, S M

1998-01-01

22

A novel method for analyzing solanesyl esters in tobacco leaves using atmospheric pressure chemical ionization/mass spectrometer.  

PubMed

A direct and simple method for analyzing solanesyl esters found in tobacco leaves was developed. Sample preparation was performed by accelerated solvent extractor 200 (ASE200) using n-hexane followed by evaporating solution in vacuo and dissolving residue with acetone. The separation of analytes was conducted through high-performance liquid chromatography (HPLC) equipped with an SIL-C18/5C column and the non-aqueous reversed phase chromatography (NARP) technique using acetone and acetonitrile as the mobile phase with a linear gradient. Atmospheric pressure chemical ionization/mass spectrometer (APCI/MS) in positive mode was used to detect solanesyl esters in the following conditions: capillary voltage 4000 V, corona current 10 microA, drying gas flow 5 mL/min, fragmentor voltage 200 V, nebulizer pressure 60 psi, and vaporizer temperature 500 degrees C. Each solanesyl ester was identified by the comparison of analyte with synthesized solanesyl esters. Quantification was conducted by selected ion monitoring (SIM) mode in order to detect the specific product ion (613.6 m/z) fragmented from solanesyl ester. The calibration curve was made in the range of 0.1-40 microg/mL with a regression coefficient over 0.999 on almost all solanesyl esters. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.01 to 0.05 microg/mL and from 0.03 to 0.15 microg/mL, respectively, on the SIM mode of MS for quantification. Recovery (%) ranged from about 80 to 120%. The direct quantification using the developed method succeeded in showing a different amount and composition of solanesyl esters among various tobacco leaves. PMID:20691974

Ishida, Naoyuki

2010-09-10

23

Total microcystins analysis in water using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

A new approach for the analysis of the cyanobacterial microcystins (MCs) in environmental water matrices has been developed. It offers a cost efficient alternative method for the fast quantification of total MCs using mass spectrometry. This approach permits the quantification of total MCs concentrations without requiring any derivatization or the use of a suite of MCs standards. The oxidation product 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) was formed through a Lemieux oxidation and represented the total concentration of free and bound MCs in water samples. MMPB was analyzed using laser diode thermal desorption-atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). LDTD is a robust and reliable sample introduction method with ultra-fast analysis time (<15 s sample(-1)). Several oxidation and LDTD parameters were optimized to improve recoveries and signal intensity. MCs oxidation recovery yield was 103%, showing a complete reaction. Internal calibration with standard addition was achieved with the use of 4-phenylbutyric acid (4-PB) as internal standard and showed good linearity (R(2)>0.999). Limits of detection and quantification were 0.2 and 0.9 ?g L(-1), respectively. These values are comparable with the WHO (World Health Organization) guideline of 1 ?g L(-1) for total microcystin-LR congener in drinking water. Accuracy and interday/intraday variation coefficients were below 15%. Matrix effect was determined with a recovery of 91%, showing no significant signal suppression. This work demonstrates the use of the LDTD-APCI-MS/MS interface for the screening, detection and quantification of total MCs in complex environmental matrices. PMID:24745740

Roy-Lachapelle, Audrey; Fayad, Paul B; Sinotte, Marc; Deblois, Christian; Sauvé, Sébastien

2014-04-11

24

Determination of eight nitrosamines in water at the ng L ?1 levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry  

Microsoft Academic Search

In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple

Cristina Ripollés; Elena Pitarch; Juan V. Sancho; Francisco J. López; Félix Hernández

2011-01-01

25

Determination of talinolol in human plasma using automated on-line solid phase extraction combined with atmospheric pressure chemical ionization tandem mass spectrometry  

Microsoft Academic Search

A specific LC–MS\\/MS assay was developed for the automated determination of talinolol in human plasma, using on-line solid phase extraction system (prospekt 2) combined with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry. The method involved simple precipitation of plasma proteins with perchloric acid (contained propranolol) as the internal standard (IS) and injection of the supernatant onto a C8 End

Emmanuel Bourgogne; Chantal Grivet; Gérard Hopfgartner

2005-01-01

26

Development of a method for quantitation of retinol and retinyl palmitate in human serum using high-performance liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry  

Microsoft Academic Search

A method for the quantitative analysis of the vitamin A compounds all-trans-retinol and all-trans-retinyl palmitate was developed using high-performance liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry (APCI–LC–MS). Unlike previous quantitative mass spectrometric methods for vitamin A, HPLC separations were carried out using a C30 reversed-phase column instead of GC separation. Because no sample hydrolysis or derivatization was necessary, retinyl palmitate was

Richard B van Breemen; Dejan Nikolic; Xiaoying Xu; Yansan Xiong; Machteld van Lieshout; Clive E West; Alexander B Schilling

1998-01-01

27

Identification of acylated xanthone glycosides by liquid chromatography–atmospheric pressure chemical ionization mass spectrometry in positive and negative modes from the lichen Umbilicaria proboscidea  

Microsoft Academic Search

The xanthoside composition of the crude extract of Umbilicaria proboscidea (L.) Schrader was characterized using LC–UV diode array detection and LC–atmospheric pressure chemical ionization (APCI) MS methods. The presence of acylated xanthone-O-glucosides was determined by both positive and negative ion LC–APCI-MS methods. Based on UV and MS spectral data and NMR spectroscopy, a total of 14 compounds (6-O-acylated umbilicaxanthosides A

Tomáš ?ezanka; Valery M. Dembitsky

2003-01-01

28

Sensitive and comprehensive detection of chemical warfare agents in air by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow introduction.  

PubMed

A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs. PMID:24678766

Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Yamashiro, Shigeharu; Sano, Yasuhiro; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Sekiguchi, Hiroyuki; Iura, Kazumitsu; Nagashima, Hisayuki; Nagoya, Tomoki; Tsuge, Kouichiro; Ohsawa, Isaac; Okumura, Akihiko; Takada, Yasuaki; Ezawa, Naoya; Watanabe, Susumu; Hashimoto, Hiroaki

2014-05-01

29

Sensitive monitoring of volatile chemical warfare agents in air by atmospheric pressure chemical ionization mass spectrometry with counter-flow introduction.  

PubMed

A new method for sensitively and selectively detecting chemical warfare agents (CWAs) in air was developed using counter-flow introduction atmospheric pressure chemical ionization mass spectrometry (MS). Four volatile and highly toxic CWAs were examined, including the nerve gases sarin and tabun, and the blister agents mustard gas (HD) and Lewisite 1 (L1). Soft ionization was performed using corona discharge to form reactant ions, and the ions were sent in the direction opposite to the airflow by an electric field to eliminate the interfering neutral molecules such as ozone and nitrogen oxide. This resulted in efficient ionization of the target CWAs, especially in the negative ionization mode. Quadrupole MS (QMS) and ion trap tandem MS (ITMS) instruments were developed and investigated, which were movable on the building floor. For sarin, tabun, and HD, the protonated molecular ions and their fragment ions were observed in the positive ion mode. For L1, the chloride adduct ions of L1 hydrolysis products were observed in negative ion mode. The limit of detection (LOD) values in real-time or for a 1 s measurement monitoring the characteristic ions were between 1 and 8 ?g/m(3) in QMS instrument. Collision-induced fragmentation patterns for the CWAs were observed in an ITMS instrument, and optimized combinations of the parent and daughter ion pairs were selected to achieve real-time detection with LOD values of around 1 ?g/m(3). This is a first demonstration of sensitive and specific real-time detection of both positively and negatively ionizable CWAs by MS instruments used for field monitoring. PMID:23339735

Seto, Yasuo; Kanamori-Kataoka, Mieko; Tsuge, Koichiro; Ohsawa, Isaac; Iura, Kazumitsu; Itoi, Teruo; Sekiguchi, Hiroyuki; Matsushita, Koji; Yamashiro, Shigeharu; Sano, Yasuhiro; Sekiguchi, Hiroshi; Maruko, Hisashi; Takayama, Yasuo; Sekioka, Ryoji; Okumura, Akihiko; Takada, Yasuaki; Nagano, Hisashi; Waki, Izumi; Ezawa, Naoya; Tanimoto, Hiroyuki; Honjo, Shigeru; Fukano, Masumi; Okada, Hidehiro

2013-03-01

30

Identification of acylated xanthone glycosides by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in positive and negative modes from the lichen Umbilicaria proboscidea.  

PubMed

The xanthoside composition of the crude extract of Umbilicaria proboscidea (L.) Schrader was characterized using LC-UV diode array detection and LC-atmospheric pressure chemical ionization (APCI) MS methods. The presence of acylated xanthone-O-glucosides was determined by both positive and negative ion LC-APCI-MS methods. Based on UV and MS spectral data and NMR spectroscopy, a total of 14 compounds (6-O-acylated umbilicaxanthosides A and B) were identified in U. proboscidea for the first time. In order to further develop the applicability of LC-MS techniques in phytochemical characterization, the effect of different ionization energy on fragmentation was studied using APCI. The optimal ionization conditions were achieved in positive ion APCI by using ammonium acetate buffer and in negative ion APCI by using formic acid (pH 4). PMID:12800927

Rezanka, Tomás; Dembitsky, Valery M

2003-05-01

31

High-throughput walkthrough detection portal for counter terrorism: detection of triacetone triperoxide (TATP) vapor by atmospheric-pressure chemical ionization ion trap mass spectrometry.  

PubMed

With the aim of improving security, a high-throughput portal system for detecting triacetone triperoxide (TATP) vapor emitted from passengers and luggage was developed. The portal system consists of a push-pull air sampler, an atmospheric-pressure chemical ionization (APCI) ion source, and an explosives detector based on mass spectrometry. To improve the sensitivity of the explosives detector, a novel linear ion trap mass spectrometer with wire electrodes (wire-LIT) is installed in the portal system. TATP signals were clearly obtained 2?s after the subject under detection passed through the portal system. Preliminary results on sensitivity and throughput show that the portal system is a useful tool for preventing the use of TATP-based improvised explosive devices by screening persons in places where many people are coming and going. PMID:21818804

Takada, Yasuaki; Nagano, Hisashi; Suzuki, Yasutaka; Sugiyama, Masuyuki; Nakajima, Eri; Hashimoto, Yuichiro; Sakairi, Minoru

2011-09-15

32

HPLC-PAD-atmospheric pressure chemical ionization-MS metabolite profiling of cytotoxic carotenoids from the echinoderm Marthasterias glacialis (spiny sea-star).  

PubMed

An HPLC-PAD-atmospheric pressure chemical ionization-MS metabolite profiling analysis was conducted on the marine echinoderm Marthasterias glacialis (spiny sea-star). Bio-guided purification of the methanolic extract led to the isolation of several carotenoids, namely zeaxanthin, astaxanthin and lutein. These compounds were characterized using both UV-Vis characteristics and MS spectra interpretation. No previous works addressed the MS analysis of carotenoids present in this organism. The purified carotenoid fraction displayed a strong cell proliferation inhibition against rat basophilic leukemia RBL-2H3 (IC(25)=268 microg/mL) cancer cell line. Against healthy V79 (rat lung fibroblasts (IC(25)=411 microg/mL)) cell line, however, toxicity was lower, as it is desired for anti-cancer molecules. This study suggests that M. glacialis may constitute a good source of bioactive compounds that can be used as lead compounds for the pharmaceutical industry. PMID:20574958

Ferreres, Federico; Pereira, David M; Gil-Izquierdo, Angel; Valentão, Patrícia; Botelho, João; Mouga, Teresa; Andrade, Paula B

2010-08-01

33

Application of gas chromatography-(triple quadrupole) mass spectrometry with atmospheric pressure chemical ionization for the determination of multiclass pesticides in fruits and vegetables.  

PubMed

A multi-residue method for the determination of 142 pesticide residues in fruits and vegetables has been developed using a new atmospheric pressure chemical ionization (APCI) source for coupling gas chromatography (GC) to tandem mass spectrometry (MS). Selected reaction monitoring (SRM) mode has been applied, acquiring three transitions for each compound. In contrast to the extensive fragmentation typically obtained in classical electron ionization (EI), the soft APCI ionization allowed the selection of highly abundant protonated molecules ([M+H](+)) as precursor ions for most compounds. This was favorable for both sensitivity and selectivity. Validation of the method was performed in which both quantitative and qualitative parameters were assessed using orange, tomato and carrot samples spiked at two levels, 0.01 and 0.1mg/kg. The QuEChERS method was used for sample preparation, followed by a 10-fold dilution of the final acetonitrile extract with a mixture of hexane and acetone. Recovery and precision were satisfactory in the three matrices, at both concentration levels. Very low limits of detection (down 0.01?g/kg for the most sensitive compounds) were achieved. Ion ratios were consistent and identification according to EU criteria was possible in 80% (0.01mg/kg) to 96% (0.1mg/kg) of the pesticide/matrix combinations. The method was applied to the analysis of various fruits and vegetables from the Mediterranean region of Spain. PMID:24070626

Cherta, Laura; Portolés, Tania; Beltran, Joaquim; Pitarch, Elena; Mol, Johannes G J; Hernández, Félix

2013-11-01

34

[Isolation and purification of solanesol from potato leaves by high-speed counter-current chromatography and identification by atmospheric pressure chemical ionization mass spectrometry].  

PubMed

Preparative high-speed counter-current chromatography (HSCCC) was used for the isolation and purification of solanesol from potato leaves. Experimental conditions of the extraction of solanesol from potato leaves have been optimized. An ultrafine extraction method was applied in this study. The efficiency using an ultrafine extraction was found to be improved in the investigation, the yields of solanesol by different extraction methods were 0.083% by ultrafine extraction and 0.050% by ultrasonic extraction. Using n-hexane-methanol (10:7, v/v) as the two-phase solvent system, preparative HSCCC was successfully performed with the yield of 5 mg solanesol at 98.7% of purity from 60 mg of crude extract in the one-step separation. The mobile phase was the lower phase and operated at a flow rate of 1.5 mL/min, while the apparatus rotated at 800 r/min. The solanesol was identified by the atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The ionization and cleavage mechanisms of solanesol in APCI-MS and APCI-MS/MS are discussed. PMID:17970112

Hu, Jiangyong; Liang, Yong; Xie, Ya; Huang, Zhaofeng; Zhong, Hanzuo

2007-07-01

35

Online atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-IT-MSn) for measuring organic acids in concentrated bulk aerosol - a laboratory and field study  

NASA Astrophysics Data System (ADS)

The field application of an aerosol concentrator in conjunction with an atmospheric pressure chemical ionization ion trap mass spectrometer (APCI-IT-MS) at the boreal forest station SMEAR II at Hyytiälä, Finland, is demonstrated in this study. APCI is a soft ionization technique allowing online measurements of organic acids in the gas and particle phase. The detection limit for the acid species in the particle phase was increased by a factor of 7.5 to 11 (e.g. ~40 ng m-3 for pinonic acid) by using the miniature Versatile Aerosol Concentration Enrichment System (mVACES) upstream of the mass spectrometer. The APCI-IT-MS was calibrated in the negative ion mode with two biogenic organic acid standards - pinic acid and pinonic acid. Pinic acid was used as a surrogate for the quantification of the total amount of organic acids in the ambient aerosol based on the total signal intensities in the negative ion mode. The results were compared with the total organic signal of a C-ToF-AMS during the HUMPPA-COPEC 2010 field campaign. The campaign average contribution of organic acids measured by APCI-IT-MS to the total sub-micron organic aerosol mass was estimated to be about 60%. Very good correlation between APCI-IT-MS and C-ToF-AMS (Pearson's R = 0.94) demonstrates soft ionization mass spectrometry as a complimentary technique to AMS with electron impact ionization. MS2 studies of specific m/z ratios recorded during the HUMPPA-COPEC 2010 field campaign were compared to MS2 studies of selected monoterpene oxidation products formed in simulation chamber experiments. The comparison of the resulting fragments shows that oxidation products of the main VOCs emitted at Hyytiälä (?-pinene and ?3-carene) cannot account for all of the measured fragments, which illustrates the complexity of ambient aerosol and possibly indicates unidentified or underestimated biogenic SOA precursor in the boreal forest.

Vogel, A. L.; Äijälä, M.; Brüggemann, M.; Ehn, M.; Junninen, H.; Petäjä, T.; Worsnop, D. R.; Kulmala, M.; Williams, J.; Hoffmann, T.

2012-08-01

36

Gas chromatography-atmospheric pressure chemical ionization-time of flight mass spectrometry for profiling of phenolic compounds in extra virgin olive oil.  

PubMed

A new analytical approach based on gas chromatography coupled to atmospheric pressure chemical ionization-time of flight mass spectrometry was evaluated for its applicability for the analysis of phenolic compounds from extra-virgin olive oil. Both chromatographic and MS parameters were optimized in order to improve the sensitivity and to maximize the number of phenolic compounds detected. We performed a complete analytical validation of the method with respect to its linearity, sensitivity, precision, accuracy and possible matrix effects. The LODs ranged from 0.13 to 1.05ppm for the different tested compounds depending on their properties. The RSDs for repeatability test did not exceed 6.07% and the accuracy ranged from 95.4% to 101.5%. To demonstrate the feasibility of our method for analysis of real samples, we analyzed the extracts of three different commercial extra-virgin olive oils. We have identified unequivocally a number of phenolic compounds and obtained quantitative information for 21 of them. In general, our results show that GC-APCI-TOF MS is a flexible platform which can be considered as an interesting tool for screening, structural assignment and quantitative determination of phenolic compounds from virgin olive oil. PMID:21241992

García-Villalba, Rocío; Pacchiarotta, Tiziana; Carrasco-Pancorbo, Alegría; Segura-Carretero, Antonio; Fernández-Gutiérrez, Alberto; Deelder, André M; Mayboroda, Oleg A

2011-02-18

37

Liquid chromatography/atmospheric pressure chemical ionization ion trap mass spectrometry of bilobalide in plasma and brain of rats after oral administration of its phospholipidic complex.  

PubMed

Standardized extracts of Ginkgo biloba L. leaves are widely used in clinical practice for the symptomatic treatment of mild to moderate dementia syndromes, cerebral insufficiency and for the enhancement of cognitive function. The main active components present in G. biloba extracts are flavonol-glycosides and terpene-lactones. In recent investigations, the sesquiterpene trilactone bilobalide has been described to exert an interesting neuroprotective effect when administered systemically to experimental animals. Oral administration of terpene-lactones either as standardized extracts or purified products is characterized by a low bioavailability. While preparing phospholipidic complex of G. biloba extracts or bilobalide, plasma levels of terpenes and sesquiterpene increase. In the present study, phospholipidic complex of bilobalide (IDN 5604) has been administered orally to rats and bilobalide levels have been determined in plasma and brain by means of a validated method based on liquid chromatography coupled to atmospheric pressure chemical ionization ion trap mass spectrometry (LC/APCI-ITMS). Due to its sensitivity (about 3pmol/ml) and specificity, LC/APCI-ITMS method proved to be a very powerful tool for pharmacokinetic studies of Ginkgo terpene-lactones. The results of the present study clearly confirm the improvement of oral bioavailability of bilobalide administered as phospholipidic complex and, for the first time, demonstrate the detection of significative amounts of bilobalide in brain. This last finding agrees with the neuroprotective activity observed for bilobalide. PMID:19473802

Rossi, Rossana; Basilico, Fabrizio; Rossoni, Giuseppe; Riva, Antonella; Morazzoni, Paolo; Mauri, Pier Luigi

2009-09-01

38

Separation and identification of various carotenoids by C30 reversed-phase high-performance liquid chromatography coupled to UV and atmospheric pressure chemical ionization mass spectrometric detection.  

PubMed

In this paper the application of on-line HPLC-UV-APCI (atmospheric pressure chemical ionization) mass spectrometry (MS) coupling for the separation and determination of different carotenoids as well as cis/trans isomers of beta-carotene is reported. All HPLC separations were carried out under RP conditions on self-synthesized polymeric C30 phases. The analysis of a carotenoid mixture containing astaxanthin, canthaxanthin, zeaxanthin, echinenone and beta-carotene by HPLC-APCI-MS was achieved by scanning the mass range from m/z 200 to 700. For the characterization of a sample containing cis/trans isomers of beta-carotene as well as their oxidation products, a photodiode-array UV-visible absorbance detector was used in addition between the column and the mass spectrometer for structural elucidation of the geometrical isomers. The detection limit for beta-carotene in positive-ion APCI-MS was determined to be 1 pmol. In addition, an extract of non-polar substances in vegetable juice has been analyzed by HPLC-APCI-MS. The included carotenoids could be identified by their masses and their retention times. PMID:10497926

Lacker, T; Strohschein, S; Albert, K

1999-08-27

39

Trace analysis of selected hormones and sterols in river sediments by liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

In this paper, development and optimization of new LC-MS method for determination of twenty selected hormones, human/animal and plant sterols in river sediments were described. Sediment samples were prepared using ultrasonic extraction and clean up with silica gel/anhydrous sodium sulphate cartridge. Extracts were analyzed by liquid chromatography-linear ion trap-tandem mass spectrometry, with atmospheric pressure chemical ionization. The optimized extraction parameters were extraction solvent (methanol), weight of the sediment (2g) and time of ultrasonic extraction (3× 10min). Successful chromatographic separation of hormones (estriol and estrone, 17?- and 17?-estradiol) and four human/animal sterols (epicoprostanol, coprostanol, ?-cholestanol and ?-cholestanol) that have identical fragmentation reactions was achieved. The developed and optimized method provided high recoveries (73-118%), low limits of detection (0.8-18ngg(-1)) and quantification (2.5-60ngg(-1)) with the RSDs generally lower than 20%. Applicability of the developed method was confirmed by analysis of six river sediment samples. A widespread occurrence of human/animal and plant sterols was found. The only detected hormone was mestranol in just one sediment sample. PMID:25182857

Mati?, Ivana; Gruji?, Svetlana; Jaukovi?, Zorica; Lauševi?, Mila

2014-10-17

40

Screening of pesticides and polycyclic aromatic hydrocarbons in feeds and fish tissues by gas chromatography coupled to high-resolution mass spectrometry using atmospheric pressure chemical ionization.  

PubMed

This paper reports a wide-scope screening for detection and identification of pesticides and polycyclic aromatic hydrocarbons (PAHs) in feeds and fish tissues. QuEChERS sample treatment was applied, using freezing as an additional cleanup. Analysis was carried out by gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC-(APCI) QTOF MS). The qualitative validation was performed for over 133 representative pesticides and 24 PAHs at 0.01 and 0.05 mg/kg. Subsequent application of the screening method to aquaculture samples made it possible to detect several compounds from the target list, such as chlorpyrifos-methyl, pirimiphos-methyl, and ethoxyquin, among others. Light PAHs (?4 rings) were found in both animal and vegetable samples. The reliable identification of the compounds was supported by accurate mass measurements and the presence of at least two representative m/z ions in the spectrum together with the retention time of the peak, in agreement with the reference standard. Additionally, the search was widened to include other pesticides for which standards were not available, thanks to the expected presence of the protonated molecule and/or molecular ion in the APCI spectra. This could allow the detection and tentative identification of other pesticides different from those included in the validated target list. PMID:24559176

Nácher-Mestre, Jaime; Serrano, Roque; Portolés, Tania; Berntssen, Marc H G; Pérez-Sánchez, Jaume; Hernández, Félix

2014-03-12

41

Identification and quantification of antitumor thioproline and methylthioproline in Korean traditional foods by a liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

A liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometric method (LC-APCI-MS/MS) has been developed for the sensitive determination of antitumor thioproline and methylthioproline from fermented foods. Thioproline and methylthioproline were derivatized in one step with ethyl chloroformate at room temperature. These compounds were identified and quantified in various traditional Korean fermented foods by LC-APCI-MS/MS. The concentration range of thioproline of each food was found for doenjang (0.011-0.032mg/kg), gochujang (0.010-0.038mg/kg), and ganjang (0.010-0.038mg/kg). Those of methylthioproline of each food was found for doenjang (0.098-0.632mg/kg), gochujang (0.015-0.112mg/kg), and ganjang (0.023-1.468mg/kg). A prolonged aging time leads to an increase in both the thioproline and methylthioproline contents, suggesting that the storage time plays a key role in the formation of thioproline and methylthioproline in Korean traditional foods. The results here suggest that thioproline and methylthioproline are related to the biological activities of traditional Korean fermented foods. PMID:25128876

Kim, Sun Hyo; Kim, Hyun-Ji; Shin, Ho-Sang

2014-11-01

42

Characterization of gamma-irradiated polyethylene terephthalate by liquid-chromatography mass-spectrometry (LC MS) with atmospheric-pressure chemical ionization (APCI)  

NASA Astrophysics Data System (ADS)

Low-molecular-weight (low-MW) constituents of polyethylene terephthalate (PET), irradiated with 60Co gamma rays at 25 and 50 kGy, were analyzed by HPLC-MS with atmospheric-pressure chemical ionization (APCI). Consistent with earlier results, the concentrations of the major compounds that are present in the non-irradiated PET do not change perceptibly. However, we find a small but significant increase in terephthalic acid ethylester, from less than 1 mg/kg in the non-irradiated control to ca. 2 mg/kg after 50 kGy, which has not been described before. The finding is important because it gives an impression of the sensitivity of the analytical method. Additionally, it shows that even very radiation-resistant polymers can form measurable amounts of low-MW radiolysis products. The potential and limitations of LC-MS for the analysis of radiolysis products and unidentified migrants are briefly discussed in the context of the question: How can we validate our analytical methods for unknown analytes?

Buchalla, Rainer; Begley, Timothy H.

2006-01-01

43

Online atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-IT-MSn) for measuring organic acids in concentrated bulk aerosol - a laboratory and field study  

NASA Astrophysics Data System (ADS)

The field application of an aerosol concentrator in conjunction with an atmospheric pressure chemical ionization ion trap mass spectrometer (APCI-IT-MS) at the boreal forest station SMEAR II at Hyytiälä, Finland, is demonstrated in this study. APCI is a soft-ionization technique allowing online measurements of organic acids in the gas and particle phase. The detection limit for the acid species in the particle phase was improved by a factor of 7.5 to 11 (e.g. ∼40 ng m3 for pinonic acid) by using the miniature versatile aerosol concentration enrichment system (mVACES) upstream of the mass spectrometer. The APCI-IT-MS was calibrated in the negative ion mode with two biogenic organic acid standards - pinic acid and pinonic acid. Pinic acid was used as a surrogate for the quantification of the total amount of organic acids in the ambient aerosol based on the total signal intensities in the negative ion mode. The results were compared with the total organic signal of a C-ToF-AMS during the HUMPPA-COPEC 2010 field campaign. The campaign average contribution of organic acids measured by APCI-IT-MS to the total submicron organic aerosol mass was estimated to be about 60%, based on the response of pinic acid. Very good correlation between APCI-IT-MS and C-ToF-AMS (Pearson's R = 0.94) demonstrates soft-ionization mass spectrometry as a complimentary technique to AMS with electron impact ionization. MS2 studies of specific m/z ratios recorded during the HUMPPA-COPEC 2010 field campaign were compared to MS2 studies of selected monoterpene oxidation products formed in simulation chamber experiments. The comparison of the resulting fragments shows that oxidation products of the main VOCs emitted at Hyytiälä (?-pinene and ?3-carene) cannot account for all of the measured fragments. Possible explanations for those unaccounted fragments are the presence of unidentified or underestimated biogenic SOA precursors, or that different products are formed by a different oxidant mixture of the ambient air compared to the chamber ozonolysis.

Vogel, A. L.; Äijälä, M.; Brüggemann, M.; Ehn, M.; Junninen, H.; Petäjä, T.; Worsnop, D. R.; Kulmala, M.; Williams, J.; Hoffmann, T.

2013-02-01

44

Enantioselective determination of cetirizine in human plasma by normal-phase liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

A highly sensitive and enantioselective method has been developed and validated for the determination of levocetirizine [(R)-cetirizine] in human plasma by normal-phase liquid chromatography coupled to tandem mass spectrometry with an atmospheric pressure chemical ionization (APCI) interface in the positive ion mode. Enantioselective separation was achieved on a CHIRALPAK AD-H column using an isocratic mobile phase consisting of a mixture of n-hexane, ethyl alcohol, diethylamine, and acetic acid (60:40:0.1:0.1, v/v/v/v). Levocetirizine-D(8) was used as an internal standard (IS). Levocetirizine and the IS were detected by multiple-reaction monitoring (MRM). Mass transitions of analyte and IS were m/z 389.2?201.1 and 397.2?201.1, respectively. Under optimized analytical conditions, a baseline separation of two enantiomers and IS was obtained in less than 11 min. Samples were prepared by a simple two-step extraction by protein precipitation using acetonitrile followed by liquid-liquid extraction with a n-hexane-dichloromethane mixture (50:50, v/v). The standard curve for levocetirizine was linear (r(2)>0.995) in the concentration range 0.5-300 ng/mL. Recovery was between 97.0 and 102.2% at low, medium, and high concentration. The limit of quantification (LOQ) was 0.5 ng/mL. Other method validation parameters, such as precision, accuracy, and stability, were very satisfactory. Finally, the proposed method was successfully applied to the study of enantioselective oral pharmacokinetics of levocetirizine in healthy Korean volunteers. PMID:21081290

Kang, Seung Woo; Jang, Hae Jong; Moore, Victor S; Park, Ji-Young; Kim, Kyoung-Ah; Youm, Jeong-Rok; Han, Sang Beom

2010-12-15

45

Analysis of chemical warfare agents in food products by atmospheric pressure ionization-high field asymmetric waveform ion mobility spectrometry-mass spectrometry.  

PubMed

Flow injection high field asymmetric waveform ion mobility spectrometry (FAIMS)-mass spectrometry (MS) methodology was developed for the detection and identification of chemical warfare (CW) agents in spiked food products. The CW agents, soman (GD), sarin (GB), tabun (GA), cyclohexyl sarin (GF), and four hydrolysis products, ethylphosphonic acid (EPA), methylphosphonic acid (MPA), pinacolyl methylphosphonic acid (Pin MPA), and isopropyl methylphosphonic acid (IMPA) were separated and detected by positive ion and negative ion atmospheric pressure ionization-FAIMS-MS. Under optimized conditions, the compensation voltages were 7.2 V for GD, 8.0 V for GA, 7.2 V for GF, 7.6 V for GB, 18.2 V for EPA, 25.9 V for MPA, -1.9 V for PinMPA, and +6.8 V for IMPA. Sample preparation was kept to a minimum, resulting in analysis times of 3 min or less per sample. The developed methodology was evaluated by spiking bottled water, canola oil, cornmeal, and honey samples at low microgram per gram (or microg/mL) levels with the CW agents or CW agent hydrolysis products. The detection limits observed for the CW agents in the spiked food samples ranged from 3 to 15 ng/mL in bottled water, 1-33 ng/mL in canola oil, 1-34 ng/g in cornmeal, and 13-18 ng/g in honey. Detection limits were much higher for the CW agent hydrolysis products, with only MPA being detected in spiked honey samples. PMID:17896827

Kolakowski, Beata M; D'Agostino, Paul A; Chenier, Claude; Mester, Zoltán

2007-11-01

46

Determination and differentiation of triacylglycerol molecular species in Antarctic and non-Antarctic yeasts by atmospheric pressure-chemical ionization-mass spectrometry.  

PubMed

Yeast, particularly Saccharomyces cerevisiae, has long served as a model eukaryotic system for studies on the regulation of lipid metabolism. We developed a high performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry method for the detailed analysis of triacylglycerols (TAGs) in 14 species of yeast consisting of seven Antarctic yeasts (grown at 15°C and 5°C) and seven non-Antarctic yeasts (grown at 25°C and 15°C), the latter including 3 strains of S. cerevisiae. Analysis of TAG molecular species established that the sn-2 position was invariably occupied by an unsaturated fatty acyl moiety. In S. cerevisiae the preference was for oleic acid 18:1>palmitoleic acid 16:1, in Candida albicans, Cryptococcus humicolus and Rhodotorula mucilaginosa 18:1>linoleic acid 18:2 and in Zygosaccharomyces rouxii 18:2>18:1. In the Antarctic yeasts (Cryptococcus watticus, Cryptococcus victoriae, Cryptococcus nyarrowii, Leucosporidium antarcticum, Leucosporidium fellii, Candida psychrophila and Rhodotorula mucilaginosa) the general pattern was for the sn-2 position to be occupied by 18:1, 18:2 or linolenic acid 18:3. A trend towards synthesis of increased unsaturated fatty acid in TAGs was observed as the growth temperature was lowered. The application of principal component analysis demonstrated that the yeasts were differentiated into three distinct groups. One group consisted of the three S. cerevisiae strains, a second the other four non-Antarctic yeasts and the third the seven Antarctic yeasts. The data for the Antarctic yeasts, to the best of our knowledge, have not been previously reported. PMID:23831436

Bhuiyan, Mohammad; Tucker, David; Watson, Kenneth

2013-09-01

47

Development and Comparison of Three Liquid Chromatography-Atmospheric Pressure Chemical Ionization/Mass Spectrometry Methods for Determining Vitamin D Metabolites in Human Serum  

PubMed Central

Liquid chromatographic methods with atmospheric pressure chemical ionization mass spectrometry were developed for the determination of the vitamin D metabolites 25-hydroxyvitamin D2 (25(OH)D2), 25-hydroxyvitamin D3 (25(OH)D3), and 3-epi-25-hydroxyvitamin-D3 (3-epi-25(OH)D3) in the four Levels of SRM 972, Vitamin D in Human Serum. One method utilized a C18 column, which separates 25(OH)D2 and 25(OH)D3, and one method utilized a CN column that also resolves the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. Both methods utilized stable isotope labeled internal standards for quantitation of 25(OH)D2 and 25(OH)D3. These methods were subsequently used to evaluate SRM 909c Human Serum, and 25(OH)D3 was the only vitamin D metabolite detected in this material. However, SRM 909c samples contained matrix peaks that interfered with the determination of the [2H6]-25(OH)D3 peak area. The chromatographic conditions for the C18 column were modified to remove this interference, but conditions that separated the matrix peaks from [2H6]-25(OH)D3 on the CN column could not be identified. The alternate internal standard [2H3]-25(OH)D3 did not suffer from matrix interferences and was used for quantitation of 25(OH)D3 in SRM 909c. During the evaluation of SRM 909c samples, a third method was developed using a pentafluorophenylpropyl column that also separates the diastereomers 25(OH)D3 and 3-epi-25(OH)D3. The 25(OH)D3 was measured in SRM 909c using all three methods, and the results were compared. PMID:22533908

Bedner, Mary; Phinney, Karen W.

2012-01-01

48

Determination and confirmation of malachite green and leucomalachite green residues in salmon using liquid chromatography/mass spectrometry with no-discharge atmospheric pressure chemical ionization.  

PubMed

A liquid chromatography/mass spectrometry (LC/MS) method was developed to quantitate and confirm residues of leucomalachite green (LMG) in salmon tissue after their conversion to chromic malachite green (MG) in the extraction process. The method uses no-discharge atmospheric pressure chemical ionization (APCI) in conjunction with an ion-trap instrument to generate product-ion spectra. In the sample preparation procedure, salmon tissue is extracted with acetonitrile/buffer, the LMG residue is partitioned into methylene chloride, the LMG is converted to MG using an organic oxidizing agent, and the MG is isolated on alumina/propylsulfonic acid solid-phase extraction cartridges. The method was validated by fortifying salmon with different levels of LMG, and then detecting the residue as MG The LC/MS conditions, including a comparison of electrospray and no-discharge APCI, were evaluated and optimized. MG was not confirmed in any of the control tissue extracts, and all fortified samples analyzed during validation met the confirmation criteria as described. In addition to providing confirmatory data, this method can provide an alternative method for quantitation of MG in salmon. The recoveries of LMG measured as MG by this LC/MS method, at fortification levels of 1-10 ng/g were very high (86-109%), with low relative standard deviation(RSD) values (6.4-13%). The results agreed very closely with those obtained for the same extracts using an LCNIS procedure, indicating that matrix suppression was not an issue. The presence of LMG in salmon tissue samples fortified at 0.25 ng/g was confirmed by this method, with an average recovery of 70.1% and an RSD of 12.0%. Sample extracts from fish exposed to MG were also analyzed. PMID:16385980

Turnipseed, Sherri B; Andersen, Wendy C; Roybal, José E

2005-01-01

49

Use of electron ionization and atmospheric pressure chemical ionization in gas chromatography coupled to time-of-flight mass spectrometry for screening and identification of organic pollutants in waters.  

PubMed

A new approach has been developed for multiclass screening of organic contaminants in water based on the use of gas chromatography coupled to hybrid quadrupole high-resolution time-of-flight mass spectrometry with atmospheric pressure chemical ionization (GC-(APCI)QTOF MS). The soft ionization promoted by the APCI source allows effective and wide-scope screening based on the investigation of the molecular ion and/or protonated molecule. This is in contrast to electron ionization (EI) where ionization typically results in extensive fragmentation, and diagnostic ions and/or spectra need to be known a priori to facilitate detection of the analytes in the raw data. Around 170 organic contaminants from different chemical families were initially investigated by both approaches, i.e. GC-(EI)TOF and GC-(APCI)QTOF, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and a notable number of pesticides and relevant metabolites. The new GC-(APCI)QTOF MS approach easily allowed widening the number of compounds investigated (85 additional compounds), with more pesticides, personal care products (UV filters, musks), polychloronaphthalenes (PCNs), antimicrobials, insect repellents, etc., most of them considered as emerging contaminants. Both GC-(EI)TOF and GC-(APCI)QTOF methodologies have been applied, evaluating their potential for a wide-scope screening in the environmental field. PMID:24674644

Portolés, Tania; Mol, Johannes G J; Sancho, Juan V; Hernández, Félix

2014-04-25

50

Screening and quantification of pesticide residues in fruits and vegetables making use of gas chromatography-quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization.  

PubMed

An atmospheric pressure chemical ionization source has been used to enhance the potential of gas chromatography coupled with quadrupole time-of-flight (QTOF) mass spectrometry (MS) for screening and quantification purposes in pesticide residue analysis. A screening method developed in our laboratory for around 130 pesticides has been applied to fruit and vegetable samples, including strawberries, oranges, apples, carrots, lettuces, courgettes, red peppers, and tomatoes. Samples were analyzed together with quality control samples (at 0.05 mg/kg) for each matrix and for matrix-matched calibration standards. The screening strategy consisted in first rapid searching and detection, and then a refined identification step using the QTOF capabilities (MS(E) and accurate mass). Identification was based on the presence of one characteristic m/z ion (Q) obtained with the low collision energy function and at least one fragment ion (q) obtained with the high collision energy function, both with mass errors of less than 5 ppm, and an ion intensity ratio (q/Q) within the tolerances permitted. Following this strategy, 15 of 130 pesticides were identified in the samples. Afterwards, the quantitation capabilities were tested by performing a quantitative validation for those pesticides detected in the samples. To this aim, five matrices were selected (orange, apple, tomato, lettuce, and carrot) and spiked at two concentrations (0.01 and 0.1 mg/kg), and quantification was done using matrix-matched calibration standards (relative responses versus triphenyl phosphate used as an internal standard). Acceptable average recoveries and relative standard deviations were obtained for many but not all pesticide-matrix combinations. These figures allowed us to perform a retrospective quantification of positives found in the screening without the need for additional analysis. Taking advantage of the accurate-mass full-spectrum data provided by QTOF MS, we searched for a higher number of compounds (up to 416 pesticides) in a second stage by performing extra data processing without any new sample injection. Several more pesticides were detected, confirmed, and/or tentatively identified when the reference standard was unavailable, illustrating in this way the potential of gas chromatography-QTOF MS to detect pesticides in addition to the ones targeted in quantitative analysis of pesticides in food matrices. PMID:24828980

Cervera, M I; Portolés, T; López, F J; Beltrán, J; Hernández, F

2014-11-01

51

Laser diode thermal desorption atmospheric pressure chemical ionization tandem mass spectrometry applied for the ultra-fast quantitative analysis of BKM120 in human plasma.  

PubMed

A sensitive and ultra-fast method utilizing the laser diode thermal desorption ion source using atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS) was developed for the quantitative analysis of BKM120, an investigational anticancer drug in human plasma. Samples originating from protein precipitation (PP) followed by salting-out assisted liquid-liquid extraction (SALLE) were spotted onto the LazWell™ plate prior to their thermal desorption and detection by tandem mass spectrometry in positive mode. The validated method described in this paper presents a high absolute extraction recovery (>90 %) for BKM120 and its internal standard (ISTD) [D8]BKM120, with precision and accuracy meeting the acceptance criteria. Standard curves were linear over the range of 5.00 to 2000 ng mL(-1) with a coefficient of determination (R (2)) >0.995. The method specificity was demonstrated in six different batches of human plasma. Intra- and inter-run precision as well as accuracy within ±20 % at the lower limit of quantification (LLOQ) and ±15 % (other levels) were achieved during a three-run validation for quality control (QC) samples. The post-preparative stability on the LazWell™ plate at room temperature was 72 h and a 200-fold dilution of spiked samples was demonstrated. The method was applied successfully to three clinical studies (n?=?847) and cross-checked with the validated LC-ESI-MS/MS reference method. The sample analysis run time was 10 s as compared to 4.5 min for the current validated LC-ESI-MS/MS method. The resultant data were in agreement with the results obtained using the validated reference LC-ESI-MS/MS assay and the same pharmacokinetic (PK) parameters were calculated for both analytical assays. This work demonstrates that LDTD-APCI-MS/MS is a reliable method for the ultra-fast quantitative analysis of BKM120 which can be used to speed-up and support its bioanalysis in the frame of the clinical trials. PMID:24958346

Lanshoeft, Christian; Heudi, Olivier; Leuthold, Luc Alexis; Schlotterbeck, Götz; Elbast, Walid; Picard, Franck; Kretz, Olivier

2014-09-01

52

The method for on-site determination of trace concentrations of methyl mercaptan and dimethyl sulfide in air using a mobile mass spectrometer with atmospheric pressure chemical ionization, combined with a fast enrichment/separation system.  

PubMed

A method for fast simultaneous on-site determination of methyl mercaptan and dimethyl sulfide in air was developed. The target compounds were actively collected on silica gel, followed by direct flash thermal desorption, fast separation on a short chromatographic column and detection by means of mass spectrometer with atmospheric pressure chemical ionization. During the sampling of ambient air, water vapor was removed with a Nafion selective membrane. A compact mass spectrometer prototype, which was designed earlier at Trofimuk Institute of Petroleum Geology and Geophysics, was used. The minimization of gas load of the atmospheric pressure ion source allowed reducing the power requirements and size of the vacuum system and increasing its ruggedness. The measurement cycle is about 3 min. Detection limits in a 0.6 L sample are 1 ppb for methyl mercaptan and 0.2 ppb for dimethyl sulfide. PMID:24725876

Kudryavtsev, Andrey S; Makas, Alexey L; Troshkov, Mikhail L; Grachev, Mikhail ?; Pod'yachev, Sergey P

2014-06-01

53

The ionization mechanisms in direct and dopant-assisted atmospheric pressure photoionization and atmospheric pressure laser ionization.  

PubMed

A novel, gas-tight API interface for gas chromatography-mass spectrometry was used to study the ionization mechanism in direct and dopant-assisted atmospheric pressure photoionization (APPI) and atmospheric pressure laser ionization (APLI). Eight analytes (ethylbenzene, bromobenzene, naphthalene, anthracene, benzaldehyde, pyridine, quinolone, and acridine) with varying ionization energies (IEs) and proton affinities (PAs), and four common APPI dopants (toluene, acetone, anisole, and chlorobenzene) were chosen. All the studied compounds were ionized by direct APPI, forming mainly molecular ions. Addition of dopants suppressed the signal of the analytes with IEs above the IE of the dopant. For compounds with suitable IEs or Pas, the dopants increased the ionization efficiency as the analytes could be ionized through dopant-mediated gas-phase reactions, such as charge exchange, proton transfer, and other rather unexpected reactions, such as formation of [M?+?77](+) in the presence of chlorobenzene. Experiments with deuterated toluene as the dopant verified that in case of proton transfer, the proton originated from the dopant instead of proton-bound solvent clusters, as in conventional open or non-tight APPI sources. In direct APLI using a 266 nm laser, a narrower range of compounds was ionized than in direct APPI, because of exceedingly high IEs or unfavorable two-photon absorption cross-sections. Introduction of dopants in the APLI system changed the ionization mechanism to similar dopant-mediated gas-phase reactions with the dopant as in APPI, which produced mainly ions of the same form as in APPI, and ionized a wider range of analytes than direct APLI. PMID:25248413

Kauppila, Tiina J; Kersten, Hendrik; Benter, Thorsten

2014-11-01

54

Development of an Atmospheric Pressure Ionization Mass Spectrometer  

NASA Technical Reports Server (NTRS)

A commercial atmospheric pressure ionization mass spectrometer (APIMS) was purchased from EXTREL Mass Spectrometry, Inc. (Pittsburgh, PA). Our research objectives were to adapt this instrument and develop techniques for real-time determinations of the concentrations of trace species in the atmosphere. The prototype instrument is capable of making high frequency measurements with no sample preconcentrations. Isotopically labeled standards are used as an internal standard to obtain high precision and to compensate for changes in instrument sensitivity and analyte losses in the sampling manifold as described by Bandy and coworkers. The prototype instrument is capable of being deployed on NASA C130, Electra, P3, and DC8 aircraft. After purchasing and taking delivery by June 1994, we assembled the mass spectrometer, data acquisition, and manifold flow control instrumentation in electronic racks and performed tests.

1998-01-01

55

Sequential solid phase extraction protocol followed by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry for the trace determination of non ionic polyethoxylated surfactants in tannery wastewaters  

SciTech Connect

Automated solid-phase extraction (SPE) with C18 and styrene-divinylbenzene cartridges in series was used for the preconcentration of non ionic polyethoxylated surfactants in tannery wastewater. Fractionated extracts were analyzed by LC-MS using Atmospheric Pressure Chemical Ionization (APCI) in the Positive and Negative Ion modes. Recoveries for nonionic surfactants were approximately of 72, 90 and 80% for polyethylene glycols, nonylphenol and alcohol ethoxylates in the polar, aromatic and medium polarity fractions, respectively. Data acquisition in the selected ion monitoring mode afforded limits of quantification from 0.1 to 0.8 {micro}g/l for tridecylic polyethoxylated alcohol and polyethoxylated glycol, respectively, in the complex tannery wastewaters. The tannery effluents investigated contained between 0.03 to 3.0 mg/l of polyethylene glycol and nonylphenol polyethoxylate, respectively.

Castillo, M.; Barcelo, D. [IIQAB-CSIC, Barcelona (Spain). Dept. of Environmental Chemistry] [IIQAB-CSIC, Barcelona (Spain). Dept. of Environmental Chemistry; Ventura, F. [AGBAR, Barcelona (Spain)] [AGBAR, Barcelona (Spain)

1999-06-01

56

The role of physical and chemical properties of Pd nanostructured materials immobilized on inorganic carriers on ion formation in atmospheric pressure laser desorption/ionization mass spectrometry.  

PubMed

Fundamental parameters influencing the ion-producing efficiency of palladium nanostructures (nanoparticles [Pd-NP], nanoflowers, nanofilms) during laser irradiation were studied in this paper. The nanostructures were immobilized on the surface of different solid inorganic carrier materials (porous and mono-crystalline silicon, anodic porous aluminum oxide, glass and polished steel) by using classical galvanic deposition, electroless local deposition and sputtering. It was the goal of this study to investigate the influence of both the nanoparticular layer as well as the carrier material on ion production for selected analyte molecules. Our experiments demonstrated that the dimensions of the synthesized nanostructures, the thickness of the active layers, surface disorders, thermal conductivity and physically or chemically adsorbed water influenced signal intensities of analyte ions during surface-assisted laser desorption/ionization (SALDI) while no effects such as plasmon resonance, photoelectric effect or catalytic activity were expected to occur. Excellent LDI abilities were seen for Pd-NPs immobilized on steel, while Pd nanoflowers on porous silicon exhibited several disadvantages; viz, strong memory effects, dependency of the analytical signal on amount of physically and chemically adsorbed water inside porous carrier, reduced SALDI activity from unstable connections between Pd and semiconductor material, decrease of the melting point of pure silicon after Pd immobilization and resulting strong laser ablation of metal/semiconductor complex, as well as significantly changed surface morphology after laser irradiation. The analytical performance of Pd-NP/steel was further improved by applying a hydrophobic coating to the steel surface before galvanic deposition. This procedure increased the distance between Pd-NPs, thus reducing thermal stress upon LDI; it simultaneously decreased spot sizes of deposited sample solutions. PMID:24913399

Silina, Yuliya E; Koch, Marcus; Volmer, Dietrich A

2014-06-01

57

Real-time flavor analysis: optimization of a proton-transfer-mass spectrometer and comparison with an atmospheric pressure chemical ionization mass spectrometer with an MS-nose interface.  

PubMed

Two techniques are recognized for the real-time analysis of flavors during eating and drinking, atmospheric pressure chemical ionization mass spectrometry (APCI-MS), and proton transfer reaction mass spectrometry (PTR-MS). APCI-MS was developed for the analysis of flavors and fragrances, whereas PTR-MS was originally developed and optimized for the analysis of atmospheric pollutants. Here, the suitability of the two techniques for real-time flavor analysis is compared, using a varied range of common flavor compounds. An Ionicon PTR-MS was first optimized and then its performance critically compared with that of APCI-MS. Performance was gauged using the capacity for soft ionization, dynamic linear range, and limit of detection. Optimization of the PTR-MS increased the average sensitivity by a factor of more than 3. However, even with this increase in sensitivity, the Limit of Detection was typically 10 times higher and the Dynamic Linear Range ten times narrower than that of the APCI-MS. PMID:23394597

Avison, Shane J

2013-03-01

58

Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisation.  

PubMed

Polycyclic aromatic sulfur-containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI-MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI-MS/MS), either alone or in conjunction with liquid or gas chromatography. PMID:19177505

Herrera, Lisandra Cubero; Ramaley, Louis; Grossert, J Stuart

2009-03-01

59

Atmospheric Pressure Plasma Induced Sterilization and Chemical Neutralization  

NASA Astrophysics Data System (ADS)

We are studying chemical neutralization and surface decontamination using atmospheric pressure plasma discharges. The plasma is produced by corona discharge from an array of pins and a ground plane. The array is constructed so that various gases, like argon or helium, can be flowed past the pins where the discharge is initiated. The pin array can be biased using either DC, AC or pulsed discharges. Results indicate that the atmospheric plasma is effective in sterilizing surfaces with biological contaminants like E-coli and bacillus subtilus cells. Exposure times of less than four minutes in an air plasma result in a decrease in live colony counts by six orders of magnitude. Greater exposure times result in a decrease of live colony counts of up to ten orders of magnitude. The atmospheric pressure discharge is also effective in decomposing organic phosphate compounds that are simulants for chemical warfare agents. Details of the decomposition chemistry, by-product formation, and electrical energy consumption of the system will be discussed.

Garate, Eusebio; Evans, Kirk; Gornostaeva, Olga; Alexeff, Igor; Lock Kang, Weng; Wood, Thomas K.

1998-11-01

60

Established and Emerging Atmospheric Pressure Surface Sampling/Ionization Techniques for Mass Spectrometry  

SciTech Connect

The number and type of atmospheric pressure techniques suitable for sampling analytes from surfaces, forming ions from those analytes, and subsequently transporting those ions into vacuum for interrogation by mass spectrometry has rapidly expanded over the last several years. Moreover, the literature in this area is complicated by an explosion in acronyms for these techniques, many of which provide no information relating to the chemical or physical processes involved. In this review, we sort this vast array of techniques into a relatively few categories on the basis of the approaches used for surface sampling and ionization. For each technique, we explain, as best known, many of the underlying principles of operation, describe representative applications, and in some cases, discuss needed research or advancements and attempt to forecast their future analytical utility.

Van Berkel, Gary J [ORNL; Pasilis, Sofie P [ORNL; Ovchinnikova, Olga S [ORNL

2008-01-01

61

Screening, library-assisted identification and validated quantification of 23 benzodiazepines, flumazenil, zaleplone, zolpidem and zopiclone in plasma by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization.  

PubMed

A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid-liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs. PMID:15329838

Kratzsch, Carsten; Tenberken, Oliver; Peters, Frank T; Weber, Armin A; Kraemer, Thomas; Maurer, Hans H

2004-08-01

62

A novel derivatization method for the determination of Fosfomycin in human plasma by liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometric detection via phase transfer catalyzed derivatization.  

PubMed

An analytical method employing novel sample preparation and liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometric detection (LC-APCI/MS) was developed for the determination of fosfomycin in human plasma. Sample preparation involves derivatization through phase transfer catalysis (PTC) which offers multiple advantages due to the simultaneous extraction, preconcentration and derivatization of the analyte. Using a PT catalyst, fosfomycin was extracted from plasma in an organic phase and, then converted to a pentafluorobenzyl ester with the use of pentafluorobenzyl bromide (PFBBr) derivatization reagent. The method was fully optimized by taking into account both PTC and derivatization parameters. Several catalysts, in a wide range of concentrations, with different counter ions and polarities were tested along with different extraction solvents and pH values. Thereafter, the derivatization procedure was optimized by altering the amount of the derivatization reagent, the temperature of the reaction and finally, the derivatization duration. As internal standard (I.S.) ethylphosphonic acid was chosen and underwent the same pretreatment. The derivatives were separated on a pentafluorophenyl (PFP)-C18 analytical column, which provides unique selectivity, using an isocratic elution with acetonitrile-water (70-30, v/v). The method was validated according to US Food and Drug Administration (FDA) guidelines and can be used for a bioequivalence study of fosfomycin in human plasma. The correlation coefficient (r(2)) of the calibration curve of spiked plasma solutions in the range of 50-12000 ng/mL was found greater than 0.999 with a limit of quantitation (LOQ) equal to 50 ng/ml (for 500 ?L plasma sample). PMID:24508398

Papakondyli, Theodora A; Gremilogianni, Aikaterini M; Megoulas, Nikolaos C; Koupparis, Michael A

2014-03-01

63

Part-per-trillion level determination of antifouling pesticides and their byproducts in seawater samples by off-line solid-phase extraction followed by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.  

PubMed

A new method for the simultaneous determination of antifouling pesticides and some of their byproducts such as dichlofluanid, diuron and its byproducts [demethyldiuron and 1-(3,4-dichlorophenyl)urea], (2-thiocyanomethylthio)ben: zothiazole, chlorothalonil, Sea-nine 211, Irgarol 1051 and one of its byproducts (2-methylthio-4-tert.-butylamino-s-triazine) in seawater was developed. The extraction of these compounds from the filtered seawater samples was performed off-line with different solid-phase extraction sorbents using (I) a 500 mg graphitized carbon black cartridge (ENVI-Carb) and (II) 200 mg polymeric cartridges (LiChrolut EN and Isolute ENV+) and passing 500 ml of the sample through these cartridges. The detection was carried out by reversed-phase high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry both in the negative and positive ion modes. The recovery ranged from 76 to 96% for the whole antifouling group with the ENVI-Carb cartridges and the detection limit was at the part-per-trillion level except for TCMTB. The method utilizing the polymeric cartridge proved to be very useful, time saving and with good recoveries when only Irgarol and its byproduct, Sea-nine 211 and diuron and its byproducts, have to be analyzed. The different cartridges were applied to the analysis of these pesticides in different marinas of the Catalan coast; diuron, dichlofluanid, Sea-nine 211, Irgarol as well as demethyldiuron and the Irgarol byproduct being the must ubiquitous pollutants. Maximum concentration levels were 2-3.5 microg/l of diuron and Sea-nine 211, respectively. PMID:10870693

Martínez, K; Ferrer, I; Barceló, D

2000-05-19

64

Transmission geometry laser desorption atmospheric pressure photochemical ionization mass spectrometry for analysis of complex organic mixtures.  

PubMed

We present laser desorption atmospheric pressure photochemical ionization mass spectrometry (LD/APPCI MS) for rapid throughput analysis of complex organic mixtures, without the need for matrix, electric discharge, secondary electrospray, or solvents/vaporizers. Analytes dried on a microscope slide are vaporized in transmission geometry by a laser beam aligned with the atmospheric pressure inlet of the mass spectrometer. The laser beam initiates a cascade of reactions in the region between the glass slide and MS inlet, leading to generation of reagent ions for chemical ionization of vaporized analyte. Positive analyte ions are generated predominantly by proton transfer, charge exchange, and hydride abstraction, whereas negative ions are generated by electron capture or proton transfer reactions, enabling simultaneous analysis of saturated, unsaturated, and heteroatom-containing hydrocarbons. The absence of matrix interference renders LD/APPCI MS particularly useful for analysis of small molecules (<2000 Da) such as those present in petroleum crude oil and petroleum deposits. [M + H](+) and M(+•) dominate the positive-ion mass spectra for olefins and polyaromatic hydrocarbons, whereas saturated hydrocarbons are observed mainly as [M - H](+) and/or M(+•). Heteroatom-containing hydrocarbons are observed predominantly as [M + H](+). [M - H](-) and M(-•) are the dominant negative ions observed for analytes of lower gas-phase basicity or higher electron affinity than O2. The source was coupled with a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) to resolve and identify thousands of peaks from Athabasca bitumen heavy vacuum gas oil distillates (400-425 and 500-538 °C), enabling simultaneous characterization of their polar and nonpolar composition. We also applied LD/APPCI FTICR MS for rapid analysis of sodium and calcium naphthenate deposits with little to no sample pretreatment to provide mass spectral fingerprints that enable reliable compositional characterization. PMID:25347814

Nyadong, Leonard; Mapolelo, Mmilili M; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

2014-11-18

65

Atmospheric Pressure Ionization Permanent Magnet Fourier Transform Ion Cyclotron Resonance Mass Spectrometry  

PubMed Central

A new Fourier Transform Ion Cyclotron Resonance mass spectrometer based on a permanent magnet with an atmospheric pressure ionization source was designed and constructed. A mass resolving power (full-width-at-half-maximum) of up to 80,000 in the electron ionization mode and 25,000 in the electrospray mode was obtained. Also, a mass measurement accuracy at low-ppm level has been demonstrated for peptide mixtures in a mass range of up to 1,200 m/z in the isotopically resolved mass spectra. PMID:17587594

Vilkov, Andrey N.; Gamage, Chaminda M.; Misharin, Alexander S.; Doroshenko, Vladimir M.; Tolmachev, Dmitry A.; Tarasova, Irina A.; Kharybin, Oleg N.; Novoselov, Konstantin P.; Gorshkov, Michael V.

2007-01-01

66

Microplasma Discharge Vacuum Ultraviolet Photoionization Source for Atmospheric Pressure Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate the first use of an atmospheric pressure microplasma-based vacuum ultraviolet (VUV) photoionization source in atmospheric pressure mass spectrometry applications. The device is a robust, easy-to-operate microhollow cathode discharge (MHCD) that enables generation of VUV photons from Ne and Ne/H2 gas mixtures. Photons were detected by excitation of a microchannel plate detector and by analysis of diagnostic sample ions using a mass spectrometer. Reactive ions, charged particles, and metastables produced in the discharge were blocked from entering the ionization region by means of a lithium fluoride window, and photoionization was performed in a nitrogen-purged environment. By reducing the output pressure of the MHCD, we observed heightened production of higher-energy photons, making the photoionization source more effective. The initial performance of the MHCD VUV source has been evaluated by ionizing model analytes such as acetone, azulene, benzene, dimethylaniline, and glycine, which were introduced in solid or liquid phase. These molecules represent species with both high and low proton affinities, and ionization energies ranging from 7.12 to 9.7 eV.

Symonds, Joshua M.; Gann, Reuben N.; Fernández, Facundo M.; Orlando, Thomas M.

2014-09-01

67

Electron density and temperature measurement by continuum radiation emitted from weakly ionized atmospheric pressure plasmas  

NASA Astrophysics Data System (ADS)

The electron-atom neutral bremsstrahlung continuum radiation emitted from weakly ionized plasmas is investigated for electron density and temperature diagnostics. The continuum spectrum in 450-1000 nm emitted from the argon atmospheric pressure plasma is found to be in excellent agreement with the neutral bremsstrahlung formula with the electron-atom momentum transfer cross-section given by Popovi?. In 280-450 nm, however, a large discrepancy between the measured and the neutral bremsstrahlung emissivities is observed. We find that without accounting for the radiative H2 dissociation continuum, the temperature, and density measurements would be largely wrong, so that it should be taken into account for accurate measurement.

Park, Sanghoo; Choe, Wonho; Youn Moon, Se; Park, Jaeyoung

2014-02-01

68

Capillary atmospheric pressure electron capture ionization (cAPECI): a highly efficient ionization method for nitroaromatic compounds.  

PubMed

We report on a novel method for atmospheric pressure ionization of compounds with elevated electron affinity (e.g., nitroaromatic compounds) or gas phase acidity (e.g., phenols), respectively. The method is based on the generation of thermal electrons by the photo-electric effect, followed by electron capture of oxygen when air is the gas matrix yielding O2(-) or of the analyte directly with nitrogen as matrix. Charge transfer or proton abstraction by O2(-) leads to the ionization of the analytes. The interaction of UV-light with metals is a clean method for the generation of thermal electrons at atmospheric pressure. Furthermore, only negative ions are generated and neutral radical formation is minimized, in contrast to discharge- or dopant assisted methods. Ionization takes place inside the transfer capillary of the mass spectrometer leading to comparably short transfer times of ions to the high vacuum region of the mass spectrometer. This strongly reduces ion transformation processes, resulting in mass spectra that more closely relate to the neutral analyte distribution. cAPECI is thus a soft and selective ionization method with detection limits in the pptV range. In comparison to standard ionization methods (e.g., PTR), cAPECI is superior with respect to both selectivity and achievable detection limits. cAPECI demonstrates to be a promising ionization method for applications in relevant fields as, for example, explosives detection and atmospheric chemistry. PMID:24399666

Derpmann, Valerie; Mueller, David; Bejan, Iustinian; Sonderfeld, Hannah; Wilberscheid, Sonja; Koppmann, Ralf; Brockmann, Klaus J; Benter, Thorsten

2014-03-01

69

Universal screening method for the determination of US Environmental Protection Agency phenols at the lower ng l ?1 level in water samples by on-line solid-phase extraction–high-performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry within a single run  

Microsoft Academic Search

The applicability of a previously optimized method for the analysis of the US Environmental Protection Agency (EPA) regulations phenols, based on on-line solid-phase extraction coupled to liquid chromatography with mass spectrometric (MS) detection in different matrix loaded water samples is demonstrated. The comprehensive optimization of the mobile phase conditions and their influence on the ionization process in atmospheric pressure ionization

R. Wissiack; E. Rosenberg

2002-01-01

70

Liquid Sampling-Atmospheric Pressure Glow Discharge Ionization Source for Elemental Mass Spectrometry  

SciTech Connect

A new, low power ionization source for elemental MS analysis of aqueous solutions is described. The liquid sampling-atmospheric pressure glow discharge (LSAPGD) operates by a process wherein the surface of the liquid emanating from a 75 ?m i.d. glass capillary acts as the cathode of the direct current glow discharge. Analytecontaining solutions at a flow rate of 100 ?L min-1 are vaporized by the passage of current, yielding gas phase solutes that are subsequently ionized in the < 5 W (maximum of 60 mA and 500 V), ~1 mm3 volume, plasma. The LS-APGD is mounted in place of the normal electrospray ionization source of a Thermo Scientific Exactive orbitrap mass spectrometer system. Basic operating characteristics are described, including the role of discharge power on mass spectral composition, the ability to obtain ultra-high resolution elemental isotopic patterns, and preliminary limits of detection attainable based on the injection of aliquots of multielement standards. While much optimization remains, it is believed that the LS-APGD may present a practical alternative to high-powered (>1 kW) plasma sources typically employed in elemental mass spectrometry, particularly for those cases where costs, operational overhead, and simplicity considerations are important.

Marcus, R. Kenneth; Quarles, C. Derrick; Barinaga, Charles J.; Carado, Anthony J.; Koppenaal, David W.

2011-04-01

71

Destruction of simulated chemical warfare agents in non-thermal atmospheric-pressure air plasma  

Microsoft Academic Search

The decontamination of chemical warfare agents (CWA) using an atmospheric pressure dielectric barrier discharge in air was investigated. Stainles s steel samples inoculated with malathion (a surrogate for nerve agent VX) were placed on the ca thode, where they were treated by the chemical active species produced in the streamers. An effect ive decontamination (>99.7 %) was achieved after 10

J. Jarrige; P. Vervisch

72

Investigations of analyte-specific response saturation and dynamic range limitations in atmospheric pressure ionization mass spectrometry.  

PubMed

With this study, we investigated why some small molecules demonstrate narrow dynamic ranges in electrospray ionization-mass spectrometry (ESI-MS) and sought to establish conditions under which the dynamic range could be extended. Working curves were compared for eight flavonoids and two alkaloids using ESI, atmospheric pressure chemical ionization (APCI), and heated electrospray ionization (HESI) sources. Relative to reserpine, the flavonoids exhibited narrower linear dynamic ranges with ESI-MS, primarily due to saturation in response at relatively low concentrations. Saturation was overcome by switching from ESI to APCI, and our experiments utilizing a combination HESI/APCI source suggest that this is due in part to the ability of APCI to protonate neutral quercetin molecules in the gas phase. Thermodynamic equilibrium calculations indicate that quercetin should be fully protonated in solution, and thus, it appears that some factor inherent in the ESI process favors the formation of neutral quercetin at high concentration. The flavonoid saturation concentration was increased with HESI as compared to ESI, suggesting that inefficient transfer of ions to the gas phase can also contribute to saturation in ESI-MS response. In support of this conclusion, increasing auxiliary gas pressure or switching to a more volatile spray solvent also increased the ESI dynamic range. Among the sources investigated herein, the HESI source achieved the best analytical performance (widest linear dynamic range, lowest LOD), but the APCI source was less subject to saturation in response at high concentration. PMID:25268329

Alfaro, Clint M; Uwakweh, Agbo-Oma; Todd, Daniel A; Ehrmann, Brandie M; Cech, Nadja B

2014-11-01

73

Stabilization of the ionization overheating thermal instability in atmospheric pressure microplasmas  

SciTech Connect

Stable direct current atmospheric pressure plasmas can regularly be generated in air using microplasma systems, and rapid cooling due to the small size is typically suggested as the thermally stabilizing mechanism. However, temperatures of the stable discharges are significantly higher than ambient, and stable operation is not easily achieved in all gases at similar sizes. Revisiting a traditional analysis of the thermal instability, we find that the inclusion of the simple ballasted external circuit in the analysis leads to additional stabilizing mechanisms. This stabilization occurs in microplasmas due to the characteristic times of the external circuit and the instability being comparable, which allows the electric field to change during the time frame of the instability. Experimentally this is implemented by reducing the stray capacitance of the external circuit. This stabilizing mechanism is verified in several gases and its application in a plasma enhanced chemical vapor deposition system leads to a more uniform film deposition.

Staack, D.; Farouk, B.; Gutsol, A.; Fridman, A. [Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

2009-07-01

74

Atmospheric pressure chemical ionisation mass spectrometry for in vivo analysis of volatile flavour release  

Microsoft Academic Search

To follow volatile flavour release in the expired air of people during eating, several physiological and analytical constraints must be observed to obtain good quality data. An interface has been developed to sample air from the nose and ionise the volatile compounds contained therein by atmospheric pressure chemical ionisation. The ions formed are detected in a quadrupole mass spectrometer. The

A. J. Taylor; R. S. T. Linforth; B. A. Harvey; A. Blake

2000-01-01

75

Decontamination of chemical and biological warfare (CBW) agents using an atmospheric pressure plasma jet (APPJ)  

NASA Astrophysics Data System (ADS)

The atmospheric pressure plasma jet (APPJ) [A. Schütze et al., IEEE Trans. Plasma Sci. 26, 1685 (1998)] is a nonthermal, high pressure, uniform glow plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g., He/O2/H2O), which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered at 13.56 MHz rf. While passing through the plasma, the feedgas becomes excited, dissociated or ionized by electron impact. Once the gas exits the discharge volume, ions and electrons are rapidly lost by recombination, but the fast-flowing effluent still contains neutral metastable species (e.g., O2*, He*) and radicals (e.g., O, OH). This reactive effluent has been shown to be an effective neutralizer of surrogates for anthrax spores and mustard blister agent. Unlike conventional wet decontamination methods, the plasma effluent does not cause corrosion and it does not destroy wiring, electronics, or most plastics, making it highly suitable for decontamination of sensitive equipment and interior spaces. Furthermore, the reactive species in the effluent rapidly degrade into harmless products leaving no lingering residue or harmful by-products.

Herrmann, H. W.; Henins, I.; Park, J.; Selwyn, G. S.

1999-05-01

76

Decontamination of Chemical/Biological Warfare (CBW) Agents Using an Atmospheric Pressure Plasma Jet (APPJ)  

NASA Astrophysics Data System (ADS)

The atmospheric pressure plasma jet (APPJ) is a non-thermal, high pressure, uniform glow discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g. He/O_2/H_2O) which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered at 13.56 MHz RF. While passing through the plasma, the feedgas becomes excited, dissociated or ionized by electron impact. Once the gas exits the discharge volume, ions and electrons are rapidly lost by recombination, but the fast-flowing effluent still contains metastables (e.g. O2*, He*) and radicals (e.g. O, OH). These reactive species have been shown to be effective neutralizers of surrogates for anthrax spores, mustard blister agent and VX nerve gas. Unlike conventional, wet decontamination methods, the plasma effluent does not cause corrosion of most surfaces and does not damage wiring, electronics, nor most plastics. This makes it highly suitable for decontamination of high value sensitive equipment such as is found in vehicle interiors (i.e. tanks, planes...) for which there is currently no good decontamination technique. Furthermore, the reactive species rapidly degrade into harmless products leaving no lingering residue or harmful byproducts. Physics of the APPJ will be discussed and results of surface decontamination experiments using simulant and actual CBW agents will be presented.

Herrmann, Hans W.

1998-11-01

77

Effect of H 2 ambient annealing on silicon nanowires prepared by atmospheric pressure chemical vapor deposition  

Microsoft Academic Search

We report the effect of H2 ambient annealing on the microstructure and vibrational properties of silicon nanowires (SiNWs) grown by atmospheric pressure chemical vapor depositions. The SiNWs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Field-Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). The HRTEM study revealed that the thickness of oxide sheath surrounded by core silicon

Bhabani S. Swain; Sung S. Lee; Sang H. Lee; Bibhu P. Swain; Nong M. Hwang

2010-01-01

78

Characterization of CuInS 2 films prepared by atmospheric pressure spray chemical vapor deposition  

Microsoft Academic Search

Copper indium disulfide films were deposited by atmospheric pressure spray chemical vapor deposition (CVD). Films were deposited at 390°C using [(PPh3)2CuIn(SEt)4] as a single source precursor in an argon atmosphere. The films range in thickness from 0.75 to 1.0 ?m and exhibit a crystallographic gradient, with the leading edge having a (220) preferred orientation and the trailing edge having a

Jerry D. Harris; Kulbinder K. Banger; David A. Scheiman; Mark A. Smith; Michael H.-C. Jin; Aloysius F. Hepp

2003-01-01

79

Decontamination of chemical and biological warfare (CBW) agents using an atmospheric pressure plasma jet (APPJ)  

Microsoft Academic Search

The atmospheric pressure plasma jet (APPJ) [A. Schütze et al., IEEE Trans. Plasma Sci. 26, 1685 (1998)] is a nonthermal, high pressure, uniform glow plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g., He\\/O2\\/H2O), which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode

H. W. Herrmann; I. Henins; G. S. Selwyn

1999-01-01

80

Decontamination of Chemical\\/Biological Warfare (CBW) Agents Using an Atmospheric Pressure Plasma Jet (APPJ)  

Microsoft Academic Search

The atmospheric pressure plasma jet (APPJ) is a non-thermal, high pressure, uniform glow discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g. He\\/O_2\\/H_2O) which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered at 13.56 MHz RF. While passing through the plasma, the feedgas

Hans W. Herrmann

1998-01-01

81

Decontamination of chemical and biological warfare (CBW) agents using an atmospheric pressure plasma jet (APPJ)  

Microsoft Academic Search

The atmospheric pressure plasma jet (APPJ) [A. Schu¨tze &etal;, IEEE Trans. Plasma Sci. 26, 1685 (1998)] is a nonthermal, high pressure, uniform glow plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g., He\\/O2\\/H2O), which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered

H. W. Herrmann; I. Henins; G. S. Selwyn

1999-01-01

82

Planar differential mobility spectrometer as a pre-filter for atmospheric pressure ionization mass spectrometry  

PubMed Central

Ion filters based on planar DMS can be integrated with the inlet configuration of most mass spectrometers, and are able to enhance the quality of mass analysis and quantitative accuracy by reducing chemical noise, and by pre-separating ions of similar mass. This paper is the first in a series of three papers describing the optimization of DMS / MS instrumentation. In this paper the important physical parameters of a planar DMS-MS interface including analyzer geometry, analyzer coupling to a mass spectrometer, and transport gas flow control are considered. The goal is to optimize ion transmission and transport efficiency, provide optimal and adjustable resolution, and produce stable operation under conditions of high sample contamination. We discuss the principles of DMS separations and highlight the theoretical underpinnings. The main differences between planar and cylindrical geometries are presented, including a discussion of the advantages and disadvantages of RF ion focusing. In addition, we present a description of optimization of the frequency and amplitude of the DMS fields for resolution and ion transmission, and a discussion of the influence and importance of ion residence time in DMS. We have constructed a mass spectrometer interface for planar geometries that takes advantage of atmospheric pressure gas dynamic principles, rather than ion focusing, to minimize ion losses from diffusion in the analyzer and to maximize total ion transport into the mass spectrometer. A variety of experimental results has been obtained that illustrate the performance of this type of interface, including tests of resistance to high contamination levels, and the separation of stereoisomers. In a subsequent publication the control of the chemical interactions that drive the separation process of a DMS / MS system will be considered. In a third publication we describe novel electronics designed to provide the high voltages asymmetric waveform fields (SV) required for these devices as well as the effects of different waveforms. PMID:21278836

Schneider, Bradley B.; Covey, Thomas R.; Coy, Stephen L.; Krylov, Evgeny V.

2010-01-01

83

Determination of organonitrogen pesticides in large volumes of surface water by liquid–liquid and solid-phase extraction using gas chromatography with nitrogen–phosphorus detection and liquid chromatography with atmospheric pressure chemical ionization mass spectrometry  

Microsoft Academic Search

During a recent study to determine the fluxes and fates of contaminants in the St. Lawrence River, the majority of organonitrogen pesticides analysed in samples of surface water were found in the dissolved phase. This paper compares two extraction techniques and two analytical techniques for 10 chemicals (metolachlor, seven triazines and two degradation products of atrazine–cyanazine–propazine and simazine) in the

Hassan Sabik; Roger Jeannot

1998-01-01

84

What Is the Opposite of Pandora's Box? Direct Analysis, Ambient Ionization, and a New Generation of Atmospheric Pressure Ion Sources  

PubMed Central

The introduction of DART and DESI sources approximately seven years ago led to the development of a new series of atmospheric pressure ion sources referred to as “ambient ionization” sources. These fall into two major categories: spray techniques like DESI or plasma techniques like DART. The selectivity of “direct ionization,” meaning analysis without chromatography and with little or no sample preparation, depends on the mass spectrometer selectivity. Although high resolution and tandem mass spectrometry are valuable tools, rapid and simple sample preparation methods can improve the utility of ambient ionization methods. The concept of ambient ionization has led to the realization that there are many more ways to form ions than might be expected. An interesting example is the use of a flint-and-steel spark source to generate ions from compounds such as phenolphthalein and Gramicidin S. PMID:24349926

B. Cody, Robert

2013-01-01

85

Desorption/ionization of acrylamide in aqueous solutions in atmospheric pressure air using a microdischarge with vortex focusing of ions  

NASA Astrophysics Data System (ADS)

A method of desorption/ionization in a microdischarge with ion vortex focusing (vortex focusing microdischarge, VFM) is suggested. A glow microdischarge is initiated in an air flow, and resulting ions act on the surface of interest. As a model compound, an aqueous solution of acrylamide is taken. Desorption/ionization taking place under atmospheric pressure is followed by the mass-spectrometric identification of the ions. The operating parameters of the VFM system are studied and optimized. Upon optimization of the system, the detection limit of acrylamide trace amounts in aqueous solutions is determined using the suggested method of desorption/ionization and analyte ion focusing with a vortex (swirling) jet. The acrylamide detection limit is found to be 2 × 10-3 g/L.

Pervukhin, V. V.; Sheven', D. G.

2014-09-01

86

Aliphatic Hydrocarbon Spectra by Helium Ionization Mass Spectrometry (HIMS) on a Modified Atmospheric-Pressure Source Designed for Electrospray Ionization  

NASA Astrophysics Data System (ADS)

Chemical-ionization techniques that use metastable species to ionize analytes traditionally use a flat pin or a sharp solid needle onto which the high potential needed to generate the discharge plasma is applied. We report here that direct analysis of samples containing volatile and semivolatile compounds, including saturated and unsaturated aliphatic hydrocarbons, can be achieved on any electrospray-ionization mass spectrometer by passing helium though the sample delivery metal capillary held at a high potential. In the helium plasma ionization source (HPIS) described here, the typical helium flow required (about 20-30 mL/min), was significantly lower than that needed for other helium-ionization sources. By this procedure, positive ions were generated by nominal hydride ion removal from molecules emanating from heated saturated hydrocarbons as large as tetratetracontane (C44H90), at capillary voltages ranging from 2.0 to 4.0 kV. Unsaturated hydrocarbons, on the other hand, underwent facile protonation under much lower capillary voltages (0.9 to 2.0 kV). Although saturated and monounsaturated hydrocarbons bearing the same number of carbon atoms generate ions of the same m/z ratio, a gas-phase deuterium exchange method is described to ascertain the identity of these isomeric ions originating from either protonation or hydride abstraction mechanisms. Moreover, mass spectrometric results obtained by exposing unsaturated hydrocarbons to D2O vapor in an HPIS-MS instrument confirmed that the proton donor for ionization of unsaturated hydrocarbons is protonated water.

Yang, Zhihua; Attygalle, Athula B.

2011-08-01

87

Investigation on plasma parameters and step ionization from discharge characteristics of an atmospheric pressure Ar microplasma jet  

SciTech Connect

In this communication, we report a technique to estimate the plasma parameters from the discharge characteristics of a microplasma device, operated in atmospheric pressure on the basis of homogeneous discharge model. By this technique, we investigate the plasma parameters of a microplasma jet produced by microplasma device consisting of coaxial capillary electrodes surrounded by dielectric tube. Our results suggest that the complex dependence of electrical discharge characteristics observed for microplasma device operated with Ar or it admixtures probably signify the existence of step ionization, which is well known in inductively coupled plasma.

Bora, B.; Bhuyan, H.; Favre, M.; Chuaqui, H.; Wyndham, E. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Ave. Vicuna Mackenna 4860, Santiago (Chile); Kakati, M. [Thermal Plasma Processed Materials Laboratory, Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402, Assam (India)

2012-06-15

88

Chemical modification of amino acids by atmospheric-pressure cold plasma in aqueous solution  

NASA Astrophysics Data System (ADS)

Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

Takai, Eisuke; Kitamura, Tsuyoshi; Kuwabara, Junpei; Ikawa, Satoshi; Yoshizawa, Shunsuke; Shiraki, Kentaro; Kawasaki, Hideya; Arakawa, Ryuichi; Kitano, Katsuhisa

2014-07-01

89

Analysis of mass transport in an atmospheric pressure remote plasma-enhanced chemical vapor deposition process  

SciTech Connect

In remote microwave plasma enhanced chemical vapor deposition processes operated at atmospheric pressure, high deposition rates are associated with the localization of precursors on the treated surface. We show that mass transport can be advantageously ensured by convection for the heavier precursor, the lighter being driven by turbulent diffusion toward the surface. Transport by laminar diffusion is negligible. The use of high flow rates is mandatory to have a good mixing of species. The use of an injection nozzle with micrometer-sized hole enables us to define accurately the reaction area between the reactive species. The localization of the flow leads to high deposition rates by confining the reactive species over a small area, the deposition yield being therefore very high. Increasing the temperature modifies nonlinearly the deposition rates and the coating properties.

Cardoso, R. P.; Belmonte, T.; Henrion, G.; Gries, T. [Department of Chemistry and Physics of Solids and Surfaces, Institut Jean Lamour, Nancy-Universite, CNRS, Parc de Saurupt, CS 14234, F-54042 Nancy Cedex (France); Tixhon, E. [AGC Flat Coating, 2 Rue de l'aurore, B-6040 Jumet (Belgium)

2010-01-15

90

Studies of the mechanism of the cluster formation in a thermally sampling atmospheric pressure ionization mass spectrometer.  

PubMed

In this study a thermally sampling atmospheric pressure ionization mass spectrometer is described and characterized. The ion transfer stage offers the capability to sample cluster ions at thermal equilibrium and during this transfer fundamental processes possibly affecting the cluster distribution are also readily identified. Additionally, the transfer stage combines optional collision-induced dissociation (CID) analysis of the cluster composition with thermal equilibrium sampling of clusters. The performance of the setup is demonstrated with regard to the proton-bound water cluster system. The benefit of the studied processes is that they can help to improve future transfer stages and to understand cluster ion reactions in ion mobility tubes and high-pressure ion sources. In addition, the instrument allows for the identification of fragmentation and protonation reactions caused by CID. PMID:24517784

Albrecht, Sascha; Klopotowski, Sebastian; Derpmann, Valerie; Klee, Sonja; Brockmann, Klaus J; Stroh, Fred; Benter, Thorsten

2014-01-01

91

Plasma-Spray Ionization (PLASI): A Multimodal Atmospheric Pressure Ion Source for Liquid Stream Analysis  

NASA Astrophysics Data System (ADS)

A new ion generation method, named plasma-spray ionization (PLASI) for direct analysis of liquid streams, such as in continuous infusion experiments or liquid chromatography (LC), is reported. PLASI addresses many of the analytical limitations of electrospray ionization (ESI) and has potential for real time process stream analysis and reaction monitoring under atmospheric conditions in non-ESI friendly scenarios. In PLASI-mass spectrometry (MS), the liquid stream is pneumatically nebulized and partially charged at low voltages; the resultant aerosol is thus entrained with a gaseous plasma plume from a distal glow discharge prior to MS detection. PLASI-MS not only overcomes ESI-MS limitations but also generates simpler mass spectra with minimal adduct and cluster formation. PLASI utilizes the atomization capabilities of an ESI sprayer operated below the ESI threshold to generate gas-phase aerosols that are then ionized by the plasma stream. When operated at or above the ESI threshold, ionization by traditional ESI mechanisms is achieved. The multimodal nature of the technique enables readily switching between plasma and ESI operation. It is expected that PLASI will enable analyzing a wide range of analytes in complex matrices and less-restricted solvent systems, providing more flexibility than that achievable by ESI alone.

Kaylor, Adam; Dwivedi, Prabha; Pittman, Jennifer J.; Monge, María Eugenia; Cheng, Guilong; Li, Shelly; Fernández, Facundo M.

2014-10-01

92

A systematic study of atmospheric pressure chemical vapor deposition growth of large-area monolayer graphene†  

PubMed Central

Graphene has attracted considerable interest as a potential material for future electronics. Although mechanical peel is known to produce high quality graphene flakes, practical applications require continuous graphene layers over a large area. The catalyst-assisted chemical vapor deposition (CVD) is a promising synthetic method to deliver wafer-sized graphene. Here we present a systematic study on the nucleation and growth of crystallized graphene domains in an atmospheric pressure chemical vapor deposition (APCVD) process. Parametric studies show that the mean size of the graphene domains increases with increasing growth temperature and CH4 partial pressure, while the density of domains decreases with increasing growth temperature and is independent of the CH4 partial pressure. Our studies show that nucleation of graphene domains on copper substrate is highly dependent on the initial annealing temperature. A two-step synthetic process with higher initial annealing temperature but lower growth temperature is developed to reduce domain density and achieve high quality full-surface coverage of monolayer graphene films. Electrical transport measurements demonstrate that the resulting graphene exhibits a high carrier mobility of up to 3000 cm2 V?1 s?1 at room temperature.

Liu, Lixin; Zhou, Hailong; Cheng, Rui; Chen, Yu; Lin, Yung-Chen; Qu, Yongquan; Bai, Jingwei; Ivanov, Ivan A.; Liu, Gang

2012-01-01

93

Surface Decontamination of Chemical Agent Surrogates Using an Atmospheric Pressure Air Flow Plasma Jet  

NASA Astrophysics Data System (ADS)

An atmospheric pressure dielectric barrier discharge (DBD) plasma jet generator using air flow as the feedstock gas was applied to decontaminate the chemical agent surrogates on the surface of aluminum, stainless steel or iron plate painted with alkyd or PVC. The experimental results of material decontamination show that the residual chemical agent on the material is lower than the permissible value of the National Military Standard of China. In order to test the corrosion effect of the plasma jet on different material surfaces in the decontamination process, corrosion tests for the materials of polymethyl methacrylate, neoprene, polyvinyl chloride (PVC), polyethylene (PE), phenolic resin, iron plate painted with alkyd, stainless steel, aluminum, etc. were carried out, and relevant parameters were examined, including etiolation index, chromatism, loss of gloss, corrosion form, etc. The results show that the plasma jet is slightly corrosive for part of the materials, but their performances are not affected. A portable calculator, computer display, mainboard, circuit board of radiogram, and a hygrometer could work normally after being treated by the plasma jet.

Li, Zhanguo; Li, Ying; Cao, Peng; Zhao, Hongjie

2013-07-01

94

Determination of vertical fluxes of sulfur dioxide and dimethyl sulfide in the remote marine atmosphere by eddy correlation and an airborne isotopic dilution atmospheric pressure ionization mass spectrometer  

Microsoft Academic Search

Vertical fluxes of dimethyl sulfide (DMS) and sulfur dioxide (SO 2) were determined by eddy correlation and an isotopic dilution atmospheric pressure ionization mass spectrometer (APIMS) on an aircraft platform. The sampling frequency of the isotopic dilution APIMS ranged from 1 Hz to 25 Hz for real-time measurements. Measurements were made near the surface in the marine boundary layer to

Glenn M. Mitchell

2001-01-01

95

Atmospheric Pressure Spray Chemical Vapor Deposited CuInS2 Thin Films for Photovoltaic Applications  

NASA Technical Reports Server (NTRS)

Solar cells have been prepared using atmospheric pressure spray chemical vapor deposited CuInS2 absorbers. The CuInS2 films were deposited at 390 C using the single source precursor (PPh3)2CuIn(SEt)4 in an argon atmosphere. The absorber ranges in thickness from 0.75 - 1.0 micrometers, and exhibits a crystallographic gradient, with the leading edge having a (220) preferred orientation and the trailing edge having a (112) orientation. Schottky diodes prepared by thermal evaporation of aluminum contacts on to the CuInS2 yielded diodes for films that were annealed at 600 C. Solar cells were prepared using annealed films and had the (top down) composition of Al/ZnO/CdS/CuInS2/Mo/Glass. The Jsc, Voc, FF and (eta) were 6.46 mA per square centimeter, 307 mV, 24% and 0.35%, respectively for the best small area cells under simulated AM0 illumination.

Harris, J. D.; Raffaelle, R. P.; Banger, K. K.; Smith, M. A.; Scheiman, D. A.; Hepp, A. F.

2002-01-01

96

Atmospheric-Pressure Chemical Vapor Deposition of Iron Pyrite Thin Films  

SciTech Connect

Iron pyrite (cubic FeS{sub 2}) is a promising candidate absorber material for earth-abundant thin-film solar cells. In this report, single-phase, large-grain, and uniform polycrystalline pyrite thin films are fabricated on glass and molybdenum-coated glass substrates by atmospheric-pressure chemical vapor deposition (AP-CVD) using the reaction of iron(III) acetylacetonate and tert-butyl disulfide in argon at 300 C, followed by sulfur annealing at 500--550 C to convert marcasite impurities to pyrite. The pyrite-marcasite phase composition depends strongly on the concentration of sodium in the growth substrate and the sulfur partial pressure during annealing. Phase and elemental composition of the films are characterized by X-ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy. The in-plane electrical properties are surprisingly insensitive to phase and elemental impurities, with all films showing p-type, thermally activated transport with a small activation energy ({approx}30 meV), a room- temperature resistivity of {approx}1 {Omega} cm, and low mobility. These ubiquitous electrical properties may result from robust surface effects. These CVD pyrite thin films are well suited to fundamental electrical studies and the fabrication of pyrite photovoltaic device stacks.

Berry, Nicholas; Cheng, Ming; Perkins, Craig L.; Limpinsel, Moritz; Hemminger, John C.; Law, Matt (NREL); (UCI)

2012-10-23

97

Desorption electrospray ionization (DESI) with atmospheric pressure ion mobility spectrometry for drug detection.  

PubMed

Desorption electrospray ionization (DESI) was coupled to an ambient pressure drift tube ion mobility time-of-flight mass spectrometer (IM-TOFMS) for the direct analysis of active ingredients in pharmaceutical samples. The DESI source was also coupled with a standalone IMS demonstrating potential of portable and inexpensive drug-quality testing platforms. The DESI-IMS required no sample pretreatment as ions were generated directly from tablets and cream formulations. The analysis of a range of over-the-counter and prescription tablet formations was demonstrated for amphetamine (methylphenidate), antidepressant (venlafaxine), barbiturate (Barbituric acid), depressant (alprazolam), narcotic (3-methylmorphine) and sympatholytic (propranolol) drugs. Active ingredients from soft and liquid formulations, such as Icy Hot cream (methyl salicylate) and Nyquil cold medicine (acetaminophen, dextromethorphan, doxylamine) were also detected. Increased sensitivity for selective drug responses was demonstrated through the formation of sodiated adduct ions by introducing small quantities of NaCl into the DESI solvent. Of the drugs and pharmaceuticals tested in this study, 68% (22 total samples) provided a clear ion mobility response at characteristic mobilities either as (M + H)(+), (M - H)(-), or (M + Na)(+) ions. PMID:24551872

Roscioli, Kristyn M; Tufariello, Jessica A; Zhang, Xing; Li, Shelly X; Goetz, Gilles H; Cheng, Guilong; Siems, William F; Hill, Herbert H

2014-04-01

98

Combination of suppressed and non-suppressed ion chromatography with atmospheric pressure ionization mass spectrometry for the determination of anions.  

PubMed

Non-suppressed and suppressed ion chromatography in combination with atmospheric pressure ionization mass spectrometry are compared with special respect to sensitivity for the analysis of low-molecular-mass anions. Iodate, bromate, bromide, sulfate, thiosulfate and bromide could be separated by non-suppressed ion chromatography using a low-capacity anion-exchange column and ammonium citrate as mobile phase. Absolute detection limits between 0.4 and 0.7 ng could be achieved; employing a column requiring a flow-rate of 1 ml/min for optimum performance, splitting was necessary so that only 120 microliters/min entered the interface of the mass spectrometer resulting in detection limits between 0.03 and 0.06 mg/l. The same stationary phase (packed into a narrow-bore column which allowed operation without splitting) was suitable for the separation of oxyhalides in the suppressed mode with detection limits of 0.5 microgram/l (50 pg) with sodium carbonate as eluent. The method was applied to the analysis of drinking water for oxyhalides. The sample pretreatment for the removal of matrix anions (sulfate, chloride and hydrogencarbonate) is described. PMID:10457470

Buchberger, W; Ahrer, W

1999-07-30

99

Capillary electrochromatography-atmospheric pressure ionization mass spectrometry of pesticides using a surfactant-bound monolithic column  

PubMed Central

A surfactant bound poly (11-acrylaminoundecanoic acid-ethylene dimethacrylate) (AAUA-EDMA) monolithic column was simply prepared by in-situ co-polymerization of AAUA and EDMA with 1-propanol, 1,4-butanediol and water as porogens in 100 µm id fused silica capillary in one step. This column was used in capillary electrochromatography (CEC)-atmospheric pressure photoionization (APPI)-mass spectrometry system for separation and detection of N-methylcarbamates (NMCs) pesticides. Numerous parameters are optimized for CEC-APPI-MS. After evaluation of the mobile phase composition, sheath liquid composition and the monolithic capillary outlet position, a fractional factorial design (FFD) was selected as a screening procedure to identify factors of ionization source parameters, such as sheath liquid flow rate, drying gas flow rate, drying gas temperature, nebulizing gas pressure, vaporizer temperature, and capillary voltage, which significantly influence APPI-MS sensitivity. A face-centered central composite design (CCD) was further utilized to optimize the most significant parameters and predict the best sensitivity. Under optimized conditions signal-to-noise ratios (S/N) around 78 were achieved for an injection of 100 ng/mL of each pesticide. Finally, this CEC-APPI-MS method was successfully applied to the analysis of nine NMCs in spiked apple juice sample after solid phase extraction with recoveries in the range of 65 to 109%. PMID:20349511

Gu, Congying; Shamsi, Shahab A.

2011-01-01

100

Automatic Sampling and Analysis of Organics and Biomolecules by Capillary Action-Supported Contactless Atmospheric Pressure Ionization Mass Spectrometry  

PubMed Central

Contactless atmospheric pressure ionization (C-API) method has been recently developed for mass spectrometric analysis. A tapered capillary is used as both the sampling tube and spray emitter in C-API. No electric contact is required on the capillary tip during C-API mass spectrometric analysis. The simple design of the ionization method enables the automation of the C-API sampling system. In this study, we propose an automatic C-API sampling system consisting of a capillary (?1 cm), an aluminium sample holder, and a movable XY stage for the mass spectrometric analysis of organics and biomolecules. The aluminium sample holder is controlled by the movable XY stage. The outlet of the C-API capillary is placed in front of the orifice of a mass spectrometer, whereas the sample well on the sample holder is moved underneath the capillary inlet. The sample droplet on the well can be readily infused into the C-API capillary through capillary action. When the sample solution reaches the capillary outlet, the sample spray is readily formed in the proximity of the mass spectrometer applied with a high electric field. The gas phase ions generated from the spray can be readily monitored by the mass spectrometer. We demonstrate that six samples can be analyzed in sequence within 3.5 min using this automatic C-API MS setup. Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells. Therefore, the C-API capillary could be readily flushed between runs. No carryover problems are observed during the analyses. The sample volume required for the C-API MS analysis is minimal, with less than 1 nL of the sample solution being sufficient for analysis. The feasibility of using this setup for quantitative analysis is also demonstrated. PMID:23762484

Hsieh, Cheng-Huan; Meher, Anil Kumar; Chen, Yu-Chie

2013-01-01

101

On-line coating of glass with tin oxide by atmospheric pressure chemical vapor deposition.  

SciTech Connect

Atmospheric pressure chemical vapor deposition (APCVD) of tin oxide is a very important manufacturing technique used in the production of low-emissivity glass. It is also the primary method used to provide wear-resistant coatings on glass containers. The complexity of these systems, which involve chemical reactions in both the gas phase and on the deposition surface, as well as complex fluid dynamics, makes process optimization and design of new coating reactors a very difficult task. In 2001 the U.S. Dept. of Energy Industrial Technologies Program Glass Industry of the Future Team funded a project to address the need for more accurate data concerning the tin oxide APCVD process. This report presents a case study of on-line APCVD using organometallic precursors, which are the primary reactants used in industrial coating processes. Research staff at Sandia National Laboratories in Livermore, CA, and the PPG Industries Glass Technology Center in Pittsburgh, PA collaborated to produce this work. In this report, we describe a detailed investigation of the factors controlling the growth of tin oxide films. The report begins with a discussion of the basic elements of the deposition chemistry, including gas-phase thermochemistry of tin species and mechanisms of chemical reactions involved in the decomposition of tin precursors. These results provide the basis for experimental investigations in which tin oxide growth rates were measured as a function of all major process variables. The experiments focused on growth from monobutyltintrichloride (MBTC) since this is one of the two primary precursors used industrially. There are almost no reliable growth-rate data available for this precursor. Robust models describing the growth rate as a function of these variables are derived from modeling of these data. Finally, the results are used to conduct computational fluid dynamic simulations of both pilot- and full-scale coating reactors. As a result, general conclusions are reached concerning the factors affecting the growth rate in on-line APCVD reactors. In addition, a substantial body of data was generated that can be used to model many different industrial tin oxide coating processes. These data include the most extensive compilation of thermochemistry for gas-phase tin-containing species as well as kinetic expressions describing tin oxide growth rates over a wide range of temperatures, pressures, and reactant concentrations.

Allendorf, Mark D.; Sopko, J.F. (PPF Industries, Pittsburgh, PA); Houf, William G.; Chae, Yong Kee; McDaniel, Anthony H.; Li, M. (PPF Industries, Pittsburgh, PA); McCamy, J.W. (PPF Industries, Pittsburgh, PA)

2006-11-01

102

Determination of food emulsifiers in commercial additives and food products by liquid chromatography\\/atmospheric-pressure chemical ionisation mass spectrometry  

Microsoft Academic Search

A new, reliable liquid chromatography\\/atmospheric-pressure chemical ionisation mass spectrometry (LC–APCI-MS) method was developed for the quantitative determination of food emulsifiers composed of mono- and diacylglycerols of fatty acids (E471 series) in complex food matrices. These additives are extremely interesting for the food industry because of their useful properties. Indeed, they improve the manufacture of products by acting as foams and

M. Suman; G. Silva; D. Catellani; U. Bersellini; V. Caffarra; M. Careri

2009-01-01

103

Screening of lake sediments for emerging contaminants by liquid chromatography atmospheric pressure photoionization and electrospray ionization coupled to high resolution mass spectrometry.  

PubMed

We developed a multiresidue method for the target and suspect screening of more than 180 pharmaceuticals, personal care products, pesticides, biocides, additives, corrosion inhibitors, musk fragrances, UV light stabilizers, and industrial chemicals in sediments. Sediment samples were freeze-dried, extracted by pressurized liquid extraction, and cleaned up by liquid-liquid partitioning. The quantification and identification of target compounds with a broad range of physicochemical properties (log K(ow) 0-12) was carried out by liquid chromatography followed by electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) coupled to high resolution Orbitrap mass spectrometry (HRMS/MS). The overall method average recoveries and precision are 103% and 9% (RSD), respectively. The method detection limits range from 0.010 to 4 ng/g(dw), while limits of quantification range from 0.030 to 14 ng/g(dw). The use of APPI as an alternative ionization source helped to distinguish two isomeric musk fragrances by means of different ionization behavior. The method was demonstrated on sediment cores from Lake Greifensee located in northeastern Switzerland. The results show that biocides, musk fragrances, and other personal care products were the most frequently detected compounds with concentrations ranging from pg/g(dw) to ng/g(dw), whereas none of the targeted pharmaceuticals were found. The concentrations of many urban contaminants originating from wastewater correlate with the highest phosphorus input into the lake as a proxy for treatment efficiency. HRMS enabled a retrospective analysis of the full-scan data acquisition allowing the detection of suspected compounds like quaternary ammonium surfactants, the biocide triclocarban, and the tentative identification of further compounds without reference standards, among others transformation products of triclosan and triclocarban. PMID:23215447

Chiaia-Hernandez, Aurea C; Krauss, Martin; Hollender, Juliane

2013-01-15

104

Application of electrospray ionization product ion spectra for identification with atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry - a case study with seized drugs.  

PubMed

Product ion spectra obtained with liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) were applied to the identification of seized drug samples from atmospheric pressure matrix-assisted laser desorption/ionization product ion spectra (AP-MALDI-MS/MS spectra). Data acquisition was performed in the information-dependent acquisition (IDA) mode, and the substance identification was based on a spectral library previously created with LC-ESI/MS/MS using protonated molecules as precursor ions. A total of 39 seized drug samples were analyzed with both AP-MALDI and LC-ESI techniques using the same triple-quadrupole instrument (AB Sciex 4000QTRAP). The study shows that ESI-MS/MS spectra can be directly utilized in AP-MALDI-MS/MS measurements as the average fit and purity score percentages with AP-MALDI were 90% and 85%, respectively, being similar to or even better than those obtained with the reference LC/ESI-MS/MS method. This fact enables the possibility to use large ESI spectral libraries, not only to ESI analyses but also to analyses with other ionization techniques which produce protonated molecules as the base peak. The data obtained shows that spectral library search works also for analytical techniques which produce multi-component mass spectra, such as AP-MALDI, unless isobaric compounds are encountered. The spectral library search was successfully applied to rapid identification of confiscated drugs by AP-MALDI-IDA-MS/MS. PMID:22987621

Östman, Pekka; Ketola, Raimo A; Ojanperä, Ilkka

2013-02-01

105

The use of proton-transfer reactions to detect low levels of impurities in bulk oxygen using an atmospheric pressure ionization mass spectrometer  

Microsoft Academic Search

Atmospheric pressure ionization mass spectrometry (APIMS) is being routinely used to quantify trace impurities in bulk gases used in the manufacture of semiconductor devices. APIMS has been successfully applied for the quantification of ppt levels of O2, H2O, CO2, and CH4 in Ar, N2, and He. However, it has not been successfully used to quantify trace impurities in bulk O2

S. N. Ketkar; A. D. Scott; E. J. Hunter

2001-01-01

106

Rapid screening procedures for the hydrolysis products of chemical warfare agents using positive and negative ion liquid chromatography–mass spectrometry with atmospheric pressure chemical ionisation  

Microsoft Academic Search

Qualitative screening procedures have been developed for the rapid detection and identification of the hydrolysis products of chemical warfare agents in aqueous samples and extracts, using liquid chromatography–mass spectrometry with positive and negative atmospheric pressure chemical ionisation (APCI). Previously reported screening procedures, which used positive APCI or electrospray ionisation (ESI), were modified by using LC conditions that allowed acquisition of

Robert W Read; Robin M Black

1999-01-01

107

Determination of selected antifouling booster biocides by high-performance liquid chromatography–atmospheric pressure chemical ionisation mass spectrometry  

Microsoft Academic Search

A simple and rapid technique is described for the quantitative determination of four antifouling booster biocides [diuron, 4,5-dichloro-2-n-octyl-4-isothazolin-3-one (Kathon 5287), (2-thiocyanomethylthio)benzothiazole (TCMTB) and (2,3,5,6-tetrachloro-4-methylsulphonyl) (TCMS pyridine) in aqueous samples. The analytes were extracted with high recoveries (ca. 100±?15%) from 2.7-l water samples, using C18 solid-phase extraction. Sample extracts were quantitatively analysed by reversed-phase HPLC and polarity switching atmospheric pressure chemical

Kevin V Thomas

1998-01-01

108

Three-dimensional modelling of horizontal chemical vapor deposition. I - MOCVD at atmospheric pressure  

NASA Technical Reports Server (NTRS)

A systematic numerical study of the MOCVD of GaAs from trimethylgallium and arsine in hydrogen or nitrogen carrier gas at atmospheric pressure is reported. Three-dimensional effects are explored for CVD reactors with large and small cross-sectional aspect ratios, and the effects on growth rate uniformity of tilting the susceptor are investigated for various input flow rates. It is found that, for light carrier gases, thermal diffusion must be included in the model. Buoyancy-driven three-dimensional flow effects can greatly influence the growth rate distribution through the reactor. The importance of the proper design of the lateral thermal boundary conditions for obtaining layers of uniform thickness is emphasized.

Ouazzani, Jalil; Rosenberger, Franz

1990-01-01

109

On-line measurements of ?-pinene ozonolysis products using an atmospheric pressure chemical ionisation ion-trap mass spectrometer  

NASA Astrophysics Data System (ADS)

An on-line technique to investigate complex organic oxidation reactions in environmental chamber experiments is presented. The method is based on the direct introduction of the chamber air into an atmospheric pressure ion source of a commercial ion-trap mass spectrometer. To demonstrate the analytical potential of the method (atmospheric pressure chemical ionisation/mass spectrometry, APCI/MS), the ozonolysis of ?-pinene was investigated in a series of experiments performed in various sized reaction chambers at atmospheric pressure and 296 K in synthetic air. Investigations were focussed on the influence of the water vapour concentration on the formation of the predominant oxidation product, pinonaldehyde, derived from the ?-pinene/ozone reaction. Quantification of pinonaldehyde was achieved by conducting a standard addition technique. The molar yield of pinonaldehyde was found to depend strongly on the actual water vapour concentration between <1 and 80% relative humidity. Starting with an average yield of 0.23±0.05 at dry conditions, pinonaldehyde formation was approximately doubled by reaching a yield of 0.53±0.05 at a relative humidity of around 60%. Furthermore, the formation mechanism of pinonaldehyde was investigated in greater detail using isotopically labelled water. Applying on-line APCI/MS, pinonaldehyde formation under incorporation of 18O was observed, strongly supporting the reaction of the stabilised Criegee radical with water in the gas phase as suggested by Alvarado et al. (Journal of Geophysical Research 103 (1998) 25541-25551). Furthermore, the mass spectra recorded on-line were used to perform a semi-quantitative estimation of the decomposition pathway of the primary ozonide, indicating a branching ratio of 0.35/0.65.

Warscheid, Bettina; Hoffmann, Thorsten

110

Natural products in Glycyrrhiza glabra (licorice) rhizome imaged at the cellular level by atmospheric pressure matrix-assisted laser desorption/ionization tandem mass spectrometry imaging.  

PubMed

The rhizome of Glycyrrhiza glabra (licorice) was analyzed by high-resolution mass spectrometry imaging and tandem mass spectrometry imaging. An atmospheric pressure matrix-assisted laser desorption/ionization imaging ion source was combined with an orbital trapping mass spectrometer in order to obtain high-resolution imaging in mass and space. Sections of the rhizome were imaged with a spatial resolution of 10 ?m in the positive ion mode, and a large number of secondary metabolites were localized and identified based on their accurate mass and MS/MS fragmentation patterns. Major tissue-specific metabolites, including free flavonoids, flavonoid glycosides and saponins, were successfully detected and visualized in images, showing their distributions at the cellular level. The analytical power of the technique was tested in the imaging of two isobaric licorice saponins with a mass difference of only 0.02 Da. With a mass resolving power of 140 000 and a bin width of 5 ppm in the image processing, the two compounds were well resolved in full-scan mode, and appeared with different distributions in the tissue sections. The identities of the compounds and their distributions were validated in a subsequent MS/MS imaging experiment, thereby confirming their identities and excluding possible analyte interference. The use of high spatial resolution, high mass resolution and tandem mass spectrometry in imaging experiments provides significant information about the biosynthetic pathway of flavonoids and saponins in legume species, combing the spatially resolved chemical information with morphological details at the microscopic level. Furthermore, the technique offers a scheme capable of high-throughput profiling of metabolites in plant tissues. PMID:25040821

Li, Bin; Bhandari, Dhaka Ram; Janfelt, Christian; Römpp, Andreas; Spengler, Bernhard

2014-10-01

111

Application of liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry, and tandem mass spectrometry, to the analysis and identification of degradation products of chemical warfare agents  

Microsoft Academic Search

A qualitative screening procedure was developed for the detection of the hydrolysis and related products of chemical warfare agents using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionisation. A mixed C8\\/C18 reversed-phase column gave acceptable chromatography for the range of acidic, neutral and basic analytes. Detection limits for pure standards were less than 0.2 ng injected for the simple hydrolysis

Robin M. Black; Robert W. Read

1997-01-01

112

Chemically reactive species in liquids generated by atmospheric-pressure plasmas and their roles in plasma medicine  

SciTech Connect

Plasmas whose gas temperatures are close to room temperature may be generated in ambient air or a gas at atmospheric pressure with the use of low-frequency high voltage or low-power radio-frequency (RF) or microwave power applied to electrodes. Such plasmas can serve as a powerful source of free radicals and/or chemically reactive species that arise from atoms and molecules of the ambient gas. Recently use of such plasmas for medical purposes has attracted much attention as they can be implemented in possible medical devices that can cause blood coagulation, heal wounds, facilitate angiogenesis, sterilize surgical devices as well as living tissues without harming healthy cells, and selectively inactivate cancer cells. Especially of interest among reactive species generated by atmospheric-pressure plasmas (APP) are reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are generated in liquid phase. Since most living tissues and cells are immersed in liquids (such as blood or culture media), reactive species generated by APPs in the gas phase are transported to the liquid phase and possibly converted to different types of reactive species therein before causing some influence on the tissues or cells. In this study, the rate equations are solved to evaluate concentrations of various reactive species in pure water that are originated by plasma reactions in atmosphere and possible effects of such species (including ROS/RNS) on living tissues and cells are discussed.

Hamaguchi, Satoshi [Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2013-07-11

113

Method of Atmospheric Pressure Charge Stripping for Electrospray Ionization Mass Spectrometry and Its Application for the Analysis of Large Poly(Ethylene Glycol)s.  

PubMed

We introduce a new atmospheric pressure charge stripping (AP-CS) method for the electrospray ionization mass spectrometry (ESI-MS) analysis of heterogeneous mixtures, utilizing ion/ion proton transfer reactions within an experimental ion source to remove excess charge from sample ions and thereby reduce spectral congestion. The new method enables the extent of charge stripping to be easily controlled, independent of primary ionization, and there are no complications due to adduct formation. Here, we demonstrate AP-CS with a Xevo G2-S Q-TOF from Waters-Micromass using an ion source originally designed for atmospheric pressure-electron capture dissociation (AP-ECD) experiments; repurposing the AP-ECD ion source for AP-CS requires only adding a supplemental reagent (e.g., a perfluorocompound) to scavenge the electrons and generate anions for the charge-stripping reactions. Results from model peptides are first presented to demonstrate the basic method, including differences between the AP-CS and AP-ECD operating modes, and how the extent of charge stripping may be controlled. This is followed by a demonstration of AP-CS for the ESI-MS analysis of several large poly(ethylene glycol)s (PEGs), up to 40 kDa, typical of those used in biopharmaceutical development. PMID:25188777

Robb, Damon B; Brown, Jeffery M; Morris, Michael; Blades, Michael W

2014-10-01

114

Determination of food emulsifiers in commercial additives and food products by liquid chromatography/atmospheric-pressure chemical ionisation mass spectrometry.  

PubMed

A new, reliable liquid chromatography/atmospheric-pressure chemical ionisation mass spectrometry (LC-APCI-MS) method was developed for the quantitative determination of food emulsifiers composed of mono- and diacylglycerols of fatty acids (E471 series) in complex food matrices. These additives are extremely interesting for the food industry because of their useful properties. Indeed, they improve the manufacture of products by acting as foams and creams stabilisers, crumb-softeners, or antistaling agents. The proposed method also allows us to qualitatively characterise new food emulsifiers composed of other acid esters of mono- and diacylglycerols (E472 series). The validation of the method was performed on blank minicake spiked samples for detection limits (reaching ppm levels), linearity, recovery, precision, and accuracy. The method was then successfully applied to commercial additives containing mixtures of emulsifiers, as well as to food products such as margarines and minicakes. PMID:19286189

Suman, M; Silva, G; Catellani, D; Bersellini, U; Caffarra, V; Careri, M

2009-05-01

115

Halo-shaped Flowing Atmospheric Pressure Afterglow - a Heavenly New Design for Simplified Sample Introduction and Improved Ionization in Ambient Mass Spectrometry  

PubMed Central

The flowing atmospheric pressure afterglow (FAPA) is a promising new source for atmospheric pressure, ambient desorption/ionization mass spectrometry. However, problems exist with reproducible sample introduction into the FAPA source. To overcome this limitation, a new FAPA geometry has been developed in which concentric tubular electrodes are utilized to form a halo-shaped discharge; this geometry has been termed the halo-FAPA or h-FAPA. With this new geometry, it is still possible to achieve direct desorption and ionization from a surface; however, sample introduction through the inner capillary is also possible and improves interaction between the sample material (solution, vapor, or aerosol) and the plasma to promote desorption and ionization. The h-FAPA operates with a helium gas flow of 0.60 L/min outer, 0.30 L/min inner, applied current of 30 mA at 200 V for 6 watts of power. In addition, separation of the discharge proper and sample material prevents perturbations to the plasma. Optical-emission characterization and gas rotational temperatures reveal that the temperature of the discharge is not significantly affected (< 3% change at 450K) by water vapor during solution-aerosol sample introduction. The primary mass-spectral background species are protonated water clusters, and the primary analyte ions are protonated molecular ions (M+H+). Flexibility of the new ambient sampling source is demonstrated by coupling it with a laser ablation unit, a concentric nebulizer and a droplet-on-demand system for sample introduction. A novel arrangement is also presented in which the central channel of the h-FAPA is used as the inlet to a mass spectrometer. PMID:23808829

Pfeuffer, Kevin P.; Schaper, J. Niklas; Shelley, Jacob T.; Ray, Steven J.; Chan, George C.-Y.; Bings, Nicolas H.; Hieftje, Gary M.

2013-01-01

116

Plasma decontamination of chemical & biological warfare agents by a cold arc plasma jet at atmospheric pressure  

Microsoft Academic Search

The cold arc plasma jet was introduced to decontaminate chemical and biological warfare (CBW) agents for the application of a portable CBW decontamination system. The cold arc plasma jet is a low temperature, high density plasma that produces highly reactive species such as oxygen atoms and ozone. Moreover, it is possible to maintain stable plasma without He or Ar. The

Man Hyeop Han; Joo Hyun Noh; Ki Wan Park; Hyeon Seok Hwang; Hong Koo Baik

2008-01-01

117

Atmospheric Pressure Plasma-Initiated Chemical Vapor Deposition (AP-PiCVD) of Poly(diethylallylphosphate) Coating: A Char-Forming Protective Coating for Cellulosic Textile.  

PubMed

An innovative atmospheric pressure chemical vapor deposition method toward the deposition of polymeric layers has been developed. This latter involves the use of a nanopulsed plasma discharge to initiate the free-radical polymerization of an allyl monomer containing phosphorus (diethylallylphosphate, DEAP) at atmospheric pressure. The polymeric structure of the film is evidence by mass spectrometry. The method, highly suitable for the treatment of natural biopolymer substrate, has been carried out on cotton textile to perform the deposition of an efficient and conformal protective coating. PMID:25362895

Hilt, Florian; Boscher, Nicolas D; Duday, David; Desbenoit, Nicolas; Levalois-Grützmacher, Joëlle; Choquet, Patrick

2014-11-12

118

Continuous Flow Atmospheric Pressure Laser Desorption/Ionization Using a 6-7-um-Band Mid-Infrared Tunable Laser for Biomolecular Mass Spectrometry  

PubMed Central

A continuous flow atmospheric pressure laser desorption/ionization technique using a porous stainless steel probe and a 6–7-µm-band mid-infrared tunable laser was developed. This ion source is capable of direct ionization from a continuous flow with a high temporal stability. The 6–7-µm wavelength region corresponds to the characteristic absorption bands of various molecular vibration modes, including O–H, C=O, CH3 and C–N bonds. Consequently, many organic compounds and solvents, including water, have characteristic absorption peaks in this region. This ion source requires no additional matrix, and utilizes water or acetonitrile as the solvent matrix at several absorption peak wavelengths (6.05 and 7.27 µm, respectively). The distribution of multiply-charged peptide ions is extremely sensitive to the temperature of the heated capillary, which is the inlet of the mass spectrometer. This ionization technique has potential for the interface of liquid chromatography/mass spectrometry (LC/MS). PMID:24937686

Hiraguchi, Ryuji; Hazama, Hisanao; Senoo, Kenichirou; Yahata, Yukinori; Masuda, Katsuyoshi; Awazu, Kunio

2014-01-01

119

Detection of chemical warfare agent degradation products in foods using liquid chromatography coupled to inductively coupled plasma mass spectrometry and electrospray ionization mass spectrometry  

Microsoft Academic Search

The following work presents the exploration of three chromatographic separations in combination with inductively coupled plasma mass spectrometry (ICP-MS) for the analysis of chemical warfare agent degradation products (CWADPs). The robust ionization of ICP is virtually matrix independent thus enabling the examination of sample matrices generally considered too complicated for analysis by electrospray ionization (ESI) or atmospheric pressure chemical ionization

Kevin M. Kubachka; Douglas D. Richardson; Douglas T. Heitkemper; Joseph A. Caruso

2008-01-01

120

Atmospheric pressure plasma jet applications  

SciTech Connect

The atmospheric pressure plasma jet (APPJ) is a non-thermal, high pressure plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g., He/O2/H2O) which flows between two concentric cylindrical electrodes: an outer grounded electrode and an inner electrode powered at 13.56 MHz RF. While passing through the plasma, the feedgas becomes excited, ionized or dissociated by electron impact. The fast-flowing effluent consists of ions and electrons, which are rapidly lost by recombination, highly reactive radicals (e.g., O, OH), and metastable species (e.g., O2). The metastable O2, which is reactive to hydrocarbon and other organic species, has been observed through optical emission spectroscopy to decrease by a factor of 2 from the APPJ nozzle exit to a distance of 10 cm. Unreacted metastable O2, and that which does not impinge on a surface, will then decay back to ordinary ground state O2, resulting in a completely dry, environmentally-benign form of surface cleaning. Applications such as removal of photoresist, oxide films and organic residues from wafers for the electronics industry, decontamination of civilian and military areas and personnel exposed to chemical or biological warfare agents, and paint (e.g., graffiti) removal are being considered.

Park, J.; Herrmann, H.W.; Henins, I.; Selwyn, G.S. [Los Alamos National Lab., NM (United States)

1998-12-31

121

The determination of carbon dioxide concentration using atmospheric pressure ionization mass spectrometry/isotopic dilution and errors in concentration measurements caused by dryers.  

PubMed

An atmospheric pressure ionization mass spectrometry/isotopically labeled standard (APIMS/ILS) method has been developed for the determination of carbon dioxide (CO(2)) concentration. Descriptions of the instrumental components, the ionization chemistry, and the statistics associated with the analytical method are provided. This method represents an alternative to the nondispersive infrared (NDIR) technique, which is currently used in the atmospheric community to determine atmospheric CO(2) concentrations. The APIMS/ILS and NDIR methods exhibit a decreased sensitivity for CO(2) in the presence of water vapor. Therefore, dryers such as a nafion dryer are used to remove water before detection. The APIMS/ILS method measures mixing ratios and demonstrates linearity and range in the presence or absence of a dryer. The NDIR technique, on the other hand, measures molar concentrations. The second half of this paper describes errors in molar concentration measurements that are caused by drying. An equation describing the errors was derived from the ideal gas law, the conservation of mass, and Dalton's Law. The purpose of this derivation was to quantify errors in the NDIR technique that are caused by drying. Laboratory experiments were conducted to verify the errors created solely by the dryer in CO(2) concentration measurements post-dryer. The laboratory experiments verified the theoretically predicted errors in the derived equations. There are numerous references in the literature that describe the use of a dryer in conjunction with the NDIR technique. However, these references do not address the errors that are caused by drying. PMID:18574165

DeLacy, Brendan G; Bandy, Alan R

2008-01-01

122

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method  

NASA Astrophysics Data System (ADS)

Diamond-like carbon (DLC) films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure and their hardness and gas barrier properties were measured. A decrease in size of grains and heating substrate temperature improved nano-hardness up to 3.3 GPa. The gas barrier properties of DLC-coated poly(ethylene terephthalate) (PET) sheets were obtained by 3-5 times of non-coated PET with approximately 0.5 µm in film thickness. The high-gas-barrier DLC films deposited on PET sheets are expected to wrap elevated bridge of the super express and prevent them from neutralization of concrete. We also deposited DLC films inside PET bottles by the microwave surface-wave plasma chemical vapor deposition (CVD) method at near-atmospheric pressure. Under atmospheric pressure, the films were coated uniformly inside the PET bottles, but did not show high gas barrier properties. In this paper, we summarize recent progress of DLC films synthesized at atmospheric pressure with the aimed of food packaging and concrete pillar.

Noborisaka, Mayui; Hirako, Tomoaki; Shirakura, Akira; Watanabe, Toshiyuki; Morikawa, Masashi; Seki, Masaki; Suzuki, Tetsuya

2012-09-01

123

Analysis of wax ester molecular species by high performance liquid chromatography/atmospheric pressure chemical ionisation mass spectrometry.  

PubMed

High chromatographic resolution of wax esters (WEs) was achieved by non-aqueous reversed-phase liquid chromatography on a Nova-Pak C18 column by optimising the acetonitrile/ethyl acetate mobile phase gradient. The retention behaviour of WEs was studied in this chromatographic system. The WEs eluted according to their equivalent carbon number (ECN) values; within the group of WEs with the identical ECN, the most unsaturated species tended to elute first. The isobaric WEs with different positions of the ester moiety were separated from each other whenever the lengths of the chains were sufficiently different. The methyl-branched esters eluted at shorter retention times than the straight-chained analogues, and the resolution among methyl-branched WEs depended on the position of the branching. The analytes were detected by atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) using data-dependent scanning. WEs provided simple full-scan spectra with abundant protonated molecules and low-intensity fragments. Collision-induced dissociation (CID) promoted identification of the WE molecular species. The responses of WEs were found to be dependent on the number of double bonds and on the alkyl-chain length; the limits of the detection ranged from 20micromol/L to 200nmol/L. The HPLC/APCI-MS was applied for the analysis of the WEs isolated from honeycomb beeswax, jojoba oil and human hair. Good agreement between reported results and the literature data was achieved, with several novel polyunsaturated WEs also being found. PMID:20079497

Vrkoslav, Vladimír; Urbanová, Klára; Cvacka, Josef

2010-06-18

124

Optimization of ultraviolet emission and chemical species generation from a pulsed dielectric barrier discharge at atmospheric pressure  

SciTech Connect

One of the attractive features of nonthermal atmospheric pressure plasmas is the ability to achieve enhanced gas phase chemistry without the need for elevated gas temperatures. This attractive characteristic recently led to their extensive use in applications that require low temperatures, such as material processing and biomedical applications. The agents responsible for the efficient plasma reactivity are the ultraviolet (UV) photons and the chemically reactive species. In this paper, in order to optimize the UV radiation and reactive species generation efficiency, the plasma was generated by a dielectric barrier discharge driven by unipolar submicrosecond square pulses. To keep the discharge diffuse and to maintain low operating temperatures, helium (He) was used as a carrier gas. Mixed with helium, varying amounts of nitrogen (N{sub 2}) with the presence of trace amounts of air were used. The gas temperature was determined to be about 350 K at a 1-kHz pulse frequency for all cases and only slightly increased with frequency. The UV emission power density, P{sub UV}, reached its highest level when 5% to 10% of N{sub 2} is mixed to a balance of He. A maximum P{sub UV} of about 0.8 mW/cm{sup 2} at 10-kHz pulse frequency for a He(90%)+N{sub 2}(10%) mixture was measured. This was more than four times higher than that when He or N{sub 2} alone was used. Furthermore, the emission spectra showed that most of the UV was emitted by excited NO radicals, where the oxygen atoms came from residual trace amounts of air. In addition to NO, NO{sub 2}, and excited N{sub 2}, N{sub 2}{sup +}, OH, and He were also present in the plasma.

Lu Xinpei; Laroussi, Mounir [Old Dominion University, Norfolk, Virginia 23529 (United States)

2005-07-15

125

Negative atmospheric pressure chemical ionisation low-energy collision activation mass spectrometry for the characterisation of flavonoids in extracts of fresh herbs  

Microsoft Academic Search

The flavonoid composition of commonly eaten fresh herbs such as dill, oregano and parsley was analysed by combined LC, MS and low-energy collision induced dissociation (CID) MS–MS. Negative atmospheric pressure chemical ionisation (APCI) MS and MS–MS were used to provide molecular mass information and product-ion spectra of the glycosyl compounds. The most prominent fragment was found to arise from the

Ulla Justesen

2000-01-01

126

Atmospheric pressure chemical vapor deposition of CdTe for high efficiency thin film PV devices: Annual subcontract report, 26 January 1999--25 January 2000  

Microsoft Academic Search

ITN's three year project Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High Efficiency Thin Film PV Devices has the overall objectives of improving thin film CdTe PV manufacturing technology and increasing CdTe PV device power conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16% efficient CdTe PV films, i.e.,

P. V. Meyers; R. Kee; C. Wolden; J. Kestner; L. Raja; V. Kaydanov; T. Ohno; R. Collins; A. Fahrenbruch

2000-01-01

127

Atmospheric Pressure Chemical Vapor Deposition of CdTe for High-Efficiency Thin-Film PV Devices; Annual Report, 26 January 1998-25 January 1999  

Microsoft Academic Search

ITN's 3-year project, titled ''Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High-Efficiency Thin-Film Photovoltaic (PV) Devices,'' has the overall objectives of improving thin-film CdTe PV manufacturing technology and increasing CdTe PV device power conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16%-efficient CdTe PV films, i.e., close-spaced sublimation, but

P. V. Meyers; R. Kee; C. Wolden; L. Raja; V. Kaydanov; T. Ohno; R. Collins; M. Aire; J. Kestner; A. Fahrenbruch

1999-01-01

128

The effects of deposition and test conditions on nanomechanical behaviour of ultrathin films produced by plasma-enhanced chemical vapour deposition process at atmospheric pressure  

Microsoft Academic Search

Nanometer thick films have been deposited on silicon substrate by plasma-enhanced chemical vapour deposition (PE-CVD) process using non-homogenous, filamentary dielectric-barrier discharge (DBD) at atmospheric pressure. This film deposition technique enables the introduction some organic fragments into the coating material—silicon dioxide (or oxynitride)—resulting in good properties for self-lubrication of micro-electro-mechanical systems (MEMS) devices. The effect of the deposition conditions and loading

Zygmunt Rymuza; Maciej Misiak; Zenobia Rzanek-Boroch; Krzysztof Schmidt-Sza?owski; Jadwiga Janowska

2004-01-01

129

Multilayer coatings by chemical vapor deposition in a fluidized bed reactor at atmospheric pressure (AP\\/FBR-CVD): TiN\\/TaN and TiN\\/W  

Microsoft Academic Search

TiN\\/W and TiN\\/TaN multilayer coatings were deposited on stainless steel by Chemical Vapor Deposition in a Fluidized Bed Reactor at Atmospheric Pressure (AP\\/FBR-CVD). First, the conditions for the deposition of TiN single layers were investigated, both from the experiment and thermochemical estimations. TiN was deposited from TiCl4 and NH3 at temperatures in the range of 750–950 °C. In the synthesis of

J. Perez-Mariano; K.-H. Lau; A. Sanjurjo; J. Caro; J. M. Prado; C. Colominas

2006-01-01

130

TiSiN nanocomposite coatings by chemical vapor deposition in a fluidized bed reactor at atmospheric pressure (AP\\/FBR-CVD)  

Microsoft Academic Search

TiSiN nanocomposite coatings were deposited on stainless steel by chemical vapor deposition in a fluidized bed reactor at atmospheric pressure (AP\\/FBR-CVD) by reaction of TiCl4 and SiCl4 with NH3 at 850 °C. Coatings were characterized by means of GD-OES, XPS and XRD. TiSiN coatings with a Si content of 9 at.% showed a hardness of 28 GPa (the hardness of TiN and

J. Perez-Mariano; K.-H. Lau; A. Sanjurjo; J. Caro; D. Casellas; C. Colominas

2006-01-01

131

Pharmacokinetic screening for the selection of new drug discovery candidates is greatly enhanced through the use of liquid chromatography-atmospheric pressure ionization tandem mass spectrometry.  

PubMed

Selection of a new drug discovery candidate from a series of compounds requires a means of performing rapid analytical method development and sensitive quantitation of each drug in serum, plasma or other biological matrices. Information on serum/plasma concentration, bioavailability and half-life can often aid the discovery process by selecting those candidates with the desired pharmacokinetic parameters. In one series of farnesyl protein transferase (FPT) inhibitors, gas chromatography with nitrogen-phosphorus detection (NPD) was initially used to analyze samples from pharmacokinetic studies in mice and monkeys. Typical turnaround times using this technique approached 2-4 weeks for method development, quantitation of study samples and calculation of pharmacokinetic parameters. Once LC-atmospheric pressure ionization (API) MS-MS analysis was implemented in these same studies, they could be completed in less than one week. The advantages of using LC-API-MS-MS to aid in the drug candidate selection process is demonstrated for one compound (SCH 44342) in this series of FPT inhibitors. PMID:9297838

Bryant, M S; Korfmacher, W A; Wang, S; Nardo, C; Nomeir, A A; Lin, C C

1997-08-01

132

Simultaneous determination of selected endocrine disrupters (pesticides, phenols and phthalates) in water by in-field solid-phase extraction (SPE) using the prototype PROFEXS followed by on-line SPE (PROSPEKT) and analysis by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry  

Microsoft Academic Search

In this study, a new procedure, based on on-line solid-phase extraction (SPE) and analysis by liquid-chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), has been developed for the simultaneous, multianalyte determination of 21 selected pesticides, phenols and phthalates in water. SPE was carried out on polymeric PLRP-s cartridges by percolating 20 mL-samples. For sample preconcentration, the performance of a prototype programmable field extraction

P. López-Roldán; M. J. López de Alda; D. Barceló

2004-01-01

133

Evaluation of the operating parameters of the liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source for elemental mass spectrometry.  

PubMed

The liquid sampling-atmospheric pressure glow discharge (LS-APGD) has been assessed as an ionization source for elemental analysis with an interdependent, parametric evaluation regarding sheath/cooling gas flow rate, discharge current, liquid flow rate, and the distance between the plasma and the sampling cone of the mass spectrometer. In order to better understand plasma processes (and different from previous reports), no form of collision/reaction processing was performed to remove molecular interferents. The evaluation was performed employing five test elements: cesium, silver, lead, lanthanum and nickel (10(-4) mol L(-1) in 1 mol L(-1) HNO3). The intensity of the atomic ions, levels of spectral background, the signal-to-background ratios, and the atomic-to-oxide/hydroxide adduct ratios were monitored in order to obtain fundamental understanding with regards to not only how each parameter effects the performance of this LS-APGD source, but also the inter-parametric effects. The results indicate that the discharge current and the liquid sampling flow rates are the key aspects that control the spectral composition. A compromise set of operating conditions was determined: sheath gas flow rate?=?0.9 L min(-1), discharge current?=?10 mA, solution flow rate?=?10 ?L min(-1), and sampling distance?=?1 cm. Limits of detection (LODs) were calculated using the SBR-RSDB (signal-to-background ratio/relative standard deviation of the background) approach under the optimized condition. The LODs for the test elementals ranged from 15 to 400 ng mL(-1) for 10 ?L injections, with absolute mass values from 0.2 to 4 ng. PMID:25002336

Zhang, Lynn X; Manard, Benjamin T; Kappel, Stefanie Konegger; Marcus, R Kenneth

2014-11-01

134

Atmospheric-pressure plasma jet  

DOEpatents

Atmospheric-pressure plasma jet. A .gamma.-mode, resonant-cavity plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two concentric cylindrical electrodes are employed to generate a plasma in the annular region therebetween. A "jet" of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly shaping the rf-powered electrode. Because of the atmospheric pressure operation, no ions survive for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike low-pressure plasma sources and conventional plasma processing methods.

Selwyn, Gary S. (Los Alamos, NM)

1999-01-01

135

Quantification and remote detection of nitro explosives by helium plasma ionization mass spectrometry (HePI-MS) on a modified atmospheric pressure source designed for electrospray ionization.  

PubMed

Helium Plasma Ionization (HePI) generates gaseous negative ions upon exposure of vapors emanating from organic nitro compounds. A simple adaptation converts any electrospray ionization source to a HePI source by passing helium through the sample delivery metal capillary held at a negative potential. Compared with the demands of other He-requiring ambient pressure ionization sources, the consumption of helium by the HePI source is minimal (20-30?ml/min). Quantification experiments conducted by exposing solid deposits to a HePI source revealed that 1?ng of 2,4,6-trinitrotoluene (TNT) on a filter paper (about 0.01?ng/mm(2)) could be detected by this method. When vapor emanating from a 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) sample was subjected to helium plasma ionization mass spectrometry (HePI-MS), a peak was observed at m/z 268 for (RDX?NO(2))(-). This facile formation of NO(2)(-) adducts was noted without the need of any extra additives as dopants. Quantitative evaluations showed RDX detection by HePI-MS to be linear over at least three orders of magnitude. TNT samples placed even 5?m away from the source were detected when the sample headspace vapor was swept by a stream of argon or nitrogen and delivered to the helium plasma ion source via a metal tube. Among the tubing materials investigated, stainless steel showed the best performance for sample delivery. A system with a copper tube, and air as the carrier gas, for example, failed to deliver any detectable amount of TNT to the source. In fact, passing over hot copper appears to be a practical way of removing TNT or other nitroaromatics from ambient air. PMID:22791251

Yang, Zhihua; Pavlov, Julius; Attygalle, Athula B

2012-07-01

136

Formation of fractal structures from silicon dioxide nanoparticles synthesized by RF atmospheric pressure plasma enhanced chemical vapor deposition.  

PubMed

Fractal structures were formed on silicon substrates from SiO2 nanoparticles homogeneously synthesized in low temperature atmospheric pressure plasma from tetraethoxysilane (TEOS). RF discharge (power absorbed was about 10 W) sustained between two parallel mesh electrodes was used to generate plasma. The average size of nanoparticles was in the range of 8-20 nm and was determined by process parameters. The obtained products were analyzed by SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy). Values of fractal dimension parameter of bidimensionals agglomerates formed on the substrate surface from nanoparticles were calculated with the use of Gwyddion and others. It was found that values of this parameter of the deposited structures varied in the range of 1.48-2 and were determined by combination of the process parameters. An empirical model explaining mechanism of the fractal structures formation and variation of the fractal dimension parameter with the process parameters was proposed. PMID:22097514

Alexandrov, S E; Kretusheva, I V; Mishin, M V; Yasenovets, G M

2011-09-01

137

Special issue: diagnostics of atmospheric pressure microplasmas  

NASA Astrophysics Data System (ADS)

In recent decades, a strong revival of non-equilibrium atmospheric pressure plasma studies has developed in the form of microplasmas. Microplasmas have typical scales of 1 mm or less and offer a very exciting research direction in the field of plasma science and technology as the discharge physics can be considerably different due to high collisionality and the importance of plasma-surface interaction. These high-pressure small-scale plasmas have a diverse range of physical and chemical properties. This diversity coincides with various applications including light/UV sources [1], material processing [2], chemical analysis [3], material synthesis [4], electromagnetics [5], combustion [6] and even medicine [7]. At atmospheric pressure, large scale plasmas have the tendency to become unstable due to the high collision rates leading to enhanced heating and ionization compared to their low-pressure counterparts. As low-pressure plasmas typically operate in reactors with sizes of tens of centimetres, scaling up the pressure to atmospheric pressure the size of the plasma reduces to typical sizes below 1 mm. A natural approach of stabilizing atmospheric pressure plasmas is thus the use of microelectrode geometries. Traditionally microplasmas have been produced in confined geometries which allow one to stabilize dc excited discharges. This stabilization is intrinsically connected to the large surface-to-volume ratio which enhances heat transfer and losses of charged and excited species to the walls. Currently challenging boundaries are pushed by producing microcavity geometries with dimensions of the order of 1 µm [8]. The subject of this special issue, diagnostics of microplasmas, is motivated by the many challenges in microplasma diagnostics in view of the complex chemistry and strong spatial (and even temporal) gradients of species densities and plasma properties. Atmospheric pressure plasmas have a very long history dating back more than 100 years, with early work of, e.g. Werner von Siemens [9], who studied a dielectric barrier discharge (DBD) in the context of ozone generation. DBD discharges often consist of numerous filamentary discharges which are inherently transient in nature and with a characteristic size similar to the dimensions of microplasmas. Several groups are investigating the stabilization of such plasma filaments to perform temporal and spatial resolved diagnostics. To this end and due to the many similar challenges for diagnostics, this type of discharge is also included in this special issue. Research on microplasmas is performed in many groups spread all over the world, and a biannual workshop is devoted to the topic. The 7th edition of this International Workshop on Microplasmas was held in Beijing in May 2013. Large research programs consisting of clusters of research labs such as in Japan, Germany, France and the USA have been producing a wealth of information available in the literature. As the editors of this special issue, we are very pleased to have attracted a collection of excellent papers from leading experts in the field covering most of the current diagnostics performed in microplasmas. As an introduction to the regular special issue papers, a review paper is included [10]. It describes the key characteristics of atmospheric pressure plasmas and microplasmas in particular, and reviews the state of the art in plasma diagnostics. Special attention has been given in this review to highlighting the issues and challenges to probe microplasmas. The regular papers cover a large range of different diagnostics including coherent anti-Stokes Raman scattering (CARS) [11], (two-photon) laser induced fluorescence ((Ta)LIF) [12, 13, 18, 24], absorption spectroscopy [13-18], optical emission spectroscopy [12, 16-21, 24], imaging [22, 23], surface diagnostics [24, 25] and mass spectrometry [26, 27]. Different aspects of microplasmas are broadly investigated from a perspective of diagnostics, modelling and applications. Diagnostics are pivotal to both the development of models and the optimization and explorat

Bruggeman, Peter; Czarnetzki, Uwe; Tachibana, Kunihide

2013-11-01

138

Determination of vertical fluxes of sulfur dioxide and dimethyl sulfide in the remote marine atmosphere by eddy correlation and an airborne isotopic dilution atmospheric pressure ionization mass spectrometer  

NASA Astrophysics Data System (ADS)

Vertical fluxes of dimethyl sulfide (DMS) and sulfur dioxide (SO 2) were determined by eddy correlation and an isotopic dilution atmospheric pressure ionization mass spectrometer (APIMS) on an aircraft platform. The sampling frequency of the isotopic dilution APIMS ranged from 1 Hz to 25 Hz for real-time measurements. Measurements were made near the surface in the marine boundary layer to over 6 km in the free troposphere. The APIMS demonstrated an average sensitivity of 80 cps/pptv for DMS and SO2 with a signal-to-noise (S/N) ratio > 5. A lower limit of detection of 0.1 pptv in a one second integration period was also determined for DMS and SO2 in airborne atmospheric measurements. Use of the isotopic dilution technique provided an internal calibration of every ambient sample along with manifold conditioning for rapid and efficient transport of the ambient species through the manifold. As a result the eddy correlation flux determinations were accurate, precise, and reproducible. Laboratory results suggest the addition of ozone in excess of 45 ppbv to the APIMS sampling manifold to ensure unaltered formation of SO5 - ion (the ion detected for SO2). Use of a Nafion dryer was warranted for sensitive APIMS detection of SO2 in humid air. A Nafion dryer along with an air temperature of 400°C was required for sensitive APIMS detection of DMS in humid air. Results from an initial airborne test deployment in continental air include a successful SO2 intercomparison between the APIMS and a GC/MS/ILS (isotopically labeled standard-gas chromatography/mass spectrometer). Fast SO2 measurements in thin moist layers and pollution plumes demonstrated the utility of the fast isotopic dilution APIMS technique. Results from a second airborne test deployment in the remote marine boundary layer include a successful DMS intercomparison and eddy correlation fluxes of DMS and SO2 from isotopic dilution APIMS measurements. The average DMS flux near the surface was (1.7 +/- 0.2) × 1013 molecules m-2 s-1. A flux gradient for DMS generated a DMS surface flux of (2.3 +/- 0.7) × 10 13 molecules in m-2 s-1 and a DMS entrainment flux of (7.5 +/- 4.4) × 1012 molecules m-2 s-1. High resolution altitude profiles of DMS allowed for the determination of the DMS entrainment velocity (1.9 +/- 1.1 cm/s). A SO2 flux of (4.3 +/- 1.9) × 1012 molecules m-2 s-1 and a deposition velocity of 2.4 +/- 1.1 mm/s also was determined. All values reported are in good agreement with the literature.

Mitchell, Glenn M.

2001-08-01

139

Development of an ion mobility spectrometer for use in an atmospheric pressure ionization ion mobility spectrometer/mass spectrometer instrument for fast screening analysis.  

PubMed

An ion mobility spectrometer that can easily be installed as an intermediate component between a commercial triple-quadrupole mass spectrometer and its original atmospheric pressure ionization (API) sources was developed. The curtain gas from the mass spectrometer is also used as the ion mobility spectrometer drift gas. The design of the ion mobility spectrometer allows reasonably fast installation (about 1 h), and thus the ion mobility spectrometer can be considered as an accessory of the mass spectrometer. The ion mobility spectrometer module can also be used as an independently operated device when equipped with a Faraday cup detector. The drift tube of the ion mobility spectrometer module consists of inlet, desolvation, drift, and extraction regions. The desolvation, drift and extraction regions are separated by ion gates. The inlet region has the shape of a stainless steel cup equipped with a small orifice. Ion mobility spectrometer drift gas is introduced through a curtain gas line from an original flange of the mass spectrometer. After passing through the drift tube, the drift gas serves as a curtain gas for the ion-sampling orifice of the ion mobility spectrometer before entering the ion source. Counterflow of the drift gas improves evaporation of the solvent from the electrosprayed sample. Drift gas is pumped away from the ion source through the original exhaust orifice of the ion source. Initial characterization of the ion mobility spectrometer device includes determination of resolving power values for a selected set of test compounds, separation of a simple mixture, and comparison of the sensitivity of the electrospray ionization ion mobility spectrometry/mass spectrometry (ESI-IMS/MS) mode with that of the ESI-MS mode. A resolving power of 80 was measured for 2,6-di-tert-butylpyridine in a 333 V/cm drift field at room temperature and with a 0.2 ms ion gate opening time. The resolving power was shown to be dependent on drift gas flow rate for all studied ion gate opening times. Resolving power improved as the drift gas flow increased, e.g. at a 0.5 ms gate opening time, a resolving power of 31 was obtained with a 0.65 L/min flow rate and 47 with a 1.3 L/min flow rate for tetrabutylammonium iodide. The measured limits of detection with ESI-MS and with ESI-IMS/MS modes were similar, demonstrating that signal losses in the IMS device are minimal when it is operated in a continuous flow mode. Based on these preliminary results, the IMS/MS instrument is anticipated to have potential for fast screening analysis that can be applied, for example, in environmental and drug analysis. PMID:15565719

Sysoev, Alexey; Adamov, Alexey; Viidanoja, Jyrki; Ketola, Raimo A; Kostiainen, Risto; Kotiaho, Tapio

2004-01-01

140

Aircraft Performance: Atmospheric Pressure  

E-print Network

· Factors in: ­ Weather ­ Aerodynamic Lift ­ Flight Instrument · Altimeter · Vertical Speed Indicator is less efficient in thin air) ­ Reduces Lift (thin air exerts less force on the airfoils) #12;High Density Altitude (worse performance) · High elevations · Low atmospheric pressures · High

141

Electrochromic and optical study of atmospheric pressure chemical vapour deposition MoO3-Cr2O3 films.  

PubMed

Electrochromism (EC) is a phenomenon in which materials are able to change their optical properties in a reversible and persistent way under the action of a voltage pulse. The studied MoO3-Cr2O3 films are obtained by atmospheric pressure CVD. Mixing MoO3 films with Cr2O3 is expected to enhance optical transparency and to modulate electrochromic properties of MoO3 films. In the present work, the study is focused on the morphological, structural and optical properties of MoO3-Cr2O3 films as a function of annealing temperatures. Raman spectroscopy and optical spectrophotometry are used for the film characterization. The mixed oxide films obtained on ordinary glass substrates show transmittance values in the range of 70-80%. Surface morphology is analyzed by SEM and AFM methods. The microanalysis of MoO3-Cr2O3 films reveals uniform distribution of the elements, which is a sign of homogeneous structure. PMID:22097522

Ivanova, T; Gesheva, K A; Kozlov, M; Abrashev, M

2011-09-01

142

Investigations of structure and morphology of the AlN nano-pillar crystal films prepared by halide chemical vapor deposition under atmospheric pressure  

NASA Astrophysics Data System (ADS)

Aluminum nitride (AlN) prepared under atmospheric pressure using a halide chemical vapor deposition method has been examined by means of a variety of analytical techniques. Scanning electron microscopic observations showed that the crystals deposited onto a Si(100) substrate have hexagonal pillar structure. Based on the X-ray diffraction and X-ray pole-figure analyses, it was deduced that the each AlN pillar crystal grows with a different rotation angle around the <001> axis. Transmission electron diffraction showed that they are of single-like form. This was also confirmed by the selected area electron diffraction image as well. It was found that the diameter of pillar which constitutes an AlN film was significantly dependent upon the ratio of NH3/AlCl3 used as source materials and the growth temperature.

Takahashi, Naoyuki; Matsumoto, Yoriko; Nakamura, Takato

2006-04-01

143

Determination of the sum of malachite green and leucomalachite green in salmon muscle by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry.  

PubMed

A sensitive method for the determination and confirmation of the sum of malachite green (MG) and leucomalachite green (LMG) in salmon muscle has been developed. It is based on the use of an oxidative pre-column reaction which converts LMG into MG previous to liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (LC-APCI-MS) analysis. The determination of both compounds together constitutes a good screening method to confirm the presence of this kind of residue, taking into account that the combined signals will provide a gain of sensitivity. The detection limit, determined for spiked salmon samples using the confirmatory ion m/z 313, was 0.15 microg/kg. The recoveries determined at a spiking level of 2 microg/kg were 85 and 70% for LMG and MG, respectively, with respective relative standard deviations of 1.3 and 3.1%. PMID:15844514

Valle, Luis; Díaz, Cecilia; Zanocco, Antonio L; Richtera, Pablo

2005-03-01

144

Self-organization of SiO{sub 2} nanodots deposited by chemical vapor deposition using an atmospheric pressure remote microplasma  

SciTech Connect

Self-organization of SiO{sub 2} nanodots is obtained by chemical vapor deposition out of hexamethyldisiloxane (HMDSO) and atmospheric pressure remote Ar-O{sub 2} plasma operating at high temperature (1200-1600 K). The dewetting of the film being deposited when it is still thin enough (<500 nm) is found to be partly responsible for this self-organization. When the coating becomes thicker (approx1 mum), and for relatively high contents in HMDSO, SiO{sub 2} walls forming hexagonal cells are obtained on a SiO{sub 2} sublayer. For thicker coatings (>1 mum), droplet-shaped coatings with a Gaussian distribution in thickness over their width are deposited. The coatings are submitted to high compressive stress. When it is relaxed, 'nestlike structures' made of nanoribbons are synthesized.

Arnoult, G.; Belmonte, T.; Henrion, G. [Department of Physics and Chemistry of Solids and Surfaces, Institut Jean Lamour, Nancy-Universite, CNRS, Parc de Saurupt, CS 14234, F-54042 Nancy Cedex (France)

2010-03-08

145

Two-temperature chemically non-equilibrium modelling of high-power Ar N2 inductively coupled plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A two-dimensional thermal and chemical non-equilibrium model was developed for high-power Ar-N2 inductively coupled plasmas (ICPs) at atmospheric pressure, which are conventionally assumed to be under local thermal equilibrium condition. The energy conservation equation of electrons was treated separately from that of heavy particles. These equations consider reaction heat effects and energy transfer between electrons and heavy particles as well as enthalpy flow resulting from diffusion due to the particle density gradient. Chemical non-equilibrium effects were also accounted for by solving mass conservation equations for each particle, considering diffusion, convection and net production terms resulting from 30 reactions. Transport and thermodynamic properties of Ar-N2 plasmas were self-consistently calculated using the first-order approximation of the Chapman-Enskog method at each iteration using the local particle composition, heavy particle temperature and electron temperature. Power balance for the electron energy and the mass balance of atoms and ions in a high-power Ar-N2 ICP were investigated using the model developed. Calculational results obtained by the present model were compared with results from two other models such as a one-temperature chemical equilibrium model and a one-temperature chemical non-equilibrium model. This comparison supported the discussion of chemical and thermal non-equilibrium effects in the high-power induction plasma.

Tanaka, Yasunori

2004-04-01

146

Time-dependent two-temperature chemically non-equilibrium modelling of high-power Ar N2 pulse-modulated inductively coupled plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A time-dependent, two-dimensional, two-temperature and chemical non-equilibrium model was developed for high-power Ar-N2 pulse-modulated inductively coupled plasmas (PMICPs) at atmospheric pressure. The high-power PMICP is a new technique for sustaining high-power induction plasmas. It can control the plasma temperature and radical densities in the time domain. The PMICP promotes non-equilibrium effects by a sudden application of electric field, even in the high-power density plasmas. The developed model accounts separately for the time-dependent energy conservation equations of electrons and heavy particles. This model also considers reaction heat effects and energy transfer between electrons and heavy particles as well as enthalpy flow resulting from diffusion caused by the particle density gradient. Chemical non-equilibrium effects are also taken into account by solving time-dependent mass conservation equations for each particle, considering diffusion, convection and net production terms resulting from 30 chemical reactions. Transport and thermodynamic properties of Ar-N2 plasmas are calculated self-consistently using the first order approximation of the Chapman-Enskog method at each position and iteration using the local particle composition, heavy particle temperature and electron temperature. This model is useful to discuss time evolution in temperature, gas flow fields and distribution of chemical species.

Tanaka, Yasunori

2006-01-01

147

Determination of validamycin A in agricultural food samples by solid-phase extraction combined with liquid chromatography-atmospheric pressure chemical ionisation-tandem mass spectrometry.  

PubMed

For the first time, a rapid, sensitive and accurate liquid chromatography-atmospheric pressure chemical ionisation-tandem mass spectrometry (LC-APCI-MS/MS) method was developed for determination of validamycin A in agricultural food samples (rice, agaric, almond, cabbage, green onion, carrot, tomato, cucumber and spinach). The validamycin A residue was extracted with methanol-water (9/1, v/v) or methanol by vortex, and a HLB solid-phase extraction cartridge was used for cleaning up the extracts. LC-APCI-MS/MS data acquisition was carried out in multiple reaction monitoring (MRM) mode. A series of matrix-matched calibration solutions ranging from 2.5 to 50ngmL(-1) were used to record calibration curve. The limit of quantification (LOQ) was 10?gkg(-1). The average recoveries, measured at three concentrations levels (10.0, 50.0, 100.0?gkg(-1)) were in the range 83.5-109.6%. The proposed method offers the best sensitivity and specificity for the routine analysis of validamycin A in agricultural food samples. PMID:25236210

Wang, Chuanxian; Zhang, Zhigang; Shen, Yan; Tian, Zhengan; Xu, Dunming; Han, Chao

2015-02-15

148

Scalable high-mobility MoS2 thin films fabricated by an atmospheric pressure chemical vapor deposition process at ambient temperature.  

PubMed

Nano-scale MoS2 thin films are successfully deposited on a variety of substrates by atmospheric pressure chemical vapor deposition (APCVD) at ambient temperature, followed by a two-step annealing process. These annealed MoS2 thin films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS-NIR spectrometry, photoluminescence (PL) and Hall Effect measurement. Key optical and electronic properties of APCVD grown MoS2 thin films are determined. This APCVD process is scalable and can be easily incorporated with conventional lithography as the deposition is taking place at room temperature. We also find that the substrate material plays a significant role in the crystalline structure formation during the annealing process and single crystalline MoS2 thin films can be achieved by using both c-plane ZnO and c-plane sapphire substrates. These APCVD grown nano-scale MoS2 thin films show great promise for nanoelectronic and optoelectronic applications. PMID:25226424

Huang, Chung-Che; Al-Saab, Feras; Wang, Yudong; Ou, Jun-Yu; Walker, John C; Wang, Shuncai; Gholipour, Behrad; Simpson, Robert E; Hewak, Daniel W

2014-10-01

149

Scalable high-mobility MoS2 thin films fabricated by an atmospheric pressure chemical vapor deposition process at ambient temperature  

NASA Astrophysics Data System (ADS)

Nano-scale MoS2 thin films are successfully deposited on a variety of substrates by atmospheric pressure chemical vapor deposition (APCVD) at ambient temperature, followed by a two-step annealing process. These annealed MoS2 thin films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS-NIR spectrometry, photoluminescence (PL) and Hall Effect measurement. Key optical and electronic properties of APCVD grown MoS2 thin films are determined. This APCVD process is scalable and can be easily incorporated with conventional lithography as the deposition is taking place at room temperature. We also find that the substrate material plays a significant role in the crystalline structure formation during the annealing process and single crystalline MoS2 thin films can be achieved by using both c-plane ZnO and c-plane sapphire substrates. These APCVD grown nano-scale MoS2 thin films show great promise for nanoelectronic and optoelectronic applications.

Huang, Chung-Che; Al-Saab, Feras; Wang, Yudong; Ou, Jun-Yu; Walker, John C.; Wang, Shuncai; Gholipour, Behrad; Simpson, Robert E.; Hewak, Daniel W.

2014-10-01

150

Determination of hexabromocyclododecane by flowing atmospheric pressure afterglow mass spectrometry.  

PubMed

The first application of a flowing atmospheric-pressure afterglow ion source for mass spectrometry (FAPA-MS) for the chemical characterization and determination of hexabromocyclododecane (HBCD) is presented. The samples of technical HBCD and expanded polystyrene foam (EPS) containing HBCD as a flame retardant were prepared by dissolving the appropriate solids in dichloromethane. The ionization of HBCD was achieved with a prototype FAPA source. The ions were detected in the negative-ion mode. The ions corresponding to a deprotonated HBCD species (m/z 640.7) as well as chlorine (m/z 676.8), nitrite (m/z 687.8) and nitric (m/z 703.8) adducts were observed in the spectra. The observed isotope pattern is characteristic for a compound containing six bromine atoms. This technique is an effective approach to detect HBCD, which is efficiently ionized in a liquid phase, resulting in high detection efficiency and sensitivity. PMID:25059130

Smoluch, Marek; Silberring, Jerzy; Reszke, Edward; Kuc, Joanna; Grochowalski, Adam

2014-10-01

151

Development of a liquid chromatography/atmospheric pressure photo-ionization high-resolution mass spectrometry analytical method for the simultaneous determination of polybrominated diphenyl ethers and their metabolites: application to BDE-47 metabolism in human hepatocytes.  

PubMed

Polybrominated diphenyl ethers (PBDEs) are flame retardants widely used in electronic and domestic goods. These persistent pollutants are present in the environment and in humans, and their toxicological properties are of growing concern. PBDEs can be metabolised into compounds suspected to be responsible for their toxicity. These metabolites have been characterised quite well in rodents and fish, but available information in humans remains scarce. For their identification, an efficient method for the simultaneous analysis of PBDEs, hydroxylated PBDEs (OH-PBDEs), and other PBDE metabolites in a single run was needed and has been developed in this work. Atmospheric pressure ionisation modes were compared, and Atmospheric Pressure Photo-Ionization (APPI) was selected. After careful setting of APPI parameters such as dopant and operating temperature, the optimised method was based on APPI ionization coupled to High-Resolution Mass Spectrometry operating in the full scan mode at a resolution of 60 000. This provided excellent sensitivity and specificity, allowing the discrimination of signals which could not be resolved on a triple quadrupole used as a reference. The full-scan high-resolution acquisition mode allowed monitoring of both parent PBDEs and their metabolites, including hydroxylated PBDEs, with detection limits ranging from 0.1?pg to 4.5?pg injected on-column based on the investigated standard compounds. The method was applied to the study of BDE-47 metabolism after incubation with human primary cultures of hepatocytes, and proved to be efficient not only for monitoring the parent compound and expected hydroxylated metabolites, but also for the identification of other non-targeted metabolites. In addition to hydroxy-BDE-47, several conjugated metabolites could be located, and the formation of a dihydrodiol derivative was evidenced for the first time in the case of PBDEs in this work. PMID:22328212

Marteau, Charlotte; Chevolleau, Sylvie; Jouanin, Isabelle; Perdu, Elisabeth; De Sousa, Georges; Rahmani, Roger; Antignac, Jean-Philippe; LeBizec, Bruno; Zalko, Daniel; Debrauwer, Laurent

2012-03-30

152

Atmospheric-pressure plasma technology  

Microsoft Academic Search

Major industrial plasma processes operating close to atmospheric pressure are discussed. Applications of thermal plasmas include electric arc furnaces and plasma torches for generation of powders, for spraying refractory materials, for cutting and welding and for destruction of hazardous waste. Other applications include miniature circuit breakers and electrical discharge machining. Non-equilibrium cold plasmas at atmospheric pressure are obtained in corona

U. Kogelschatz

2004-01-01

153

Comparing Laser Desorption Ionization and Atmospheric Pressure Photoionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry To Characterize Shale Oils at the Molecular Level  

USGS Publications Warehouse

Laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze shale oils. Previous work showed that LDI is a sensitive ionization technique for assessing aromatic nitrogen compounds, and oils generated from Green River Formation oil shales are well-documented as being rich in nitrogen. The data presented here demonstrate that LDI is effective in ionizing high-double-bond-equivalent (DBE) compounds and, therefore, is a suitable method for characterizing compounds with condensed structures. Additionally, LDI generates radical cations and protonated ions concurrently, the distribution of which depends upon the molecular structures and elemental compositions, and the basicity of compounds is closely related to the generation of protonated ions. This study demonstrates that LDI FT-ICR MS is an effective ionization technique for use in the study of shale oils at the molecular level. To the best of our knowledge, this is the first time that LDI FT-ICR MS has been applied to shale oils.

Cho, Yunjo; Jin, Jang Mi; Witt, Matthias; Birdwell, Justin E.; Na, Jeong-Geol; Roh, Nam-Sun; Kim, Sunghwan, Kim

2013-01-01

154

Atmospheric pressure chemical vapor deposition of CdTe for high efficiency thin film PV devices: Annual subcontract report, 26 January 1999--25 January 2000  

SciTech Connect

ITN's three year project Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High Efficiency Thin Film PV Devices has the overall objectives of improving thin film CdTe PV manufacturing technology and increasing CdTe PV device power conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16% efficient CdTe PV films, i.e., close spaced sublimation, but employs forced convection rather than diffusion as a mechanism of mass transport. Tasks of the APCVD program center on demonstration of APCVD of CdTe films, discovery of fundamental mass transport parameters, application of established engineering principles to the deposition of CdTe films, and verification of reactor design principles which could be used to design high throughput, high yield manufacturing equipment. Additional tasks relate to improved device measurement and characterization procedures that can lead to a more fundamental understanding of CdTe PV device operation and ultimately to higher device conversion efficiency and greater stability. Under the APCVD program, device analysis goes beyond conventional one-dimensional device characterization and analysis toward two dimension measurements and modeling. Accomplishments of the second year of the APCVD subcontract include: deposition of the first APCVD CdTe; identification of deficiencies in the first generation APCVD reactor; design, fabrication and testing of a ``simplified'' APCVD reactor; deposition of the first dense, adherent APCVD CdTe films; fabrication of the first APCVD CdTe PV device; modeling effects of CdSTe and SnOx layers; and electrical modeling of grain boundaries.

Meyers, P. V.; Kee, R.; Wolden, C.; Kestner, J.; Raja, L.; Kaydanov, V.; Ohno, T.; Collins, R.; Fahrenbruch, A.

2000-05-30

155

Atmospheric Pressure Chemical Vapor Deposition and Jet Vapor Deposition of CdTe for High Efficiency Thin Film PV Devices: Final Technical Report, 26 January 2000 - 15 August 2002  

Microsoft Academic Search

ITN's three-year project, Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High Efficiency Thin Film PV Devices, had the overall objectives of improving thin-film CdTe PV manufacturing technology and increasing CdTe PV device power-conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16%-efficient CdTe PV films, i.e., close-spaced sublimation, but employs

L Woods; P. Meyers

2002-01-01

156

The application of gas chromatography/atmospheric pressure chemical ionisation time-of-flight mass spectrometry to impurity identification in Pharmaceutical Development.  

PubMed

Accurate mass measurement (used to determine elemental formulae) is an essential tool for impurity identification in pharmaceutical development for process understanding. Accurate mass liquid chromatography/mass spectrometry (LC/MS) is used widely for these types of analyses; however, there are still many occasions when gas chromatography (GC)/MS is the appropriate technique. Therefore, the provision of robust technology to provide accurate mass GC/MS (and GC/MS/MS) for this type of activity is essential. In this report we describe the optimisation and application of a newly available atmospheric pressure chemical ionisation (APCI) interface to couple GC to time-of-flight (TOF) MS.To fully test the potential of the new interface the APCI source conditions were optimised, using a number of standard compounds, with a variety of structures, as used in synthesis at AstraZeneca. These compounds were subsequently analysed by GC/APCI-TOF MS. This study was carried out to evaluate the range of compounds that are amenable to analysis using this technique. The range of compounds that can be detected and characterised using the technique was found to be extremely broad and include apolar hydrocarbons such as toluene. Both protonated molecules ([M + H](+)) and radical cations (M(+.)) were observed in the mass spectra produced by APCI, along with additional ion signals such as [M + H + O](+).The technique has been successfully applied to the identification of impurities in reaction mixtures from organic synthesis in process development. A typical mass accuracy of 1-2 mm/zunits (m/z 80-500) was achieved allowing the reaction impurities to be identified based on their elemental formulae. These results clearly demonstrate the potential of the technique as a tool for problem solving and process understanding in pharmaceutical development. The reaction mixtures were also analysed by GC/electron ionisation (EI)-MS and GC/chemical ionisation (CI)-MS to understand the capability of GC/APCI-MS relative to these two firmly established techniques. PMID:20486265

Bristow, Tony; Harrison, Mark; Sims, Martin

2010-06-15

157

Laserspray Ionization, a New Atmospheric Pressure MALDI Method for Producing Highly Charged Gas-phase Ions of Peptides and Proteins Directly from Solid Solutions*  

PubMed Central

The first example of a matrix-assisted laser desorption/ionization (MALDI) process producing multiply charged mass spectra nearly identical to those observed with electrospray ionization (ESI) is presented. MALDI is noted for its ability to produce singly charged ions, but in the experiments described here multiply charged ions are produced by laser ablation of analyte incorporated into a common MALDI matrix, 2,5-dihydroxybenzoic acid, using standard solvent-based sample preparation protocols. Laser ablation is known to produce matrix clusters in MALDI provided a threshold energy is achieved. We propose that these clusters (liquid droplets) are highly charged, and under conditions that produce sufficient matrix evaporation, ions are field-evaporated from the droplets similarly to ESI. Because of the multiple charging, advanced mass spectrometers with limited mass-to-charge range can be used for protein characterization. Thus, using an Orbitrap mass spectrometer, low femtomole quantities of proteins produce full-range mass spectra at 100,000 mass resolution with <5-ppm mass accuracy and with 1-s acquisition. Furthermore, the first example of protein fragmentation using electron transfer dissociation with MALDI is presented. PMID:19955086

Trimpin, Sarah; Inutan, Ellen D.; Herath, Thushani N.; McEwen, Charles N.

2010-01-01

158

Atmospheric-Pressure Plasma Process and Applications.  

National Technical Information Service (NTIS)

This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those ...

P. Kong

2006-01-01

159

Large area atmospheric-pressure plasma jet  

DOEpatents

Large area atmospheric-pressure plasma jet. A plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two planar, parallel electrodes are employed to generate a plasma in the volume therebetween. A "jet" of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly spacing the rf-powered electrode. Because of the atmospheric pressure operation, there is a negligible density of ions surviving for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike the situation for low-pressure plasma sources and conventional plasma processing methods.

Selwyn, Gary S. (Los Alamos, NM); Henins, Ivars (Los Alamos, NM); Babayan, Steve E. (Huntington Beach, CA); Hicks, Robert F. (Los Angeles, CA)

2001-01-01

160

On-Chip Solid-Phase Extraction Preconcentration/Focusing Substrates Coupled to Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Ion Trap Mass Spectrometry for High Sensitivity Biomolecule Analysis  

PubMed Central

Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric analysis of biomolecules. AP-MALDI and electrospray ion sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise (S/N) ratio gains observed when an on-chip dynamic preconcentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200–900 for hydrophobic substrates, and 150–400 for weak cation exchange (WCX) substrates; (2) improved detection limits as low as 5 fmol/?L for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem MS sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads. PMID:19140128

Navare, Arti; Nouzova, Marcela; Noriega, Fernando G.; Hernandez-Martinez, Salvador; Menzel, Christoph; Fernandez, Facundo M.

2009-01-01

161

Identification of Organic Nitrates in the NO3 Radical Initiated Oxidation of ?-Pinene by Atmospheric Pressure Chemical Ionization Mass Spectrometry  

SciTech Connect

The gas-phase reactions of nitrate radicals (NO3) with biogenic organic compounds are a major sink for these organics during night-time. These reactions form secondary organic aerosols, including organic nitrates thatcanundergolongrange transport, releasing NOx downwind. We report here studies of the reaction of NO3 with R-pinene at 1 atm in dry syntheticair(relativehumidity?3%)andat298Kusingatmospheric pressurechemicalionizationtriplequadrupolemassspectrometry (APCI-MS) to identify gaseous and particulate products. The emphasis is on the identification of individual organic nitrates in the particle phase that were obtained by passing the product mixture through a denuder to remove gas-phase reactants and products prior to entering the source region of the mass spectrometer. Filter extracts were also analyzed by GCMS and by APCI time-of-flight mass spectrometry (APCI-ToFMS) with methanol as the proton source. In addition to pinonaldehyde and pinonic acid, five organic nitrates were identified in the particles as well as in the gas phase: 3-oxopinane- 2-nitrate, 2-hydroxypinane-3-nitrate, pinonaldehyde-PAN, norpinonaldehyde-PAN, and (3-acetyl-2,2-dimethyl-3-nitrooxycyclobutyl) acetaldehyde. Furthermore, therewasanadditional firstgeneration organic nitrate product tentatively identified as a carbonyl hydroxynitrate with a molecular mass of 229. These studies suggest that a variety of organic nitrates would partition between the gas phase and particles in the atmosphere, and serve as a reservoir for NO.

Perraud, Veronique M.; Bruns, Emily A.; Ezell, Michael J.; Johnson, Stanley N.; Greaves, John; Finlayson-Pitts, Barbara J.

2010-07-07

162

Quantitative determination of dexamethasone in bovine milk by liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

Dexamethasone (DXM) is a synthetic glucocorticoid that is authorized for therapeutic use in veterinary medicine. The European Community (EC) fixed a maximum residue limit (MRL) at 2ng/g for liver, 0.75ng/g for muscle and kidney tissues, and 0.3ng/ml for milk, while its use as growth-promoter is completely banned. The purpose of this study was to develop and validate a simple and reliable method to determine DXM residues in bovine milk. Milk proteins were removed by the addition of concentrated trichloroacetic acid and paper filtration. Solid-phase extraction clean-up on a C18 reversed phase column was performed to obtain an extract suitable for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Chromatographic separation of DXM and the internal standard desoximetasone, was achieved on a PLRP-S polymeric reversed phase column, using a mixture of 0.1% (v/v) acetic acid in water (mobile phase A) and acetonitrile (mobile phase B) as the mobile phases. They were identified using the MS/MS detection technique, and were subsequently quantified. The method has been validated according to the requirements of the EC at 0.15, 0.30 and 0.60ng/ml (being half the MRL, the MRL and double the MRL levels fixed by the EC). Calibration graphs were prepared in the 0.15-5ng/ml range and good linearity was achieved (r>or=0.99 and goodness of fit

Cherlet, Marc; De Baere, Siegrid; De Backer, Patrick

2004-06-01

163

Atmospheric-pressure plasma technology  

NASA Astrophysics Data System (ADS)

Major industrial plasma processes operating close to atmospheric pressure are discussed. Applications of thermal plasmas include electric arc furnaces and plasma torches for generation of powders, for spraying refractory materials, for cutting and welding and for destruction of hazardous waste. Other applications include miniature circuit breakers and electrical discharge machining. Non-equilibrium cold plasmas at atmospheric pressure are obtained in corona discharges used in electrostatic precipitators and in dielectric-barrier discharges used for generation of ozone, for pollution control and for surface treatment. More recent applications include UV excimer lamps, mercury-free fluorescent lamps and flat plasma displays.

Kogelschatz, U.

2004-12-01

164

CHEMICAL PROTECTION AGAINST IONIZING RADIATION  

Microsoft Academic Search

Recent work on chemical protection against radiation effects in mammals ; is reviewed, especially with respect to whole-body exposure to external radiation. ; This survey shows that many explanations are being offered to account for the ; action of radioprotective agents. In general, the proposed mechanisms are ; concerned with inactivation of radicals and other chemical intermediates, ; depletion of

R. L. Straube; H. M. Patt

1963-01-01

165

Microwave Atmospheric-Pressure Sensor  

NASA Technical Reports Server (NTRS)

Report describes tests of microwave pressure sounder (MPS) for use in satellite measurements of atmospheric pressure. MPS is multifrequency radar operating between 25 and 80 GHz. Determines signal absorption over vertical path through atmosphere by measuring strength of echoes from ocean surface. MPS operates with cloud cover, and suitable for use on current meteorological satellites.

Flower, D. A.; Peckham, G. E.; Bradford, W. J.

1986-01-01

166

Analysis of degradation products of organophosphorus chemical warfare agents and related compounds by liquid chromatography–mass spectrometry using electrospray and atmospheric pressure chemical ionisation  

Microsoft Academic Search

A qualitative screening procedure was developed for the detection and identification of phosphonic acid hydrolysis products of organophosphorus chemical warfare agents, using liquid chromatography–mass spectrometry with electrospray ionisation (LC–ESP-MS). A mixed C8\\/C18 reversed-phase column with gradient elution gave good chromatography for a series of phosphonic acids. Detection limits for aqueous solutions of standards were <50 ng\\/ml (<0.25 ng injected), providing

Robin M Black; Robert W Read

1998-01-01

167

Ion chemistry in gaseous discharges at atmospheric pressure  

NASA Astrophysics Data System (ADS)

The role of ions in plasma chemistry is briefly reviewed on the basis of recent literature reports. In addition, different chemical processes induced by gaseous discharges at atmospheric pressure are discussed here, with particular emphasis on the elucidation of some aspects of the ion chemistry occurring in benzene/air dielectric barrier and corona discharges. Through a multi-technique approach relying on gas chromatographic, mass spectrometric, spectroscopic and computational analyses, we have been able to reveal subtle mechanistic aspects involved in the ionic processes leading to the synthesis of covalent adducts. In particular, we report here the experimental conditions and the thermochemical reasons whereby we can access the synthesis (i) of benzenediazonium ion {\\rmC}_6H_{5}N_2^+ from the reaction of phenylium ion C_6H_5^+ with N2, (ii) of protonated biphenyl ions C_12H_{11}^+ from electrophilic aromatic attack of phenylium ion on C6H6, (iii) of phenol radical cations C6H5OH+. via O radical addition on the benzene ring followed by ionization of the neutral product and finally (iv) of biphenyl-oxonium ions C12H11O+ and hydroxylbiphenyl-oxonium ions C_12H_{11}O_2^+ as end-products of the electrophilic attack of phenol ions on benzene and phenol, respectively. Finally, intriguing chemical paths involved in the corona discharge ionization of acetonitrile are also discussed.

Tosi, Paolo; Ascenzi, Daniela; Franceschi, Pietro; Guella, Graziano

2009-08-01

168

Application of Ni-63 photo and corona discharge ionization for the analysis of chemical warfare agents and toxic wastes  

NASA Technical Reports Server (NTRS)

Over the past decade, advances in instrumental design and refinements in the understanding of ion molecule reactions at atmospheric pressure enabled the application of Ion Mobility Spectrometry (IMS) as a simple inexpensive and sensitive analytical method for the detection of organic trace compounds. Positive and negative gas-phase ions for ion mobility spectrometry have been produced by a variety of methods, including photo-ionization, laser multi photon ionization, surface ionization, corona discharge ionization. The most common ion source used in ion mobility spectrometry is a radioactive Ni-63 foil which is favored due to simplicity, stability, convenience, and high selectivity. If reactant ions like (H2O(n)H)(+) or (H2O(n)O2)(-) dominate in the reaction region, nearly all kinds of compounds with a given proton or electron affinity; are ionized. However, the radioactivity of the Ni-63 foil is one disadvantage of this ion source that stimulates the development and application of other ionization techniques. In this paper, we report analyses of old chemical warfare agents and toxic wastes using Bruker RAID ion mobility spectrometers. Due to the modular construction of the measuring cell, the spectrometers can be equipped with different ion sources. The combined use of Ni-63, photo- and corona discharge ionization allows the identification of different classes of chemical compounds and yields in most cases comparable results.

Stach, J.; Adler, J.; Brodacki, M.; Doring, H.-R.

1995-01-01

169

ATMOSPHERIC-PRESSURE PLASMA PROCESS AND APPLICATIONS  

Microsoft Academic Search

This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those produced in high intensity arcs, plasma torches, or in high intensity, high frequency discharges. Although nonthermal plasmas are at room temperatures, they are extremely effective in producing activated species, e.g., free

Peter Kong

170

Infrared laser ablation atmospheric pressure photoionization mass spectrometry.  

PubMed

In this paper we introduce laser ablation atmospheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 ?m wavelength. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ~300 ?m lateral resolution comparable to, e.g., matrix-assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves. PMID:22242626

Vaikkinen, Anu; Shrestha, Bindesh; Kauppila, Tiina J; Vertes, Akos; Kostiainen, Risto

2012-02-01

171

Spacecraft Sterilization Using Non-Equilibrium Atmospheric Pressure Plasma  

NASA Technical Reports Server (NTRS)

As a solution to chemically and thermally destructive sterilization methods currently used for spacecraft, non-equilibrium atmospheric pressure plasmas are used to treat surfaces inoculated with Bacillus subtilis and Deinococcus radiodurans. Evidence of significant morphological changes and reduction in viability due to plasma exposure will be presented, including a 4-log reduction of B. subtilis after 2 minutes of dielectric barrier discharge treatment.

Cooper, Moogega; Vaze, Nachiket; Anderson, Shawn; Fridman, Gregory; Vasilets, Victor N.; Gutsol, Alexander; Tsapin, Alexander; Fridman, Alexander

2007-01-01

172

The effect of thermal annealing on the properties of alumina films prepared by metal organic chemical vapour deposition at atmospheric pressure  

Microsoft Academic Search

Thin films deposited at 330°C by metal organic chemical vapour deposition on stainless steel, type AISI 304, were annealed in a nitrogen atmosphere for 1, 2 and 4 h at 600, 700 and 800°C. The film properties, including the protection of the underlying substrate against high temperature corrosion, the chemical composition of the film and the microstructure, were investigated.\\u000a\\u000aCorrosion

V. A. C. Haanappel; Corbach van H. D; T. Fransen; P. J. Gellings

1994-01-01

173

The Dawn of Atmospheric-pressure Plasma  

NASA Astrophysics Data System (ADS)

As never before, atmospheric-pressure plasma technology is poised to transform the world of plasma processing. Many corporate and academic researchers are betting that the future holds tremendous opportunity for atmospheric-pressure plasma, which offers low cost and sometimes surprisingly high performance. A recent example of research is presented.

Ono, Shigeru

174

Liquid chromatography/mass spectrometric determination of patulin in apple juice using atmospheric pressure photoionization.  

PubMed

This paper describes a comparison between atmospheric pressure chemical ionization (APCI) and the recently introduced atmospheric pressure photoionization (APPI) technique for the liquid chromatography/mass spectrometric (LC/MS) determination of patulin in clear apple juice. A column switching technique for on-line extraction of clear apple juice was developed. The parameters investigated for the optimization of APPI were the ion source parameters fragmentor voltage, capillary voltage, and vaporizer temperature, and also mobile phase composition and flow rate. Furthermore, chemical noise and signal suppression of analyte signals due to sample matrix interference were investigated for both APCI and APPI. The results indicated that APPI provides lower chemical noise and signal suppression in comparison with APCI. The linear range for patulin in apple juice (correlation coefficient >0.999) was 0.2-100 ng mL(-1). Mean recoveries of patulin in three apple juices ranged from 94.5 to 103.2%, and the limit of detection (S/N = 3), repeatability and reproducibility were 1.03-1.50 ng mL(-1), 3.9-5.1% and 7.3-8.2%, respectively. The total analysis time was 10.0 min. PMID:12913860

Takino, Masahiko; Daishima, Shigeki; Nakahara, Taketoshi

2003-01-01

175

Plasma enhanced chemical vapor deposition of TiO 2 films on silica gel powders at atmospheric pressure in a circulating fluidized bed reactor  

Microsoft Academic Search

Anatase TiO2 thin films were deposited on silica gel powders by plasma enhanced chemical vapor deposition (PECVD) method in a circulating fluidized bed (CFB) reactor using TTIP [Ti(O-i-C3H7)4] and oxygen without any post-treatment. The optimum solid circulation rates were determined for the stable He-plasma glow discharge with He fluidizing gas. The optimum deposition conditions of TiO2 thin films by PECVD

Gook Hee Kim; Sang Done Kim; Soung Hee Park

2009-01-01

176

Simultaneous determination of volatile and non-volatile nitrosamines in processed meat products by liquid chromatography tandem mass spectrometry using atmospheric pressure chemical ionisation and electrospray ionisation.  

PubMed

A sensitive, selective and generic method has been developed for the simultaneous determination of the contents (?gkg(-1) range) of both volatile nitrosamines (VNA) and non-volatile nitrosamines (NVNA) in processed meat products. The extraction procedure only requires basic laboratory equipment and a small volume of organic solvent. Separation and quantification were performed by the developed LC-(APCI/ESI)MS/MS method. The method was validated using spiked samples of three different processed meat products. Satisfactory recoveries (50-130%) and precisions (2-23%) were obtained for eight VNA and six NVNAs with LODs generally between 0.2 and 1?gkg(-1), though for a few analyte/matrix combinations higher LODs were obtained (3 to 18?gkg(-1)). The validation results show that results obtained for one meat product is not always valid for other meat products. We were not able to obtain satisfactory results for N-nitrosohydroxyproline (NHPRO), N-nitrosodibenzylamine (NDBzA) and N-nitrosodiphenylamine (NDPhA). Application of the APCI interface improved the sensitivity of the method, because of less matrix interference, and gave the method a wider scope, as some NAs were ionisable only by APCI. However, it was only possible to ionize N-nitroso-thiazolidine-4-carboxylic acid (NTCA) and N-nitroso-2-methyl-thiazolidine-4-carboxylic acid (NMTCA) by ESI. The validated method was applied for the analysis of processed meat products and contents of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosomethylaniline (NMA), N-nitrosoproline (NPRO), NTCA, and NMTCA were found in one or several nitrite cured meat products, whereas none were detected in non-nitrite cured bacon. PMID:24468241

Herrmann, S S; Duedahl-Olesen, L; Granby, K

2014-02-21

177

Combinatorial atmospheric pressure chemical vapor deposition of graded TiO?-VO? mixed-phase composites and their dual functional property as self-cleaning and photochromic window coatings.  

PubMed

A combinatorial film with a phase gradient from V:TiO? (V: Ti ? 0.08), through a range of TiO?-VO? composites, to a vanadium-rich composite (V: Ti = 1.81) was grown by combinatorial atmospheric pressure chemical vapor deposition (cAPCVD). The film was grown from the reaction of TiCl?, VCl?, ethyl acetate (EtAc), and H?O at 550 °C on glass. The gradient in gas mixtures across the reactor induced compositional film growth, producing a single film with numerous phases and compositions at different positions. Seventeen unique positions distributed evenly along a central horizontal strip were investigated. The physical properties were characterized by wavelength dispersive X-ray (WDX) analysis, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-visible spectroscopy. The functional properties examined included the degree of photoinduced hydrophilicity (PIH), UVC-photocatalysis, and thermochromism. Superhydrophilic contact angles could be achieved at all positions, even within a highly VO?-rich composite (V: Ti = 1.81). A maximum level of UVC photocatalysis was observed at a position bordering the solubility limit of V:TiO? (V: Ti ? 0.21) and fragmentation into a mixed-phase composite. Within the mixed-phase TiO?: VO? composition region (V: Ti = 1.09 to 1.81) a decrease in the semiconductor-to-metal transition temperature of VO? from 68 to 51 °C was observed. PMID:23688025

Wilkinson, Mia; Kafizas, Andreas; Bawaked, Salem M; Obaid, Abdullah Y; Al-Thabaiti, Shaeel A; Basahel, Sulaiman N; Carmalt, Claire J; Parkin, Ivan P

2013-06-10

178

Thermal and chemical ionization in flames  

Microsoft Academic Search

Conclusions We have determined the rate constants of the potassium ionization process A?A++e? in the flames of 2H2+O2+X (Ar, He) mixtures on the temperature interval 1500–2500° K. The activation energy of this process is close to the ionization potential of potassium (100 kcal).

E. S. Semenov; A. S. Sokolik

1970-01-01

179

Tantalum Etching with an Atmospheric Pressure Plasma Jet  

NASA Astrophysics Data System (ADS)

The APPJ is a non-thermal, atmospheric-pressure, glow discharge. A feedgas, composed of an inert carrier gas (e.g., He) and small concentrations of additives (e.g., O2, or CF4), flows between closely spaced electrodes powered at 13.56 MHz rf in a coaxial or parallel plate arrangement. The plasma has Te ˜ 2 eV and ne ˜ 10^11 cm-3. Electrons are not in thermal equilibrium with ions and neutrals: the electrons are ``hot", while the overall gas temperature is quite ``cold", typically 50-300 C. In the plasma, the gas is excited, dissociated or ionized by energetic electron impact. As the gas exits the discharge volume, ions and electrons are rapidly lost by recombination, leaving metastables (e.g. O2*, He*) and radicals (e.g. O, F, OF, O2F, CFO). These reactive species are then directed onto a surface to be processed. The APPJ has been developed for decontaminating nuclear, chemical, and biological agents. Atomic fluorine, and possibly other reactive species, can be used to convert actinides (e.g., U and Pu), into volatile fluorides (e.g., UF6, PuF6) that can be trapped, resulting in significant volume reduction of radioactive waste. In this talk, we will present results on using Ta as a surrogate for Pu in He/O2/CF4 etching plasmas. Results of experimental measurements of Ta etch rates for various gas mixtures and plasma jet standoff distance will be compared with plasma chemistry modeling of the concentrations of several active species produced in the plasma.

Teslow, Hilary; Herrmann, Hans; Rosocha, Louis

2002-10-01

180

High-performance liquid chromatography-mass spectrometry of porphyrins by using an atmospheric pressure interface.  

PubMed

A method is described for the high-performance liquid chromatography (HPLC) mass spectrometry analysis of porphyrin mixtures by using an atmospheric pressure interface, which can operate in two modes: pneumatically assisted elecrrospray and atmospheric pressure chemical ionization (APCI). Optimization of the conditions and evaluation of spectral information has been carried out by using direct injection of free-base and metallo porphyrin standards. The most effective results were obtained using APCI. HPLC-APCI mass spectrometry analysis of the demetallated vanadyl porphyrin fraction from the Triassic Serpiano oil shale has allowed rapid characterization of the distribution; more than 50 significant components are present. The presence of trace amounts of high molecular weight (>C33) cycloalkano porphyrins indicates the occurrence of photic zone anoxia in the ancient water column. This example illustrates the potential of the approach for studies of porphyrin mixtures of environmental or biological significance, which should be applicable to other types of metallo and free-base components that can be separated by HPLC under normal or reversed-phase conditions. PMID:24203611

Rosell-Melé, A; Carter, J F; Maxwell, J R

1996-09-01

181

Effect of Swirling Desolvation Gas Flow in an Atmospheric Pressure Ion Source  

NASA Astrophysics Data System (ADS)

A numerical study is performed to examine the effect of introducing a swirling desolvation gas flow on the flow transport characteristics in an electrospray and an atmospheric pressure chemical ionization (APCI) system. An ion source having three coaxial tubes is considered: (1) an inner capillary tube to inject the liquid sample, (2) a center coaxial tube to provide a room temperature gas flow to nebulize the liquid, referred to as the nebulizing gas flow, and (3) an outer coaxial tube having a converging exit to supply a high temperature gas for droplet desolvation, referred to as the desolvation gas flow. The results show that a swirling desolvation gas flow reduces the dispersion of the nebulizing gas and suppresses turbulent diffusion. The effect of swirling desolvation flow on the trajectory of a range of droplet sizes emitted from a source is also considered.

Savtchenko, Serguei; Ashgriz, Nasser; Jolliffe, Chuck; Cousins, Lisa; Gamble, Heather

2014-09-01

182

Leidenfrost Phenomenon-assisted Thermal Desorption (LPTD) and Its Application to Open Ion Sources at Atmospheric Pressure Mass Spectrometry  

NASA Astrophysics Data System (ADS)

This work describes the development and application of a new thermal desorption technique that makes use of the Leidenfrost phenomenon in open ion sources at atmospheric pressure for direct mass spectrometric detection of ultratrace levels of illicit, therapeutic, and stimulant drugs, toxicants, and peptides (molecular weight above 1 kDa) in their unaltered state from complex real world samples without or with minor sample pretreatment. A low temperature dielectric barrier discharge ion source was used throughout the experiments and the analytical figures of merit of this technique were investigated. Further, this desorption technique coupled with other ionization sources such as electrospray ionization (ESI) and dc corona discharge atmospheric pressure chemical ionization (APCI) in open atmosphere was also investigated. The use of the high-resolution `Exactive Orbitrap' mass spectrometer provided unambiguous identification of trace levels of the targeted compounds from complex mixtures and background noise; the limits of detection for various small organic molecules and peptides treated with this technique were at the level of parts per trillion and 10-9 M, respectively. The high sensitivity of the present technique is attributed to the spontaneous enrichment of analyte molecules during the slow evaporation of the solvent, as well as to the sequential desorption of molecules from complex mixtures based on their volatilities. This newly developed desorption technique is simple and fast, while molecular ions are observed as the major ions.

Saha, Subhrakanti; Chen, Lee Chuin; Mandal, Mridul Kanti; Hiraoka, Kenzo

2013-03-01

183

Low-voltage back-gated atmospheric pressure chemical vapor deposition based graphene-striped channel transistor with high-? dielectric showing room-temperature mobility > 11,000 cm(2)/V·s.  

PubMed

Utilization of graphene may help realize innovative low-power replacements for III-V materials based high electron mobility transistors while extending operational frequencies closer to the THz regime for superior wireless communications, imaging, and other novel applications. Device architectures explored to date suffer a fundamental performance roadblock due to lack of compatible deposition techniques for nanometer-scale dielectrics required to efficiently modulate graphene transconductance (gm) while maintaining low gate capacitance-voltage product (CgsVgs). Here we show integration of a scaled (10 nm) high-? gate dielectric aluminum oxide (Al2O3) with an atmospheric pressure chemical vapor deposition (APCVD)-derived graphene channel composed of multiple 0.25 ?m stripes to repeatedly realize room-temperature mobility of 11,000 cm(2)/V·s or higher. This high performance is attributed to the APCVD graphene growth quality, excellent interfacial properties of the gate dielectric, conductivity enhancement in the graphene stripes due to low tox/Wgraphene ratio, and scaled high-? dielectric gate modulation of carrier density allowing full actuation of the device with only ±1 V applied bias. The superior drive current and conductance at Vdd = 1 V compared to other top-gated devices requiring undesirable seed (such as aluminum and poly vinyl alcohol)-assisted dielectric deposition, bottom gate devices requiring excessive gate voltage for actuation, or monolithic (nonstriped) channels suggest that this facile transistor structure provides critical insight toward future device design and process integration to maximize CVD-based graphene transistor performance. PMID:23777434

Smith, Casey; Qaisi, Ramy; Liu, Zhihong; Yu, Qingkai; Hussain, Muhammad Mustafa

2013-07-23

184

Diagnostic methods used for atmospheric pressure thermal arc plasma  

NASA Astrophysics Data System (ADS)

Diagnostic methods used for atmospheric pressure thermal arc plasmas are presented in this paper. An experimental direct current arc plasma torch was used as a source for plasma generation at atmospheric pressure. Overheated water vapor was employed as a plasma-forming gas with an admixture of argon as a shielding gas. A couple of plasma diagnostic methods were invoked to perform the analysis of the generated plasma jet at the nozzle exhaust of the torch. Firstly, an optical emission spectroscopy method was used to determine the chemical composition of the water vapor plasma, and from the obtained spectra, the rotational and excitation temperatures were calculated roughly. Secondly, an enthalpy probe measurement was performed in order to measure the mean temperature and the velocity lengthwise and crosswise in the plasma stream.

Tamoši?nas, A.; Valatkevi?ius, P.; Valin?ius, V.; Grigaitien?, V.; Kavaliauskas, Ž.

2014-05-01

185

Surface Modification by Atmospheric Pressure Plasma for Improved Bonding  

NASA Astrophysics Data System (ADS)

An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from <5° to 40° over a period of 12 hours. When stored under a nitrogen purge, the water contact angle of a clean surface increased from <5° to 30° over a period of 40-60 hours. The change in contact angle resulted from the adsorption of nonanal onto the exposed surface hydroxyl groups. The rate of adsorption of nonanal under a nitrogen purged atmosphere ranged from 0.378+/-0.011 hr-1 to 0.182+/-0.008 hr -1 molecules/(cm2•s), decreasing as the fraction of hydrogen-bonded hydroxyl groups increased from 49% to 96% on the SiO 2 surface. The adsorption of the organic contaminant could be suppressed indefinitely by storing the silicon wafers in the presence of activated carbon or in a freezer at -22°C. The enhancement of adhesive bond strength and durability for carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024 was demonstrated with the atmospheric pressure helium-oxygen plasma. All surfaces studied were converted from a hydrophobic state with a water contact angle of 65° to 80° into a hydrophilic state with a water contact angle between 20° and 40° within 5 seconds of plasma exposure. X-ray photoelectron spectroscopy confirmed that the carbon atoms on the carbon-fiber/epoxy composite were oxidized, yielding 17 atom% carboxylic acid groups, 10% ketones or aldehydes and 9% alcohols. Analysis of stainless steel and aluminum by XPS illustrate oxidation of the metal surface and an increase in the concentration of hydroxyl groups in the oxide film. Following plasma activation, the total hydroxyl species concentration on stainless steel increased from 31% to 57%, while aluminum exhibited an increase from 4% to 16% hydroxyl species. Plasma activation of the surface led to an increase in bond strength of the different surfaces by up to 150% when using Cytec FM300 and FM300-2 epoxy adhesives. Wedge crack extension tests following plasma activation revealed cohesive failure percentages of 97% for carbon-fiber/epoxy composite bonded to stainless steel, and 96% for aluminum bonded to itself. The bond strength and durability of the substrates correlated with changes in the specific surface chemistry, not the wetting angle or the morphological properties of the material. This suggests that enhanced chemical bonding at the interface was responsible for the improvement in mechanical properties following plasma activation. The surface preparation of polymers and composites using atmospheric pressure plasmas is a promising technique for replacing traditional methods of surface preparation by sanding, grit blasting or peel ply. After oxygen plasma activation and joining the materials together with epoxy, one observes 100% cohesive failure within the c

Williams, Thomas Scott

186

Atmospheric Pressure Plasma Process And Applications  

SciTech Connect

This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those produced in high intensity arcs, plasma torches, or in high intensity, high frequency discharges. Although nonthermal plasmas are at room temperatures, they are extremely effective in producing activated species, e.g., free radicals and excited state atoms. Thus, both thermal and nonthermal atmosphericpressure plasmas are finding applications in a wide variety of industrial processes, e.g. waste destruction, material recovery, extractive metallurgy, powder synthesis, and energy conversion. A brief discussion of recent plasma technology research and development activities at the Idaho National Laboratory is included.

Peter C. Kong; Myrtle

2006-09-01

187

Determining Atmospheric Pressure Using a Water Barometer  

ERIC Educational Resources Information Center

The atmosphere is an envelope of compressible gases that surrounds Earth. Because of its compressibility and nonuniform heating by the Sun, it is in constant motion. The atmosphere exerts pressure on Earth's surface, but that pressure is in constant flux. This experiment allows students to directly measure atmospheric pressure by measuring the…

Lohrengel, C. Frederick, II; Larson, Paul R.

2012-01-01

188

Atmospheric Pressure Chemical Vapor Deposition and Jet Vapor Deposition of CdTe for High Efficiency Thin Film PV Devices: Final Technical Report, 26 January 2000 - 15 August 2002  

SciTech Connect

ITN's three-year project, Atmospheric Pressure Chemical Vapor Deposition (APCVD) of CdTe for High Efficiency Thin Film PV Devices, had the overall objectives of improving thin-film CdTe PV manufacturing technology and increasing CdTe PV device power-conversion efficiency. CdTe deposition by APCVD employs the same reaction chemistry as has been used to deposit 16%-efficient CdTe PV films, i.e., close-spaced sublimation, but employs forced convection rather than diffusion as a mechanism of mass transport. Tasks of the APCVD program center on demonstration of APCVD of CdTe films, discovery of fundamental mass-transport parameters, application of established engineering principles to the deposition of CdTe films, and verification of reactor design principles that could be used to design high-throughput, high-yield manufacturing equipment. Additional tasks relate to improved device measurement and characterization procedures that can lead to a more fundamental understanding of CdTe PV device operation, and ultimately, to higher device conversion efficiency and greater stability. Under the APCVD program, device analysis goes beyond conventional one-dimensional device characterization and analysis toward two-dimensional measurements and modeling. Accomplishments of the concluding year and extension of the APCVD subcontract included: incorporation of high-resistivity transparent buffer layers and achievement of 12.3%-efficient (NREL-measured, but not certified) devices by APCVD; analysis of scale-up issues related to APCVD, analysis of dust formation dynamics; demonstration of the inherent deficiencies of APCVD for CdTe manufacturing; modeling effects of CdSTe and SnOx layers; and electrical modeling of grain boundaries; design and construction of a low-pressure jet vapor deposition (JVD) reactor; JVD CdTe film characterization as a function of substrate and source temperature; demonstration of high growth rates using JVD; and superstrate-type and substrate-type device fabrication using low-substrate-temperature JVD CdTe films.

Woods, L; Meyers, P.

2002-08-01

189

Performance of a corona ion source for measurement of sulfuric acid by chemical ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The performance of an ion source based on corona discharge has been studied. This source is used for the detection of gaseous sulfuric acid by chemical ionization mass spectrometry (CIMS) through the reaction of NO3- ions with H2SO4. The ion source is operated under atmospheric pressure and its design is similar to the one of a radioactive (americium-241) ion source which has been used previously. The results show that the detection limit for the corona ion source is sufficiently good for most applications. For an integration time of 1 min it is ~6 × 104 molecule cm-3 of H2SO4. In addition, only a small cross-sensitivity to SO2 has been observed for concentrations as high as 1 ppmv in the sample gas. This low sensitivity to SO2 is achieved even without the addition of an OH scavenger. When comparing the new corona ion source with the americium ion source for the same provided H2SO4 concentration, both ion sources yield almost identical values. These features make the corona ion source investigated here favorable over the more commonly used radioactive ion sources for most applications where H2SO4 is measured by CIMS.

Kürten, A.; Rondo, L.; Ehrhart, S.; Curtius, J.

2011-03-01

190

Performance of a corona ion source for measurement of sulfuric acid by chemical ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The performance of an ion source based on corona discharge has been studied. This source is used for the detection of gaseous sulfuric acid by chemical ionization mass spectrometry (CIMS) through the reaction of NO3- ions with H2SO4. The ion source is operated under atmospheric pressure and its design is similar to the one of a radioactive (Americium 241) ion source which has been used previously. Our results show that the detection limit for the corona ion source is sufficiently good for most applications. For an integration time of one minute it is ~6 × 104 molecules of H2SO4 per cm3. In addition, only a small cross-sensitivity to SO2 has been observed for concentrations as high as 1 ppmv in the sample gas. This low sensitivity to SO2 is achieved even without the addition of an OH scavenger. When comparing the new corona ion source with the americium ion source for the same provided H2SO4 concentration, both ion sources yield almost identical values. These features make the corona ion source investigated here favorable over the more commonly used radioactive ion sources for most applications where H2SO4 is measured by CIMS.

Kürten, A.; Rondo, L.; Ehrhart, S.; Curtius, J.

2010-11-01

191

NEGATIVE CHEMICAL IONIZATION STUDIES OF HUMAN AND FOOD CHAIN CONTAMINATION WITH XENOBIOTIC CHEMICALS  

EPA Science Inventory

Negative chemical ionization mass spectrometry with a mixture of isobutane, methylene chloride, and oxygen as the reagent gas has been used to explore contamination of environmental substrates with xenobiotic chemicals. The substrates in question, fish tissue, human seminal plasm...

192

Facilities: NHMFL 9.4 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer Citation: Atmospheric Pressure Laser-Induced Acoustic Desorption Chemical Ionization Mass Spectrometry  

E-print Network

Facilities: NHMFL 9.4 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer Citation with the ability of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyze complex

Weston, Ken

193

Localization of double bonds in wax esters by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry utilizing the fragmentation of acetonitrile-related adducts.  

PubMed

Unsaturated wax esters (WEs) provided molecular adducts with C(3)H(5)N ([M + 55](+•)) in APCI sources in the presence of acetonitrile. CID MS/MS of [M + 55](+•) yielded fragments allowing the localization of double bond(s) in the hydrocarbon chains of the WEs. These fragments were formed by a cleavage on each side of the double bond. In methylene-interrupted polyunsaturated WEs, diagnostic fragments related to each double bond were detected; the most abundant were those corresponding to the cleavage of the C-C bond next to the first and the last double bond. To differentiate between those fragments differing in their structure or origin, a simple nomenclature based on ? and ? ions has been introduced. Fragmentation of the ?-type ions (fragments containing an ester bond) provided information on the occurrence of a double bond in the acid or alcohol part of the WEs. While no significant differences between the spectra of the WEs differing by cis/trans isomerism were found, the isomers were separated chromatographically. A data-dependent HPLC/APCI-MS(2) method for the comprehensive characterization of WEs in their complex mixtures has been developed and applied to natural mixtures of WEs isolated from jojoba oil and beeswax. More than 50 WE molecular species were completely identified, including the information on the acid and alcohol chain length and the position of the double bonds. PMID:21428309

Vrkoslav, Vladimír; Háková, Martina; Pecková, Karolina; Urbanová, Klára; Cva?ka, Josef

2011-04-15

194

Rapid and sensitive analysis of euonine and wilforidine in human plasma by high-performance liquid chromatography-atmospheric-pressure chemical ionization-mass spectrometry.  

PubMed

Euonine and wilforidine are biologically active Tripterygium wilfordii Hook. f. alkaloids. In this paper, a rapid and sensitive high-performance liquid chromatography-mass spectrometry (MS) method was developed and validated for the simultaneous determination of trace euonine and wilforidine in human plasma. An Oasis® mixed-mode cation-exchange polymeric sorbent was used for solid-phase extraction. The separation was carried out on a reversed-phase Zorbax Plus C18 column (50 mm × 2.1 mm, 1.8 ?m) by using ammonium acetate (5 mmol/L)/acetonitrile (30/70, v/v) as the mobile phase at a flow rate of 0.7 mL/min. The quantification was carried out via ion trap MS in the positive selected ion monitoring mode using aconitine as an internal standard. Calibration curves showed good linearity ranging from 0.5 to 100.0 ?g/L with correlation coefficient values >0.9990. The average recoveries of euonine and wilforidine ranged from 85.4 to 101.0% and 92.0 to 97.5%, respectively. The intra- and interday relative standard deviations were <8.7 and 12.9%, respectively. The limits of quantification for both euonine and wilforidine were 0.5 ?g/L, which is suitable in the clinical pharmaceutical research of volunteer patients with rheumatoid arthritis. PMID:23852638

Cai, Meiqiang; He, Shiwei; Shi, Yuejin; Shen, Chenyi; Jin, Micong

2013-09-01

195

Research on atmospheric pressure plasma processing sewage  

NASA Astrophysics Data System (ADS)

The water pollution has become more and more serious with the industrial progress and social development, so it become a worldwide leading environmental management problem to human survival and personal health, therefore, countries are looking for the best solution. Generally speaking, in this paper the work has the following main achievements and innovation: (1) Developed a new plasma device--Plasma Water Bed. (2) At atmospheric pressure condition, use oxygen, nitrogen, argon and helium as work gas respectively, use fiber spectrometer to atmospheric pressure plasma discharge the emission spectrum of measurement, due to the different work gas producing active particle is different, so can understand discharge, different particle activity, in the treatment of wastewater, has the different degradation effects. (3) Methyl violet solution treatment by plasma water bed. Using plasma drafting make active particles and waste leachate role, observe the decolorization, measurement of ammonia nitrogen removal.

Song, Gui-cai; Na, Yan-xiang; Dong, Xiao-long; Sun, Xiao-liang

2013-08-01

196

[Spectral investigation of atmospheric pressure plasma column].  

PubMed

Atmospheric pressure plasma column has many important applications in plasma stealth for aircraft. In the present paper, a plasma column with a length of 65 cm was generated in argon at atmospheric pressure by using dielectric barrier discharge device with water electrodes in coaxial configurations. The discharge mechanism of the plasma column was studied by optical method and the result indicates that a moving layer of light emission propagates in the upstream region. The propagation velocity of the plasma bullet is about 0.6 x 10(5) m x s(-1) through optical measurement. Spectral intensity ratios as functions of the applied voltage and driving frequency were also investigated by spectroscopic method. The variation in spectral intensity ratio implies a change in the averaged electron energy. Results show that the averaged electron energy increases with the increase in the applied voltage and the driving frequency. These results have significant values for industrial applications of the atmospheric pressure discharge and have extensive application potentials in stealth for military aircraft. PMID:23016319

Li, Xue-Chen; Chang, Yuan-Yuan; Xu, Long-Fei

2012-07-01

197

Evaluation of the Performance of Small Diode Pumped UV Solid State (DPSS) Nd:YAG Lasers as New Radiation Sources for Atmospheric Pressure Laser Ionization Mass Spectrometry (APLI-MS)  

NASA Astrophysics Data System (ADS)

The performance of a KrF* bench top excimer laser and a compact diode pumped UV solid state (DPSS) Nd:YAG laser as photo-ionizing source in LC-APLI MS is compared. The commonly applied bench-top excimer laser, operating at 248 nm, provides power densities of the order of low MW/cm2 on an illuminated area of 0.5 cm2 (8 mJ/pulse, 5 ns pulse duration, beam waist area 0.5 cm2, 3 MW/cm2). The DPSS laser, operating at 266 nm, provides higher power densities, however, on a two orders of magnitude smaller illuminated area (60 ?J/pulse, 1 ns pulse duration, beam waist area 2 × 10-3 cm2, 30 MW/cm2). In a common LC-APLI MS setup with direct infusion of a 10 nM pyrene solution, the DPSS laser yields a significantly smaller ion signal (0.9%) and signal to noise ratio (1.4%) compared with the excimer laser. With respect to the determined low detection limits (LODs) for PAHs of 0.1 fmol using an excimer laser, LODs in DPSS laser LC-APLI MS in the low pmol regime are expected. The advantages of the DPSS laser with respect to applicability (size, cost, simplicity) may render this light source the preferred one for APLI applications not focusing on ultimately high sensitivities. Furthermore, the impact of adjustable ion source parameters on the performance of both laser systems is discussed in terms of the spatial sensitivity distribution described by the distribution of ion acceptance (DIA) measurements. Perspectives concerning the impact on future APLI-MS applications are given.

Kersten, Hendrik; Lorenz, Matthias; Brockmann, Klaus J.; Benter, Thorsten

2011-06-01

198

Development of Ion Drift-Chemical Ionization Mass Spectrometry  

E-print Network

as their oxidation products can be quantified simultaneously by PTR-MS. Some desirable features offered by PTR are chemically ionized into positive or negative product ions with a well- controlled ion-molecule reaction time to yield a product ion, which is analyzed by a quadrupole mass analyzer for species identification

199

Atmospheric-pressure plasma decontamination/sterilization chamber  

DOEpatents

An atmospheric-pressure plasma decontamination/sterilization chamber is described. The apparatus is useful for decontaminating sensitive equipment and materials, such as electronics, optics and national treasures, which have been contaminated with chemical and/or biological warfare agents, such as anthrax, mustard blistering agent, VX nerve gas, and the like. There is currently no acceptable procedure for decontaminating such equipment. The apparatus may also be used for sterilization in the medical and food industries. Items to be decontaminated or sterilized are supported inside the chamber. Reactive gases containing atomic and metastable oxygen species are generated by an atmospheric-pressure plasma discharge in a He/O.sub.2 mixture and directed into the region of these items resulting in chemical reaction between the reactive species and organic substances. This reaction typically kills and/or neutralizes the contamination without damaging most equipment and materials. The plasma gases are recirculated through a closed-loop system to minimize the loss of helium and the possibility of escape of aerosolized harmful substances.

Herrmann, Hans W. (Los Alamos, NM); Selwyn, Gary S. (Los Alamos, NM)

2001-01-01

200

Atmospheric pressure plasma jet for decontamination purposes  

NASA Astrophysics Data System (ADS)

Advanced oxidation processes, especially induced by non-thermal plasmas, are widely known for their high sanitation efficiency. The paper presents general overview of atmospheric pressure plasma jet (APPJ) reactors for bactericidal decontamination purposes. In the conclusion part, the basic requirements for APPJ as a tool for biomedical applications including the treatment of living tissues are highlighted. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Paw?at, Joanna

2013-02-01

201

Characteristics of atmospheric pressure microwave plasma torch  

NASA Astrophysics Data System (ADS)

Atmospheric pressure microwave (2.45 GHz) plasma torch has been designed and built. The plasma optical and electrical characteristic have been investigated. The data has been compared with the kHz frequency rf torch. Electron temperature, density and gas temperatures are measured for different flow rates and for different gases. Optical emission spectrometer and ICCD camera are used to measure the argon and helium plasma characteristics and the results are compared for both designs. This Work has been supported by TUBITAK TEYDEB project no:9100036

Bozduman, Ferhat; Teke, Erdogan; Gulec, Ali; Oksuz, Lutfi

2012-10-01

202

Healing burns using atmospheric pressure plasma irradiation  

NASA Astrophysics Data System (ADS)

An experiment testing the effects of plasma irradiation with an atmospheric-pressure plasma (APP) reactor on rats given burns showed no evidence of electric shock injuries upon pathology inspection of the irradiated skin surface. In fact, the observed evidence of healing and improvement of the burns suggested healing effects from plasma irradiation. The quantities of neovascular vessels in the living tissues at 7 days were 9.2 ± 0.77 mm-2 without treatment and 18.4 ± 2.9 mm-2 after plasma irradiation.

Hirata, Takamichi; Kishimoto, Takumi; Tsutsui, Chihiro; Kanai, Takao; Mori, Akira

2014-01-01

203

Seasonal buffering of atmospheric pressure on Mars  

NASA Technical Reports Server (NTRS)

An isothermal reservoir of carbon dioxide in gaseous contact with the Martian atmosphere would reduce the amplitude and advance the phase of global atmospheric pressure fluctuations caused by seasonal growth and decline of polar CO2 frost caps. Adsorbed carbon dioxide in the upper roughly 10 m of Martian regolith is sufficient to buffer the present atmosphere on a seasonal basis. Available observations and related polar cap models do not confirm or refute the operation of such a mechanism. Implications for the amplitude and phase of seasonal pressure fluctuations are subject to direct test by the upcoming Viking mission to Mars.

Dzurisin, D.; Ingersoll, A. P.

1975-01-01

204

Protein destruction by atmospheric pressure glow discharges  

SciTech Connect

It is well established that atmospheric pressure glow discharges are capable of bacterial inactivation. Much less known is their ability to destruct infectious proteins, even though surgical instruments are often contaminated by both bacteria and proteinaceous matters. In this letter, the authors present a study of protein destruction using a low-temperature atmospheric dielectric-barrier discharge jet. Clear evidences of protein removal are presented with data of several complimentary experiments using scanning electron microscopy, electron dispersive x-ray analysis, electrophoresis, laser-induced fluorescence microscopy, and protein reduction kinetics. Considerable degradation is observed of protein fragments that remain on their substrate surface after plasma treatment.

Deng, X. T.; Shi, J. J.; Chen, H. L.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom); MRC Toxicology Unit, University of Leicester, Leicester, Leicestershire LE1 9HN (United Kingdom); Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom)

2007-01-01

205

Diagnostics of plasma-biological surface interactions in low pressure and atmospheric pressure plasmas  

NASA Astrophysics Data System (ADS)

Mechanisms of plasma-surface interaction are required to understand in order to control the reactions precisely. Recent progress in atmospheric pressure plasma provides to apply as a tool of sterilization of contaminated foodstuffs. To use the plasma with safety and optimization, the real time in situ detection of free radicals - in particular dangling bonds by using the electron-spin-resonance (ESR) technique has been developed because the free radical plays important roles for dominantly biological reactions. First, the kinetic analysis of free radicals on biological specimens such as fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge. We have obtained information that the in situ real time ESR signal from the spores was observed and assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal was correlated with a link to the inactivation of the fungal spore. Second, we have studied to detect chemical modification of edible meat after the irradiation. Using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF-MS) and ESR, signals give qualification results for chemical changes on edible liver meat. The in situ real-time measurements have proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

Ishikawa, Kenji; Hori, Masaru

2014-08-01

206

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2010-05-03

207

Atmospheric pressure photoionization mass spectrometry as a tool for the investigation of the hydrolysis reaction mechanisms of phosphite antioxidants  

NASA Astrophysics Data System (ADS)

The hydrolysis reaction mechanism of phosphite antioxidants is investigated by liquid chromatography-mass spectrometry (LC/MS). The phosphites were chosen because they differed in chemical structure and phosphorus content. Dopant assisted-atmospheric pressure photoionization (DA-APPI) is chosen as the ion source for the ionization of the compounds. In our previous work, DA-APPI was shown to offer an attractive alternative to atmospheric pressure chemical ionization (APCI) since it provided background-ion free mass spectra and higher sensitivity [M. Papanastasiou, et al., Polymer Degradation and Stability 91 (11) (2006) 2675-2682]. In positive ion mode, the molecules are generally detected in their protonated form. In negative ion mode, the phosphites are unstable and only fragment ions are observed; these however, are characteristic of each phosphite and may be used for the identification of the analytes in complex mixtures. The analytes under investigation are exposed to accelerated humid ageing conditions and their hydrolytic pathway and stability is investigated. Different substituents around the phosphorus atom are shown to have a significant effect on the stability of the phosphites, with phenol substituents producing very hydrolytically stable structures. Alkanox P24 and PEP-36 follow a similar hydrolytic pathway via the scission of the first and then the second POphenol bonds, eventually leading to the formation of phenol, phosphorous acid and pentaerythritol as end products. HP-10 exhibits a rather different structure and the products detected suggest scission of either the POhydrocarbon or one of the POphenol bonds. A phenomenon similar to that of autocatalysis is observed for all phosphites and is attributed to the formation of dialkyl phosphites as intermediate products.

Papanastasiou, M.; McMahon, A. W.; Allen, N. S.; Johnson, B. W.; Keck-Antoine, K.; Santos, L.; Neumann, M. G.

2008-08-01

208

Direct determination of trace nitrogen dioxide by atmospheric pressure lonization mass spectrometry (APIMS) without conversion to nitric oxide  

Microsoft Academic Search

The aim of this study was to develop a new method for the determination of NO2 levels encountered in clinical settings as well as in environmental studies, using a bi-component atmospheric pressure ionization\\u000a mass spectrometry (APIMS). Hydrogen (1%) diluted in pure argon was ionized by corona discharge in the first ionization component.\\u000a Fifty ml of the analyte diluted in 250

Takaaki Kinoue; Satoshi Asai; Yukimoto Ishii; Koichi Ishikawa; Masashi Fujii; Kazuo Nakano; Keiji Hasumi

2000-01-01

209

Air circulation under reduced atmospheric pressures  

NASA Astrophysics Data System (ADS)

The control of heat exchange is vital for plant life in off-world, low pressure, greenhouses. The ability to control this process was limited by methodology and technology. Mathematical models, based on classical mechanics are created to enhance our control capabilities. Data is collected using various sensors placed inside the Low Pressure Test Bed (LPTB) Chamber at Kennedy Space Center. Data from those sensors became non-linear at various pressures below 25 kPa. We introduced mathematical calibration corrections and found that sensor data linearity could be extended to a greater range of pressures. These calibration corrections allow for sensor calibration corrections in operational environments that differ from the environment of calibration (normal Earth atmospheric pressure).

Hillhouse, Lendell E.

210

Atmospheric pressure loading displacement of SLR stations  

NASA Astrophysics Data System (ADS)

This paper addresses the local displacement at ground stations of the world-wide Satellite Laser Ranging (SLR) network induced by atmospheric pressure variations. Since currently available modelling options do not satisfy the requirements for the target application (real-time availability, complete coverage of SLR network), a new representation is developed. In a first step, the 3-dimensional displacements are computed from a 6-hourly grid of 1°×1° global pressure data obtained from the ECMWF, for the period 1997-2002. After having been converted into pressure anomalies, this pressure grid is propagated into horizontal and vertical station displacements using Green's functions and integrating contributions covering the entire globe; oceans are assumed to follow the inverted barometer (IB) approximation. In the next step, a linear regression model is developed for each station that approximates the time-series of the predicted vertical displacements as well as possible; this regression model relates the vertical displacement of a particular station to the local (and instantaneous) pressure anomaly. It is shown that such a simple model may represent the actual vertical displacements with an accuracy of better than 1 mm; horizontal displacements are shown to be negligible. Finally, the regression model is tested on actual SLR data on the satellites LAGEOS-1 and LAGEOS-2, covering the period January 2002 until April 2003 (inclusive). Also, two model elements are shown to be potential risk factors: the global pressure field representation (for the convolution method) and the local reference pressure (for the regression method). The inclusion of the atmospheric pressure displacement model gives improvements on most of the elements of the computations, although the effects are smaller than expected since the nominal effect is absorbed by solved-for satellite parameters.

Bock, D.; Noomen, R.; Scherneck, H.-G.

2005-04-01

211

Fat Liquefaction of Adipose Tissue Using Atmospheric-Pressure Plasma Irradiation  

NASA Astrophysics Data System (ADS)

The liquefaction of fat in adipose tissue for potential medical applications was achieved by direct irradiation using an atmospheric-pressure plasma source and a catheter-type apparatus. When fat was irradiated with plasma generated from a catheter tip, it was liquefied through ozonolysis, although little production and diffusion of ozone originating from the collision/ionization of gas molecules was observed in preliminary experiments. Furthermore, surface damage to fat cells, such as thermal carbonization or electric shock injuries, was not observed.

Hirata, Takamichi; Tsutsui, Chihiro; Kishimoto, Takumi; Mori, Akira; Akiya, Masahiro; Yamamoto, Toshiaki; Taguchi, Akira

2011-08-01

212

Protein patterning utilizing region-specific control of wettability by surface modification under atmospheric pressure  

NASA Astrophysics Data System (ADS)

Wettability control can be crucial in improving the uniformity of selective protein immobilization in high-density microarrays. In this study, we propose an atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD)-based method in conjunction with photolithography to implement region-specific control of wettability on Si substrate. The proposed PECVD method under atmospheric pressure condition would be a useful alternative of conventional reactive plasma-based treatments methods requiring vacuum condition for uniform protein patterning. Layers with dissimilar wettability and roughness prepared by AP-PECVD process using tetraethoxysilane (TEOS) or TEOS-O2 as precursors could realize uniform protein patterning in a micrometer-scale.

Lee, Donghee; Kwon, Min-Sung; Hyun, Ji-Chul; Jun, Chang-Duk; Chung, Euiheon; Yang, Sung

2013-09-01

213

Reforming of methane and carbon dioxide by DC water plasma at atmospheric pressure  

Microsoft Academic Search

An experimental plasma chemical reactor, equipped with a novel water plasma torch, was used for reforming methane and carbon dioxide mixture to produce synthesis gas (syngas). Water plasma is generated by the torch at atmospheric pressure, in the absence of carrier gases, water cooling system and special steam supply system. The influence of the ratio of CO2 to CH4 and

Guohua Ni; Yan Lan; Cheng Cheng; Yuedong Meng; Xiangke Wang

2011-01-01

214

Chaos in atmospheric-pressure plasma jets  

NASA Astrophysics Data System (ADS)

We report detailed characterization of a low-temperature atmospheric-pressure plasma jet that exhibits regimes of periodic, quasi-periodic and chaotic behaviors. Power spectra, phase portraits, stroboscopic section and bifurcation diagram of the discharge current combine to comprehensively demonstrate the existence of chaos, and this evidence is strengthened with a nonlinear dynamics analysis using two control parameters that maps out periodic, period-multiplication, and chaotic regimes over a wide range of the input voltage and gas flow rate. In addition, optical emission signatures of excited plasma species are used as the second and independent observable to demonstrate the presence of chaos and period-doubling in both the concentrations and composition of plasma species, suggesting a similar array of periodic, quasi-periodic and chaotic regimes in plasma chemistry. The presence of quasi-periodic and chaotic regimes in structurally unbounded low-temperature atmospheric plasmas not only is important as a fundamental scientific topic but also has interesting implications for their numerous applications. Chaos may be undesirable for industrial applications where cycle-to-cycle reproducibility is important, yet for treatment of cell-containing materials including living tissues it may offer a novel route to combat some of the major challenges in medicine such as drug resistance. Chaos in low-temperature atmospheric plasmas and its effective control are likely to open up new vistas for medical technologies.

Walsh, J. L.; Iza, F.; Janson, N. B.; Kong, M. G.

2012-06-01

215

DC powered atmospheric pressure micro-plasmajet for biomedical applications  

Microsoft Academic Search

Summary form only given. Nonthermal (cold) plasmas operated in air at atmospheric pressure offer an appealing method for the processing and decontamination of surfaces. Most existing devices are operated with radiofrequency high voltages. Microhollow cathode discharges (MHCDs), on the other hand, allow us to generate a direct current driven plasma jet in atmospheric pressure gases, including air. The discharge is

J. F. Kolb; R. O. Price; A.-A. H. Mohamed; K. H. Schoenbach

2006-01-01

216

Atmospheric pressure loading effects on Global Positioning System coordinate determinations  

Microsoft Academic Search

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is

Tonie M. vanDam; Geoffrey Blewitt; Michael B. Heflin

1994-01-01

217

Driven Motion and Instability of an Atmospheric Pressure Arc  

E-print Network

Driven Motion and Instability of an Atmospheric Pressure Arc Max Karasik A Dissertation Presented. All rights reserved. #12; Abstract Atmospheric pressure arcs are used extensively in applications to my parents, Isak and Natalie, and to my grandparents, Stashek and Nina. #12; vi #12; Acknowledgments

218

Driven Motion and Instability of an Atmospheric Pressure Arc  

E-print Network

Driven Motion and Instability of an Atmospheric Pressure Arc Max Karasik A Dissertation Presented rights reserved. #12;Abstract Atmospheric pressure arcs are used extensively in applications to my parents, Isak and Natalie, and to my grandparents, Stashek and Nina. #12;vi #12;Acknowledgments I

219

Atmospheric pressure helium afterglow discharge detector for gas chromatography  

Microsoft Academic Search

An electrodeless discharge apparatus is described for use in producing atmospheric pressure afterglows from helium as an element specific, multielemental gas chromatography detector comprising: a discharge tube having an upper open end, and a lower end means for supplying helium at atmospheric pressure to the discharge tube, a first electrode concentrically encircling at least a portion of the tube near

G. Rice; A. DSilva; V. A. Fassel

1986-01-01

220

Methods for estimating the bioconcentration factor of ionizable organic chemicals.  

PubMed

The bioaccumulation potential is an important criterion in risk assessment of chemicals. Several regressions between bioconcentration factor (BCF) in fish and octanol-water partition coefficient (K(OW)) have been developed for neutral organic compounds, but very few approaches address the BCF of ionizable compounds. A database with BCFs of 73 acids and 65 bases was collected from the literature. The BCF estimation method recommended by the Technical Guidance Document (TGD) for chemical risk assessment in the European Union was tested for ionizing substances using log K(OW) (corrected for the neutral species, log[ f(n) x K(OW)]) and log D (sum of log K(OW) of neutral and ionic molecule, apparent log K(OW)) as predictors. In addition, the method of Meylan et al. (Environ Toxicol Chem 1999; 18:664-672) for ionizable compounds and a dynamic cell model based on the Fick- Nernst-Planck equation were tested. Moreover, our own regressions for the BCF were established from log K(OW) and pK(a). The bioaccumulation of lipophilic compounds depends mainly on their lipophilicity, and the best predictor is log D. Dissociation, the pH-dependent ion trap, and electrical attraction of cations impact the BCF. Several methods showed acceptable results. The TGD regressions gave good predictions when log( f(n) x K(OW)) or log D were used as a predictor instead of log K(OW). The new regressions to log K(OW) and pK(a) performed similarly, with mean errors of approximately 0.4. The method of Meylan et al. did not perform as well. The cell model showed weak results for acids but was among the best methods for bases. PMID:19245273

Fu, Wenjing; Franco, Antonio; Trapp, Stefan

2009-07-01

221

Atmospheric pressure plasma jet with high-voltage power supply based on piezoelectric transformer.  

PubMed

The dielectric barrier discharge plasma jet, an example of the nonthermal atmospheric pressure plasma jet (APPJ), generates low-temperature plasmas that are suitable for the atomization of volatile species and can also be served as an ionization source for ambient mass and ion mobility spectrometry. A new design of APPJ for mass spectrometry has been built in our group. In these plasma sources magnetic transformers (MTs) and inductors are typically used in power supplies but they present several drawbacks that are even more evident when dealing with high-voltage normally used in APPJs. To overcome these disadvantages, high frequency generators with the absence of MT are proposed in the literature. However, in the case of miniaturized APPJs these conventional power converters, built of ferromagnetic cores and inductors or by means of LC resonant tank circuits, are not so useful as piezoelectric transformer (PT) based power converters due to bulky components and small efficiency. We made and examined a novel atmospheric pressure plasma jet with PT supplier served as ionization source for ambient mass spectrometry, and especially mobile spectrometry where miniaturization, integration of components, and clean plasma are required. The objective of this paper is to describe the concept, design, and implementation of this miniaturized piezoelectric transformer-based atmospheric pressure plasma jet. PMID:24880391

Babij, Micha?; Kowalski, Zbigniew W; Nitsch, Karol; Silberring, Jerzy; Gotszalk, Teodor

2014-05-01

222

Comparison of electrospray ionization and atmospheric pressure chemical ionization for multi-residue analysis of biocides, UV-filters and benzothiazoles in aqueous matrices and activated sludge by liquid chromatography–tandem mass spectrometry  

Microsoft Academic Search

This paper describes the development of a multi-residue method for the determination of 36 emerging organic pollutants (26 biocides, 5 UV-filters and 5 benzothiazoles) in raw and treated wastewater, activated sludge and surface water using liquid chromatography–tandem mass spectrometry (LC–MS\\/MS). The target analytes were enriched from water samples adjusted to pH 6 by solid-phase extraction (SPE) on Oasis HLB 200mg

Arne Wick; Guido Fink; Thomas A. Ternes

2010-01-01

223

Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy  

NASA Astrophysics Data System (ADS)

An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

2013-11-01

224

Design and performance of an atmospheric pressure sampling interface for ion-trap/time-of-flight mass spectrometry  

SciTech Connect

An ion-trap/time-of-flight mass spectrometer in combination with an atmospheric pressure sampling interface was developed in order to simultaneously profit from the ease of sample handling at ambient pressure, from the storage and accumulation capabilities of an ion trap, and from the acquisition speed and sensitivity of a time-of-flight mass spectrometer. The sampling interface is an intermediate-pressure vacuum manifold that serves to enrich sampled analytes by jet separation with respect to the carrier gas (air) and simultaneously maintain vacuum conditions inside the ion-trap/time-of-flight instrument. Neutral analyte molecules are sampled and later ionized either by electron impact or chemical ionization. Ion accumulation is performed with a rf-only quadrupole ion trap with ground potential on the end caps during storage. For mass analysis, the trap's electrodes serve as a pulsed ion source for the attached linear time-of-flight mass spectrometer. In addition, laser desorbed molecules can also be sampled with this kind of instrument. Successful operation is shown by analyzing volatile substances (aniline, bromobenzene, styrene, and perfluorotributylamine), as well as laser-desorbed organic solids. Figures of merit include a sensitivity of 10 ppm, resolving power of 300 and demonstration of a mass spectrum of laser-desorbed anthracene with a signal-to-noise ratio of 270.

Setz, Patrick D.; Schmitz, Thomas A.; Zenobi, Renato [Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich (Switzerland)

2006-02-15

225

Visualization of a Copper Wire Explosion in Atmospheric Pressure Air  

E-print Network

Experimental and computational images of a 90-?m thick copper wire explosion in atmospheric pressure air are presented. A Marx generator is used to produce a pulsed current density into the wire with a maximum rate of rise ...

Jadidian, Jouya

226

Investigating Atmospheric Pressure with a Cup, Straw and Water  

NSDL National Science Digital Library

This activity is a reinforcement lab activity where students experiment with ways to get water to flow out of a cup and up a straw causing an imbalance in the atmospheric pressure surrounding the water.

227

Atmospheric pressure non-thermal plasma: Sources and applications  

Microsoft Academic Search

Non-thermal plasma at atmospheric pressure is an inherently unstable object. Nature of discharge plasma instabilities and conditions for observation of uniform non-thermal plasma at atmospheric pressure in different environments will be discussed. Various discharge techniques have been developed, which could support uniform non-thermal plasma with parameters varied in a wide range. Time limitation by plasma instabilities can be overcome by

A. P. Napartovich

2008-01-01

228

Characterization of a steam plasma jet at atmospheric pressure  

NASA Astrophysics Data System (ADS)

An atmospheric steam plasma jet generated by an original dc water plasma torch is investigated using electrical and spectroscopic techniques. Because it directly uses the water used for cooling electrodes as the plasma-forming gas, the water plasma torch has high thermal efficiency and a compact structure. The operational features of the water plasma torch and the generation of the steam plasma jet are analyzed based on the temporal evolution of voltage, current and steam pressure in the arc chamber. The influence of the output characteristics of the power source, the fluctuation of the arc and current intensity on the unsteadiness of the steam plasma jet is studied. The restrike mode is identified as the fluctuation characteristic of the steam arc, which contributes significantly to the instabilities of the steam plasma jet. In addition, the emission spectroscopic technique is employed to diagnose the steam plasma. The axial distributions of plasma parameters in the steam plasma jet, such as gas temperature, excitation temperature and electron number density, are determined by the diatomic molecule OH fitting method, Boltzmann slope method and H? Stark broadening, respectively. The steam plasma jet at atmospheric pressure is found to be close to the local thermodynamic equilibrium (LTE) state by comparing the measured electron density with the threshold value of electron density for the LTE state. Moreover, based on the assumption of LTE, the axial distributions of reactive species in the steam plasma jet are estimated, which indicates that the steam plasma has high chemical activity.

Ni, Guohua; Zhao, Peng; Cheng, Cheng; Song, Ye; Toyoda, Hirotaka; Meng, Yuedong

2012-02-01

229

Martian Atmospheric Pressure Static Charge Elimination Tool  

NASA Technical Reports Server (NTRS)

A Martian pressure static charge elimination tool is currently in development in the Electrostatics and Surface Physics Laboratory (ESPL) at NASA's Kennedy Space Center. In standard Earth atmosphere conditions, static charge can be neutralized from an insulating surface using air ionizers. These air ionizers generate ions through corona breakdown. The Martian atmosphere is 7 Torr of mostly carbon dioxide, which makes it inherently difficult to use similar methods as those used for standard atmosphere static elimination tools. An initial prototype has been developed to show feasibility of static charge elimination at low pressure, using corona discharge. A needle point and thin wire loop are used as the corona generating electrodes. A photo of the test apparatus is shown below. Positive and negative high voltage pulses are sent to the needle point. This creates positive and negative ions that can be used for static charge neutralization. In a preliminary test, a floating metal plate was charged to approximately 600 volts under Martian atmospheric conditions. The static elimination tool was enabled and the voltage on the metal plate dropped rapidly to -100 volts. This test data is displayed below. Optimization is necessary to improve the electrostatic balance of the static elimination tool.

Johansen, Michael R.

2014-01-01

230

Inactivation of microbes and macromolecules by atmospheric-pressure plasma jets.  

PubMed

Plasma is ionized gas, which is found in various forms in nature and can also be generated artificially. A variety of cold atmospheric-pressure plasmas are currently being investigated for their clinical utility, and first studies reporting on the treatment of patients showed that plasma treatment may support the wound healing process. One of the benefits of plasma treatment is the effective inactivation of bacteria including tenacious pathogens such as Pseudomonas aeruginosa or multiresistant Staphylococcus aureus (MRSA). Neither the molecular mechanisms promoting wound healing nor those underlying bacterial inactivation are fully understood yet. The review has a focus on plasma jets, a particular type of cold atmospheric-pressure plasma sources featuring an indirect treatment whereby the treated substrates do not come into contact with the plasma directly but are exposed to the plasma-emitted reactive species and photons. Such plasma jets are being employed as tools in basic research regarding the effects of plasmas on biological samples. This review provides a brief overview on the recent clinical investigations into the benefits of cold atmospheric-pressure plasmas. It then describes our current understanding of the mechanisms leading to bacterial inactivation and inactivation of biomacromolecules gained by employing plasma jets. PMID:24841116

Lackmann, Jan-Wilm; Bandow, Julia Elisabeth

2014-07-01

231

Analysis of Ternary InGaN Layers Grown By Atmospheric Pressure Vertical MOVPE  

SciTech Connect

We present a study on the n-type ternary InGaN layers grown by atmospheric pressure vertical metal organic chemical vapor deposition on GaN template/(0001) sapphire substrate. An investigation in the different growth conditions on n-type of the InxGa1-xN, alloys was made for three series samples. Structural, electrical and optical properties were characterized by High X-Ray Diffraction, Hall effect and Photoluminescence respectively.

Yildiz, A.; Ozturk, M. K.; Kasap, M. [Department of Physics, Gazi University, Ankara (Turkey)

2007-04-23

232

Investigation of ion-ion-recombination at atmospheric pressure with a pulsed electron gun.  

PubMed

For future development of simple miniaturized sensors based on pulsed atmospheric pressure ionization as known from ion mobility spectrometry, we investigated the reaction kinetics of ion-ion-recombination to establish selective ion suppression as an easy to apply separation technique for otherwise non-selective ion detectors. Therefore, the recombination rates of different positive ion species, such as protonated water clusters H(+)(H(2)O)(n) (positive reactant ions), acetone, ammonia and dimethyl-methylphosphonate ions, all recombining with negative oxygen clusters O(2)(-)(H(2)O)(n) (negative reactant ions) in a field-free reaction region, are measured and compared. For all experiments, we use a drift tube ion mobility spectrometer equipped with a non-radioactive electron gun for pulsed atmospheric pressure ionization of the analytes. Both, ionization and recombination times are controlled by the duty cycle and repetition rate of the electron emission from the electron gun. Thus, it is possible to investigate the ion loss caused by ion-ion-recombination depending on the recombination time defined as the time delay between the end of the electron emission and the ion injection into the drift tube. Furthermore, the effect of the initial total ion density in the reaction region on the ion-ion-recombination rate is investigated by varying the density of the emitted electrons. PMID:22977880

Heptner, Andre; Cochems, Philipp; Langejuergen, Jens; Gunzer, Frank; Zimmermann, Stefan

2012-11-01

233

Alfvén ionization in exoplanetary atmospheres  

NASA Astrophysics Data System (ADS)

Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest such objects harbour an atmospheric, localized plasma. For lowmass objects, the degree of thermal ionization is insufficient to qualify the ionized gas as a plasma, posing the question: what ionization processes can efficiently produce the required plasma? We propose Alfvén ionization as a simple mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficiently large degrees of ionization (? 10^-7) that they constitute plasmas. We outline the criteria required for Alfvén ionization to occur and justify it's applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs and M-dwarfs for both solar and sub-solar metallicities. We find that Alfvén ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization ranging from 10^-6-1 can be obtained. Observable consequences include continuum Bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g. He, Mg, H2 or CO lines). Forbidden lines are also expected from the metastable population as a consequence of the Penning Effect. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models.

Stark, C. R.; Helling, Ch.; Diver, D. A.; Rimmer, P. B.

2013-09-01

234

Emission properties of an atmospheric-pressure helium plasma jet generated by a barrier discharge  

NASA Astrophysics Data System (ADS)

The emission properties of an atmospheric-pressure helium plasma jet generated by a barrier discharge in a capillary blown with helium are studied. The spectral composition of the radiation of the studied plasma jet and the spatial-spectral distribution of its intensity are investigated in detail. It is shown that the emission spectrum of the generated plasma jet outside the capillary consists mainly of electronic-vibrational transitions of the first negative system of ionized nitrogen molecules N{2/+}( B 2?{/u +} ? X 2?{/g +}) and the second positive system of neutral nitrogen molecules N2( C 3? u ? B 3? g ).

Korbut, A. N.; Kelman, V. A.; Zhmenyak, Yu. V.; Klenovskii, M. S.

2014-06-01

235

A Micro-Orifice Volatilization Impactor coupled to a Chemical Ionization Mass Spectrometer for the detection of organic acids in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Significant uncertainties related to sources and removal processes of particulate organic matter persist due, in part, to a poor understanding of the molecular-level composition. To address these issues, we are developing a novel technique that couples a micro-orifice volatilization impactor (MOVI) to a chemical ionization mass spectrometer (CIMS) for fast, in situ measurements of specific organic acids expected to be in atmospheric particles. The MOVI-CIMS process has three steps: 1) aerosol collection by inertial impaction, 2) volatilization and sample transfer, and 3) chemical ionization and detection using a quadrupole mass spectrometer. We present results from laboratory characterization of two MOVI designs, one operating at low pressure (60 Torr) and the other at near ambient pressure. The low-pressure impactor has a theoretical cut point of 40nm while the atmospheric pressure impactor (API) has a theoretical cut point of 280nm with a pressure drop of less than 5%. We compare the advantages and disadvantages of these two designs in terms of typical atmospheric particle size distributions. Experimental tests of their theoretical cut-points are used to assess the importance of jet-to- plate distance and particle bounce. In addition, we demonstrate the utility of the MOVI-CIMS technique by employing it in studies of heterogeneous oxidation of particle organics and of secondary organic aerosol formation from biogenic hydrocarbon oxidation. Based on typical signal-to-noise ratio, the MOVI-CIMS demonstrates a detection limit of ~50 ng for monocarboxylic acids when using the LPI version and the iodide ion as a chemical ionization reagent. Preliminary results suggest even lower detection limits are possible with other reagent ions.

Yatavelli, R. L.; Thornton, J. A.

2007-12-01

236

Free radicals induced in aqueous solution by non-contact atmospheric-pressure cold plasma  

SciTech Connect

To understand plasma-induced chemical processing in liquids, we investigated the formation of free radicals in aqueous solution exposed to different types of non-contact atmospheric-pressure helium plasma using the spin-trapping technique. Both hydroxyl radical (OH{center_dot}) and superoxide anion radical (O{sub 2}{sup -}{center_dot}) adducts were observed when neutral oxygen gas was additionally supplied to the plasma. In particular, O{sub 2}{sup -}{center_dot} can be dominantly induced in the solution via oxygen flow into the afterglow gas of helium plasma. This type of plasma treatment can potentially be used in medical applications to control infectious diseases, because the O{sub 2}{sup -}{center_dot} is crucial for sterilization of liquids via atmospheric-pressure plasma.

Tani, Atsushi; Fukui, Satoshi [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Ono, Yusuke; Kitano, Katsuhisa [Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Ikawa, Satoshi [Technology Research Institute of Osaka Prefecture, Izumi, Osaka 594-1157 (Japan)

2012-06-18

237

Atmospheric Pressure non-thermal plasmas for surface treatment of polymer films  

NASA Astrophysics Data System (ADS)

Interest has grown over the past few years in applying atmospheric pressure non-thermal plasmas to surface treatment. In this work, we used an asymmetric glow dielectric-barrier discharge (GDBD), at atmospheric pressure in nitrogen, to improve the surface hydrophilicity of three kinds of polymer films, biaxially oriented polypropylene (BOPP), polyimide (PI), and triacetyl cellulose (TAC). This set-up consists of two asymmetric electrodes covered by dielectrics. And to prevent the filamentary discharge occur, the frequency, gas flow rate and uniformity of gas flow distribution should be carefully controlled. The discharge performance is monitored through an oscilloscope, which is connected to a high voltage probe and a current monitor. The physical and chemical properties of polymer surfaces before and after GDBD treatment were analyzed via water contact angle (CA) measurements, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) techniques.

Huang, Hsiao-Feng; Wen, Chun-Hsiang; Wei, Hsiao-Kuan; Kou, Chwung-Shan

2006-10-01

238

Tailoring non-equilibrium atmospheric pressure plasmas for healthcare technologies  

NASA Astrophysics Data System (ADS)

Non-equilibrium plasmas operated at ambient atmospheric pressure are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. This includes the unique opportunity to deliver short-lived highly reactive species such as atomic oxygen and atomic nitrogen. Reactive oxygen and nitrogen species can initiate a wide range of reactions in biochemical systems, both therapeutic and toxic. The toxicological implications are not clear, e.g. potential risks through DNA damage. It is anticipated that interactions with biological systems will be governed through synergies between two or more species. Suitable optimized plasma sources are improbable through empirical investigations. Quantifying the power dissipation and energy transport mechanisms through the different interfaces from the plasma regime to ambient air, towards the liquid interface and associated impact on the biological system through a new regime of liquid chemistry initiated by the synergy of delivering multiple energy carrying species, is crucial. The major challenge to overcome the obstacles of quantifying energy transport and controlling power dissipation has been the severe lack of suitable plasma sources and diagnostic techniques. Diagnostics and simulations of this plasma regime are very challenging; the highly pronounced collision dominated plasma dynamics at very small dimensions requires extraordinary high resolution - simultaneously in space (microns) and time (picoseconds). Numerical simulations are equally challenging due to the inherent multi-scale character with very rapid electron collisions on the one extreme and the transport of chemically stable species characterizing completely different domains. This presentation will discuss our recent progress actively combining both advance optical diagnostics and multi-scale computer simulations.

Gans, Timo

2012-10-01

239

The kinetic ion mobility mass spectrometer: Measurements of ion-molecule reaction rate constants at atmospheric pressure  

SciTech Connect

This paper discusses how the kinetic ion mobility mass spectrometer is used to measure the rate constants of ion-molecule reactions in an atmospheric pressure buffer gas. One operational mode of the instrument avoids measurement errors associated with aperture sampling of a high-pressure ionized gas. This instrument is used to study the S{sub N}2 nucleophilic displacement reactions of chloride anions with a series of alkyl bromides in nitrogen. 40 refs., 13 figs., 2 tabs.

Giles, K.; Grimsrud, E.P. [Montana State Univ., Bozeman, MT (United States)

1992-08-06

240

Volume 52, number 3 CHEMICAL PHYSICS LETTERS 15 December 1977 MULTIPHOTON IONIZATION  

E-print Network

Volume 52, number 3 CHEMICAL PHYSICS LETTERS 15 December 1977 MULTIPHOTON IONIZATION: A METHOD state distribution of this molecule. A tunable dye laser is swept through the w.ivclen$h region of the Naz B-X system and positive ions are counted as a function of laser wavelength. Multiphoton ionization

Zare, Richard N.

241

The morphology and chemistry evolution of fused silica surface after Ar/CF4 atmospheric pressure plasma processing  

NASA Astrophysics Data System (ADS)

In order to reveal the plasma etching processes on fused silica, the surface characterizations of fused silica after Ar/CF4 atmospheric pressure plasma processing were investigated. The morphology and chemistry evolution of fused silica surface were analyzed by AFM and XPS respectively. The AFM micrographs exhibited the three-dimensional surface topography and the RMS roughness changed with the increase of the material removal depth. The surfaces appeared to become smoother when the plasma etching occurred on the surface top layer. However, after the chemically modified layer was removed, etching resulted in the formation of a series of pits. During extended etching, the individual pits coalesced with one another, and the coalescence provided a means of reducing the depth of subsurface damage and the RMS roughness. The XPS results illustrated that small amount of radicals including C-CFn and CF-CFn could be introduced onto the fused silica surface during the Ar/CF4 plasma process, the fluorocarbon radicals were generated during CF4 plasma ionization. And the changes in relative concentration of the fluorocarbon radicals C-CFn with the removal depth were also studied.

Jin, Huiliang; Xin, Qiang; Li, Na; Jin, Jiang; Wang, Bo; Yao, Yingxue

2013-12-01

242

PULSED POSITIVE ION NEGATIVE ION CHEMICAL IONIZATION MASS SPECTROMETRIC APPLICATONS TO ENVIRONMENTAL AND HAZARDOUS WASTE ANALYSIS  

EPA Science Inventory

The simultaneous acquisition of both positive ion and negative ion data under chemical ionization mass spectrometric conditions can aid in the confirmation of assignments made by electron impact gas chromatography mass spectrometry or electron capture gas chromatography. Pulsed p...

243

A study of the tropospheric oxidation of volatile organic compounds using chemical ionization mass spectrometry  

E-print Network

The mechanisms and kinetics of reactions important to the troposphere have been investigated using a high pressure, turbulent, discharge-flow technique coupled to a chemical ionization mass spectrometer. The ability to ...

Broekhuizen, Keith Edward, 1974-

2002-01-01

244

ANNUAL REPORT. ATMOSPHERIC-PRESSURE PLASMA CLEANING OF CONTAMINATED SURFACES  

EPA Science Inventory

The objective of this work is to demonstrate a practical, atmospheric pressure plasma tool for the surface decontamination of nuclear waste. Decontamination of radioactive materials that have accumulated on the surfaces of equipment and structures is a challenging and costly unde...

245

Atmospheric Pressure Plasma Jet Treatment of Polyethylene Surfaces for  

E-print Network

, composite materials and metals need a pretreatment step before adhesive bonding or painting.[1 analysis and adhesive bonding experiments. The plasma is characterized by optical emission spectroscopy) samples were activated by an atmospheric pressure plasma jet. The improvement in adhesive bond strength

Greifswald, Ernst-Moritz-Arndt-Universität

246

Atmospheric pressure helium afterglow discharge detector for gas chromatography  

Microsoft Academic Search

An apparatus for providing a simple, low-frequency electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

Gary Rice; Arthur P. DSilva; Velmer A. Fassel

1986-01-01

247

Atmospheric pressure helium afterglow discharge detector for gas chromatography  

Microsoft Academic Search

An apparatus for providing a simple, low-frequency, electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

G. Rice; A. P. DSilva; V. A. Fassel

1985-01-01

248

Atmospheric pressure and suicide attempts in Helsinki, Finland  

NASA Astrophysics Data System (ADS)

The influence of weather on mood and mental health is commonly debated. Furthermore, studies concerning weather and suicidal behavior have given inconsistent results. Our aim was to see if daily weather changes associate with the number of suicide attempts in Finland. All suicide attempts treated in the hospitals in Helsinki, Finland, during two separate periods, 8 years apart, were included. Altogether, 3,945 suicide attempts were compared with daily weather parameters and analyzed with a Poisson regression. We found that daily atmospheric pressure correlated statistically significantly with the number of suicide attempts, and for men the correlation was negative. Taking into account the seasonal normal value during the period 1971-2000, daily temperature, global solar radiation and precipitation did not associate with the number of suicide attempts on a statistically significant level in our study. We concluded that daily atmospheric pressure may have an impact on suicidal behavior, especially on suicide attempts of men by violent methods ( P < 0.001), and may explain the clustering of suicide attempts. Men seem to be more vulnerable to attempt suicide under low atmospheric pressure and women under high atmospheric pressure. We show only statistical correlations, which leaves the exact mechanisms of interaction between weather and suicidal behavior open. However, suicidal behavior should be assessed from the point of view of weather in addition to psychiatric and social aspects.

Hiltunen, Laura; Ruuhela, Reija; Ostamo, Aini; Lönnqvist, Jouko; Suominen, Kirsi; Partonen, Timo

2012-11-01

249

Atmospheric pressure variation and the climate of Mars  

NASA Technical Reports Server (NTRS)

If Mars has permanent CO2 polar caps, atmospheric heat transport may cause the atmospheric pressure to be extremely sensitive to variations of solar heating at the poles. This could happen because atmospheric heating depends on density, which depends strongly on the polar temperature through the vapor pressure relation. A simple climatological model is used to study the question.

Gierasch, P. J.; Toon, O. B.

1973-01-01

250

Global Atmospheric Pressure Effects of the October 30, 1961, Explosion  

Microsoft Academic Search

The atmospheric pressure waves set off by the explosion of October 30, 1961, were traced over a large portion of the world, including the antipodes in the Antarctic, by means of analyses of available ordinary microbarograph records. The observed geographic variations in propagation speed and maximum amplitude are examined with the aid of air density and wind analyses. Comparison is

H. Wexler; W. A. Hass

1962-01-01

251

Low and atmospheric pressure plasma treatment of natural textile fibers  

Microsoft Academic Search

In this contribution we report on plasma modification of natural textile fibres, like raw wool and wool yarn and cotton wool and cotton yarn. Radiofrequency plasmas (13.56 MHz) generated in parallel plate configuration at low pressure and in dielectric barrier discharge (DBD) configuration at atmospheric pressure have been used. At low pressure the samples were treated at different times (1-30

I. Luciu; B. Mitu; V. Satulu; A. Matei; G. Dinescu

2008-01-01

252

Atmospheric Pressure Molecular Imaging by Infrared MALDI Mass Spectrometry  

E-print Network

was developed for an orthogonal acceleration time-of-flight mass spectrometer and utilized to analyze peptides to the ultraviolet laser shots, spatially correlated mass spectra are acquired. Application of MALDI imaging to largeAtmospheric Pressure Molecular Imaging by Infrared MALDI Mass Spectrometry Yue Li, Bindesh Shrestha

Vertes, Akos

253

Variations in atmospheric pressure and height of maximal electron concentration  

NASA Astrophysics Data System (ADS)

The latitude distribution of atmospheric pressure is compared with that of the height of the maximal electron concentration of the ionospheric F 2 region. Use is made of the atmospheric pressure data of Shkodrov and Ivanova (1980) and of data obtained by Watanabe (1967) based on solar-activity-averaged observations of day and night variations of the proportion of radio waves reaching distances of 3000 km at 40 ionospheric stations. A well-defined similarity between the two parameters is observed at the equatorial regions which decreases at high northern latitudes and disappears at high southern latitudes. It is also found that relative variations in the northern and southern hemisphere atmospheric pressure maxima are accompanied by analogous relative variations in maximal electron concentration height, while the values of the minima of the two parameters remain constant throughout the year. It is concluded that variations in meridional plane atmospheric pressure and maximal electron density height in the F 2 region are probably due to a common cause acting in the equatorial region, possibly the geomagnetic field.

Shkodrov, V. G.; Ivanova, V. G.

254

Novel applications of atmospheric pressure plasma on textile materials  

Microsoft Academic Search

Various applications of atmospheric pressure plasma are investigated in conjunction with polymeric materials including paper, polypropylene non-woven fabric, and cotton. The effect of plasma on bulk and surface properties is examined by treating both cellulosic pulp and prefabricated paper with various plasma-gas compositions. After treatment, pulp is processed into paper and the properties are compared. The method of pulp preparation

Carrie Elizabeth Cornelius

2009-01-01

255

Flow injection of liquid samples to a mass spectrometer with ionization under vacuum conditions: a combined ion source for single-photon and electron impact ionization.  

PubMed

Electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo-ionization (APPI) are the most important techniques for the ionization of liquid samples. However, working under atmospheric pressure conditions, all these techniques involve some chemical rather than purely physical processes, and therefore, side reactions often yield to matrix-dependent ionization efficiencies. Here, a system is presented that combines both soft single-photon ionization (SPI) and hard 70 eV electron impact ionization (EI) of dissolved compounds under vacuum conditions. A quadrupole mass spectrometer was modified to enable direct EI, a technique developed by Cappiello et al. to obtain library-searchable EI mass spectra as well as soft SPI mass spectra of sample solutions. An electron beam-pumped rare gas excimer lamp working at 126 nm was used as well as a focusable vacuum UV light source for single-photon ionization. Both techniques, EI and SPI, were applied successfully for flow injection experiments providing library-matchable EI fragment mass spectra and soft SPI mass spectra, showing dominant signals for the molecular ion. Four model compounds were analyzed: hexadecane, propofol, chlorpropham, and eugenol, with detection limits in the picomolar range. This novel combination of EI and SPI promises great analytical benefits, thanks to the possibility of combining database alignment for EI data and molecular mass information provided by SPI. Possible applications for the presented ionization technology system are a matrix-effect-free detection and a rapid screening of different complex mixtures without time-consuming sample preparation or separation techniques (e.g., for analysis of reaction solutions in combinatorial chemistry) or a switchable hard (EI) and soft (SPI) MS method as detection step for liquid chromatography. PMID:23812882

Schepler, Claudia; Sklorz, Martin; Passig, Johannes; Famiglini, Giorgio; Cappiello, Achille; Zimmermann, Ralf

2013-09-01

256

Application of an atmospheric pressure sampling mass spectrometer to chlorination reactions  

NASA Technical Reports Server (NTRS)

An atmospheric pressure mass spectrometric sampling system, based on a free jet expansion was used to study certain M-Cl-O reactions at high temperatures. The apparatus enables the volatile species from a 1-atm chemical process to be directly identified with a mass spectrometer which operates at approx. 10 to the minus 8th power torr. Studies for both pure metals and alloys are discussed. It is shown that this mass spectrometer system aids in identifying the volatile species, and provides fundamental information on the reaction mechanism.

Jacobson, N. S.

1986-01-01

257

Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium  

SciTech Connect

Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.

Li Guo; Li Heping; Wang Sen; Sun Wenting; Bao Chengyu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Wang Liyan; Zhao Hongxin; Xing Xinhui [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

2008-06-02

258

Molecular-structure variation of organic materials irradiated with atmospheric pressure plasma  

NASA Astrophysics Data System (ADS)

The effect of atmospheric pressure He plasma on the molecular structure of polyethylene terephthalate (PET) has been investigated. The plasma composition was analyzed using optical emission spectroscopy. In addition to strong He emission lines, lines due to O and N radicals were also detected. The change in the molecular structure of the PET film surface was investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. It was found that plasma irradiation led to oxidation and degradation of the surface due to chemical and physical effects of the active species. The results demonstrate the feasibility of observing the interaction of plasma with organic material on a local scale.

Takenaka, K.; Miyazaki, A.; Setsuhara, Y.

2014-06-01

259

Surface properties and hydrophobic recovery of polymers treated by atmospheric-pressure plasma  

NASA Astrophysics Data System (ADS)

This paper provides an analysis on the relation between plasma effects on polymers exposed to inert gas atmospheric-pressure plasma, polymer structure characteristics and surface recovery during post-processing ageing. Polymers offering variety of structure, functionality, degree of oxidation, polarity, crystallinity are tested, using contact angle, XPS, XRD and solvent absorption measurement, thus exploring the relationship linking the surface polarity, the chemical structure and composition contribution in the combined functionalization/crosslinking surface modification mechanisms of plasma-exposed polymers. The limiting level of modification attainable, the surface stability and the factors controlling these are examined, concluding on the plasma capacity to provide operational stability for modified polymer surfaces.

Borcia, C.; Punga, I. L.; Borcia, G.

2014-10-01

260

Characteristics of nanocomposite films deposited by atmospheric pressure uniform RF glow plasma  

Microsoft Academic Search

Characteristics of nanocomposite films synthesized and deposited by atmospheric pressure Radio-Frequency (RF) (13.56 MHz) uniform glow discharge are examined. The nanocomposite thin film deposition is carried out in the presence of titanium dioxide (TiO2) with polymerization of pyrrole, thiophene and furan monomers in acetonitrile medium containing lithium perchlorate (LiClO4). The chemical, morphological, thermal and electrical characteristics of polypyrrole\\/TiO2 (PPy\\/TiO2), polythiophene\\/TiO2 (PT\\/TiO2)

Aysegul Uygun; Lutfi Oksuz; Ayse Gul Yavuz; Ali Guleç; Songul Sen

2011-01-01

261

Atmospheric-pressure plasma sources for biomedical applications  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure plasmas (APPs) have attracted great interest and have been widely applied in biomedical applications, as due to their non-thermal and reactive properties, they interact with living tissues, cells and bacteria. Various types of plasma sources generated at atmospheric pressure have been developed to achieve better performance in specific applications. This article presents an overview of the general characteristics of APPs and a brief summary of their biomedical applications, and reviews a wide range of these sources developed for biomedical applications. The plasma sources are classified according to their power sources and cover a wide frequency spectrum from dc to microwaves. The configurations and characteristics of plasma sources are outlined and their biomedical applications are presented.

Park, G. Y.; Park, S. J.; Choi, M. Y.; Koo, I. G.; Byun, J. H.; Hong, J. W.; Sim, J. Y.; Collins, G. J.; Lee, J. K.

2012-08-01

262

Cellular membrane collapse by atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation, and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.

Kim, Kangil; Jun Ahn, Hak; Lee, Jae-Hyeok; Kim, Jae-Ho; Sik Yang, Sang; Lee, Jong-Soo

2014-01-01

263

Atmospheric-pressure guided streamers for liposomal membrane disruption  

SciTech Connect

The potential to use liposomes (LIPs) as a cellular model in order to study interactions of cold atmospheric-pressure plasma with cells is herein investigated. Cold atmospheric-pressure plasma is formed by a dielectric-barrier discharge reactor. Large multilamellar vesicle liposomes, consisted of phosphatidylcholine and cholesterol, are prepared by the thin film hydration technique, to encapsulate a small hydrophilic dye, i.e., calcein. The plasma-induced release of calcein from liposomes is then used as a measure of liposome membrane integrity and, consequently, interaction between the cold atmospheric plasma and lipid bilayers. Physical mechanisms leading to membrane disruption are suggested, based on the plasma characterization including gas temperature calculation.

Svarnas, P.; Aleiferis, Sp. [High Voltage Laboratory, Department of Electrical and Computer Engineering, University of Patras, Rion 26504 (Greece); Matrali, S. H. [Pharmaceutical Technology Laboratory, Department of Pharmacy, University of Patras, Rion 26504 (Greece); Gazeli, K. [High Voltage Laboratory, Department of Electrical and Computer Engineering, University of Patras, Rion 26504 (Greece); IPREM-LCABIE, Plasmas et Applications, UPPA, 64000 Pau (France); Clement, F. [IPREM-LCABIE, Plasmas et Applications, UPPA, 64000 Pau (France); Antimisiaris, S. G. [Pharmaceutical Technology Laboratory, Department of Pharmacy, University of Patras, Rion 26504 (Greece); Institute of Chemical Engineering Sciences (ICES)-FORTH, Rion 26504 (Greece)

2012-12-24

264

Thermally induced atmospheric pressure gas discharges using pyroelectric crystals  

NASA Astrophysics Data System (ADS)

Using a heated pyroelectric crystal, an atmospheric pressure gas discharge was generated through the input of heat. When put through a change in temperature, the polarization of a pyroelectric can change significantly, creating a substantial electric potential at its surface. When configured with a grounded sharp counter electrode, a large inhomogeneous electric field forms in the interstitial gas to initiate a corona-like discharge. Under constant heating conditions, gaseous ions drifting to the pyroelectric accumulate and screen the electric field, extinguishing the discharge. By thermally cycling the pyroelectric, negative and positive discharges are generated during heating and cooling, respectively, with peak currents on the order of 80 nA. Time-integrated visualization confirmed the generation of both a corona-like discharge and a surface discharge on the pyroelectric. Parametric studies identified that thermal cycling conditions significantly influence discharge formation for this new atmospheric pressure discharge approach.

Johnson, Michael J.; Linczer, John; Go, David B.

2014-12-01

265

Cooperative biological effects between ionizing radiation and other physical and chemical agents  

Microsoft Academic Search

Exposure to ionizing radiation (IR), at environmentally and therapeutically relevant doses or as a result of diagnostics or accidents, causes cyto- and genotoxic damage. However, exposure to IR alone is a rare event as it occurs in spatial and temporal combination with several physico-chemical agents. Some of these are of known noxiousness, as is the case with chemical compounds at

Lorenzo Manti; Annalisa D’Arco

2010-01-01

266

Fundamentals of interaction of ionizing radiations with chemical, biochemical, and pharmaceutical systems  

Microsoft Academic Search

A literature review is presented of the chemical and biological effects ; of ionizing radiations with special reference to the pharmaceutical sciences. A ; review of the theoretical principles of interactions of high energy radiations ; with matter is presented with re gard to three stages of the process: physical, ; physiocochemical, and chemical. In a discussion of the irradiation

Stephen G. Schulman

1973-01-01

267

Characterization of pulsed atmospheric-pressure plasma streams (PAPS) generated by a plasma gun  

NASA Astrophysics Data System (ADS)

An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107-108 cm s-1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications.

Robert, E.; Sarron, V.; Riès, D.; Dozias, S.; Vandamme, M.; Pouvesle, J.-M.

2012-06-01

268

Visualization of volatile substances in different organelles with an atmospheric-pressure mass microscope.  

PubMed

We have developed a mass microscope (mass spectrometry imager with spatial resolution higher than the naked eye) equipped with an atmospheric pressure ion-source chamber for laser desorption/ionization (AP-LDI) and a quadrupole ion trap time-of-flight (QIT-TOF) analyzer. The optical microscope combined with the mass spectrometer permitted us to precisely determine the relevant tissue region prior to performing imaging mass spectrometry (IMS). An ultraviolet laser tightly focused with a triplet lens was used to achieve high spatial resolution. An atmospheric pressure ion-source chamber enables us to analyze fresh samples with minimal loss of intrinsic water or volatile compounds. Mass-microscopic AP-LDI imaging of freshly cut ginger rhizome sections revealed that 6-gingerol ([M + K](+)at m/z 333.15, positive mode; [M - H](-) at m/z 293.17, negative mode) and the monoterpene ([M + K](+) at m/z 191.09), which are the compounds related to pungency and flavor, respectively, were localized in oil drop-containing organelles. AP-LDI-tandem MS/MS analyses were applied to compare authentic signals from freshly cut ginger directly with the standard reagent. Thus, our atmosphere-imaging mass spectrometer enabled us to monitor a quality of plants at the organelle level. PMID:19788281

Harada, Takahiro; Yuba-Kubo, Akiko; Sugiura, Yuki; Zaima, Nobuhiro; Hayasaka, Takahiro; Goto-Inoue, Naoko; Wakui, Masatoshi; Suematsu, Makoto; Takeshita, Kengo; Ogawa, Kiyoshi; Yoshida, Yoshikazu; Setou, Mitsutoshi

2009-11-01

269

Detection of chemical weapon agents and simulants using chemical ionization reaction time-of-flight mass spectrometry.  

PubMed

Chemical ionization reaction time-of-flight mass spectrometry (CIR-TOF-MS) has been used for the analysis of prepared mixtures of chemical weapon agents (CWAs) sarin and sulfur mustard. Detection of the CWA simulants 2-chloroethyl ethyl sulfide, triethyl phosphate, and dimethyl methyl phosphonate has also been investigated. Chemical ionization of all the agents and simulants was shown to be possible using the CIR-TOF-MS technique with a variety of reagent ions, and the sensitivity was optimized by variation of instrument parameters. The ionization process was found to be largely unaffected by sample humidity levels, demonstrating the potential suitability of the method to a range of environmental conditions, including the analysis of CWAs in air and in the breath of exposed individuals. PMID:17894471

Cordell, Rebecca L; Willis, Kerry A; Wyche, Kevin P; Blake, Robert S; Ellis, Andrew M; Monks, Paul S

2007-11-01

270

Flame spread over electric wire in sub-atmospheric pressure  

Microsoft Academic Search

Flame spread along the single wire harness (thin-metal wire with coating of polyethylene film) in sub-atmospheric pressure has been examined experimentally to gain better understandings of the electric fire in the aircraft and space habitats. Two kinds of sample wires, made by nickel-chrome (NiCr) and iron (Fe) as core metal, are used in this study. Ambient gas is fixed as

Yuji Nakamura; Nobuko Yoshimura; Hiroyuki Ito; Keisuke Azumaya; Osamu Fujita

2009-01-01

271

Spectroscopic investigations of atmospheric pressure microwave torch nitrogen plasma jet  

Microsoft Academic Search

Microwave (MW) torches are typically used to produce equilibrium plasmas for various industrial applications. We present spectroscopic\\u000a investigations of atmospheric pressure afterglow plasmas generated by a Litmas Red MW torch (2.45 GHz, 3 kW) in nitrogen.We\\u000a employ optical diagnostics: emission spectroscopy and digital photography to characterise the plasma jet. Contrary to standard\\u000a MW torch geometries (where the gas flows upstream

V. Foltin; L. Lestinská; Z. Machala

2006-01-01

272

Modification of wool fibers by atmospheric pressure plasma treatment  

Microsoft Academic Search

Shrink?proofing processing of wool fabrics by vacuum plasma treatment has been studied for many years. However, as a wool shrink?proofing processing method, discharge treatment under atmospheric pressure, such as corona and low?temperature electric plasma treatment, has been studied recently. In this study, an attempt was made to improve shrink?proofing and other properties of a wool fabric by low?temperature plasma treatment.

Masukuni Mori; Volkmar von Arnim; Albrecht Dinkelmann; Mitsuo Matsudaira; Tomiji Wakida

2011-01-01

273

Beta-type Stirling engine operating at atmospheric pressure  

Microsoft Academic Search

In this study, a beta-type Stirling engine, with a 192 cc total swept-volume, was manufactured and its performance tested at atmospheric pressure. The hot-source temperature is chosen as a fundamental parameter of the experimental study. Experiments were performed with an electrical heater at 800, 900 and 1000 °C temperatures. Torque and output-power variations were obtained for different engine speeds. The

Serdar Yucesu; Tolga Topgul; Melih Okur

2005-01-01

274

Engineering a laser remote sensor for atmospheric pressure and temperature  

NASA Technical Reports Server (NTRS)

A system for the remote sensing of atmospheric pressure and temperature is described. Resonant lines in the 7600 Angstrom oxygen A band region are used and an organic dye laser beam is tuned to measure line absorption changes with temperature or pressure. A reference beam outside this band is also transmitted for calibration. Using lidar techniques, profiling of these parameters with altitude can be accomplished.

Kalshoven, J. E., Jr.; Korb, C. L.

1978-01-01

275

Hypobaric biology: Arabidopsis gene expression at low atmospheric pressure.  

PubMed

As a step in developing an understanding of plant adaptation to low atmospheric pressures, we have identified genes central to the initial response of Arabidopsis to hypobaria. Exposure of plants to an atmosphere of 10 kPa compared with the sea-level pressure of 101 kPa resulted in the significant differential expression of more than 200 genes between the two treatments. Less than one-half of the genes induced by hypobaria are similarly affected by hypoxia, suggesting that response to hypobaria is unique and is more complex than an adaptation to the reduced partial pressure of oxygen inherent to hypobaric environments. In addition, the suites of genes induced by hypobaria confirm that water movement is a paramount issue at low atmospheric pressures, because many of gene products intersect abscisic acid-related, drought-induced pathways. A motivational constituent of these experiments is the need to address the National Aeronautics and Space Administration's plans to include plants as integral components of advanced life support systems. The design of bioregenerative life support systems seeks to maximize productivity within structures engineered to minimize mass and resource consumption. Currently, there are severe limitations to producing Earth-orbital, lunar, or Martian plant growth facilities that contain Earth-normal atmospheric pressures within light, transparent structures. However, some engineering limitations can be offset by growing plants in reduced atmospheric pressures. Characterization of the hypobaric response can therefore provide data to guide systems engineering development for bioregenerative life support, as well as lead to fundamental insights into aspects of desiccation metabolism and the means by which plants monitor water relations. PMID:14701916

Paul, Anna-Lisa; Schuerger, Andrew C; Popp, Michael P; Richards, Jeffrey T; Manak, Michael S; Ferl, Robert J

2004-01-01

276

Model of a stationary microwave argon discharge at atmospheric pressure  

SciTech Connect

The many applications of microwave gas discharges at atmospheric pressure in various fields of science, technology and medicine require an adequate model of these discharges. Such a model is based on the electromagnetic wave's propagation properties and on the elementary processes in the discharge bulk. In contrast to the microwave discharges at low-gas pressures, where many elementary processes might be ignored because of their negligible contribution to the electron and heavy particle's balance equations, for such discharges at atmospheric pressure the consideration of a large number of collisional processes is mandatory. For the build of a successful discharge-column model one needs three important quantities, notably the power {theta} necessary for sustaining an electron - ion pair, electron - neutral collision frequency for momentum transfer v{sub en}, and gas temperature T{sub g}. The first two key parameters are obtained by a collisional-radiative model of the argon at atmospheric pressure, while the microwave frequency {omega}/2{pi} = 2.45 GHz, plasma column radius R, gas pressure p and gas temperature T{sub g} are fixed external parameters determined by the experimental conditions. Here, we present a model of a capillary argon microwave plasma column with a length L {approx_equal} 14 cm, sustained by wave power of 110 W - the model yields the longitudinal distributions of the plasma density, expended wave power, wave electric field magnitude, and complex wave number.

Zhelyazkov, I. [Faculty of Physics, Sofia University, BG-1164 Sofia (Bulgaria); Pencheva, M.; Benova, E. [Department for Language Teaching and International Students, Sofia University, BG-1111 Sofia (Bulgaria)

2008-03-19

277

Characteristics of atmospheric-pressure, radio-frequency glow discharges operated with argon added ethanol  

SciTech Connect

Rf, atmospheric-pressure glow discharge (APGD) plasmas with bare metal electrodes have promising prospects in the fields of plasma-aided etching, thin film deposition, disinfection and sterilization, etc. In this paper, the discharge characteristics are presented for the rf APGD plasmas generated with pure argon or argon-ethanol mixture as the plasma-forming gas and using water-cooled, bare copper electrodes. The experimental results show that the breakdown voltage can be reduced significantly when a small amount of ethanol is added into argon, probably due to the fact that the Penning ionization process is involved, and a pure {alpha}-mode discharge can be produced more easily with the help of ethanol. The uniformity of the rf APGDs of pure argon or argon-ethanol mixtures using bare metallic electrodes is identified with the aid of the intensified charge coupled device images.

Sun Wenting; Li Guo; Li Heping; Bao Chengyu; Wang Huabo; Zeng Shi; Gao Xing; Luo Huiying [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); School of Public Health and Family Medicine, Capital University of Medical Sciences, Beijing 100069 (China); Beijing Center for Diseases Control and Prevention, Beijing 100013 (China)

2007-06-15

278

Bidimensional characterization of the emission spectra in a direct current atmospheric pressure glow discharge  

NASA Astrophysics Data System (ADS)

An in-house atmospheric pressure glow discharge source, designed to be used as ionization/desorption source for ambient mass spectrometry, has been electrically characterized, and its optical emission spectra evaluated in detail. Electrical characterization showed that the plasma regime can vary from glow discharge to arc discharge depending on operating conditions (i.e. He flow rate and inter electrode distance). Furthermore, bidimensional images of the optical emission of some plasma species using filters as wavelength selectors, were registered from inside and outside the discharge chamber (inner region and afterglow region respectively), showing the spatial distribution of excited species (i.e. He*, N2+ and O*). These distribution patterns are useful to study the chemistry of the discharge plasma, since different production pathways and different excitation energies affect the presence of these species in the plasma regions.

Orejas, Jaime; Pisonero, Jorge; Bordel, Nerea; Nelis, Thomas; Guillot, Philippe; Sanz-Medel, Alfredo

2012-10-01

279

Identifying alkylbenzene isomers with chemical ionization-proton exchange mass spectrometry  

SciTech Connect

Chemical ionization-proton exchange mass spectrometry (CIPE) allows the number of unsubstituted aromatic carbons in alkylbenzene isomers to be determined. Only the aromatic hydrogens undergo exchange with deuterium when deuterated water, methanol, or ethanol is used as the reagent gas. Chemical ionization with deuterated methanol gives an acceptable mass spectral background and allows the determination of the number of unsubstituted positions on the benzene ring yielding structural information often unavailable from conventional electron impact spectra. Structural isomers such as propyl-, methylethyl-, and trimethylbenzene can easily be identified. The comparison of CIPE spectra from standard compounds, which are often unavailable, is not required to determine the number of unsubstituted aromatic carbons in alkylbenzene isomers. The method also allows ortho and para to be distinguished from meta disubstituted alkylbenzenes. Deuteriomethanol chemical ionization is used to characterize alkylbenzenes in a complex and relatively well studied sample, diesel exhaust. 14 references, 3 figures, 3 tables.

Hawthorne, S.B.; Miller, D.J.

1985-03-01

280

Investigation of spectrochemical matrix effects in the liquid sampling-atmospheric pressure glow discharge source  

NASA Astrophysics Data System (ADS)

The liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma was evaluated with regard to its spectrochemical robustness in its application as a miniaturized optical emission spectroscopy (OES) source for liquid samples. The susceptibility to perturbations in excitation/ionization conditions was probed across a wide range test species, including transition metals, easily ionized elements (group I), and elements with low second ionization potentials (group II). Spectrochemical metrics included the plasma excitation temperature (Texc), ionization temperatures (Tion), and magnesium (Mg) ionic:atomic (Mg II:Mg I) ratios. The introduction of the 11 different matrix elements into the LS-APGD at concentrations of 500 ?g mL- 1 yielded no significant changes in the optically-determined plasma characteristics, indicating a relative immunity to spectrochemical matrix effects. Texe values for the plasma, using He I as the spectrometric species averaged 2769 ± 79 K across the test matrix, with Mg-based ionization temperature values centered at 6665 ± 151 K. Typical Mg II:Mg I ratios (the so-called robustness parameter) were 0.95 ± 0.3. The lack of appreciable perturbation in excitation/ionization conditions observed here is also manifested in virtually no changes in the probe Mg II and I species' intensities, even at matrix loadings of up to 1000 ?g mL- 1 of Ba. These observations indicate that the LS-APGD could serve as an OES source for the analysis of diverse aqueous samples without appreciable spectroscopic matrix effects, though potential physical matrix effects including vaporization effects must be evaluated.

Manard, Benjamin T.; Gonzalez, Jhanis J.; Sarkar, Arnab; Mao, Xianglei; Zhang, Lynn X.; Konegger-Kappel, Stefanie; Marcus, R. Kenneth; Russo, Richard E.

2014-10-01

281

Comparison of the Structures of Triacylglycerols from Native and Transgenic Medium-Chain Fatty Acid-Enriched Rape Seed Oil by Liquid Chromatography–Atmospheric Pressure Chemical Ionization Ion-Trap Mass Spectrometry (LC–APCI-ITMS)  

Microsoft Academic Search

The sn position of fatty acids in seed oil lipids affects physiological function in pharmaceutical and dietary applications. In\\u000a this study the composition of acyl-chain substituents in the sn positions of glycerol backbones in triacylglycerols (TAG) have been compared. TAG from native and transgenic medium-chain\\u000a fatty acid-enriched rape seed oil were analyzed by reversed-phase high performance liquid chromatography coupled with

Christopher Beermann; Nadine Winterling; Angelika Green; Michael Möbius; Joachim J. Schmitt; Günther Boehm

2007-01-01

282

Part-per-trillion level determination of antifouling pesticides and their byproducts in seawater samples by off-line solid-phase extraction followed by high-performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry  

Microsoft Academic Search

A new method for the simultaneous determination of antifouling pesticides and some of their byproducts such as dichlofluanid, diuron and its byproducts [demethyldiuron and 1-(3,4-dichlorophenyl)urea], (2-thiocyanomethylthio)benzothiazole, chlorothalonil, Sea-nine 211, Irgarol 1051 and one of its byproducts (2-methylthio-4-tert.-butylamino-s-triazine) in seawater was developed. The extraction of these compounds from the filtered seawater samples was performed off-line with different solid-phase extraction sorbents using

Karell Mart??nez; Imma Ferrer; Damiá Barceló

2000-01-01

283

In vivo pharmacokinetic screening in cassette dosing experiments; the use of on-line Pprospekt liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry technology in drug discovery.  

PubMed

Drug discovery is a fast growing field and the number of compounds generated daily by the pharmecutical industry is enormous. The necessity of developing new experimental strategies and analytical methods to rapidly screen the pharmacokinetics (PK) behavior of these compounds becomes a real challenge. A novel strategy to support in vivo PK screening in cassette doing experiments, using a fully automated system capable of analyzing between 320 to 960 samples a day by instrument in n-in-one experiment ( n = 64 in this work), has been developed. Using an on-line extraction technique, the average observed recovery was 64% using a single C18 procedure. A weighted (1/x) linear equation was used to perform standard calibration (0.5 to 500 ng/microL) and the average R value obtained was 0.994 (R2 = 0.997) for 63 analytes. The limit of detection, defined as a signal-to-noise ratio of 3 or greater, was found to be 25 pg for 41 of the 63 analytes (65%) and 250 pg for 57 of the 63 analytes (90%). The complete automation procedure using the Prospekt-LC-APCI/MS/MS system has substantially improved throughput in the area of drug discovery and bioanalysis. PMID:9737010

Beaudry, F; Le Blanc, J C; Coutu, M; Brown, N K

1998-01-01

284

Simulation of an Atmospheric Pressure Plasma Jet in a Stagnation Flow  

NASA Astrophysics Data System (ADS)

Pulsed atmospheric pressure plasma jets (APPJs) have generated significant interest for their ability to generate non-thermal plasma in open air gaps without the risk of arcing. The plasma typically forms due to a sequence of fast ionization waves which propagate within a noble gas jet exhausting into ambient air. The resulting luminous plasma plume is safe to touch due to the non-equilibrium nature of the plasma and low gas temperatures. At the same time, high energy electrons in the ionizing head can generate reactive radical species (N and O) in addition to ions and UV radiation, which may be beneficial for biomedical applications. In order to gauge the effectiveness of these jets for treating surfaces, it is desirable to know how the plasma jet interacts with a surface and the flux of reactive species to that surface. In this work, the propagation of a single ionization wave in the stagnation flow of a helium jet impinging on a solid surface is modeled. The plasma discharge dynamics are modeled using a self-consistent, two temperature plasma solver with finite rate chemistry. The helium-jet stagnation flow is modeled using a compressible, multiple species Navier-Stokes solver. The primary objective is to determine the net delivery of reactive species to the surface and the role of parameters such as dielectric thickness.

Breden, Doug; Raja, Laxminarayan

2012-10-01

285

Direct Laser Ablation and Ionization of Solids for Chemical Analysis by Mass Spectrometry  

SciTech Connect

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). Single pulse experiments have demonstrated simultaneous detection of up to 14 elements present in glasses in the ppm range. However, detection of the components has produced non-stoichiometric results due to difference in ionization potentials and fractionation effects. Time-of-flight secondary ionization mass spectrometry (TOF-SIMS) was used to spatially map elemental species on the surface and provide further evidence of fractionation effects. Resolution (m/Dm) of 1500 and detection limits of approximately 10 pg have been achieved with a single laser pulse. The system configuration and related operating principles for accurately measuring low concentrations of isotopes are described.

Holt, J K; Nelson, E J; Klunder, G L

2005-09-02

286

Experimental Investigation Of Atmospheric Pressure Surface Wave Discharges  

SciTech Connect

Microwave atmospheric pressure discharge in neon sustained by surface waves in a dielectric tube is considered. The plasma column length was measured versus absorbed microwave power for different discharge conditions. This gives a view on the wave propagation characteristics. The predicted dependence of discharge length on the total flux of wave power based on the modified model of non-equilibrium plasma is compared with experimental values. Moreover, we present results of spectroscopic investigations of the electron density. The electron density was determined using the method based on the Stark broadening of H{beta} spectral line. The spectroscopic results we shall use developing of a model of propagation of surface wave.

Czylkowski, D.; Jasinski, M.; Nowakowska, H.; Zakrzewski, Z. [The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk (Poland)

2006-01-15

287

Pluto's Insolation History: Latitudinal Variations and Effects on Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Since previous insolation modeling in the early 1990’s, new atmospheric pressure data, increased computational power, and the upcoming flyby of the Pluto system by NASA’s New Horizons spacecraft have generated new motivation and increased capabilities for the study of Pluto’s complex long-term (million-years) insolation history. The two primary topics of interest in studying Pluto’s insolation history are the variations in insolation patterns when integrated over different intervals and the evolution of diurnal insolation patterns over the last several decades. We find latitudinal dichotomies when comparing average insolation over timescales of days, decades, centuries, and millennia. Depending on the timescales of volatile migration, some consequences of these insolation patterns may be manifested in the surface features revealed by New Horizons. For any single rotation of Pluto there is a latitude that receives more insolation relative to the others. Often this is the sub-subsolar latitude but it can also be an arctic circle latitude when near-polar regions of Pluto experience the "midnight sun". We define the amount of that greatest insolation value over the course of one rotation as the "maximum diurnal insolation" (MDI). We find that MDI is driven to its highest values when Pluto’s obliquity creates a long arctic summer (or “midnight sun”) beginning just after perihelion. Pluto’s atmospheric pressure, as measured through stellar occultation observations during the past three decades, appears to correlate with Pluto's currently occurring midnight sun as quantified by the MDI parameter. If insolation (as parameterized by the MDI value) is the single dominant factor driving Pluto's atmospheric pressure, this “Midnight Sun Model” predicts that Pluto's maximum atmospheric pressure will be reached in 2017 followed by a steady decline. Pluto's maximum diurnal insolation value begins dropping after 2017 due to two factors: Pluto’s sub-solar point becomes more equatorial (lessening the midnight sun effect) and the planet continues to recede toward aphelion. This work was supported in part by the NASA New Horizons mission to Pluto under SwRI Subcontract 299433Q.

Earle, Alissa M.; Binzel, Richard P.

2014-11-01

288

Driven Motion and Instability of an Atmospheric Pressure Arc  

SciTech Connect

Atmospheric pressure arcs are used extensively in applications such as welding and metallurgy. However, comparatively little is known of the physics of such arcs in external magnetic fields and the mechanisms of the instabilities present. In order to address questions of equilibrium and stability of such arcs, an experimental arc furnace is constructed and operated in air with graphite cathode and steel anode at currents 100-250 A. The arc is diagnosed with a gated intensified camera and a collimated photodiode array, as well as fast voltage and current probes.

Max Karasik

1999-12-01

289

Electrode erosion in arc discharges at atmospheric pressure  

NASA Technical Reports Server (NTRS)

An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, an external magnetic fields were all found to reduce electrode mass loss.

Hardy, T. L.

1985-01-01

290

Atmospheric pressure cold plasma as an antifungal therapy  

SciTech Connect

A microhollow cathode based, direct-current, atmospheric pressure, He/O{sub 2} (2%) cold plasma microjet was used to inactive antifungal resistants Candida albicans, Candida krusei, and Candida glabrata in air and in water. Effective inactivation (>90%) was achieved in 10 min in air and 1 min in water. Antifungal susceptibility tests showed drastic reduction of the minimum inhibitory concentration after plasma treatment. The inactivation was attributed to the reactive oxygen species generated in plasma or in water. Hydroxyl and singlet molecular oxygen radicals were detected in plasma-water system by electron spin resonance spectroscopy. This approach proposed a promising clinical dermatology therapy.

Sun Peng; Wu Haiyan [College of Engineering, Peking University, Beijing 100871 (China); Sun Yi; Liu Wei; Li Ruoyu [Department of Dermatology and Venereology, Peking Univ. 1st Hospital and Research Center for Medical Mycology, Peking Univ., Beijing 100034 (China); Zhu Weidong; Lopez, Jose L. [Department of Applied Science and Technology and Center for Microplasma Science and Technology, Saint Peter's College, Jersey City, New Jersey 07306 (United States); Zhang Jue; Fang Jing [College of Engineering, Peking University, Beijing 100871 (China); Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

2011-01-10

291

Heat transport of nitrogen in helium atmospheric pressure microplasma  

E-print Network

Stable DC atmospheric pressure normal glow discharges in ambient air were produced between the water surface and the metallic capillary coupled with influx of helium gas. Multiple independent repeated trials indicated that vibrational temperature of nitrogen rises from 3200 to 4622 K, and rotational temperature of nitrogen decreases from 1270 to 570 K as gas flux increasing from 20 to 80 sccm and discharge current decreasing from 11 to 3 mA. Furthermore, it was found that the vibrational degree of the nitrogen molecule has priority to gain energy than the rotational degree of nitrogen molecule in nonequilibrium helium microplasma.

Xu, Shaofeng

2013-01-01

292

Atmospheric pressure creep experiments using highly dense fine-grained mineral aggregates  

NASA Astrophysics Data System (ADS)

Historically in mineral and rock physics, atmospheric pressure creep tests have been used extensively to study the rheological properties of minerals through deformation of single crystals. This technique has several advantages including minimal friction effects on the loading column, which allows excellent stress resolution on the sample, and stable temperature control, which allows long duration experiments at relatively slow strain rates. The downside of atmospheric pressure experiments on polycrystalline samples is that cavities and cracks are easily introduced during the test, resulting in brittle failure of the specimen. It is generally found that the confining pressure should be larger than the applied differential stress to avoid failure due to microcracking. Consequently very few creep experiments under atmospheric pressure have been conducted on polycrystalline samples. We revisit this classic method of atmospheric pressure creep experiments by developing a technique to synthesize very fine grained aggregates with essentially zero porosity. So far, we are able to reach even 200 micron grain size for certain type of mineral assemblies. During grain size sensitive creep, we expect that the differential stress applied to the samples can be reduced 100 to 1000 times the stress to deform coarser grained samples at the same strain rate condition by reducing grain size of one order of magnitude. Taking into account of ~10 micron grain size as a common value in conventional experiments, we should be able to reduce the applied stress of > 2500 times. Such lowering the applied stress will help to prevent cracking and/or cavitation in the samples. Using this technique, we have been able to demonstrate (i) superplasticity, (ii) microstructural development comparable to that in observed natural mylonites, (iii) flow strength as a function of stress, grain size and temperature, (iv) the effect of the fraction of second phase on flow strength in poly-phase materials, (v) fabric development as a function of strain, (vi) grain growth behavior during deformation, (vii) deformation during chemical reaction, and (viii) the effect of melt on deformation microstructures of synthetic geomaterials.

Hiraga, T.; Miyazaki, T.; Tasaka, M.; Sueyoshi, K.; Nakakoji, S.; Koizumi, S.; Yoshida, H.

2012-12-01

293

SiOâ-like film deposition by dielectric barrier discharge plasma gun at ambient temperature under an atmospheric pressure  

Microsoft Academic Search

A medium-frequency dielectric barrier discharge (DBD) plasma gun was used to deposit SiOâ-like films at ambient temperature under atmospheric pressure. SiOâ-like films were deposited on Si and stainless-steel surfaces by flowing Ar gas containing hexamethyldisiloxane (HMDSO) monomer through the gun. The authors found that the chemical structure of the deposited SiOâ-like film strongly depended on the HMDSO monomer ratio in

Chen Qiang; Zhang Yuefei; Han Erli; Ge Yuanjing

2006-01-01

294

PENTACHLOROPHENOL IN THE ENVIRONMENT. EVIDENCE FOR ITS ORIGIN FROM COMMERCIAL PENTACHLOROPHENOL BY NEGATIVE CHEMICAL IONIZATION MASS SPECTROMETRY  

EPA Science Inventory

Commercial pentachlorophenol (PCP) contains significant quantities of tetrachlorophenol (TCP). The occurrence of TCP in environmental samples provides a chemical marker for PCP originating from commercial formulations. Negative chemical ionization mass spectrometry has been used ...

295

PENTACHLOROPHENOL IN THE ENVIRONMENT: EVIDENCE FOR ITS ORIGIN FROM COMMERCIAL PENTACHLOROPHENOL BY NEGATIVE CHEMICAL IONIZATION MASS SPECTROMETRY  

EPA Science Inventory

Commercial pentachlorophenol (PCP) contains significant quantities of tetrachlorophenol (TCP). The occurrence of TCP in environmental samples provides a chemical marker for PCP originating from commercial formulations. Negative chemical ionization mass spectrometry has been used ...

296

ELECTRON AFFINITIES OF POLYNUCLEAR AROMATIC HYDROCARBONS AND NEGATIVE ION CHEMICAL IONIZATION SENSITIVITIES  

EPA Science Inventory

Negative-ion chemical-ionization mass spectrometry (NICI MS) has the potential to be a very useful technique in identifying various polycyclic aromatic hydrocarbons (PAHs) in soil and sediment samples. Some PAHs give much stronger signals under NICI MS conditions than others. On ...

297

Sample introduction and pressure measuring system for chemical ionization mass spectrometers  

Microsoft Academic Search

One of the difficulties with using chemical ionization mass spectrometry (CIMS) in magnetic sector instruments has been that of electrical dischargers through the gaseous sample between the ion source, which may be at potentials at 10kV and ground. A sample introduction method is presented to offset this. It was first used at the University of Nebraska, Lincoln on a modified

A. J. Illies; M. T. Bowers; G. G. Meisels

1981-01-01

298

Prospect of life on cold planets with low atmospheric pressures  

NASA Astrophysics Data System (ADS)

Stable liquid water on the surface of a planet has been viewed as the major requirement for a habitable planet. Such approach would exclude planets with low atmospheric pressures and cold mean surface temperatures (like present Mars) as potential candidates for extraterrestrial life search. Here we explore a possibility of the liquid water formation in the extremely shallow (1-3 cm) subsurface layer under low atmospheric pressures (0.1-10 mbar) and low average surface temperatures (~-30 C). During brief periods of simulated daylight warming the shallow subsurface ice sublimates, the water vapor can diffuse through the porous surface layer of soil temporarily producing supersaturated conditions in the soil, which lead to the formation of liquid films. We show that non-extremophile terrestrial microorganisms (Vibrio sp.) can grow and reproduce under such conditions. The necessary conditions for metabolism and reproduction are the sublimation of ground ice through a thin layer of soil and short episodes of warm temperatures at the planetary surface.

Pavlov, A. A.; Vdovina, M.

2009-12-01

299

Atmospheric pressure loading effects on Global Positioning System coordinate determinations  

SciTech Connect

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged.

Vandam, T.M.; Blewitt, G.; Heflin, M.B. [NOAA, Silver Spring, MD (United States)]|[Univ. of Newcastle upon Tyne, Newcastle upon Tyne (United Kingdom)]|[Jet Propulsion Laboratory, Pasadena, CA (United States)

1994-12-01

300

Atmospheric-Pressure Plasma Cleaning of Contaminated Surfaces  

SciTech Connect

The purpose of this project was to demonstrate a practical, environmentally benigh technology for the surface decontamination and decommissioning of radioactive waste. A low temperature, atmospheric pressure plasma has been developed with initial support from the DOE, Environmental Management Sciences Program. This devise selectively etches radioactive metals from surfaces, rendering objects radiation free and suitable for decommissioning. The volatile reaction products are captured on filters, which yields a tremendous reduction in the volume of the waste. The technology shows a great potential for accelerating the clean-up effort for the equipment and structures contaminated with radioactive materials within the DOE complex. The viability of this technology has been demonstrated by selectively and rapidly stripping uranium from stainless steel surfaces at low temperature. Studies on uranium oxide have shown that etch rates of 4.0 microns per minute can be achieved at temperature below 473 K. Over the past three years, we have made numerous improvements in the design of the atmospheric pressure plasma source. We are now able to scale up the plasma source to treat large surface areas.

Robert F. Hicks; Hans W. Herrmann

2003-12-15

301

Repetitively pulsed atmospheric pressure discharge treatment of rough polymer surfaces: I. Humid air discharges  

NASA Astrophysics Data System (ADS)

Plasmas generated at atmospheric pressure are used to functionalize the surfaces of polymers by creating new surface-resident chemical groups. The polymers used in textiles and biomedical applications often have non-planar surfaces whose functionalization requires penetration of plasma generated species into sometimes complex surface features. In this regard, the atmospheric pressure plasma treatment of a rough polypropylene surface was computationally investigated using a two-dimensional plasma hydrodynamics model integrated with a surface kinetics model. Repetitively pulsed discharges produced in a dielectric barrier-corona configuration in humid air were considered to affix O. Macroscopic non-uniformities in treatment result from the spatial variations in radical densities which depend on the polarity of the discharge. Microscopic non-uniformities arise due to the higher reactivity of plasma produced species, such as OH radicals, which are consumed before they can diffuse deeper into surface features. The consequences of applied voltage magnitude and polarity, and the relative humidity on discharge dynamics and radical generation leading to surface functionalization, are discussed.

Bhoj, Ananth N.; Kushner, Mark J.

2008-08-01

302

Treatment of polycarbonate by dielectric barrier discharge (DBD) at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Generally most plastic materials are intrinsically hydrophobic, low surface energy materials, and thus do not adhere well to other substances. Surface treatment of polymers by discharge plasmas is of great and increasing industrial application because it can uniformly modify the surface of sample without changing the material bulk properties and is environmentally friendly. The plasma processes that can be conducted under ambient pressure and temperature conditions have attracted special attention because of their easy implementation in industrial processing. Present work deals with surface modification of polycarbonate (PC) by a dielectric barrier discharge (DBD) at atmospheric pressure. The treatment was performed in a parallel plate reactor driven by a 60Hz power supply. The DBD plasmas at atmospheric pressure were generated in air and nitrogen. Material characterization was carried out by contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The surface energy of the polymer surface was calculated from contact angle data by Owens-Wendt method using distilled water and diiodomethane as test liquids. The plasma-induced chemical modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. Due to these surface modifications the DBD-treated polymers become more hydrophilic. Aging behavior of the treated samples revealed that the polymer surfaces were prone to hydrophobic recovery although they did not completely recover their original wetting properties.

Kostov, K. G.; Hamia, Y. A. A.; Mota, R. P.; dos Santos, A. L. R.; Nascente, P. A. P.

2014-05-01

303

A theoretical insight into low-temperature atmospheric-pressure He+H2 plasmas  

NASA Astrophysics Data System (ADS)

H2-containing low-temperature plasmas are used in a wide range of industrial applications. In recent decades, efforts have been made to understand and improve the performance of these plasmas, mainly when operated at low and medium pressures. Studies of hydrogen-containing plasmas at atmospheric pressure, however, are scarce despite the potential advantage of operation in a vacuum-free environment. Here the chemistry of low-temperature atmospheric-pressure He + H2 plasmas is studied by means of a global model that incorporates 20 species and 168 reactions. It is found that for a fixed average input power the plasma density decreases sharply when the H2 concentration is higher than ˜0.2%, whereas the atomic H density peaks at a H2 concentration of ˜2%. Operation at larger H2 concentrations leads to lower plasma densities and lower H concentrations because at high H2 concentrations significant power is dissipated via vibrational excitation of H2 and there is an increasing presence of negative ions (H-). Key plasma species and chemical processes are identified and reduced sets of reactions that capture the main physicochemical processes of the discharge are proposed for use in computationally demanding models. The actual waveform of the input power is found to affect the average density of electrons, ions and metastables but it has little influence on the density of species requiring low energy for their formation, such as atomic hydrogen and vibrational states of hydrogen.

Liu, Ding-Xin; Iza, Felipe; Wang, Xiao-Hua; Ma, Zhi-Zhen; Rong, Ming-Zhe; Kong, Michael G.

2013-10-01

304

Development of antimicrobial coatings by atmospheric pressure plasma using a guanidine-based precursor.  

PubMed

Antimicrobial coatings deposited onto ultra high molecular weight polyethylene (UHMWPE) films were investigated using an atmospheric pressure - plasma enhanced chemical vapor deposition (AP-PECVD) process. Varying concentrations of a guanidine-based liquid precursor, 1,1,3,3-tetramethylguanidine, were used, and different deposition conditions were studied. Attenuated total reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were used to study the chemical structure and elemental composition of the coatings. Conformity, morphology, and coating thickness were assessed through SEM and AFM. Optimal AP-PECVD parameters were chosen and applied to deposit guanidine coatings onto woven fabrics. The coatings exhibited high antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) based on a modified-AATCC 100 test standard, where 2-5 log reductions were achieved. PMID:24164174

Yim, Jacqueline H; Fleischman, Michelle S; Rodriguez-Santiago, Victor; Piehler, Lars T; Williams, André A; Leadore, Julia L; Pappas, Daphne D

2013-11-27

305

Generation and characteristic survey of atmospheric-pressure dry, vapor, mist plasma jet using high-frequency high-voltage power supply  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure plasma jet has attracted in the various fields for example surface treatment of materials, bacterial killing and so on. The reasons why the plasma used these applications are because it is a non-thermal, high pressure, uniform glow plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. While passing through the plasma, the feed gas becomes excited, dissociated or ionized by electron impact. Once the gas exits, the discharge volume, ions and electrons are rapidly lost by recombination, but the fast-flowing effluent still contains neutral metastable species and radicals. In our previous study, GFP-7R proteins were promoted delivering into the HeLa cells by dry plasma jet. In this case, we irradiated dry plasma jet only the surface of cell suspension. Therefore, it may be expected that raising the ratio of surface area/volume exposed to plasma by to mist the cell suspension causes further improvement of protein transduction efficiency by irradiating plasma. In this study, we investigated the optimal driving parameters of the plasma jets. The length of dry, vapor, and mist plasma jets and the generated chemical species of each plasma jet will be introduced at the conference.

Takamura, Norimitsu; Wang, Douyan; Namihira, Takao; Akiyama, Hidenori

2012-10-01

306

Ambient diode laser desorption dielectric barrier discharge ionization mass spectrometry of nonvolatile chemicals.  

PubMed

In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface. PMID:23419061

Gilbert-López, Bienvenida; Schilling, Michael; Ahlmann, Norman; Michels, Antje; Hayen, Heiko; Molina-Díaz, Antonio; García-Reyes, Juan F; Franzke, Joachim

2013-03-19

307

[Development of a membrane inlet-single photon ionization/chemical ionization-mass spectrometer for online analysis of VOCs in water].  

PubMed

A home-made membrane inlet- single photon ionization/chemical ionization- time-of-flight mass spectrometer has been described. A vacuum ultraviolet (VUV) lamp with photon energy of 10.6 eV was used as the light source for single photon ionization (SPI). Chemical ionization (CI) was achieved through ion-molecule reactions with O2- reactant ions generated by photoelectron ionization. The two ionization modes could be rapidly switched by adjusting electric field in the ionization region within 2 s. Membrane inlet system used for rapid enrichment of volatile organic compounds (VOCs) in water was constructed by using a polydimethylsiloxane (PDMS) membrane with a thickness of 50 microm. A purge gas was added to accelerate desorption of analytes from the membrane surface. The purge gas could also help to prevent the pump oil back-streaming into the ionization region from the analyzer chamber and improve the signal to noise ratio (S/N). Achieved detection limits were 2 microg x L(-1) for methyl tert-butyl ether (MTBE) in SPI mode and 1 microg x L(-1) for chloroform in SPI-CI mode within 10 s analysis time, respectively. The instrument has been successfully applied to the rapid analysis of MTBE in simulated underground water nearby petrol station and VOCs in disinfected drinking water. The results indicate that the instrument has a great application prospect for online analysis of VOCs in water. PMID:22468530

Hua, Lei; Wu, Qing-Hao; Hou, Ke-Yong; Cui, Hua-Peng; Chen, Ping; Zhao, Wu-Duo; Xie, Yuan-Yuan; Li, Hai-Yang

2011-12-01

308

Fragmentation of allylmethylsulfide by chemical ionization: dependence on humidity and inhibiting role of water.  

PubMed

We report on a previously unknown reaction mechanism involving water in the fragmentation reaction following chemical ionization. This result stems from a study presented here on the humidity-dependent and energy-dependent endoergic fragmentation of allyl methyl sulfide (AMS) upon protonation in a proton transfer reaction-mass spectrometer (PTR-MS). The fragmentation pathways were studied with experimental (PTR-MS) and quantum chemical methods (polarizable continuum model (PCM), microhydration, studied at the MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) level of theory). We report in detail on the energy profiles, reaction mechanisms, and proton affinities (G4MP2 calculations). In the discovered reaction mechanism, water reduces the fragmentation of protonated species in chemical ionization. It does so by direct interaction with the protonated species via covalent binding (C3H5(+)) or via association (AMS·H(+)). This stabilizes intermediate complexes and thus overall increases the activation energy for fragmentation. Water thereby acts as a reusable inhibitor (anticatalyst) in chemical ionization. Moreover, according to the quantum chemical (QC) results, when water is present in abundance it has the opposite effect and enhances fragmentation. The underlying reason is a concentration-dependent change in the reaction principle from active inhibition of fragmentation to solvation, which then enhances fragmentation. This amphoteric behavior of water is found for the fragmentation of C3H5(+) to C3H3(+), and similarly for the fragmentation of AMS·H(+) to C3H5(+). The results support humidity-dependent quantification efforts for PTR-MS and chemical ionization mass spectrometry (CIMS). Moreover, the results should allow for a better understanding of ion-chemistry in the presence of water. PMID:23682687

Maihom, Thana; Schuhfried, Erna; Probst, Michael; Limtrakul, Jumras; Märk, Tilmann D; Biasioli, Franco

2013-06-20

309

Electron Density in Atmospheric Pressure Microwave Surface Wave Discharges  

SciTech Connect

In this paper, we present results of the spectroscopic measurements of the electron density in a microwave surface wave sustained discharges in Ar and Ne at atmospheric pressure. The discharge in the form of a plasma column was generated inside a quartz tube cooled with a dielectric liquid. The microwave power delivered to the discharge via rectangular waveguide was applied in the range of 200-1500 W. In all investigations presented in this paper, the gas flow rate was relatively low (0.5 l/min), so the plasma column was generated in the form of a single filament, and the lengths of the upstream and downstream plasma columns were almost the same. The electron density in the plasma columns was determined using the method based on the Stark broadening of H{sub {beta}} spectral line, including plasma region inside the waveguide which was not investigated earlier.

Jasinski, M.; Zakrzewski, Z. [Centre for Plasma and Laser Engineering, Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-952 Gdansk (Poland); Mizeraczyk, J. [Centre for Plasma and Laser Engineering, Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-952 Gdansk (Poland); Department of Marine Electronics, Gdynia Martime University, Morska 83, 81-225 Gdynia (Poland)

2008-03-19

310

Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma  

NASA Astrophysics Data System (ADS)

In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

Setareh, Salarieh; Davoud, Dorranian

2013-11-01

311

Development of ac corona discharge modes at atmospheric pressure  

SciTech Connect

Corona discharges in gases exist under several distinctive forms. In this paper, a survey study has been made of ac corona discharge modes generated in some different gases fed in a wire-duct reactor with a constant rate of flowing at atmospheric pressure. The properties of different corona modes are analyzed under some condition transitions from Trichel pulses to a steady glow. In the course of the presented experimental work, numerous apparent contradictions with earlier observations necessitated further study and are given to provide more information on the physical mechanisms of the ac corona discharges. Furthermore, we have gained insight into some new technologies and applications of the environmentally friendly corona and plasma discharges.

El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed [Department of Physics, Faculty of Science, Assiut University, 71516 Assiut (Egypt)

2011-02-15

312

Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth  

NASA Astrophysics Data System (ADS)

Growth stimulation characteristics of plants seeds are investigated by an atmospheric discharge irradiation into plasma seeds. Atmospheric pressure plasma torch is consisted of alumina ceramics tube and the steel mesh electrodes wind inside and outside of the tube. When AC high voltage (8 kHz) is applied to the electrode gap, the barrier discharge plasma is produced inside the alumina ceramics tube. The barrier discharge plasma is blown outside with the gas flow in ceramics tube. Radish sprouts seeds locate at 1 cm from the torch edge. The growth stimulation was observed in the length of a stem and a root after the plasma irradiation. The stem length increases approximately 2.8 times at the cultivation time of 24 h. And the growth stimulation effect is found to be maintained for 40 h, after sowing seeds. The mechanism of the growth stimulation would be the redox reaction inside plant cells induced by oxygen radicals.

Akiyoshi, Yusuke; Hayashi, Nobuya; Kitazaki, Satoshi; Koga, Kazunori; Shiratani, Masaharu

2011-11-01

313

Phenomena of oscillations in atmospheric pressure direct current glow discharges  

SciTech Connect

Self-sustained oscillations in a dc glow discharge with a semiconductor layer at atmospheric pressure were investigated by means of a one-dimensional fluid model. It is found that the dc glow discharge initially becomes unstable in the subnormal glow region and gives rise to oscillations of plasma parameters. A variety of oscillations with one or more frequencies have been observed under different conditions. The discharge oscillates between the glow discharge mode and the Townsend discharge mode in the oscillations with large amplitude while operates in the subnormal glow discharge mode all the while in the oscillations with small amplitude. Fourier Transform spectra of oscillations reveal the transition mechanism between different oscillations. The effects of semiconductor conductivity on the oscillation frequency of the dominant mode, gas voltage, as well as the discharge current have also been analyzed.

Liu, Fu-cheng [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)] [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Yan, Wen; Wang, De-zhen [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2013-12-15

314

Atmospheric pressure vapour phase decomposition: a proof of principle.  

PubMed

In the present work we demonstrated that the digestion of difficult matrices (high boiling petrochemical fractions and distillation bottoms) can be achieved by oxidation with nitric acid vapours at atmospheric pressure employing simple laboratory glassware. The application of this procedure as a digestion method prior to Total Reflection X-Ray Fluorescence (TXRF) is presented, although the employment of other detection techniques may be foreseen. The method ensured a fast, less than half an hour, treatment time and detection limits in the range 20-100 ?g/kg for As, Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Zn, whereas higher values were obtained for Ba, Ca, K, P, Rh, Ti and V (0.3-3 mg/kg). The potentialities and limitations of this procedure were discussed: the application to a broad range of matrices may be foreseen. PMID:23158304

Cinosi, Amedeo; Andriollo, Nunzio; Tibaldi, Francesca; Monticelli, Damiano

2012-11-15

315

Time and space variability of spectral estimates of atmospheric pressure  

NASA Technical Reports Server (NTRS)

The temporal and spatial behaviors of atmospheric pressure spectra over the northern Italy and the Alpine massif were analyzed using data on surface pressure measurements carried out at two microbarograph stations in the Po Valley, one 50 km south of the Alps, the other in the foothills of the Dolomites. The first 15 days of the study overlapped with the Alpex Intensive Observation Period. The pressure records were found to be intrinsically nonstationary and were found to display substantial time variability, implying that the statistical moments depend on time. The shape and the energy content of spectra depended on different time segments. In addition, important differences existed between spectra obtained at the two stations, indicating a substantial effect of topography, particularly for periods less than 40 min.

Canavero, Flavio G.; Einaudi, Franco

1987-01-01

316

Generation of reactive species by an atmospheric pressure plasma jet  

NASA Astrophysics Data System (ADS)

The role of gas mixing in reactive species delivery to treatment surfaces for an atmospheric pressure capacitively coupled plasma helium jet is investigated by numerical modelling. Atomic oxygen in the jet effluent is shown to quickly convert to ozone for increasing device to surface separation due to the molecular oxygen present in the gas mixture. Surface profiles of reactive oxygen species show narrow peaks for atomic oxygen and broader surface distributions for ozone and metastable species. Production efficiency of atomic oxygen to the helium plasma jet by molecular oxygen admixture is shown to be dependent on electro-negativity. Excessive molecular oxygen admixture results in negative ion dominance over electrons which eventually quenches the plasma. Interaction of the plasma jet with an aqueous surface showed hydrogen peroxide as the dominant species at this interface. Gas heating by the plasma is found to be dominated by elastic electron collisions and positive ion heating. Comparison with experimental measurements for atomic oxygen shows good agreement.

Kelly, S.; Turner, M. M.

2014-12-01

317

Atmospheric pressure loading effects on Global Positioning System coordinate determinations  

NASA Technical Reports Server (NTRS)

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged. The source of the remaining discrepancy between the modeled and observed loading signal may be the result of (1) anisotropic effects in the Earth's loading response, (2) errors in GPS estimates of tropospheric delay, (3) errors in the surface pressure data, or (4) annual signals in the time series of loading and station heights. In addition, we find that using site dependent coefficients, determined by fitting local pressure to the modeled radial displacements, reduces the variance of the measured station heights as well as or better than using the global convolution sum.

Vandam, Tonie M.; Blewitt, Geoffrey; Heflin, Michael B.

1994-01-01

318

Ionization mechanisms related to negative Ion APPI, APCI, and DART  

Microsoft Academic Search

A recent report found that negative ion atmospheric pressure photoionization (Ni-APPI) and direct analysis in real time (Ni-DART)\\u000a ionize compounds by electron capture, dissociative electron capture, proton abstraction, and anion adduction. The authors\\u000a of this report suggested that the common ionization of Ni-APPI and Ni-DART demonstrated that these techniques ionize a wider\\u000a array of compounds than negative ion atmospheric pressure

Charles N. McEwen; Barbara S. Larsen

2009-01-01

319

Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS  

Microsoft Academic Search

The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass\\u000a spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined.\\u000a Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified\\u000a reference materials (CRM) of CWA degradation products for the detection

Wes E. Steiner; Charles S. Harden; Feng Hong; Steve J. Klopsch; Vincent M. McHugh

2006-01-01

320

Static Water Contact Angle Analysis of Cyclonic Atmospheric Pressure Plasma-Activated Polycarbonate  

NASA Astrophysics Data System (ADS)

Polycarbonate (PC) films were activated using cyclonic atmospheric pressure plasma. The experimentally measured gas phase temperature was from 30 to 95 °C, demonstrating that this cyclonic atmospheric pressure plasma can treat heat-sensitive polymeric materials at the low temperatures. The surface hydrophilicity changes of cyclonic atmospheric pressure plasma-treated PC films were determined by water contact angle analysis. The activation effects of plasma operational parameters including treatment time, plasma power, and distance of nozzle to substrate on the PC surface features were investigated. The glow feature and luminous plasma species in the cyclonic atmospheric pressure plasma were identified by optical emission spectroscopy (OES). Cyclonic atmospheric pressure plasma-activated PC films showed a significant decrease in water contact angle. In this investigation, we developed an innovative technique for chamberless polymeric surface activation by this atmospheric pressure plasma processing.

Huang, Chun; Wu, Shin-Yi; Liu, Yu-Chia; Chang, Ya-Chi; Tsai, Ching-Yuan

2011-01-01

321

Cell immobilization on polymer by air atmospheric pressure plasma jet treatment  

NASA Astrophysics Data System (ADS)

The study of cell immobilization on delicate polymer by an air atmospheric pressure plasma jet (AAPPJ) is required for its medical application. The aim of this study was to evaluate whether AAPPJ treatment induce cell immobilization effect on delicate polymers without significant change of surface roughness by AAPPJ treatment. After surface roughness, dynamic contact angle, and chemical characteristics were investigated, the immobilization effect was evaluated with the mouse fibroblast L929 cell line. Surface roughness change was not observed (P > 0.05) in either delicate dental wax or polystyrene plate (PSP) as advancing and receding contact angles significantly decreased (P < 0.05), thanks to decreased hydrocarbon and formation of oxygen-related functional groups in treated PSP. Adherent L929 cells with elongated morphology were found in treated PSP along with the formation of immobilization markers vinculin and actin cytoskeleton. Increased PTK2 gene expression upregulated these markers on treated PSP.

Lee, Jung-Hwan; Kwon, Jae-Sung; Om, Ji-yeon; Kim, Yong-Hee; Choi, Eun-Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2014-08-01

322

Direct measurement of methyl radicals in a methane/air flame at atmospheric pressure by radar REMPI.  

PubMed

We report the direct measurements of methyl radicals (CH(3)) in methane/air flames at atmospheric pressure by using coherent microwave Rayleigh scattering (Radar) from Resonance Enhanced Multi-Photon Ionization (REMPI), also known as the Radar REMPI technique. A tunable dye laser was used to selectively induce the (2 + 1) REMPI ionization of methyl radicals (CH(3), 3p(2)A(2)('')0(0)(0) band) in a near adiabatic and premixed laminar methane/air flame, generated by a Hencken burner. In situ measurements of the REMPI electrons were made by non-intrusively using a microwave homodyne transceiver detection system. The REMPI spectrum of the CH(3) radical was obtained and a spatial distribution of the radicals limited by focused laser beam geometry, approximately 20 µm normal to the flame front and 2.4 mm parallel to the flame, was determined. The measured CH(3) was in good agreement with numerical simulations performed using the detailed kinetic mechanism of GRI-3.0. To the authors' knowledge, these experiments represent the first directly-measured spatially-resolved CH(3) in a flame at atmospheric pressure. PMID:22109424

Wu, Yue; Bottom, Andrew; Zhang, Zhili; Ombrello, Timothy M; Katta, Viswanath R

2011-11-21

323

Electron impact and chemical ionization mass spectral analysis of a volatile uranyl derivative  

SciTech Connect

Quadrupole mass spectral analysis of the volatile uranium ligand complex bis (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) dioxouranium-di-n-butyl sulfoxide is described utilizing electron impact (EI) and methane chemical ionization (CI) ion sources. All major ions are tentatively identified and the potential usefulness of this complex for determining uranium isotope /sup 235/U//sup 238/U abundance is demonstrated.

Reutter, D.J.; Hardy, D.R.

1981-01-01

324

Chemical imaging of artificial fingerprints by desorption electro-flow focusing ionization mass spectrometry.  

PubMed

Desorption electro-flow focusing ionization (DEFFI) mass spectrometry was used to image chemical distributions of endogenous, e.g., fatty acids, and trace exogenous compounds, e.g., explosives, narcotics and lotions, in deposited and lifted artificial fingerprints, directly from forensic lift tape. An artificial fingerprint mold and synthetic fingerprint material were incorporated for the controlled deposition of material for technique demonstration and evaluation. PMID:24566545

Forbes, Thomas P; Sisco, Edward

2014-06-21

325

Radioimmunoassay and chemical ionization/mass spectrometry compared for plasma cortisol determination  

SciTech Connect

A method is described for determination of cortisol in plasma and urine, based on chemical ionization/mass spectrometry with deuterium-labeled cortisol as the internal standard. The within-run precision (CV) was 2.5-5.7%, the between-run precision 4.6%. Results by this method were compared with those by a radioimmunological method (RIANEN Cortisol, New England Nuclear) for 395 plasma samples. The latter method gave significantly higher (approx. 25%) cortisol values.

Lindberg, C. (AB Draco, Lund, Sweden); Johnson, S.; Hedner, P.; Gustafsson, A.

1982-01-01

326

Real-time monitoring of volatile organic compounds using chemical ionization mass spectrometry  

DOEpatents

A system for on-line quantitative monitoring of volatile organic compounds (VOCs) includes pressure reduction means for carrying a gaseous sample from a first location to a measuring input location maintained at a low pressure, the system utilizing active feedback to keep both the vapor flow and pressure to a chemical ionization mode mass spectrometer constant. A multiple input manifold for VOC and gas distribution permits a combination of calibration gases or samples to be applied to the spectrometer.

Mowry, Curtis Dale (Albuquerque, NM); Thornberg, Steven Michael (Peralta, NM)

1999-01-01

327

The analysis of trichothecenes in wheat and human plasma samples by chemical ionization tandem mass spectrometry  

Microsoft Academic Search

Ammonia desorption chemical ionization (D\\/CI) tandem mass spectrometry (method A), isobutane D\\/CI tandem mass spectrometry using reactive collisions with ammonia (method B), and gas chromatography negative CI (GC-NCI) tandem mass spectrometry (method C) were compared for the detection and quantitation of trichothecenes in spiked human plasma and wheat samples. The trichothecenes were analyzed as their heptafluorobutyrate (HFB) esters in method

R. Kostiainen; A. Rizzo; A. Hesso

1989-01-01

328

Supersonic jet/multiphoton ionization spectrometry of chemical species resulting from thermal decomposition and laser ablation of polymers  

SciTech Connect

The chemical species resulting from thermal decomposition and laser ablation of polymers are measured by excitation/fluorescence and multiphoton ionization/mass spectrometries after supersonic jet expansion for rotational cooling to simply the optical spectrum. The signal of minor chemical species occurred is strongly enhanced by resonant excitation and multiphoton ionization, and even the isomer can be clearly differentiated. For example, p-cresol occurred by thermal decomposition of polycarbonate is detected selectively by mass-selected resonant multiphoton ionization spectrometry. Various chemical species occurred by laser ablation of even a polystyrene foam are also measured by this technique.

Hozumi, Masami; Murata, Yoshiaki; Cheng-Huang Lin; Imasaka, Totaro [Department of Chemical Science and Technology, Faculty of Engineering, Hakozaki, Higashi-Ku, Fukuoka 812 (Japan)

1995-04-01

329

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials  

NASA Technical Reports Server (NTRS)

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrate and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O and adsorbed H2O. The spectal character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micrometers, 2.2 micrometers, 2.7 micrometers, 3 micrometers, and 6 micrometers are reported here in spetra measured under Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micrometer band depth is 8-17%; this band is much stonger under moist conditions. Under Marslike atmospheric conditions the 1.9-micrometer feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micrometer feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3- micrometer band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micromter band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micrometers and 2.27 micrometers remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.; Pieters, Carle M.

1995-01-01

330

Filamentation in argon microwave plasma at atmospheric pressure  

SciTech Connect

Filamentation in an argon plasma is studied using a microwave cavity at atmospheric pressure. We show that the size and gas temperature of the filaments increase with the power absorbed by the plasma. The appearance of an additional filament occurs at specific values of the absorbed power. Each new filament appears with a smaller diameter than that of its parent filament but the sum of the diameters of all filaments evolves linearly with the absorbed power. A secondary filament emerges from a set of microfilaments created by a perturbation of the electric field (a slight increase in the incident power above a threshold value). This perturbation occurs over a larger radius than that of the parent filament. By resorting to modeling, we found that the filamentation process involves either a decrease in the effective frequency for momentum-transfer collisions, i.e., a lower electron temperature, or an increase in the electron density. We could show that a small change in the relative positions occupied by two filaments in the microwave cavity requires a strong variation in the electron temperature.

Cardoso, R. P.; Belmonte, T.; Noeel, C.; Kosior, F.; Henrion, G. [Departement CP2S, CNRS, Institut Jean Lamour, Nancy-Universite, UPV-Metz, Parc de Saurupt, CS 14234, 54042 Nancy Cedex (France)

2009-05-01

331

Rapid allergen inactivation using atmospheric pressure cold plasma.  

PubMed

Allergies have become a global problem, and effective control is greatly needed. Here, the inactivation effects of the atmospheric pressure cold plasma (APCP) on aerosolized allergens including Der p 1, Der f 1, Asp f 1, Alt a 1, and Can f 1 as well as those from indoor and outdoor environments were investigated. The effectiveness of the APCP treatment was further studied using blood sera from the allergen sensitized humans. In addition, the allergen samples were also analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Results revealed that the APCP was highly effective in reducing the allergenicity of both lab-prepared and environmental allergen aerosols. The airborne reductions were shown to range from 30% for Der p 1 to 80% for Can f 1 allergen for 0.12 s exposure. Allergnicity tests showed that the APCP treated Asp f 1 allergens caused 50% less binding with IgEs in the blood sera compared to the control. The observed allergenicity loss was due to hydroxyl radicals produced by the plasma device. The results from SDS-PAGE showed that the plasma treatment resulted in decreased size of the Asp f 1 allergen. The developed technology holds great promise in combating the allergic diseases. PMID:24490983

Wu, Yan; Liang, Yongdong; Wei, Kai; Li, Wei; Yao, Maosheng; Zhang, Jue

2014-03-01

332

Atmospheric Pressure Plasma Jet for Chem/Bio Warfare Decontamination  

NASA Astrophysics Data System (ADS)

Atmospheric Pressure Plasma Jet (APPJ) technology may provide a much needed method of CBW decontamination which, unlike traditional decon methods, is dry and nondestructive to sensitive equipment and materials. The APPJ discharge uses a high-flow feedgas consisting primarily of an inert carrier gas, such as He, and a small amount of a reactive additive, such as O2, which flows between capacitively-coupled electrodes powered at 13.56 MHz. The plasma generates highly reactive metastable and atomic species of oxygen which are then directed onto a contaminated surface. The reactive effluent of the APPJ has been shown to effectively neutralize VX nerve agent as well as simulants for anthrax and mustard blister agent. Research efforts are now being directed towards reducing He consumption and increasing the allowable stand-off distance. Recent results demonstrate that by replacing the O2 reactive additive with CO2, ozone formation is greatly reduced. This has the result of extending the lifetime of atomic oxygen by an order of magnitude or more. A recirculating APP Decon Chamber which combines heat, vacuum, forced convection and reactivity is currently being developed for enhanced decontamination of sensitive equipment. Several techniques are also being evaluated for use in an APP Decon Jet for decontamination of items which cannot be placed inside a chamber.

Herrmann, Hans W.; Henins, Ivars; Park, Jaeyoung; Selwyn, Gary S.

1999-11-01

333

Power modulation in an atmospheric pressure plasma jet  

NASA Astrophysics Data System (ADS)

Power modulation in an atmospheric pressure capacitively coupled radio frequency plasma jet is investigated by numerical modelling. The dynamics of successively pulsing the applied power on and off for a helium-oxygen (˜0.6%) plasma is investigated. The impact of power pulsing on reactive species generation and gas heating is discussed with control opportunities emphasized. Power modulation shows linear control for reactive species and heat flux delivery to a treatment surface above an initial phase of power growth. Power is found to be coupled primarily to the electrons with electron loss rates determining the interference between successive power modulation phases. Plasma decay in the power off phase is characterized by a large initial electron loss in the first 0.5 µs followed by ambipolar decay dominated by ions of opposite charge. Power modulation effects on gas heating show a larger range of temperature control when compared with convection cooling. Reactive oxygen species reaching a treatment surface are shown to typically vary over an order of magnitude for variation in the duty cycle.

Kelly, S.; Turner, M. M.

2014-12-01

334

DETERMINATION OF PHTHALATES IN WATER AND SOIL BY TANDEM MASS SPECTROMETRY UNDER CHEMICAL IONIZATION CONDITIONS WITH ISOBUTANE AS REAGENT GAS  

EPA Science Inventory

Phthalate determination is important because phthalates often are major impurities in samples and can have significant health effects. Tandem mass spectrometry under chemical ionization mass spectrometry conditions with isobutane as the reagent gas was used to determine 11 phthal...

335

Form control in atmospheric pressure plasma processing of ground fused silica  

NASA Astrophysics Data System (ADS)

Atmospheric Pressure Plasma Processing (APPP) using inductively coupled plasma has demonstrated that it can achieve comparable removal rate on the optical surface of fused silica under the atmosphere pressure and has the advantage of inducing no sub-surface damage for its non-contact and chemical etching mechanism. APPP technology is a cost effective way, compared with traditional mechanical polishing, magnetorheological finishing and ion beam figuring. Thus, due to these advantages, this technology is being tested to fabricate large aperture optics of fused silica to help shorten the polishing time in optics fabrication chain. Now our group proposes to use inductively coupled plasma processing technology to fabricate ground surface of fused silica directly after the grinding stage. In this paper, form control method and several processing parameters are investigated to evaluate the removal efficiency and the surface quality, including the robustness of removal function, velocity control mode and tool path strategy. However, because of the high heat flux of inductively coupled plasma, the removal depth with time can be non-linear and the ground surface evolvement will be affected. The heat polishing phenomenon is founded. The value of surface roughness is reduced greatly, which is very helpful to reduce the time of follow-up mechanical polishing. Finally, conformal and deterministic polishing experiments are analyzed and discussed. The form error is less 3%, before and after the APPP, when 10?m depth of uniform removal is achieved on a 60×60mm ground fused silica. Also, a basin feature is fabricated to demonstrate the figuring capability and stability. Thus, APPP is a promising technology in processing the large aperture optics.

Li, Duo; Wang, Bo; Xin, Qiang; Jin, Huiliang; Wang, Jun; Dong, Wenxia

2014-08-01

336

Trends in surface engineering of biomaterials: atmospheric pressure plasma deposition of coatings for biomedical applications  

NASA Astrophysics Data System (ADS)

Cold plasma processes for surface engineering of biomaterials and biomedical devices are traditionally performed at low pressure; more and more, though, surface modification plasma processes at atmospheric pressure are also gaining popularity. This short review is aimed to list briefly atmospheric pressure plasma processes reported, in the last decade, for adapting the surface of materials to the best interactions with cells, bacteria and biomolecules.

da Ponte, G.; Sardella, E.; Fanelli, F.; D'Agostino, R.; Favia, P.

2011-11-01

337

Generation of DC-Driven Non-Thermal Plasma in Atmospheric Pressure Air  

Microsoft Academic Search

The main advantage of atmospheric pressure plasma processing is that it requires much lower investment costs, because no vacuum devices are needed, in the case of ambient air, not even a housing. From these points of view, a dc-driven atmospheric pressure air plasma generator, which is pen-type, has been developed in this paper. The main experimental results are as follows.

J. Choi; T. Namihira; S. Katsuki; H. Akiyama

338

Inactivation of Salmonella Enteritidis PT 30 on Almonds with a Fluidized Bed Atmospheric Pressure Plasma  

E-print Network

Inactivation of Salmonella Enteritidis PT 30 on Almonds with a Fluidized Bed Atmospheric Pressure investigated the use of a fluidized bed atmospheric pressure plasma (APP) as a possible pasteurization method of inoculum. Almonds were placed in a fluidized bed APP treatment chamber fixed to an Enercon Dyne

Heller, Barbara

339

Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application  

NASA Astrophysics Data System (ADS)

Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

Jain, Vishal; Visani, A.; Patil, C.; Patel, B. K.; Sharma, P. K.; John, P. I.; Nema, S. K.

2014-08-01

340

Kinetic simulation of direct-current driven microdischarges in argon at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A one-dimensional, implicit particle-in-cell Monte Carlo collision model is used to simulate the plasma kinetic properties at a steady state in a parallel-plate direct current argon glow microdischarge under various operating conditions, such as driving voltage (30–1000 V) and gap size (10–1000 µm) at atmospheric pressure. First, a comparison between rf and dc modes is shown for the same pressure, driving voltage and gap spacing. Furthermore, the effect of gap size scaling (in the range of 10–1000 µm) on the breakdown voltage, peak electron density and peak electron current density at the breakdown voltage is examined. The breakdown voltage is lower than 150 V in all gaps considered. The microdischarge is found to have a neutral bulk plasma region and a cathode sheath region with size varying with the applied voltage and the discharge gap. In our calculations, the electron and ion densities are of the order of 1018–1023 m?3, which is in the glow discharge limit, as the ionization degree is lower than 1% . The electron energy distribution function shows a two-energy group distribution at a gap of 10 µm and a three-energy group distribution at larger gaps such as 200 µm and 1000 µm, emphasizing the importance of the gap spacing in dc microdischarges.

Zhang, Ya; Jiang, Wei; Bogaerts, Annemie

2014-10-01

341

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION  

SciTech Connect

Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (?10{sup –7}) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10{sup –6}-1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H{sub 2}, or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks.

Stark, C. R.; Helling, Ch.; Rimmer, P. B. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Diver, D. A., E-mail: craig.stark@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

2013-10-10

342

Vortex Threshold: Experimental Results at Martian Atmospheric Pressures  

NASA Astrophysics Data System (ADS)

Many examples of Martian dust devils and tracks left by their passage have been identified in Viking and Mars Orbital Camera images and inferred from lander data (Viking and Mars Pathfinder). Recent surveys suggest that dust devils may be common phenomena on Mars and, unlike Earth, could contribute significantly to the global dust budget. Previous studies have noted the apparent paradox that Martian airborne dust is abundant and only a few microns in diameter yet experiments at Mars pressures suggest current Martian ambient wind speeds are insufficient to lift such fine particles from the surface; speeds of the order of 10s or even 100s of m/s are required. Local wind speeds within terrestrial dust devils are typically much greater than ambient wind speeds, but we have no in-situ measurements of the velocity structure of Mars dust devils and so cannot directly quantify their ability to entrain material. However, by using laboratory simulations we can directly measure the ability of a vortex to lift material of known size and density under a variety of atmospheric pressures. We have constructed a vortex generator consisting of a large vertical cylinder containing a rotor comprising four vertical blades and capable of speeds up to 4500 RPM. Beneath the cylinder is a 2.4 by 2.4 m tabletop which can be covered in particles for threshold tests or instrumented with pressure transducers to measure the pressure structure of the vortex. The distance between the cylinder and the tabletop and the height of the blades within the cylinder can be varied to generate a wide range of geometries and intensities of vortices. Recently, the apparatus has been operated at the NASA-Ames Research Center Mars Surface Wind Tunnel facility to simulate Martian atmospheric conditions. We have measured vortex `saltation' threshold using many types of particles ranging in density from walnut shells (1.1 kg/m-3) to steel grit (7.6 kg/m-3) with particle sizes from 2 to 2000 microns and using atmospheric pressures ranging from 10 mbar (representing current Mars atmospheric conditions) to ambient. As expected, vortex threshold was more difficult to achieve with lower pressure conditions. Only the `optimum' particles (those with low densities and particle sizes ranging from 70 to 350 micron) reached full `saltation' at 10 mbar pressure before the apparatus speed limit was reached. Our results suggest that vortex threshold is directly analogous to boundary layer shear threshold for sand-sized particles at pressure from 65 mbar to ambient. We have used this result to equate vortex and boundary layer results in the sand-sized particle regime and hence to compare vortex threshold data with boundary layer results for smaller particles and lower pressures. We used empirical boundary layer expressions for threshold (corrected for particle size and particle Reynold's number). In all cases, vortex action appears more efficient than boundary layer winds at lifting small dust-sized particles and at lifting all particles at very low pressure. We conclude that Martian dust devils are more efficient mechanisms for particle entrainment than boundary layer winds, not merely because they have enhanced local wind speeds but also through another intrinsic mechanism. We suggest that a lift force caused by the passage of the low-pressure core of the dust devil over the particles would have such an effect and present examples of experimental `pressure-well' measurements at low pressures to support this.

Balme, M.; Greeley, R.; Phoreman, J.; Iversen, J.; Mickelson, B.; Beardmore, G.; Metzger, S.

2002-12-01

343

Atmospheric pressure He-air plasma jet: Breakdown process and propagation phenomenon  

SciTech Connect

In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 10{sup 11} cm{sup -3} and it reaches to the maximum of 10{sup 12} cm{sup -3}.

Begum, Asma [Independent University, Bangladesh, School of Engineering and Computer Science, Bashundhara, Dhaka (Bangladesh); Laroussi, Mounir [Old Dominion University, Department of Electrical and Computer Engineering, Norfolk, Virginia (United States); Pervez, Mohammad Rasel [Master Mind College, Department of Physics, Dhanmondi, Dhaka (Bangladesh)

2013-06-15

344

Atmospheric pressure dielectric barrier discharges interacting with liquid covered tissue  

NASA Astrophysics Data System (ADS)

The interaction of plasmas with liquids is of increasing importance in biomedical applications. Tissues treated by atmospheric pressure dielectric barrier discharges (DBDs) in plasma medicine are often covered by a thin layer of liquid, typically a blood serum like water with dissolved gases and proteins up to hundreds of micrometres thick. The liquid processes the plasma-produced radicals and ions prior to their reaching the tissue. In this paper, we report on a computational investigation of the interaction of DBDs in humid air with a thin water layer covering tissue. The water layer, 50-400 µm thick, contains dissolved O2aq (aq means an aqueous species) and alkane-like hydrocarbons (RHaq). In the model, the DBDs are operated with multiple pulses at 100 Hz followed by a 1 s afterglow. Gas phase reactive oxygen and nitrogen species (RONS) intersect the water-vapour saturated air above the liquid and then solvate when reaching the water. The photolysis of water by plasma-produced UV/VUV plays a significant role in the production of radicals. Without RHaq, O_{2aq}^{-} , ONOO_{aq}^{-} , NO_{3aq}^{-} and hydronium (H_{3} O_{aq}^{+} ) dominate the water ions with H_{3} O_{aq}^{+} determining the pH. The dominant RONS in the liquid are O3aq, H2O2aq, and HNOxaq. Dissolved O2aq assists the production of HNO3aq and HOONOaq during the afterglow. With RHaq, reactive oxygen species are largely consumed, leaving an R·aq (alkyl radical) to reach the tissue. These results are sensitive to the thickness of the water layer.

Tian, Wei; Kushner, Mark J.

2014-04-01

345

Dynamics and pattern formation during microwave breakdown at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A self-organized array of plasma filaments moving towards the source has been recently observed in microwave breakdown experiments in the millimeter range at MIT (Y. Hidaka et al., Phys. Rev. Lett. 100, 035003 (2008)). These filaments are qualitatively different from the well-known filaments observed in laser breakdown, and develop transverse to the propagation direction, along the direction of the electric field polarization. A model coupling Maxwell's equations with a simple description of the plasma dynamics has been developed and has been shown to reproduce very well the experimental observations (J.P. Boeuf et al., Phys. Rev. Lett. 104, 015002 (2010)). The propagation of the plasma toward the source is due to an ionisation-diffusion mechanism and the self-organized filamentary structure is associated with the scattered field pattern. The filaments develop in the direction of the incident field due to field enhancement by polarization at their tip and form an array with a spatial period on the order of one quarter wave length. The physics and dynamics of the filamentary plasma array will be discussed in a first part, on the basis of comparisons between model and experimental results. In a second part other aspects of microwave breakdown at atmospheric pressure will be presented, such as the development of microwave streamers (that can absorb very efficiently the microwave energy under specific, resonant conditions), the formation of complex nets of plasma filaments during breakdown in an under-critical field (breakdown is initiated next to a metallic initiator and propagates, due to thermal instabilities, in a region where the microwave field is below the critical field). The context of applications of this study (plasma aided combustion and flow control, breakdown next to an antenna) will be presented briefly.

Boeuf, Jean-Pierre

2011-11-01

346

Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

A multi-scale numerical model based on hydrodynamic equations with semi-kinetic treatment of electrons is used to investigate the influence of dual frequency excitation on the effective electron energy distribution function (EEDF) in a radio-frequency driven atmospheric pressure plasma. It is found that variations of power density, voltage ratio, and phase relationship provide separate control over the electron density and the mean electron energy. This is exploited to directly influence both the phase dependent and time averaged effective EEDF. This enables tailoring the EEDF for enhanced control of non-equilibrium plasma chemical kinetics at ambient pressure and temperature.

O'Neill, C.; Waskoenig, J. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Gans, T. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)

2012-10-08

347

Real-time monitoring of volatile organic compounds using chemical ionization mass spectroscopy: Final report  

SciTech Connect

Volatile organic compound (VOC) emission to the atmosphere is of great concern to semiconductor manufacturing industries, research laboratories, the public, and regulatory agencies. Some industries are seeking ways to reduce emissions by reducing VOCs at the point of use (or generation). This paper discusses the requirements, design, calibration, and use of a sampling inlet/quadrupole mass spectrometer system for monitoring VOCs in a semiconductor manufacturing production line. The system uses chemical ionization to monitor compounds typically found in the lithography processes used to manufacture semiconductor devices (e.g., acetone, photoresist). The system was designed to be transportable from tool to tool in the production line and to give the operator real-time feedback so the process(es) can be adjusted to minimize VOC emissions. Detection limits ranging from the high ppb range for acetone to the low ppm range fore other lithography chemicals were achieved using chemical ionization mass spectroscopy at a data acquisition rate of approximately 1 mass spectral scan (30 to 200 daltons) per second. A demonstration of exhaust VOC monitoring was performed at a working semiconductor fabrication facility during actual wafer processing.

Thornberg, S.M.; Mowry, C.D.; Keenan, M.R.; Bender, S.F.A. [Sandia National Labs., Albuquerque, NM (United States). Gas Analysis Lab.; Owen, T. [Intel Corp., Rio Rancho, NM (United States)

1997-04-01

348

Direct determination of trace nitrogen dioxide by atmospheric pressure lonization mass spectrometry (APIMS) without conversion to nitric oxide.  

PubMed

The aim of this study was to develop a new method for the determination of NO(2) levels encountered in clinical settings as well as in environmental studies, using a bi-component atmospheric pressure ionization mass spectrometry (APIMS). Hydrogen (1%) diluted in pure argon was ionized by corona discharge in the first ionization component. Fifty ml of the analyte diluted in 250 ml of composite air or carbon dioxide (CO2) was introduced into the second ionization component and analyzed. When composite air was used as the sample carrier gas, NO in the analyte was oxygenated and there was an increase in the NO(2) content from that in the original analyte. However, when CO(2) was used as the sample carrier gas, the level of NO(2) in the analyte could be determined because CO(2) did not change the NO(2) content from that in the original analyte. A calibration curve with good linearity was obtained using the UG-410 APIMS system, with a regression equation of Y(%) = 5.513*10(-2) X (ppb) and a detection limit of 0.9 ppb. Since APIMS detects NO(2) direcdy within its system, the concentration of NO does not need to be measured. This system may be of great help in the accurate detection and determination of the concentration of low levels of NO(2) during inhaled NO therapy. PMID:21432192

Kinoue, T; Asai, S; Ishii, Y; Ishikawa, K; Fujii, M; Nakano, K; Hasumi, K

2000-10-01

349

Modifying the Charge State Distribution of Proteins in Electrospray Ionization Mass Spectrometry by Chemical Derivatization  

PubMed Central

Electrospray ionization (ESI) of denatured proteins produces a broad distribution of multiply-charged ions leading to multiple peaks in the mass spectrum. We investigated changes in the positive-mode ESI charge state distribution produced by several chemical modifications of denatured proteins. Capping carboxylic acid groups with neutral functional groups yields little change in charge state distribution compared to unmodified proteins. The results indicate that carboxyl groups do not play a significant role in the positive charging of denatured proteins in ESI. The modification of proteins with additional basic sites or fixed positive charges generates substantially higher charge states, providing evidence that the number of ionizable sites, rather than molecular size and shape, determines ESI charging for denatured proteins. Fixed charge modification also significantly reduces the number of protons acquired by a protein, in that the charge state envelope is not increased by the full number of fixed charges appended. This result demonstrates that Coulombic repulsion between positive charges plays a significant role in determining charge state distribution by affecting the gas-phase basicity of ionizable sites. Addition of fixed-charge moieties to a protein is a useful approach for shifting protein charge state distributions to higher charge states, and with further work, it may help limit the distribution of protein ions to fewer charge states. PMID:19481956

Krusemark, Casey J.; Frey, Brian L.; Belshaw, Peter J.

2009-01-01

350

Plasma Decomposition of Clathrate Hydrates by 2.45 GHz Microwave Irradiation at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

The purpose of this research is to develop a process to use the plasma decomposition of clathrate hydrates to produce fuel gas. An ordinary microwave (MW) oven is used as the source of 2.45 GHz MW radiation under atmospheric-pressure. The plasma decomposition of the hydrates could pave the way for a new utilization of atmospheric pressure plasma. Cyclopentane (CP) hydrate formed at atmospheric pressure was decomposed by plasma in a MW oven generating gas with a content of 65% hydrogen, 12% CO, and 8% CO2. About 7% of the MW input power was consumed to decompose the hydrates.

Nomura, Shinfuku; Eka Putra, Andi Erwin; Mukasa, Shinobu; Yamashita, Hiroshi; Toyota, Hiromichi

2011-06-01

351

Phase-resolved measurement of electric charge deposited by an atmospheric pressure plasma jet on a dielectric surface  

NASA Astrophysics Data System (ADS)

The surface charge distribution deposited by the effluent of a dielectric barrier discharge driven atmospheric pressure plasma jet on a dielectric surface has been studied. For the first time, the deposition of charge was observed phase resolved. It takes place in either one or two events in each half cycle of the driving voltage. The charge transfer could also be detected in the electrode current of the jet. The periodic change of surface charge polarity has been found to correspond well with the appearance of ionized channels left behind by guided streamers (bullets) that have been identified in similar experimental situations. The distribution of negative surface charge turned out to be significantly broader than for positive charge. With increasing distance of the jet nozzle from the target surface, the charge transfer decreases until finally the effluent loses contact and the charge transfer stops.

Wild, R.; Gerling, T.; Bussiahn, R.; Weltmann, K.-D.; Stollenwerk, L.

2014-01-01

352

Multiscale simulation of atmospheric pressure pulsed discharges used in polymer surface functionalization  

NASA Astrophysics Data System (ADS)

Atmospheric pressure pulsed plasma discharges are widely used for surface functionalization or treatment of commodity polymers to improve properties such as adhesion and wettability. Newer applications include textile fabric treatment to improve color fastness and biomedical surface functionalization. In this work, an unstructured mesh-based two-dimensional Plasma Equipment Model (PEM) was developed to investigate the physical and chemical processes in these discharges, which occur on temporal and spatial scales spanning many orders of magnitude and affect their interaction with polymer surfaces. Better insight into these processes will enable the tailoring and optimization of processing conditions. Transient phenomena (time variation of plasma properties) during breakdown in atmospheric pressure discharges are addressed, since the spatial distribution of radicals generated in the discharge is determined by the dynamics of breakdown. The breakdown dynamics is governed by a multitude of physical and chemical processes such as reaction kinetics, photoionization, electron energy transport, charged species and neutral transport. The ability to address non-equilibrium electron energy transport in plasma discharges was developed by enhancing an existing electron Monte-Carlo simulation to address multiple regions of nonequilibrium, and was demonstrated for breakdown in high pressure discharges. A high degree of uniformity in surface treatment is important for value-added materials. Increasing the proximity of reactive plasma produced species to the surface enables better uniformity, especially with polymers having complex surface shapes. The propagation of atmospheric pressure discharges in microchannels, such as those used in lab-on-a-chip devices was investigated to determine the possibility of producing reactive gas-phase radicals within small spaces, close to the surfaces requiring treatment. An integrated surface kinetics module was developed to address the cumulative surface treatment of polypropylene with microstructure, such as rough and porous surfaces, in repetitively pulsed O2 and NH3 containing discharges. Parameters such as gas composition, humidity, discharge polarity and applied power regulate the transport and reaction processes that ultimately affect the relative abundance and uniformity of various O and N surface functional groups. Electrons may penetrate gaps in the microstructure depending on discharge polarity and surface charging dynamics. The penetration of positive ions is limited due to ambipolar effects. Higher radical densities are produced near spaces in the microstructure in negative discharges. While reactive radicals are consumed here, slow-reacting radicals diffuse deeper into these spaces, treating surfaces not directly in the line-of-sight of the discharge over time. Photons generated in the discharge react with surface sites in the line-of-sight, increasing spatial nonuniformity in functionalization. An integrated incompressible fluid dynamics model was developed to investigate the impact of gas flow on radical generation and surface treatment. Convective gas flow alters the relative abundance of reactive species in the discharge that affects the surface composition. Continuous surface processing was simulated, wherein radicals formed on the polymer move out of the discharge zone but continue to react downstream. Changes in gas composition affect the relative importance of local reaction kinetics and convective transport of reactive species in the discharge.

Bhoj, Ananth N.

353

Transitions between corona, glow, and spark regimes of nanosecond repetitively pulsed discharges in air at atmospheric pressure  

E-print Network

in air at atmospheric pressure David Z. Pai,a Deanna A. Lacoste, and Christophe O. Laux Laboratoire EM2C January 2010; published online 6 May 2010 In atmospheric pressure air preheated from 300 to 1000 K.1063/1.3309758 I. INTRODUCTION Atmospheric pressure air plasmas have potential appli- cations in biomedical

Boyer, Edmond

354

Ultrasensitive Ambient Mass Spectrometric Analysis with a Pin-to-Capillary Flowing Atmospheric-Pressure Afterglow Source  

PubMed Central

The advent of ambient desorption/ionization mass spectrometry has resulted in a strong interest in ionization sources that are capable of direct analyte sampling and ionization. One source that has enjoyed increasing interest is the Flowing Atmospheric-Pressure Afterglow (FAPA). FAPA has been proven capable of directly desorbing/ionizing samples in any phase (solid, liquid, or gas) and with impressive limits of detection (<100 fmol). The FAPA was also shown to be less affected by competitive-ionization matrix effects than other plasma-based sources. However, the original FAPA design exhibited substantial background levels, cluttered background spectra in the negative-ion mode, and significant oxidation of aromatic analytes, which ultimately compromised analyte identification and quantification. In the present study, a change in the FAPA configuration from a pin-to-plate to a pin-to-capillary geometry was found to vastly improve performance. Background signals in positive- and negative-ionization modes were reduced by 89% and 99%, respectively. Additionally, the capillary anode strongly reduced the amount of atomic oxygen that could cause oxidation of analytes. Temperatures of the gas stream that interacts with the sample, which heavily influences desorption capabilities, were compared between the two sources by means of IR thermography. The performance of the new FAPA configuration is evaluated through the determination of a variety of compounds in positive- and negative-ion mode, including agrochemicals and explosives. A detection limit of 4 amol was found for the direct determination of the agrochemical ametryn, and appears to be spectrometer-limited. The ability to quickly screen for analytes in bulk liquid samples with the pin-to-capillary FAPA is also shown. PMID:21627097

Shelley, Jacob T.; Wiley, Joshua S.; Hieftje, Gary M.

2011-01-01

355

Detection of Nonvolatile Species by Laser Desorption Atmospheric Pressure Mass Spectrometry.  

National Technical Information Service (NTIS)

This work examines the use of laser desorption as a means of volatilizing thermally labile compounds for detection in atmospheric pressure mass spectrometry. A number of different classes of compounds have been examined including amino acids, purine and p...

L. Kolaitis, D. M. Lubman

1986-01-01

356

A Double Resonance Approach to Submillimeter\\/Terahertz Remote Sensing at Atmospheric Pressure  

Microsoft Academic Search

The remote sensing of gases in complex mixtures at atmospheric pressure is a\\u000achallenging problem and much attention has been paid to it. The most\\u000afundamental difference between this application and highly successful\\u000aastrophysical and upper atmospheric remote sensing is the line width associated\\u000awith atmospheric pressure broadening, ~ 5 GHz in all spectral regions. In this\\u000apaper, we discuss

Frank C. De Lucia; Douglas T. Petkie; Henry O. Everitt

2009-01-01

357

Characteristics of negative corona discharge in the working media of atmospheric-pressure nitrogen lasers  

Microsoft Academic Search

We present the results of investigations of the electrical and optical characteristics of a negative-polarity corona discharge\\u000a excited in systems of “pins-mesh” and “pins-plane” electrodes in a He\\/N2 mixture at atmospheric pressure. In order that such a corona discharge could be applied in systems of electric pumping of\\u000a the working medium of atmospheric-pressure N2-lasers, the optimum conditions should be: the

A. K. Shuaibov; L. L. Shimon; A. I. Minya; A. I. Dashchenko

1997-01-01

358

Highly sensitive carbon nanotube-embedding gas sensors operating at atmospheric pressure  

Microsoft Academic Search

Highly sensitive palladium (Pd) decorated carbon nanotube (CNT) embedding gas sensors working at atmospheric pressure were fabricated. Two types of gas sensors of bare CNTs and Pd nanoparticle decorated CNTs were synthesized by dielectrophoresis. The CNT-containing solution was dropped onto the patterned-platinum electrodes with ac bias. The CNT-embedding sensors sensitively detected 100 ppb level of NO2 in an atmospheric pressure

Ju-Hyung Yun; Joondong Kim; Yun Chang Park; Jin-Won Song; Dong-Hun Shin; Chang-Soo Han

2009-01-01

359

Atmospheric pressure glow discharge desorption mass spectrometry for rapid screening of pesticides in food.  

PubMed

Flowing afterglow atmospheric pressure glow discharge tandem mass spectrometry (APGD-MS/MS) is used for the analysis of trace amounts of pesticides in fruit juices and on fruit peel. The APGD source was rebuilt after Andrade et al. (Andrade et al., Anal. Chem. 2008; 80: 2646-2653; 2654-2663) and mounted onto a hybrid quadrupole time-of-flight mass spectrometer. Apple, cranberry, grape and orange juices as well as fruit peel and salad leaves were spiked with aqueous solutions containing trace amounts of the pesticides alachlor, atrazine, carbendazim, carbofuran, dinoseb, isoproturon, metolachlor, metolcarb, propoxur and simazine. Best limits of determination (LODs) of pesticides in the fruit juices were achieved for metolcarb (1 microg/L in apple juice), carbofuran and dinoseb (2 microg/L in apple juice); for the analysis of apple skin best LODs were 10 pg/cm(2) of atrazine, metolcarb and propoxur which corresponds to an estimated concentration of 0.01 microg/kg apple, taking into account the surface area and the weight of the apple. The measured LODs were within or below the allowed maximum residue levels (MRLs) decreed by the European Union (1-500 microg/kg for pesticides in fruit juice and 0.01-5 microg/kg for apple skin). No sample pretreatment (extraction, pre-concentration, chromatographic separation) was necessary to analyze these pesticides by direct desorption/ionization using APGD-MS and to identify them using MS/MS. This makes APGD-MS a powerful high-throughput tool for the investigation of very low amounts of pesticides in fruit juices and on fruit peel/vegetable skin. PMID:18697232

Jecklin, Matthias Conradin; Gamez, Gerardo; Touboul, David; Zenobi, Renato

2008-09-01

360

An atmospheric-pressure plasma process for C2F6 removal.  

PubMed

Perfluorocompounds (PFCs) are widely used in the semiconductor industry for plasma etching and chemical vapor deposition (CVD). They are relatively inert gases that intensely absorb infrared radiation and, therefore, aggravate the greenhouse effect. A bench-scale experimental system was designed and constructed to evaluate the effectiveness of C2F6 conversion by using dielectric barrier discharges (DBD) with atmospheric-pressure plasma processing. Experimental results indicated that the removal efficiency of C2F6 increased with applications of higher voltage and frequency. Combined plasma catalysis (CPC) is an innovative way for abatement of PFCs, and experimental results revealed that combining plasma generation with catalysts could effectively enhance C2F6 removal efficiency achieved with DBD. The major products of C2F6 with DBD processing include CO2, COF2, and CO, when O2 was included in the discharge process. Experimental results indicated that as high as 94.5% of C2F6 were removed via CPC at applied voltage of 15 kV, frequency of 240 Hz in the gas stream of N2:Ar:O2:C2F6 = 50:40:10:0.03. PMID:11329706

Chang, M B; Yu, S J

2001-04-15

361

Atmospheric pressure, density, temperature and wind variations between 50 and 200 km  

NASA Technical Reports Server (NTRS)

Data on atmospheric pressure, density, temperature and winds between 50 and 200 km were collected from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others. These data were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of the irregular atmospheric variations are presented. Time structures of the irregular variations were determined by the analysis of residuals from harmonic analysis of time series data. The observed height variations of irregular winds and densities are found to be in accord with a theoretical relation between these two quantities. The latitude variations (at 50 - 60 km height) show an increasing trend with latitude. A possible explanation of the unusually large irregular wind magnitudes of the White Sands MRN data is given in terms of mountain wave generation by the Sierra Nevada range about 1000 km west of White Sands. An analytical method is developed which, based on an analogy of the irregular motion field with axisymmetric turbulence, allows measured or model correlation or structure functions to be used to evaluate the effective frequency spectra of scalar and vector quantities of a spacecraft moving at any speed and at any trajectory elevation angle.

Justus, C. G.; Woodrum, A.

1972-01-01

362

Stability of Atmospheric-Pressure Plasma Induced Changes on Polycarbonate Surfaces  

NASA Technical Reports Server (NTRS)

Polycarbonate films are subjected to plasma treatment in a number of applications such as improving adhesion between polycarbonate and silicon alloy in protective and optical coatings. The changes in surface chemistry due to plasma treatment have tendency to revert back. Thus stability of the plasma induced changes on polymer surfaces over desired time period is very important. The objective of this study was to examine the effect of ageing on atmospheric pressure helium-plasma treated polycarbonate (PC) sample as a function of treatment time. The ageing effects were studied over a period of 10 days. The samples were plasma treated for 0.5, 2, 5 and 10 minutes. Contact angle measurements were made to study surface energy changes. Modification of surface chemical structure was examined using, X-ray Photoelectron Spectroscopy (XPS). Contact angle measurements on untreated and plasma treated surfaces were made immediately, 24, 48, 72 and 96 hrs after treatment. Contact angle decreased from 93 deg for untreated sample to 30 deg for sample plasma treated for 10 minutes. After 10 days the contact angles for the 10 minute plasma treated sample increased to 67 deg, but it never reverted back to that of untreated surface. Similarly the O/C ratio increased from 0.136 for untreated sample to 0.321 for 10 minute plasma treated sample indication increase in surface energy.

Sharma, Rajesh; Holcomb, Edward; Trigwell, Steve

2006-01-01

363

Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores  

NASA Astrophysics Data System (ADS)

A nonequilibrium Ar /O2 plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar /O2 plasma jet at an exposure distance of 0.5-1.5cm ranges from 5 to 57s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

2007-09-01

364

Cold atmospheric pressure plasma and decontamination. Can it contribute to preventing hospital-acquired infections?  

PubMed

Healthcare-associated infections (HCAIs) affect ?4.5 million patients in Europe alone annually. With the ever-increasing number of 'multi-resistant' micro-organisms, alternative and more effective methods of environmental decontamination are being sought as an important component of infection prevention and control. One of these is the use of cold atmospheric pressure plasma (CAPP) systems with clinical applications in healthcare facilities. CAPPs have been shown to demonstrate antimicrobial, antifungal and antiviral properties and have been adopted for other uses in clinical medicine over the past decade. CAPPs vary in their physical and chemical nature depending on the plasma-generating mechanism (e.g. plasma jet, dielectric barrier discharge, etc.). CAPP systems produce a 'cocktail' of species including positive and negative ions, reactive atoms and molecules (e.g. atomic oxygen, ozone, superoxide and oxides of nitrogen), intense electric fields, and ultraviolet radiation (UV). The effects of these ions have been studied on micro-organisms, skin, blood, and DNA; thus, a range of possible applications of CAPPs has been identified, including surface decontamination, wound healing, biofilm removal, and even cancer therapy. Here we evaluate plasma devices, their applications, mode of action and their potential role specifically in combating HCAIs on clinical surfaces. PMID:25146226

O'Connor, N; Cahill, O; Daniels, S; Galvin, S; Humphreys, H

2014-10-01

365

Analysis of isomeric polycyclic aromatic hydrocarbons by charge-exchange chemical ionization mass spectrometry  

SciTech Connect

Charge-exchange chemical ionization mass spectrometry (using a 15% mixture of methane in argon) yields abundant M/sup +/, M + H/sup +/, M + C/sub 2/H/sub 5//sup +/ ions of polycyclic aromatic hydrocarbons (PAH). On the basis of the relative intensities of the M + H/sup +/ ion to the M/sup +/ ion, this technique can differentiate, in a predictable manner, isomeric structures of PAH. The operating conditions were evaluated and optimized; the most significant contributions to the variations in the (M + H)/sup +//M/sup +/ ratios are the temperature, pressure, and condition of the ion source. The optimum ion source temperature (250/sup 0/C) and pressure (0.8 torr) are easily controlled and regulated. The variable contamination of the ion source is compensated by an internal standard 1,2,3,5-tetrafluorobenzene. The analyses of Standard Reference Materials 1648 and 1649 (air particulate samples) and a carbon black extract are reported. Triphenylene and chrysene, although not chromatographically resolved, can be quantitated by using this technique. The identification of acephenanthrylene based on the measurement of ratios and calculated ionization potentials is also presented.

Simonsick, W.J. Jr.; Hites, R.A.

1984-12-01

366

Picoelectrospray Ionization Mass Spectrometry Using Narrow-bore Chemically Etched Emitters  

SciTech Connect

Electrospray ionization mass spectrometry (ESI-MS) at flow rates below ~10 nL/min has been only sporadically explored due to difficulty in reproducibly fabricating emitters that can operate at lower flow rates. Here we demonstrate narrow orifice chemically etched emitters for stable electrospray at flow rates as low as 400 pL/min. Depending on the analyte concentration, we observe two types of MS signal response as a function of flow rate. At low concentrations, an optimum flow rate is observed slightly above 1 nL/min, while the signal decreases monotonically with decreasing flow rates at higher concentrations. In spite of lower MS signal, the ion utilization efficiency increases exponentially with decreasing flow rate in all cases. No unimolecular response was observed within this flow rate range during the analysis of an equimolar mixture of peptides, indicating that ionization efficiency is an analyte-dependent characteristic in given experimental conditions. While little to no gain in signal-to-noise was achieved at ultralow flow rates for concentration-limited analyses, experiments consuming the same amount of analyte suggest that mass-limited analyses will benefit strongly from the use of low flow rates and avoiding unnecessary sample dilution. By operating under optimal conditions, consumption of just 500 zmol of sample yielded signal-to-noise ratios ~10 for some peptides. These findings have important implications for the analysis of trace biological samples.

Marginean, Ioan; Tang, Keqi; Smith, Richard D.; Kelly, Ryan T.

2014-01-01

367

Soft ionization chemical analysis of secondary organic aerosol from green leaf volatiles emitted by turf grass.  

PubMed

Globally, biogenic volatile organic compound (BVOC) emissions contribute 90% of the overall VOC emissions. Green leaf volatiles (GLVs) are an important component of plant-derived BVOCs, including cis-3-hexenylacetate (CHA) and cis-3-hexen-1-ol (HXL), which are emitted by cut grass. In this study we describe secondary organic aerosol (SOA) formation from the ozonolysis of dominant GLVs, their mixtures and grass clippings. Near-infrared laser desorption/ionization aerosol mass spectrometry (NIR-LDI-AMS) was used for chemical analysis of the aerosol. The chemical profile of SOA generated from grass clippings was correlated with that from chemical standards of CHA and HXL. We found that SOA derived from HXL most closely approximated SOA from turf grass, in spite of the approximately 5× lower emission rate of HXL as compared to CHA. Ozonolysis of HXL results in formation of low volatility, higher molecular weight compounds, such as oligomers, and formation of ester-type linkages. This is in contrast to CHA, where the hydroperoxide channel is the dominant oxidation pathway, as oligomer formation is inhibited by the acetate functionality. PMID:24666343

Jain, Shashank; Zahardis, James; Petrucci, Giuseppe A

2014-05-01

368

Solid state chemical ionization for characterization of organic compounds by laser mass spectrometry.  

PubMed

A new technique involving the addition of a compound to the analyte to serve as a source of "reagent" ions has been developed for negative-ion laser mass spectrometry. This "solid state chemical ionization" leads to ions characteristic of the analyte, owing to ion-molecule reactions between the "reagent" ion and the neutral analyte in the laser-generated plume. Polycyclic aromatic hydrocarbons show formation of an ion corresponding to (M + O - H)(-) in their negative-ion laser mass spectra when mixed with compounds such as sym-trinitrobenzene, sodium nitrate and sodium peroxide. NO(-)(2), O(-), and O(-)(2) serve as "reagent" ions in these compounds. Formation of (M + Cl)(-) is seen in the laser mass spectra of glycosides mixed with hexachlorobenzene. Chloride serves as the "reagent" ion in this case. PMID:18964680

Balasanmugam, K; Viswanadham, S K; Hercules, D M

1989-01-01

369

Water chemical ionization mass spectrometry of aldehydes, ketones esters, and carboxylic acids  

SciTech Connect

Chemical ionization mass spectrometry (CI) of aliphatic and aromatic carbonyl compounds using water as the reagent gas provides intense pseudomolecular ions and class-specific fragmentation patterns that can be used to identify aliphatic aldehydes, ketones, carboxylic acids, and esters. The length of ester acyl and alkyl groups can easily be determined on the basis of loss of alcohols from the protonated parent. Water CI provides for an approximately 200:1 selectivity of carbonyl species over alkanes. No reagent ions are detected above 55 amu, allowing species as small as acetone, propanal, acetic acid, and methyl formate to be identified. When deuterate water was used as the reagent, only the carboxylic acids and ..beta..-diketones showed significant H/D exchange. The use of water CI to identify carbonyl compounds in a wastewater from the supercritical water extraction of lignite coal, in lemon oil, and in whiskey volatiles is discussed.

Hawthorne, S.B.; Miller, D.J.

1986-11-01

370

Qualitative gas chromatography-mass spectrometry analyses using amines as chemical ionization reagent gases.  

PubMed

Ammonia is a very useful chemical ionization (CI) reagent gas for the qualitative analyses of compounds by positive ion gas chromatography-mass spectrometry (GCMS). The gas is readily available, inexpensive, and leaves no carbon contamination in the MS source. Compounds of interest to our laboratory typically yield abundant protonated or ammoniated species, which are indicative of a compound's molecular weight. Nevertheless, some labile compounds fragment extensively by substitution and elimination reactions and yield no molecular weight information. In these cases, a CI reagent gas mixture of methylamine in methane prepared dynamically was found to be very useful in obtaining molecular weight data. Likewise, deuterated ammonia and deuterated methylamine are useful CI reagent gases for determining the exchangeable protons in organic compounds. Deuterated methylamine CI reagent gas is conveniently prepared by dynamically mixing small amounts of methylamine with excess deuterated ammonia. PMID:24114260

Little, James L; Howard, Adam S

2013-12-01

371

Experimental and numerical study of an atmospheric pressure glow discharge in helium  

NASA Astrophysics Data System (ADS)

. Atmospheric pressure glow discharges in helium have been reported to produce radially uniform plasmas and to show one single current pulse per half cycle of the AC high voltage [1]. However, in other studies the appearance of multiple periodic peaks per half cycle has been reported as well. Different interpretations have been given for this effect ranging from the oscillation of the cathode sheath [2] to multiple successive breakdowns [3]. We have performed studies with different dielectrics to investigate their effect on the discharge behavior: two circular 4 cm diameter electrodes have been covered with (1) 1.7 mm thick glass plates (er = 4.6) and with (2) 0.635 mm thick alumina plates (er = 9). At a gap of 5 mm, multiple current peaks were observed with both configurations. Time resolved measurements of the emission intensity using a gated intensified CCD camera were performed, both in axial and radial direction. These indicate that the first current pulse is produced by a radially propagating ionization front, while later peaks are related to breakdowns at the electrode edges. With 0.635 mm thick alumina plates we could observe the appearance of a strong cathode fall in front of the momentary cathode, together with a Faraday dark space and a positive column that extended for a length of 2-3 mm. A two-dimensional fluid model has been realized to study the glow discharge behavior. The numerical result is qualitatively in good agreement with the observed structure of the discharge. The model reproduces the radial propagation of the ionization wave. This work is supported by the Department of Energy under grant DE-FG02-00ER54583. [1] Massines F., Rabehi A., Decomps P., Gadri R.B., Segur P., and Mayoux C., J.Appl.Phys. 83, 2950- 2957 (1998). [2] Akishev Y.S., Dem'yanov A., Karal'nik V.B., Trushkin N.I., and Pan'kin M.V., Proc. Of XXIV ICPIG, Poland, July 11-16, 137-138, (1999). [3] Mangolini L., Orlov K., Kortshagen U., Heberlein J., and Kogelschatz U., Appl.Phys.Lett.80, 1723 (2002).

Mangolini, Lorenzo; Zhang, Peng; Anderson, Curtis; Kortshagen, Uwe; Heberlein, Joachim

2002-10-01

372

Atmospheric sampling glow discharge ionization source  

DOEpatents

An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above.

McLuckey, Scott A. (Oak Ridge, TN); Glish, Gary L. (Oak Ridge, TN)

1989-01-01

373

Atmospheric sampling glow discharge ionization source  

DOEpatents

An atmospheric sampling glow discharge ionization source that can be used in combination with an analytical instrument which operates at high vacuum, such as a mass spectrometer. The atmospheric sampling glow discharge ionization source comprises a chamber with at least one pair of electrodes disposed therein, an inlet for a gaseous sample to be analyzed and an outlet communicating with an analyzer which operates at subatmospheric pressure. The ionization chamber is maintained at a pressure below atmospheric pressure, and a voltage difference is applied across the electrodes to induce a glow discharge between the electrodes, so that molecules passing through the inlet are ionized by the glow discharge and directed into the analyzer. The ionization source accepts the sample under atmospheric pressure conditions and processes it directly into the high vacuum instrument, bridging the pressure gap and drawing off unwanted atmospheric gases. The invention also includes a method for analyzing a gaseous sample using the glow discharge ionization source described above. 3 figs.

McLuckey, S.A.; Glish, G.L.

1989-07-18

374

Modeling the barotropic response of the Mediterranean sea level to atmospheric pressure forcing  

NASA Astrophysics Data System (ADS)

An important characteristic of the Earth's atmosphere with direct impact on the marine environmental and Earth's gravity field are the variations of atmospheric pressure as it often determines wind and weather patterns across the globe. Variations in atmospheric pressure and especially low atmospheric systems affect the values of radar altimeter sea level anomalies (SLA). This response of sea level is closed to the Inverse Barometer (IB) correction given by the altimeters within their geophysical data records. In this work, altimetric data sets from the satellite remote sensing mission of Jason-2, along with their total IB corrections acquired by the on-board altimeters, have been used for a period of forty days between October and November 2013. This period was characterized by extreme low-pressure fields over the Mediterranean Sea and especially in the area of the Ionian and Adriatic Seas and over the island of Rhodes, Greece. The Jason-2 along-track records of the SLA have been used to study both the sea level response to atmospheric pressure change over short time scales (such as ten days) and examine if the barometer correction (local and global) given by the altimeter is close to the expected response (-1 cm/mbar) of sea level to atmospheric pressure change. For the latter, atmospheric pressure data for the period under study were available from the Live Access Server (LAS) of NOAA, as well, provided at four times per day intervals in a grid format. From the LAS atmospheric pressure data, the IB effect was computed and compared with the one provided by the altimeter for its external evaluation. Finally, a regional multiple regression analysis between sea level anomalies, the LAS atmospheric pressure and wind speed components is carried out to model the barotropic response of the Mediterranean to atmospheric wind and pressure forcing.

Natsiopoulos, Dimitrios A.; Vergos, Georgios S.; Tziavos, Ilias N.

2014-05-01

375

Determination of BROMATE AT PARTS-PER-TRILLION LEVELS BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY WITH NEGATIVE CHEMICAL IONIZATION  

EPA Science Inventory

The ozonation of bromide-containing source waters produces bromate as a class 2B carcinogenic disinfection by-product. The present work describes the determination of bromate by gas chromatography-negative chemical ionization mass spectrometry (GC-NCIMS) following a bromate react...

376

Desorption electrospray ionization mass spectrometry reveals surface-mediated antifungal chemical defense of a tropical seaweed  

PubMed Central

Organism surfaces represent signaling sites for attraction of allies and defense against enemies. However, our understanding of these signals has been impeded by methodological limitations that have precluded direct fine-scale evaluation of compounds on native surfaces. Here, we asked whether natural products from the red macroalga Callophycus serratus act in surface-mediated defense against pathogenic microbes. Bromophycolides and callophycoic acids from algal extracts inhibited growth of Lindra thalassiae, a marine fungal pathogen, and represent the largest group of algal antifungal chemical defenses reported to date. Desorption electrospray ionization mass spectrometry (DESI-MS) imaging revealed that surface-associated bromophycolides were found exclusively in association with distinct surface patches at concentrations sufficient for fungal inhibition; DESI-MS also indicated the presence of bromophycolides within internal algal tissue. This is among the first examples of natural product imaging on biological surfaces, suggesting the importance of secondary metabolites in localized ecological interactions, and illustrating the potential of DESI-MS in understanding chemically-mediated biological processes. PMID:19366672

Lane, Amy L.; Nyadong, Leonard; Galhena, Asiri S.; Shearer, Tonya L.; Stout, E. Paige; Parry, R. Mitchell; Kwasnik, Mark; Wang, May D.; Hay, Mark E.; Fernandez, Facundo M.; Kubanek, Julia

2009-01-01

377

Generation of Atmospheric-Pressure Glow Discharge and Its Applications 3.Applications of Atmospheric-Pressure Glow Plasma 3.1 Surface Treatment of Organic Materials  

Microsoft Academic Search

Surface treatments of organic materials such as wool fabric and polymer films were done by glow plasma in two types of discharge systems at atmospheric pressure using He and Ar as carrier gases.Wool fabric was treated by C3F6\\/He plasma using a parallel plate-type reactor. On the fabric surface, fluorinated polymer was deposited. The surface has a high value of oil

Masuhiro Kogoma

2003-01-01

378

High-performance simulations for atmospheric pressure plasma reactor  

NASA Astrophysics Data System (ADS)

Plasma-assisted processing and deposition of materials is an important component of modern industrial applications, with plasma reactors sharing 30% to 40% of manufacturing steps in microelectronics production. Development of new flexible electronics increases demands for efficient high-throughput deposition methods and roll-to-roll processing of materials. The current work represents an attempt of practical design and numerical modeling of a plasma enhanced chemical vapor deposition system. The system utilizes plasma at standard pressure and temperature to activate a chemical precursor for protective coatings. A specially designed linear plasma head, that consists of two parallel plates with electrodes placed in the parallel arrangement, is used to resolve clogging issues of currently available commercial plasma heads, as well as to increase the flow-rate of the processed chemicals and to enhance the uniformity of the deposition. A test system is build and discussed in this work. In order to improve operating conditions of the setup and quality of the deposited material, we perform numerical modeling of the plasma system. The theoretical and numerical models presented in this work comprehensively describe plasma generation, recombination, and advection in a channel of arbitrary geometry. Number density of plasma species, their energy content, electric field, and rate parameters are accurately calculated and analyzed in this work. Some interesting engineering outcomes are discussed with a connection to the proposed setup. The numerical model is implemented with the help of high-performance parallel technique and evaluated at a cluster for parallel calculations. A typical performance increase, calculation speed-up, parallel fraction of the code and overall efficiency of the parallel implementation are discussed in details.

Chugunov, Svyatoslav

379

The effects of atmospheric pressure on infrared reflectance spectra of Martian analogs  

NASA Technical Reports Server (NTRS)

The use of terrestrial samples as analogs of Mars soils are complicated by the Martian atmosphere. Spectral features due to the Martian atmosphere can be removed from telescopic spectra of Mars and ISM spectra of Mars, but this does not account for any spectral differences resulting from atmospheric pressure or any interactions between the atmosphere and the surface. We are examining the effects of atmospheric pressure on reflectance spectra of powdered samples in the laboratory. Contrary to a previous experiment with granite, no significant changes in albedo or the Christiansen feature were observed from 1 bar pressure down to a pressure of 8 micrometers Hg. However, reducing the atmospheric pressure does have a pronounced affect on the hydration features, even for samples retained in a dry environment for years.

Bishop, Janice L.; Pieters, Carle M.; Pratt, Stephen F.; Patterson, William

1993-01-01

380

Effect of the atmospheric pressure nonequilibrium plasmas on the conformational changes of plasmid DNA  

SciTech Connect

The cold atmospheric pressure plasma, which has been widely used for biomedical applications, may potentially affect the conformation of DNA. In this letter, an atmospheric pressure plasma plume is used to investigate its effects on the conformational changes of DNA of plasmid pAHC25. It is found that the plasma plume could cause plasmid DNA topology alteration, resulting in the percentage of the supercoiled plasmid DNA form decreased while that of the open circular and linearized form of plasmid DNA increased as detected by agrose gel electrophoresis. On the other hand, further investigation by using polymerase chain reaction method shows that the atmospheric pressure plasma jet treatments under proper conditions does not affect the genes of the plasmid DNA, which may have potential application in increasing the transformation frequency by genetic engineering.

Yan Xu; He Guangyuan; Shi Mengjun; Gao Xuan; Li Yin; Ma Fengyun; Yu Men; Wang Changdong; Wang Yuesheng; Yang Guangxiao [Genetic Engineering International Cooperation Base of Ministry of Science and Technology, Key Laboratory of Molecular Biophysics of Ministry of Education, China-UK HUST-RRes Genetic Engineering and Genomics Joint Laboratory, College of Life Science and Technology, Huazhong University of Science and Technology (HUST), Luoyu Road 1037, Wuhan 430074 (China); Zou Fei; Lu Xinpei; Xiong Qing; Xiong Zilan [College of Electrical and Electronics Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2009-08-24

381

Biomedical Applications of Low Temperature Atmospheric Pressure Plasmas to Cancerous Cell Treatment and Tooth Bleaching  

NASA Astrophysics Data System (ADS)

Low temperature atmospheric pressure plasmas have attracted great interests and they have been widely applied to biomedical applications to interact with living tissues, cells, and bacteria due to their non-thermal property. This paper reviews the biomedical applications of low temperature atmospheric pressure plasmas to cancerous cell treatment and tooth bleaching. Gold nanoparticles conjugated with cancer-specific antibodies have been introduced to cancerous cells to enhance selective killing of cells, and the mechanism of cell apoptosis induced by plasma has been investigated. Tooth exposed to helium plasma jet with hydrogen peroxide has become brighter and the productions of hydroxyl radicals from hydrogen peroxide have been enhanced by plasma exposure.

Lee, Jae Koo; Kim, Myoung Soo; Byun, June Ho; Kim, Kyong Tai; Kim, Gyoo Cheon; Park, Gan Young

2011-08-01

382

Using weather data from the internet to study how atmospheric pressure varies with altitude  

NASA Astrophysics Data System (ADS)

This article presents a simple and motivating activity for schools and colleges that is based on active learning and the use of new technologies to study the variation in atmospheric pressure with height at the lowest altitudes. Students can learn how barometric pressure decreases with height by plotting the atmospheric pressure versus altitude using data obtained from the internet. Using similar methods to those of scientific researchers, the students can learn a practical rule to correct barometric pressure data with altitude, something that is usually expressed at sea level in weather maps.

Moya, A. A.

2014-11-01

383

Verification by Viking landers of earlier radio occultation measurements of surface atmospheric pressure on Mars  

NASA Technical Reports Server (NTRS)

The landing of Viking 1 in Chryse Planitia on July 20, 1976 provided the first opportunity to obtain measurements of atmospheric pressure directly from the surface of Mars. A computation was conducted to predict the atmospheric pressure at the landing site before the landing itself. The relative altitude between occultation points and the Viking 1 site was obtained with the aid of earth-based planetary radar data taken in 1967. The data cover Martian latitudes from 19 deg N to 24 deg N. The investigation indicates that the radio occultation results from Mariner 9 closely correspond to the actual surface pressure on Mars.

Kliore, A. J.

1977-01-01

384

Atmospheric Pressure Plasma-Electrospin Hybrid Process for Protective Applications  

NASA Astrophysics Data System (ADS)

Chemical and biological (C-B) warfare agents like sarin, sulfur mustard, anthrax are usually dispersed into atmosphere in the form of micro aerosols. They are considered to be dangerous weapon of mass destruction next to nuclear weapons. The airtight protective clothing materials currently available are able to stop the diffusion of threat agents but not good enough to detoxify them, which endangers the wearers. Extensive research efforts are being made to prepare advanced protective clothing materials that not only prevent the diffusion of C-B agents, but also detoxify them into harmless products thus ensuring the safety and comfort of the wearer. Electrospun nanofiber mats are considered to have effective filtration characteristics to stop the diffusion of submicron level particulates without sacrificing air permeability characteristics and could be used in protective application as barrier material. In addition, functional nanofibers could be potentially developed to detoxify the C-B warfare threats into harmless products. In this research, electrospun nanofibers were deposited on fabric surface to improve barrier efficiency without sacrificing comfort-related properties of the fabrics. Multi-functional nanofibers were fabricated through an electrospinning-electrospraying hybrid process and their ability to detoxify simulants of C-B agents was evaluated. Nanofibers were also deposited onto plasma-pretreated woven fabric substrate through a newly developed plasma-electrospinning hybrid process, to improve the adhesive properties of nanofibers on the fabric surface. The nanofiber adhesion and durability properties were evaluated by peel test, flex and abrasion resistance tests. In this research work, following tasks have been carried out: i) Controlled deposition of nanofiber mat onto woven fabric substrate Electrospun Nylon 6 fiber mats were deposited onto woven 50/50 Nylon/Cotton fabric with the motive of making them into protective material against submicron-level aerosol chemical and biological threats. Polymer solution concentration, electrospinning voltage, and deposition areal density were varied to establish the relationship of processing-structure-filtration efficiency for electrospun fiber mats. A high barrier efficiency of greater than 99.5% was achieved on electrospun fiber mats without sacrificing air permeability and pressure drop. ii) Fabrication and Characterization of Multifunctional ZnO/Nylon 6 nanofibers ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning-electrospraying hybrid process, The electrospinning of polymer solution and electrospraying of ZnO particles were carried out simultaneously such that the ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers. The prepared ZnO/Nylon 6 nanofiber mats were tested for detoxifying characteristics against simulants of C-B agents. The results showed that ZnO/Nylon 6 functional nanofiber mats exhibited good detoxification action against paraoxon and have antibacterial efficiency over 99.99% against both the gram-negative E. coli and gram positive B. cereus bacteria. iii) Improving adhesion of electrospun nanofiber mat onto woven fabric by plasma pretreatment of substrate fabric and plasma-electrospinning hybrid process Electrospun nanofibers were deposited onto plasma-pretreated woven fabric to improve the adhesion. In addition, the plasma-electrospinning hybrid process was developed and used in which the nanofibers were subjected to in-situ plasma treatment during electrospinning. The effects of plasma treatement on substrate fabric and electrospun fibers were characterized by water contact angle test, XPS analyses. The improvement of nanofiber adhesive properties on fabric substrate was evaluated by peel test, flex resistance test and abrasion resistance test. The test results showed that the plasma treatment caused introduction of active chemical groups on substrate fabric and electrospun nanofibers. These active chemical assisted in possible cross-linking formation between nanofiber mat and substrate fabric, and this hypothesi

Vitchuli Gangadharan, Narendiran

385

Generation of Atmospheric-Pressure Glow Discharge and Its Applications 3.Applications of Atmospheric-Pressure Glow Plasma 3.3 Practical Uses of the Atmospheric-Pressure Plasma Processing Unit “Aiplasma”  

NASA Astrophysics Data System (ADS)

We have developed and marketed a unique plasma processing unit named Aiplasma. which operates under atmospheric pressure, allowing the configuration of continuous processing lines suitable for mass production. In this unit, high density plasma is generated inside a vessel and active plasma species are emitted outside the vessel to make downstream plasma treatment. It has various potentials for modifying material surface such as increasing wettability, removing of organic contaminants to enhance bondability, and improving the adhesion strength of organic materials. Aiplasma has been used in many actual processes such as the production of LCD modules, electric components, and printed circuit boards. This report describes the process technology and its practical applications.

Sawada, Yasushi

386

Investigation of atmospheric pressure capillary non-thermal plasmas and their applications to the degradation of volatile organic compounds  

NASA Astrophysics Data System (ADS)

Atmospheric pressure capillary non-thermal plasma (AP-CNTP) has been investigated as a potential technology far the removal of volatile organic compounds (VOCs) in Advanced Life Support Systems (ALS). AP-CNTP is a destructive technology far the removal of VOCs from air streams by active plasma species, such as electrons, ions, and excited molecules. Complete VOC destruction ideally results in the formation of water, carbon dioxide (CO2), and other by-product's may also form, including ozone (O3), nitrous oxide (N2O), nitrogen dioxide (NO2), and decomposed hydrocarbons. Several organic compounds, such as BTEX, ethylene, n-heptane, isooctane, methanol and NH3, were tested in an AP-CNTP system. Parametric experiments were carried out by varying plasma discharge power, flowrates, and initial concentrations. The degradation efficiency varied depending on the chemical nature of the compounds. A plasmochemical kinetic model was derived for toluene, ethylbenzene, and m-xylene and n-heptane.

Yin, Shu-Min

387

A thorough FT-IR spectroscopy study on micrometric silicon oxide films deposited by atmospheric pressure microwave plasma torch  

NASA Astrophysics Data System (ADS)

SiOxHyCz micrometer thick films are deposited from an argon/hexamethyldisiloxane mixture on Si (100) substrate by plasma enhanced chemical vapour deposition process using an axial injection torch at atmospheric pressure. Results highlight a similar effect of low and high substrate temperatures both on the deposition process and on the microstructure of the deposited films. Mesoscopically, scanning electron microscopy analyses reveal that particles are promptly produced in the gas phase and incorporated to the film. Microscopically, a detailed infrared analysis in transmission mode demonstrates a high carbon contamination in the low and high temperature intervals resulting in a lower stoichiometry. This work allows to define an optimum growth window for the substrate temperature, leading to smooth, particle-free and carbon-free films: [60 °C; 90 °C].

Landreau, X.; Lanfant, B.; Merle, T.; Dublanche-Tixier, C.; Tristant, P.

2012-06-01

388

Real time characterization of polymer surface modifications by an atmospheric-pressure plasma jet: Electrically coupled versus remote mode  

NASA Astrophysics Data System (ADS)

We characterize and distinguish two regimes of atmospheric pressure plasma (APP) polymer interactions depending on whether the electrical interaction of the plasma plume with the surface is significant (coupled) or not (remote). When the plasma is coupled to the surface, localized energy deposition by charged species in filaments dominates the interactions with the surface and produces contained damaged areas with high etch rates that decrease rapidly with plasma source-to-sample distance. For remote APP surface treatments, when only reactive neutral species interact with the surface, we established specific surface-chemical changes and very slow etching of polymer films. Remote treatments appear uniform with etch rates that are highly sensitive to feed gas chemistry and APP source temperature.

Knoll, A. J.; Luan, P.; Bartis, E. A. J.; Hart, C.; Raitses, Y.; Oehrlein, G. S.

2014-10-01

389

Ionic wind generation by a wire-cylinder-plate corona discharge in air at atmospheric pressure  

SciTech Connect

A wire-cylinder-plate electrode configuration is presented to generate ionic wind with a dc corona discharge in air at atmospheric pressure. The objective of the work is to maximize the power supplied to the flow in order to increase acceleration while avoiding breakdown. Thus, the proposed experimental setup addresses the problem of decoupling the mechanism of ion generation from that of ion acceleration. Using a wire-plate configuration as a reference, we have focused on improving the topography of the electric field to (1) separate the ionization and acceleration zones in space, and (2) guide the trajectory of charged particles as parallel to the median axis as possible. In the proposed wire-cylinder-plate setup, a dc corona discharge is generated in the space between a wire and two cylinders. The ions produced by the corona then drift past the cylinders and into a channel between two plates, where they undergo acceleration. To maximize the ionic wind it is found that the geometric configuration must be as compact as possible and that the voltage applied must be right below breakdown. Experimentally, the optimized wire-plate reference setup provides a maximum flow velocity of 8 m s{sup -1}, a flow rate per unit electrode length of 0.034 m{sup 2} s{sup -1}, and a thrust per unit electrode length of 0.24 N m{sup -1}. The wire-cylinder-plate configuration provides a maximum flow velocity of 10 m s{sup -1}, a flow rate per unit electrode length of 0.041 m{sup 2} s{sup -1}, and a thrust per unit electrode length of 0.35 N m{sup -1}. This 46% increase in thrust is obtained by increasing the electric power per unit electrode length by only 16% (from 175 to 210 W m{sup -1}), which confirms the gain in efficiency obtained with the decoupled system. In comparison with a simple wire-wire corona configuration, the wire-cylinder-plate configuration increases the ionic wind velocity by up to a factor of 3, and the thrust by an order of magnitude.

Colas, Dorian F.; Ferret, Antoine; Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O. [Laboratoire EM2C, UPR 288, CNRS, Ecole Centrale Paris, Grande Voie des Vignes, 92290 Chatenay-Malabry (France)

2010-11-15

390

Fast Time Response Measurements of Aerosol Composition by Chemical Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Fast and accurate measurements of atmospheric aerosol composition is an important part of quantifying and understanding atmospheric pollution and its consequences. Such data can be used for studies of regional haze analysis, development of atmospheric models, atmospheric aerosol source apportionment and aerosol and gas interactions. This presentation describes the development of a new technique for the measurement of atmospheric aerosol composition. A negative ion Chemical Ionization Mass Spectrometry (CIMS) method has been used to perform 1 Hz aerosol composition measurements. A heated inlet is used to evaporate ambient aerosol with subsequent detection of the evolved gases. Two reagent ions, bromide and nitrate, have been used to selectively detect acidic components of the aerosols such as sulfate, nitrate, malonate, and oxalate. The CIMS sulfate measurements in ambient air were compared with a Particle into Liquid Sampler (PILS). These tests showed a high degree of correlation between the measurements and strongly suggest that the CIMS can measure sulfate with a high degree of selectivity and sensitivity. Further tests suggest that CIMS method may be able to also perform selective measurements of a few strong organic acids such as oxalic.

Hecobian, A.; Thompson, A.; Tanner, D.; Peltier, R.; Weber, R.; Huey, G.

2005-12-01

391

Shrinking droplets in electrospray ionization and their influence on chemical equilibria.  

PubMed

We investigated how chemical equilibria are affected by the electrospray process, using simultaneous in situ measurements by laser-induced fluorescence (LIF) and phase Doppler anemometry (PDA). The motivation for this study was the increasing number of publications in which electrospray ionization mass spectrometry is used for binding constant determination. The PDA was used to monitor droplet size and velocity, whereas LIF was used to monitor fluorescent analytes within the electrospray droplets. Using acetonitrile as solvent, we found an average initial droplet diameter of 10 microm in the electrospray. The PDA allowed us to follow the evolution of these droplets down to a size of 1 microm. Rhodamine B-sulfonylchloride was used as a fluorescent analyte within the electrospray. By spatially resolved LIF it was possible to probe the dimerization equilibrium of this dye. Measurements at different spray positions showed no influence of the decreasing droplet size on the monomer-dimer equilibrium. However, with the fluorescent dye pair DCM and oxazine 1 it was shown that a concentration increase does occur within electrosprayed droplets, using fluorescence resonance energy transfer as a probe for the average pair distance. PMID:17112736

Wortmann, Arno; Kistler-Momotova, Anna; Zenobi, Renato; Heine, Martin C; Wilhelm, Oliver; Pratsinis, Sotiris E

2007-03-01

392

Analysis of oxysterols and vitamin D metabolites in mouse brain and cell line samples by ultra-high-performance liquid chromatography-atmospheric pressure photoionization-mass spectrometry.  

PubMed

We have developed an ultra-high-performance liquid chromatography-atmospheric pressure photoionization-tandem mass spectrometric (UHPLC-APPI-MS/MS) method for the simultaneous quantitative analyses of several oxysterols and vitamin D metabolites in mouse brain and cell line samples. An UHPLC-APPI-high resolution mass spectrometric (UHPLC-APPI-HRMS) method that uses a quadrupole-time of flight mass spectrometer was also developed for confirmatory analysis and for the identification of non-targeted oxysterols. Both methods showed good quantitative performance. Furthermore, APPI provides high ionization efficiency for determining oxysterols and vitamin D related compounds without the time consuming derivatization step needed in the conventionally used electrospray ionization method to achieve acceptable sensitivity. Several oxysterols were quantified in mouse brain and cell line samples. Additionally, 25-hydroxyvitamin D3 was detected in mouse brain samples for the first time. PMID:25204266

Ahonen, Linda; Maire, Florian B R; Savolainen, Mari; Kopra, Jaakko; Vreeken, Rob J; Hankemeier, Thomas; Myöhänen, Timo; Kylli, Petri; Kostiainen, Risto

2014-10-17

393

First experimental results on the kinetic processes in a surface-wave-sustained argon discharge at atmospheric pressure  

SciTech Connect

This communication presents an advance of the results of an experimental study of the kinetic processes in a surface-wave-sustained argon discharge at atmospheric pressure. We utilize the study developed by Fujimoto on the population and depopulation processes of the excited levels of atoms and ions. This theory has been applied by S. Daviaud and A. Hirabayashi to explain the kinetic processes in helium plasma at low pressure. Fujimoto has studied the ionization and recombination mechanisms of the plasma under various conditions and its relation to the population density distributions. This study establishes, for an hydrogenic ion with a core charge z, different zones in the atomic system (level map). Each zone is characterized by the dominant mechanisms of the population and depopulation of their excited levels, A level is characterized for the effective principal quantum number p, where p = z (E{sub H}/{vert_bar}E{sub p}{vert_bar}){sup 1/2}, E{sub H} is the hydrogen ionization energy and {vert_bar}E{sub p}{vert_bar} is the energy required to ionize the atom from the level considered. The population of each level p can be expressed in terms of the parameter b(p) defined as n(p)/n{sup SB}(p), n(p) and n{sup SB}(p) being the actual population and the Saha-Boltzmann equilibrium population of the level, respectively. Figure I shows the population and depopulation processes of a level p, which are both collisional and radiative that are characterized by their respective coefficients.

Calzada, M.D.; Gamero, A.; Sola, A. [Universidad de Cordoba (Spain)] [and others

1995-12-31

394

Surface modification with a remote atmospheric pressure plasma: dc glow discharge and surface streamer regime  

Microsoft Academic Search

A remote atmospheric pressure discharge working with ambient air is used for the near room temperature treatment of polymer foils and textiles of varying thickness. The envisaged plasma effect is an increase in the surface energy of the treated material, leading, e.g., to a better wettability or adhesion. Changes in wettability are examined by measuring the contact angle or the

Eef Temmerman; Yuri Akishev; Nikolay Trushkin; Christophe Leys; Jo Verschuren

2005-01-01

395

Properties of an aqueous solution of ionic liquid [Emim][Cl] at standard atmospheric pressure  

NASA Astrophysics Data System (ADS)

The density, viscosity, electric conductivity, volumetric thermal expansion coefficient, melting point, and refractive index of an aqueous solution of the [Emim][Cl] ionic liquid are measured over wide ranges of temperature and concentrations at standard atmospheric pressure. Analytical dependences of the investigated properties on the concentration and temperature are suggested.

Klinov, A. V.; Fedorov, M. V.; Malygin, A. V.; Minibaeva, L. R.

2014-10-01

396

Non-thermal atmospheric pressure plasma for remediation of volatile organic compounds.  

E-print Network

??The University of ManchesterZaenab Abd AllahDoctor of PhilosophyNon-thermal atmospheric pressure plasma for remediation of volatile organic compounds29/02/2012Non-thermal plasma generated in a dielectric barrier packed-bed reactor… (more)

Abd Allah, Zaenab

2012-01-01

397

Characterization of a Dielectric Barrier Plasma Gun Discharging at Atmospheric Pressure  

Microsoft Academic Search

We develop a plasma gun based on dielectric barrier discharge and working at atmospheric pressure. A theoretical model to predict the gun discharge voltage is built, which is in agreement with the experimental results. After investigating the characterization of discharging gun and utilizing it for polymerization, we find that the gun can be used as a source to generate a

Guang-Qiu Zhang; Yuan-Jing Ge; Yue-Fei Zhang; Guang-Liang Chen

2004-01-01

398

Short Rise Time High Power Microwave Induced Surface Flashover at Atmospheric Pressures  

Microsoft Academic Search

High power microwave transmission is ultimately limited by window flashover at the vacuum-air dielectric boundary. While surface flashover in the presence of a vacuum has been studied in some detail, the mechanisms associated with flashover in an atmospheric environment need further investigation. For an aircraft based high power microwave system, atmospheric pressures ranging from 760 torr (sea level) to 90

Jonathan Foster; Greg Edmiston; John Krile; Herman Krompholz; Andreas Neuber

2008-01-01

399

Effects of fluid flow on the characteristics of an atmospheric pressure low temperature plasma jet  

Microsoft Academic Search

Summary form only given. Recently interest in low temperature atmospheric pressure plasma jets has increased due to their unique capabilities and novel applications, such as biomedicine. Prior experimental results showed that low temperature plasma jets are in fact trains of plasma bullets\\/packets traveling at supersonic velocities. This is especially interesting because the plasma bullets travel in a region free of

E. Karakas; M. Koklu; A. Begum; M. Laroussi

2009-01-01