Formation of Metal-Adducted Analyte Ions by Flame-Induced Atmospheric Pressure Chemical Ionization Mass Spectrometry.

PubMed

Cheng, Sy-Chyi; Wang, Chin-Hsiung; Shiea, Jentaie

2016-05-17

A flame-induced atmospheric pressure chemical ionization (FAPCI) source, consisting of a miniflame, nebulizer, and heated tube, was developed to ionize analytes. The ionization was performed by reacting analytes with a charged species generated in a flame. A stainless steel needle deposited with saturated alkali chloride solution was introduced into the mini oxyacetylene flame to generate alkali ions, which were reacted with analytes (M) generated in a heated nebulizer. The alkali-adducted 18-crown-6 ether ions, including (M + Li)(+), (M + Na)(+), (M + K)(+), (M + Rb)(+), and (M + Cs)(+), were successfully detected on the FAPCI mass spectra when the corresponding alkali chloride solutions were separately introduced to the flame. When an alkali chloride mixture was introduced, all alkali-adducted analyte ions were simultaneously detected. Their intensity order was as follows: (M + Cs)(+) > (M + Rb)(+) > (M + K)(+) > (M + Na)(+) > (M + Li)(+), and this trend agreed with the lattice energies of alkali chlorides. Besides alkali ions, other transition metal ions such as Ni(+), Cu(+), and Ag(+) were generated in a flame for analyte ionization. Other than metal ions, the reactive species generated in the fossil fuel flame could also be used to ionize analytes, which formed protonated analyte ions (M + H)(+) in positive ion mode and deprotonated analyte ions (M - H)(-) in negative ion mode.

Acetonitrile Ion Suppression in Atmospheric Pressure Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Colizza, Kevin; Mahoney, Keira E.; Yevdokimov, Alexander V.; Smith, James L.; Oxley, Jimmie C.

2016-11-01

Efforts to analyze trace levels of cyclic peroxides by liquid chromatography/mass spectrometry gave evidence that acetonitrile suppressed ion formation. Further investigations extended this discovery to ketones, linear peroxides, esters, and possibly many other types of compounds, including triazole and menadione. Direct ionization suppression caused by acetonitrile was observed for multiple adduct types in both electrospray ionization and atmospheric pressure chemical ionization. The addition of only 2% acetonitrile significantly decreased the sensitivity of analyte response. Efforts to identify the mechanism were made using various nitriles. The ion suppression was reduced by substitution of an acetonitrile hydrogen with an electron-withdrawing group, but was exacerbated by electron-donating or steric groups adjacent to the nitrile. Although current theory does not explain this phenomenon, we propose that polar interactions between the various functionalities and the nitrile may be forming neutral aggregates that manifest as ionization suppression.

Determination of glucosinolates in rapeseed and Thlaspi caerulescens plants by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Tolrà, R P; Alonso, R; Poschenrieder, C; Barceló, D; Barceló, J

2000-08-11

Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry was used to identify glucosinolates in plant extracts. Optimization of the analytical conditions and the determination of the method detection limit was performed using commercial 2-propenylglucosinolate (sinigrin). Optimal values for the following parameters were determined: nebulization pressure, gas temperature, flux of drying gas, capillar voltage, corona current and fragmentor conditions. The method detection limit for sinigrin was 2.85 ng. For validation of the method the glucosinolates in reference material (rapeseed) from the Community Bureau of Reference Materials (BCR) were analyzed. The method was applied for the determination of glucosinolates in Thlaspi caerulescens plants.

Capillary liquid chromatography-microchip atmospheric pressure chemical ionization-mass spectrometry.

PubMed

Ostman, Pekka; Jäntti, Sirkku; Grigoras, Kestas; Saarela, Ville; Ketola, Raimo A; Franssila, Sami; Kotiaho, Tapio; Kostiainen, Risto

2006-07-01

A miniaturized nebulizer chip for capillary liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (capillary LC-microchip APCI-MS) is presented. The APCI chip consists of two wafers, a silicon wafer and a Pyrex glass wafer. The silicon wafer has a DRIE etched through-wafer nebulizer gas inlet, an edge capillary insertion channel, a stopper, a vaporizer channel and a nozzle. The platinum heater electrode and pads for electrical connection were patterned on to the Pyrex glass wafer. The two wafers were joined by anodic bonding, creating a microchip version of an APCI-source. The sample inlet capillary from an LC column is directly connected to the vaporizer channel of the APCI chip. The etched nozzle in the microchip forms a narrow sample plume, which is ionized by an external corona needle, and the formed ions are analyzed by a mass spectrometer. The nebulizer chip enables for the first time the use of low flow rate separation techniques with APCI-MS. The performance of capillary LC-microchip APCI-MS was tested with selected neurosteroids. The capillary LC-microchip APCI-MS provides quantitative repeatability and good linearity. The limits of detection (LOD) with a signal-to-noise ratio (S/N) of 3 in MS/MS mode for the selected neurosteroids were 20-1000 fmol (10-500 nmol l(-1)). LODs (S/N = 3) with commercial macro APCI with the same compounds using the same MS were about 10 times higher. Fast heat transfer allows the use of the optimized temperature for each compound during an LC run. The microchip APCI-source provides a convenient and easy method to combine capillary LC to any API-MS equipped with an APCI source. The advantages and potentials of the microchip APCI also make it a very attractive interface in microfluidic APCI-MS.

Ionization enhancement in atmospheric pressure chemical ionization and suppression in electrospray ionization between target drugs and stable-isotope-labeled internal standards in quantitative liquid chromatography/tandem mass spectrometry.

PubMed

Liang, H R; Foltz, R L; Meng, M; Bennett, P

2003-01-01

The phenomena of ionization suppression in electrospray ionization (ESI) and enhancement in atmospheric pressure chemical ionization (APCI) were investigated in selected-ion monitoring and selected-reaction monitoring modes for nine drugs and their corresponding stable-isotope-labeled internal standards (IS). The results showed that all investigated target drugs and their co-eluting isotope-labeled IS suppress each other's ionization responses in ESI. The factors affecting the extent of suppression in ESI were investigated, including structures and concentrations of drugs, matrix effects, and flow rate. In contrast to the ESI results, APCI caused seven of the nine investigated target drugs and their co-eluting isotope-labeled IS to enhance each other's ionization responses. The mutual ionization suppression or enhancement between drugs and their isotope-labeled IS could possibly influence assay sensitivity, reproducibility, accuracy and linearity in quantitative liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). However, calibration curves were linear if an appropriate IS concentration was selected for a desired calibration range to keep the response factors constant. Copyright 2003 John Wiley & Sons, Ltd.

A corona discharge atmospheric pressure chemical ionization source with selective NO(+) formation and its application for monoaromatic VOC detection.

PubMed

Sabo, Martin; Matejčík, Štefan

2013-11-21

We have developed a new type of corona discharge (CD) for atmospheric pressure chemical ionization (APCI) for application in ion mobility spectrometry (IMS) as well as in mass spectrometry (MS). While the other CD-APCI sources are able to generate H3O(+)·(H2O)n as the major reactant ions in N2 or in zero air, the present CD-APCI source has the ability to generate up to 84% NO(+)·(H2O)n reactant ions in zero air. The change of the working gas from zero air to N2 allows us to change the major reactant ions from NO(+)·(H2O)n to H3O(+)·(H2O)n. In this paper we present the description of the new CD-APCI and discuss the processes associated with the NO(+) formation. The selective formation of NO(+)·(H2O)n reactant ions offers chemical ionization based on these ions which can be of great advantage for some classes of chemicals. We demonstrate here a significant increase in the sensitivity of the IMS-MS instrument for monoaromatic volatile organic compound (VOC) detection upon NO(+)·(H2O)n chemical ionization.

Tracing origins of complex pharmaceutical preparations using surface desorption atmospheric pressure chemical ionization mass spectrometry.

PubMed

Zhang, Xinglei; Jia, Bin; Huang, Keke; Hu, Bin; Chen, Rong; Chen, Huanwen

2010-10-01

A novel strategy to trace the origins of commercial pharmaceutical products has been developed based on the direct chemical profiling of the pharmaceutical products by surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). Besides the unambiguous identification of active drug components, various compounds present in the matrixes are simultaneously detected without sample pretreatment, providing valuable information for drug quality control and origin differentiation. Four sources of commercial amoxicillin products made by different manufacturers have been successfully differentiated. This strategy has been extended to secerning six sources of Liuwei Dihuang Teapills, which are herbal medicine preparations with extremely complex matrixes. The photolysis status of chemical drug products and the inferior natural herd medicine products prepared with different processes (e.g., extra heating) were also screened using the method reported here. The limit of detection achieved in the MS/MS experiments was estimated to be 1 ng/g for amoxicillin inside the capsule product. Our experimental data demonstrate that DAPCI-MS is a useful tool for rapid pharmaceutical analysis, showing promising perspectives for tracking the entire pharmaceutical supply chain to prevent counterfeit intrusions.

Flame Atmospheric Pressure Chemical Ionization Coupled with Negative Electrospray Ionization Mass Spectrometry for Ion Molecule Reactions.

PubMed

Cheng, Sy-Chyi; Bhat, Suhail Muzaffar; Shiea, Jentaie

2017-07-01

Flame atmospheric pressure chemical ionization (FAPCI) combined with negative electrospray ionization (ESI) mass spectrometry was developed to detect the ion/molecule reactions (IMRs) products between nitric acid (HNO 3 ) and negatively charged amino acid, angiotensin I (AI) and angiotensin II (AII), and insulin ions. Nitrate and HNO 3 -nitrate ions were detected in the oxyacetylene flame, suggesting that a large quantity of nitric acid (HNO 3 ) was produced in the flame. The HNO 3 and negatively charged analyte ions produced by a negative ESI source were delivered into each arm of a Y-shaped stainless steel tube where they merged and reacted. The products were subsequently characterized with an ion trap mass analyzer attached to the exit of the Y-tube. HNO 3 showed the strongest affinity to histidine and formed (M histidine -H+HNO 3 ) - complex ions, whereas some amino acids did not react with HNO 3 at all. Reactions between HNO 3 and histidine residues in AI and AII resulted in the formation of dominant [M AI -H+(HNO 3 )] - and [M AII -H+(HNO 3 )] - ions. Results from analyses of AAs and insulin indicated that HNO 3 could not only react with basic amino acid residues, but also with disulfide bonds to form [M-3H+(HNO 3 ) n ] 3- complex ions. This approach is useful for obtaining information about the number of basic amino acid residues and disulfide bonds in peptides and proteins. Graphical Abstract ᅟ.

Flame Atmospheric Pressure Chemical Ionization Coupled with Negative Electrospray Ionization Mass Spectrometry for Ion Molecule Reactions

NASA Astrophysics Data System (ADS)

Cheng, Sy-Chyi; Bhat, Suhail Muzaffar; Shiea, Jentaie

2017-07-01

Flame atmospheric pressure chemical ionization (FAPCI) combined with negative electrospray ionization (ESI) mass spectrometry was developed to detect the ion/molecule reactions (IMRs) products between nitric acid (HNO3) and negatively charged amino acid, angiotensin I (AI) and angiotensin II (AII), and insulin ions. Nitrate and HNO3-nitrate ions were detected in the oxyacetylene flame, suggesting that a large quantity of nitric acid (HNO3) was produced in the flame. The HNO3 and negatively charged analyte ions produced by a negative ESI source were delivered into each arm of a Y-shaped stainless steel tube where they merged and reacted. The products were subsequently characterized with an ion trap mass analyzer attached to the exit of the Y-tube. HNO3 showed the strongest affinity to histidine and formed (Mhistidine-H+HNO3)- complex ions, whereas some amino acids did not react with HNO3 at all. Reactions between HNO3 and histidine residues in AI and AII resulted in the formation of dominant [MAI-H+(HNO3)]- and [MAII-H+(HNO3)]- ions. Results from analyses of AAs and insulin indicated that HNO3 could not only react with basic amino acid residues, but also with disulfide bonds to form [M-3H+(HNO3)n]3- complex ions. This approach is useful for obtaining information about the number of basic amino acid residues and disulfide bonds in peptides and proteins.

Determination of polycyclic aromatic hydrocarbons in fractions in asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization.

PubMed

Nascimento, Paulo Cicero; Gobo, Luciana Assis; Bohrer, Denise; Carvalho, Leandro Machado; Cravo, Margareth Coutinho; Leite, Leni Figueiredo Mathias

2015-07-01

An analytical method using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization for the determination of polycyclic aromatic hydrocarbons in asphalt fractions has been developed. The 14 compounds determined, characterized by having two or more condensed aromatic rings, are expected to be present in asphalt and are considered carcinogenic and mutagenic. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection ranged from 0.5 to 346.5 μg/L and the limits of quantification ranged from 1.7 to 1550 μg/L. The method was validated against a diesel particulate extract standard reference material (NIST SRM 1975), and the obtained concentrations agreed with the certified values. The method was applied to asphalt samples after its fractionation according to ASTM D4124 and the method of Green. The concentrations of the seven polycyclic aromatic hydrocarbons quantified in the sample ranged from 0.86 mg/kg for benzo[ghi]perylene to 98.32 mg/kg for fluorene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel APPI-MS setup for in situ degradation product studies of atmospherically relevant compounds: capillary atmospheric pressure photo ionization (cAPPI).

PubMed

Kersten, Hendrik; Derpmann, Valerie; Barnes, Ian; Brockmann, Klaus J; O'Brien, Rob; Benter, Thorsten

2011-11-01

We report on the development of a novel atmospheric pressure photoionization setup and its applicability for in situ degradation product studies of atmospherically relevant compounds. A custom miniature spark discharge lamp was embedded into an ion transfer capillary, which separates the atmospheric pressure from the low pressure region in the first differential pumping stage of a conventional atmospheric pressure ionization mass spectrometer. The lamp operates with a continuous argon flow and produces intense light emissions in the VUV. The custom lamp is operated windowless and efficiently illuminates the sample flow through the transfer capillary on an area smaller than 1 mm(2). Limits of detection in the lower ppbV range, a temporal resolution of milliseconds in the positive as well as the quasi simultaneously operating negative ion mode, and a significant reduction of ion transformation processes render this system applicable to real time studies of rapidly changing chemical systems. The method termed capillary atmospheric pressure photo ionization (cAPPI) is characterized with respect to the lamp emission properties as a function of the operating conditions, temporal response, and its applicability for in situ degradation product studies of atmospherically relevant compounds, respectively.

A sensitive gas chromatography detector based on atmospheric pressure chemical ionization by a dielectric barrier discharge.

PubMed

Kirk, Ansgar T; Last, Torben; Zimmermann, Stefan

2017-02-03

In this work, we present a novel concept for a gas chromatography detector utilizing an atmospheric pressure chemical ionization which is initialized by a dielectric barrier discharge. In general, such a detector can be simple and low-cost, while achieving extremely good limits of detection. However, it is non-selective apart from the use of chemical dopants. Here, a demonstrator manufactured entirely from fused silica capillaries and printed circuit boards is shown. It has a size of 75×60×25mm 3 and utilizes only 2W of power in total. Unlike other known discharge detectors, which require high-purity helium, this detector can theoretically be operated using any gas able to form stable ion species. Here, purified air is used. With this setup, limits of detection in the low parts-per-billion range have been obtained for acetone. Copyright © 2017 Elsevier B.V. All rights reserved.

Identification of astaxanthin diglucoside diesters from snow alga Chlamydomonas nivalis by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Rezanka, Tomás; Nedbalová, Linda; Sigler, Karel; Cepák, Vladislav

2008-01-01

A method is described for the identification of astaxanthin glucoside esters from snow alga Chlamydomonas nivalis by means of liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The method is based on the use of preparative HPLC and subsequent identification of astaxanthin diglucoside diesters by microbore LC-MS/APCI. The combination of these two techniques was used to identify more than 100 molecular species. The astaxanthin diglucoside diester, i.e. (all-E)-[di-(6-O-oleoyl-beta-D-glucopyranosyloxy)]-astaxanthin, was also synthesized to unambiguously confirm its structure.

In-Line Reactions and Ionizations of Vaporized Diphenylchloroarsine and Diphenylcyanoarsine in Atmospheric Pressure Chemical Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Okumura, Akihiko; Takada, Yasuaki; Watanabe, Susumu; Hashimoto, Hiroaki; Ezawa, Naoya; Seto, Yasuo; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Kondo, Tomohide; Nagashima, Hisayuki; Nagoya, Tomoki

2016-07-01

We propose detecting a fragment ion (Ph2As+) using counter-flow introduction atmospheric pressure chemical ionization ion trap mass spectrometry for sensitive air monitoring of chemical warfare vomiting agents diphenylchloroarsine (DA) and diphenylcyanoarsine (DC). The liquid sample containing of DA, DC, and bis(diphenylarsine)oxide (BDPAO) was heated in a dry air line, and the generated vapor was mixed into the humidified air flowing through the sampling line of a mass spectrometer. Humidity effect on the air monitoring was investigated by varying the humidity of the analyzed air sample. Evidence of the in-line conversion of DA and DC to diphenylarsine hydroxide (DPAH) and then BDPAO was obtained by comparing the chronograms of various ions from the beginning of heating. Multiple-stage mass spectrometry revealed that the protonated molecule (MH+) of DA, DC, DPAH, and BDPAO could produce Ph2As+ through their in-source fragmentation. Among the signals of the ions that were investigated, the Ph2As+ signal was the most intense and increased to reach a plateau with the increased air humidity, whereas the MH+ signal of DA decreased. It was suggested that DA and DC were converted in-line into BDPAO, which was a major source of Ph2As+.

Transmission geometry laserspray ionization vacuum using an atmospheric pressure inlet.

PubMed

Lutomski, Corinne A; El-Baba, Tarick J; Inutan, Ellen D; Manly, Cory D; Wager-Miller, James; Mackie, Ken; Trimpin, Sarah

2014-07-01

This represents the first report of laserspray ionization vacuum (LSIV) with operation directly from atmospheric pressure for use in mass spectrometry. Two different types of electrospray ionization source inlets were converted to LSIV sources by equipping the entrance of the atmospheric pressure inlet aperture with a customized cone that is sealed with a removable glass plate holding the matrix/analyte sample. A laser aligned in transmission geometry (at 180° relative to the inlet) ablates the matrix/analyte sample deposited on the vacuum side of the glass slide. Laser ablation from vacuum requires lower inlet temperature relative to laser ablation at atmospheric pressure. However, higher inlet temperature is required for high-mass analytes, for example, α-chymotrypsinogen (25.6 kDa). Labile compounds such as gangliosides and cardiolipins are detected in the negative ion mode directly from mouse brain tissue as intact doubly deprotonated ions. Multiple charging enhances the ion mobility spectrometry separation of ions derived from complex tissue samples.

Transmission Geometry Laserspray Ionization Vacuum Using an Atmospheric Pressure Inlet

PubMed Central

2015-01-01

This represents the first report of laserspray ionization vacuum (LSIV) with operation directly from atmospheric pressure for use in mass spectrometry. Two different types of electrospray ionization source inlets were converted to LSIV sources by equipping the entrance of the atmospheric pressure inlet aperture with a customized cone that is sealed with a removable glass plate holding the matrix/analyte sample. A laser aligned in transmission geometry (at 180° relative to the inlet) ablates the matrix/analyte sample deposited on the vacuum side of the glass slide. Laser ablation from vacuum requires lower inlet temperature relative to laser ablation at atmospheric pressure. However, higher inlet temperature is required for high-mass analytes, for example, α-chymotrypsinogen (25.6 kDa). Labile compounds such as gangliosides and cardiolipins are detected in the negative ion mode directly from mouse brain tissue as intact doubly deprotonated ions. Multiple charging enhances the ion mobility spectrometry separation of ions derived from complex tissue samples. PMID:24896880

Atmospheric sampling glow discharge ionization source

DOEpatents

McLuckey, Scott A.; Glish, Gary L.

1989-01-01

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.

Atmospheric sampling glow discharge ionization source

DOEpatents

McLuckey, S.A.; Glish, G.L.

1989-07-18

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.

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

PubMed

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

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. Copyright © 2014 John Wiley & Sons, Ltd.

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

PubMed

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

2014-05-06

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.

Comparative study of fourteen alkaloids from Uncaria rhynchophylla hooks and leaves using HPLC-diode array detection-atmospheric pressure chemical ionization/MS method.

PubMed

Qu, Jialin; Gong, Tianxing; Ma, Bin; Zhang, Lin; Kano, Yoshihiro; Yuan, Dan

2012-01-01

The purpose of the study is to compare alkaloid profile of Uncaria rhynchophylla hooks and leaves. Ten oxindole alkaloids and four glycosidic indole alkaloids were identified using HPLC-diode array detection (DAD) or LC-atmospheric pressure chemical ionization (APCI)-MS method, and a HPLC-UV method for simultaneous quantification of major alkaloids was validated. The hooks are characterized by high levels of four oxindole alkaloids rhynchophylline (R), isorhynchophylline (IR), corynoxeine (C) and isocorynoxeine (IC), while the leaves contained high level of two glycosidic indole alkaloids vincoside lactam (VL) and strictosidine (S). The presented methods have proven its usefulness in chemical characterization of U. rhynchophylla hooks and leaves.

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

PubMed

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

2014-03-01

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.

High molecular weight non-polar hydrocarbons as pure model substances and in motor oil samples can be ionized without fragmentation by atmospheric pressure chemical ionization mass spectrometry.

PubMed

Hourani, Nadim; Kuhnert, Nikolai

2012-10-15

High molecular weight non-polar hydrocarbons are still difficult to detect by mass spectrometry. Although several studies have targeted this problem, lack of good self-ionization has limited the ability of mass spectrometry to examine these hydrocarbons. Failure to control ion generation in the atmospheric pressure chemical ionization (APCI) source hampers the detection of intact stable gas-phase ions of non-polar hydrocarbon in mass spectrometry. Seventeen non-volatile non-polar hydrocarbons, reported to be difficult to ionize, were examined by an optimized APCI methodology using nitrogen as the reagent gas. All these analytes were successfully ionized as abundant and intact stable [M-H](+) ions without the use of any derivatization or adduct chemistry and without significant fragmentation. Application of the method to real-life hydrocarbon mixtures like light shredder waste and car motor oil was demonstrated. Despite numerous reports to the contrary, it is possible to ionize high molecular weight non-polar hydrocarbons by APCI, omitting the use of additives. This finding represents a significant step towards extending the applicability of mass spectrometry to non-polar hydrocarbon analyses in crude oil, petrochemical products, waste or food. Copyright © 2012 John Wiley & Sons, Ltd.

Desorption atmospheric pressure photoionization high-resolution mass spectrometry: a complementary approach for the chemical analysis of atmospheric aerosols.

PubMed

Parshintsev, Jevgeni; Vaikkinen, Anu; Lipponen, Katriina; Vrkoslav, Vladimir; Cvačka, Josef; Kostiainen, Risto; Kotiaho, Tapio; Hartonen, Kari; Riekkola, Marja-Liisa; Kauppila, Tiina J

2015-07-15

On-line chemical characterization methods of atmospheric aerosols are essential to increase our understanding of physicochemical processes in the atmosphere, and to study biosphere-atmosphere interactions. Several techniques, including aerosol mass spectrometry, are nowadays available, but they all suffer from some disadvantages. In this research, desorption atmospheric pressure photoionization high-resolution (Orbitrap) mass spectrometry (DAPPI-HRMS) is introduced as a complementary technique for the fast analysis of aerosol chemical composition without the need for sample preparation. Atmospheric aerosols from city air were collected on a filter, desorbed in a DAPPI source with a hot stream of toluene and nitrogen, and ionized using a vacuum ultraviolet lamp at atmospheric pressure. To study the applicability of the technique for ambient aerosol analysis, several samples were collected onto filters and analyzed, with the focus being on selected organic acids. To compare the DAPPI-HRMS data with results obtained by an established method, each filter sample was divided into two equal parts, and the second half of the filter was extracted and analyzed by liquid chromatography/mass spectrometry (LC/MS). The DAPPI results agreed with the measured aerosol particle number. In addition to the targeted acids, the LC/MS and DAPPI-HRMS methods were found to detect different compounds, thus providing complementary information about the aerosol samples. DAPPI-HRMS showed several important oxidation products of terpenes, and numerous compounds were tentatively identified. Thanks to the soft ionization, high mass resolution, fast analysis, simplicity and on-line applicability, the proposed methodology has high potential in the field of atmospheric research. Copyright © 2015 John Wiley & Sons, Ltd.

Specific interaction between negative atmospheric ions and organic compounds in atmospheric pressure corona discharge ionization mass spectrometry.

PubMed

Sekimoto, Kanako; Sakai, Mami; Takayama, Mitsuo

2012-06-01

The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O(2)(-), HCO(3)(-), COO(-)(COOH), NO(2)(-), NO(3)(-), and NO(3)(-)(HNO(3)) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion.

Super-atmospheric pressure ionization mass spectrometry and its application to ultrafast online protein digestion analysis.

PubMed

Chen, Lee Chuin; Ninomiya, Satoshi; Hiraoka, Kenzo

2016-06-01

Ion source pressure plays a significant role in the process of ionization and the subsequent ion transmission inside a mass spectrometer. Pressurizing the ion source to a gas pressure greater than atmospheric pressure is a relatively new approach that aims to further improve the performance of atmospheric pressure ionization sources. For example, under a super-atmospheric pressure environment, a stable electrospray can be sustained for liquid with high surface tension such as pure water, because of the suppression of electric discharge. Even for nano-electrospray ionization (nano-ESI), which is known to work with aqueous solution, its stability and sensitivity can also be enhanced, particularly in the negative mode when the ion source is pressurized. A brief review on the development of super-atmospheric pressure ion sources, including high-pressure electrospray, field desorption and superheated ESI, and the strategies to interface these ion sources to a mass spectrometer will be given. Using a recent ESI prototype with an operating temperature at 220 °C under 27 atm, we also demonstrate that it is possible to achieve an online Asp-specific protein digestion analysis in which the whole processes of digestion, ionization and MS acquisition could be completed on the order of a few seconds. This method is fast, and the reaction can even be monitored on a near-real-time basis. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Gas Chromatography/Atmospheric Pressure Chemical Ionization-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Pyrolysis Oil from German Brown Coal

PubMed Central

Zuber, Jan; Kroll, Marius M.; Rathsack, Philipp; Otto, Matthias

2016-01-01

Pyrolysis oil from the slow pyrolysis of German brown coal from Schöningen, obtained at a temperature of 500°C, was separated and analyzed using hyphenation of gas chromatography with an atmospheric pressure chemical ionization source operated in negative ion mode and Fourier transform ion cyclotron resonance mass spectrometry (GC-APCI-FT-ICR-MS). Development of this ultrahigh-resolving analysis method is described, that is, optimization of specific GC and APCI parameters and performed data processing. The advantages of GC-APCI-FT-ICR-MS hyphenation, for example, soft ionization, ultrahigh-resolving detection, and most important isomer separation, were demonstrated for the sample liquid. For instance, it was possible to separate and identify nine different propylphenol, ethylmethylphenol, and trimethylphenol isomers. Furthermore, homologous series of different acids, for example, alkyl and alkylene carboxylic acids, were verified, as well as homologous series of alkyl phenols, alkyl dihydroxy benzenes, and alkoxy alkyl phenols. PMID:27066076

Atmospheric pressure chemical ionization of explosives using alternating current corona discharge ion source.

PubMed

Usmanov, D T; Chen, L C; Yu, Z; Yamabe, S; Sakaki, S; Hiraoka, K

2015-04-01

The high-sensitive detection of explosives is of great importance for social security and safety. In this work, the ion source for atmospheric pressure chemical ionization/mass spectrometry using alternating current corona discharge was newly designed for the analysis of explosives. An electromolded fine capillary with 115 µm inner diameter and 12 mm long was used for the inlet of the mass spectrometer. The flow rate of air through this capillary was 41 ml/min. Stable corona discharge could be maintained with the position of the discharge needle tip as close as 1 mm to the inlet capillary without causing the arc discharge. Explosives dissolved in 0.5 µl methanol were injected to the ion source. The limits of detection for five explosives with 50 pg or lower were achieved. In the ion/molecule reactions of trinitrotoluene (TNT), the discharge products of NOx (-) (x = 2,3), O3 and HNO3 originating from plasma-excited air were suggested to contribute to the formation of [TNT - H](-) (m/z 226), [TNT - NO](-) (m/z 197) and [TNT - NO + HNO3 ](-) (m/z 260), respectively. Formation processes of these ions were traced by density functional theory calculations. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Understanding the Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source through Optical Means

NASA Astrophysics Data System (ADS)

Shelley, Jacob T.; Chan, George C.-Y.; Hieftje, Gary M.

2012-02-01

The advent of ambient desorption/ionization mass spectrometry (ADI-MS) has led to the development of a large number of atmospheric-pressure ionization sources. The largest group of such sources is based on electrical discharges; yet, the desorption and ionization processes that they employ remain largely uncharacterized. Here, the atmospheric-pressure glow discharge (APGD) and afterglow of a helium flowing atmospheric-pressure afterglow (FAPA) ionization source were examined by optical emission spectroscopy. Spatial emission profiles of species created in the APGD and afterglow were recorded under a variety of operating conditions, including discharge current, electrode polarity, and plasma-gas flow rate. From these studies, it was found that an appreciable amount of atmospheric H2O vapor, N2, and O2 diffuses through the hole in the plate electrode into the discharge to become a major source of reagent ions in ADI-MS analyses. Spatially resolved plasma parameters, such as OH rotational temperature (Trot) and electron number density (ne), were also measured in the APGD. Maximum values for Trot and ne were found to be ~1100 K and ~4 × 1019 m-3, respectively, and were both located at the pin cathode. In the afterglow, rotational temperatures from OH and N{2/+} yielded drastically different values, with OH temperatures matching those obtained from infrared thermography measurements. The higher N{2/+} temperature is believed to be caused by charge-transfer ionization of N2 by He{2/+}. These findings are discussed in the context of previously reported ADI-MS analyses with the FAPA source.

Microplasma discharge vacuum ultraviolet photoionization source for atmospheric pressure ionization mass spectrometry.

PubMed

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

2014-09-01

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/H(2) 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.

Separation and identification of twelve catechins in tea using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry.

PubMed

Zeeb, D J; Nelson, B C; Albert, K; Dalluge, J J

2000-10-15

A method has been developed for the direct microscale determination of 12 catechins in green and black tea infusions. The method is based on liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS). Standard catechin mixtures and tea infusions were analyzed by LC/APCI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of eight major catechins and caffeine in tea were established based on LC retention times and simultaneously recorded mass spectra. In addition, monitoring of the catechin-specific retro Diels-Alder fragment ion at m/z 139 throughout the chromatogram provided a unique fingerprint for catechin content in the samples that led to the identification of four minor chemically modified catechin derivatives in the infusions. This report is the first to describe the comprehensive determination of all 12 reported catechins in a single analysis. The utility of LC/APCI-MS for providing routine separation and identification of catechins at femtomole to low-picomole levels without extraction or sample pretreatment, and its potential as a standard analytical tool for the determination of polyphenols in natural products and biological fluids, are discussed.

Differentiation of regioisomeric aromatic ketocarboxylic acids by atmospheric pressure chemical ionization CAD tandem mass spectrometry in a linear quadrupole ion trap mass spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amundson, Lucas M.; Owen, Ben C.; Gallardo, Vanessa A.

2011-01-01

Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS n ) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer. Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction products, or different relative abundances of fragment ions formed at differentmore » collision energies. The mechanisms of some of the reactions were examined by H/D exchange reactions and molecular orbital calculations.« less

Understanding the flowing atmospheric-pressure afterglow (FAPA) ambient ionization source through optical means.

PubMed

Shelley, Jacob T; Chan, George C-Y; Hieftje, Gary M

2012-02-01

The advent of ambient desorption/ionization mass spectrometry (ADI-MS) has led to the development of a large number of atmospheric-pressure ionization sources. The largest group of such sources is based on electrical discharges; yet, the desorption and ionization processes that they employ remain largely uncharacterized. Here, the atmospheric-pressure glow discharge (APGD) and afterglow of a helium flowing atmospheric-pressure afterglow (FAPA) ionization source were examined by optical emission spectroscopy. Spatial emission profiles of species created in the APGD and afterglow were recorded under a variety of operating conditions, including discharge current, electrode polarity, and plasma-gas flow rate. From these studies, it was found that an appreciable amount of atmospheric H(2)O vapor, N(2), and O(2) diffuses through the hole in the plate electrode into the discharge to become a major source of reagent ions in ADI-MS analyses. Spatially resolved plasma parameters, such as OH rotational temperature (T(rot)) and electron number density (n(e)), were also measured in the APGD. Maximum values for T(rot) and n(e) were found to be ~1100 K and ~4×10(19) m(-3), respectively, and were both located at the pin cathode. In the afterglow, rotational temperatures from OH and N(2)(+) yielded drastically different values, with OH temperatures matching those obtained from infrared thermography measurements. The higher N(2)(+) temperature is believed to be caused by charge-transfer ionization of N(2) by He(2)(+). These findings are discussed in the context of previously reported ADI-MS analyses with the FAPA source. © American Society for Mass Spectrometry, 2011

Supercritical fluid chromatography coupled with in-source atmospheric pressure ionization hydrogen/deuterium exchange mass spectrometry for compound speciation.

PubMed

Cho, Yunju; Choi, Man-Ho; Kim, Byungjoo; Kim, Sunghwan

2016-04-29

An experimental setup for the speciation of compounds by hydrogen/deuterium exchange (HDX) with atmospheric pressure ionization while performing chromatographic separation is presented. The proposed experimental setup combines the high performance supercritical fluid chromatography (SFC) system that can be readily used as an inlet for mass spectrometry (MS) and atmospheric pressure photo ionization (APPI) or atmospheric pressure chemical ionization (APCI) HDX. This combination overcomes the limitation of an approach using conventional liquid chromatography (LC) by minimizing the amount of deuterium solvents used for separation. In the SFC separation, supercritical CO2 was used as a major component of the mobile phase, and methanol was used as a minor co-solvent. By using deuterated methanol (CH3OD), AP HDX was achieved during SFC separation. To prove the concept, thirty one nitrogen- and/or oxygen-containing standard compounds were analyzed by SFC-AP HDX MS. The compounds were successfully speciated from the obtained SFC-MS spectra. The exchange ions were observed with as low as 1% of CH3OD in the mobile phase, and separation could be performed within approximately 20min using approximately 0.24 mL of CH3OD. The results showed that SFC separation and APPI/APCI HDX could be successfully performed using the suggested method. Copyright © 2016 Elsevier B.V. All rights reserved.

An Atmospheric Pressure Chemical Ionization MS/MS Assay Using Online Extraction for the Analysis of 11 Cannabinoids and Metabolites in Human Plasma and Urine.

PubMed

Klawitter, Jelena; Sempio, Cristina; Mörlein, Sophie; De Bloois, Erik; Klepacki, Jacek; Henthorn, Thomas; Leehey, Maureen A; Hoffenberg, Edward J; Knupp, Kelly; Wang, George S; Hopfer, Christian; Kinney, Greg; Bowler, Russell; Foreman, Nicholas; Galinkin, Jeffrey; Christians, Uwe; Klawitter, Jost

2017-10-01

Although, especially in the United States, there has been a recent surge of legalized cannabis for either recreational or medicinal purposes, surprisingly little is known about clinical dose-response relationships, pharmacodynamic and toxicodynamic effects of cannabinoids such as Δ9-tetrahydrocannabinol (THC). Even less is known about other active cannabinoids. To address this knowledge gap, an online extraction, high-performance liquid chromatography coupled with tandem mass spectrometry method for simultaneous quantification of 11 cannabinoids and metabolites including THC, 11-hydroxy-Δ9-tetrahydrocannabinol, 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid, 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid glucuronide (THC-C-gluc), cannabinol, cannabidiol, cannabigerol, cannabidivarin, Δ9-tetrahydrocannabivarin (THCV), and 11-nor-9-carboxy-Δ9-tetrahydrocannabivarin (THCV-COOH) was developed and validated in human urine and plasma. In contrast to atmospheric pressure chemical ionization, electrospray ionization was associated with extensive ion suppression in plasma and urine samples. Thus, the atmospheric pressure chemical ionization assay was validated showing a lower limit of quantification ranging from 0.39 to 3.91 ng/mL depending on study compound and matrix. The upper limit of quantification was 400 ng/mL except for THC-C-gluc with an upper limit of quantification of 2000 ng/mL. The linearity was r > 0.99 for all analyzed calibration curves. Acceptance criteria for intrabatch and interbatch accuracy (85%-115%) and imprecision (<15%) were met for all compounds. In plasma, the only exceptions were THCV (75.3%-121.2% interbatch accuracy) and cannabidivarin (interbatch imprecision, 15.7%-17.2%). In urine, THCV did not meet predefined acceptance criteria for intrabatch accuracy. This assay allows for monitoring not only THC and its major metabolites but also major cannabinoids that are of interest for marijuana research and clinical practice.

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

PubMed

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

2013-09-01

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. © 2013 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons, Ltd.

An Open Port Sampling Interface for Liquid Introduction Atmospheric Pressure Ionization Mass Spectrometry

DOE PAGES

Van Berkel, Gary J.; Kertesz, Vilmos

2015-08-25

RATIONALE: A simple method to introduce unprocessed samples into a solvent for rapid characterization by liquid introduction atmospheric pressure ionization mass spectrometry has been lacking. The continuous flow, self-cleaning open port sampling interface introduced here fills this void. METHODS: The open port sampling interface used a vertically aligned, co-axial tube arrangement enabling solvent delivery to the sampling end of the device through the tubing annulus and solvent aspiration down the center tube and into the mass spectrometer ionization source via the commercial APCI emitter probe. The solvent delivery rate to the interface was set to exceed the aspiration rate creatingmore » a continuous sampling interface along with a constant, self-cleaning spillover of solvent from the top of the probe. RESULTS: Using the open port sampling interface with positive ion mode APCI and a hybrid quadrupole time of flight mass spectrometer, rapid, direct sampling and analysis possibilities are exemplified with plastics, ballpoint and felt tip ink pens, skin, and vegetable oils. These results demonstrated that the open port sampling interface could be used as a simple, versatile and self-cleaning system to rapidly introduce multiple types of unprocessed, sometimes highly concentrated and complex, samples into a solvent flow stream for subsequent ionization and analysis by mass spectrometry. The basic setup presented here could be incorporated with any self-aspirating liquid introduction ionization source (e.g., ESI, APCI, APPI, ICP, etc.) or any type of atmospheric pressure sampling ready mass spectrometer system. CONCLUSIONS: The open port sampling interface provides a means to introduce and quickly analyze unprocessed solid or liquid samples with liquid introduction atmospheric pressure ionization source without fear of sampling interface or ionization source contamination.« less

Analysis of polycyclic aromatic hydrocarbons using desorption atmospheric pressure chemical ionization coupled to a portable mass spectrometer.

PubMed

Jjunju, Fred P M; Maher, Simon; Li, Anyin; Badu-Tawiah, Abraham K; Taylor, Stephen; Cooks, R Graham

2015-02-01

Desorption atmospheric pressure chemical ionization (DAPCI) is implemented on a portable mass spectrometer and applied to the direct detection of polycyclic aromatic hydrocarbons (PAHs) and alkyl substituted benzenes. The presence of these compounds in the environment poses a significant threat to the health of both humans and wildlife because of their carcinogenic, toxic, and mutagenic properties. As such, instant detection outside of the laboratory is of particular importance to allow in-situ measurement at the source. Using a rapid, high throughput, miniature, handheld mass spectrometer, several alkyl substituted benzenes and PAHs (i.e., 1,2,3,5-tetramethylbenzene, pentamethylbenzene, hexamethylbenzene, fluoranthene, anthracene, benzo[k]fluoranthene, dibenz[a,h]anthracene, acenaphthene, indeno[1,2,3-c,d]pyrene, 9-ethylfluorene, and 1-benzyl-3-methyl-naphthalene) were identified and characterized using tandem mass spectrometry (MS/MS) from ambient surfaces, in the open air. This method can provide almost instantaneous information while minimizing sample preparation, which is advantageous in terms of both cost and simplicity of analysis. This MS-based technique is applicable to a wide range of environmental organic molecules.

Development of an Atmospheric Pressure Ionization Mass Spectrometer

NASA Technical Reports Server (NTRS)

1998-01-01

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.

Trace determination of 13 haloacetamides in drinking water using liquid chromatography triple quadrupole mass spectrometry with atmospheric pressure chemical ionization.

PubMed

Chu, Wenhai; Gao, Naiyun; Yin, Daqiang; Krasner, Stuart W; Templeton, Michael R

2012-04-27

The haloacetamides (HAcAms) are disinfection by-products (DBPs) in drinking water which are currently receiving increased scientific attention due to their elevated toxicity relative to regulated disinfection by-products. A simultaneous determination method of 13 HAcAms, combining solid-phase extraction (SPE) enrichment, liquid chromatographic (LC) separation, and triple quadrupole mass spectrometry (tqMS) detection with atmospheric pressure chemical ionization (APCI) using selective reaction monitoring in positive mode, was developed to measure HAcAms, including chlorinated, brominated, and iodinated analogs. Ammonium chloride and Oasis HLB were selected as the dechlorinating reagent and polymeric SPE sorbent of HAcAm samples. The used tqMS apparatus showed higher sensitivity for the studied HAcAms in the APCI mode than electrospray ionization. 13 HAcAms were separated by LC in 9.0 min, and the detection limits ranged from 7.6 to 19.7 ng/L. The SPE-LC/tqMS method was successfully applied to quantify 13 HAcAms in drinking water samples for the first time, and first indentified tribromoacetamide and chloroiodoacetamide as DBPs in drinking water. Copyright © 2012 Elsevier B.V. All rights reserved.

Characterization of polymethoxylated flavones in Fructus aurantii by liquid chromatography with atmospheric pressure chemical ionization combined with tandem mass spectrometry.

PubMed

Zhou, Da-Yong; Chen, De-Liang; Xu, Qing; Xue, Xing-Ya; Zhang, Fei-Fang; Liang, Xin-Miao

2007-04-11

Atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was operated in positive mode (PI) to characterize polymethoxylated flavonoids (PMFs) through its specific radical cations by collision-induced dissociation (CID). The fragments of [M + H - n x 15]+ produced by loss of one or more methyl group from the protonated molecule, as well as [M + H - 29]+, [M + H - 31]+, [M + H - 33]+, [M + H - 43]+, [M + H - 46]+, and [M + H - 61]+ fragment ions were detected, which were diagnostic for the polymethoxylated species, and could be adopted to form the multiple MS (MS(n)) "fingerprint" of PMFs. Based on this "fingerprint", 29 PMFs were screened out from extracts of Fructus aurantii, among which two of them were identified as sinensetin and tangeretin. It was proved that the PI was suitable for structural characterization of PMFs by APCI-MS(n).

Highly sensitive screening method for nitroaromatic, nitramine and nitrate ester explosives by high performance liquid chromatography-atmospheric pressure ionization-mass spectrometry (HPLC-API-MS) in forensic applications.

PubMed

Xu, Xiaoma; van de Craats, Anick M; de Bruyn, Peter C A M

2004-11-01

A highly sensitive screening method based on high performance liquid chromatography atmospheric pressure ionization mass spectrometry (HPLC-API-MS) has been developed for the analysis of 21 nitroaromatic, nitramine and nitrate ester explosives, which include the explosives most commonly encountered in forensic science. Two atmospheric pressure ionization (API) methods, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), and various experimental conditions have been applied to allow for the detection of all 21 explosive compounds. The limit of detection (LOD) in the full-scan mode has been found to be 0.012-1.2 ng on column for the screening of most explosives investigated. For nitrobenzene, an LOD of 10 ng was found with the APCI method in the negative mode. Although the detection of nitrobenzene, 2-, 3-, and 4-nitrotoluene is hindered by the difficult ionization of these compounds, we have found that by forming an adduct with glycine, LOD values in the range of 3-16 ng on column can be achieved. Compared with previous screening methods with thermospray ionization, the API method has distinct advantages, including simplicity and stability of the method applied, an extended screening range and a low detection limit for the explosives studied.

Pyroelectricity Assisted Infrared-Laser Desorption Ionization (PAI-LDI) for Atmospheric Pressure Mass Spectrometry

NASA Astrophysics Data System (ADS)

Li, Yanyan; Ma, Xiaoxiao; Wei, Zhenwei; Gong, Xiaoyun; Yang, Chengdui; Zhang, Sichun; Zhang, Xinrong

2015-08-01

A new atmospheric pressure ionization method termed pyroelectricity-assisted infrared laser desorption ionization (PAI-LDI) was developed in this study. The pyroelectric material served as both sample target plate and enhancing ionization substrate, and an IR laser with wavelength of 1064 nm was employed to realize direct desorption and ionization of the analytes. The mass spectra of various compounds obtained on pyroelectric material were compared with those of other substrates. For the five standard substances tested in this work, LiNbO3 substrate produced the highest ion yield and the signal intensity was about 10 times higher than that when copper was used as substrate. For 1-adamantylamine, as low as 20 pg (132.2 fmol) was successfully detected. The active ingredient in (Compound Paracetamol and 1-Adamantylamine Hydrochloride Capsules), 1-adamantylamine, can be sensitively detected at an amount as low as 150 pg, when the medicine stock solution was diluted with urine. Monosaccharide and oligosaccharides in Allium Cepa L. juice was also successfully identified with PAI-LDI. The method did not require matrix-assisted external high voltage or other extra facility-assisted set-ups for desorption/ionization. This study suggested exciting application prospect of pyroelectric materials in matrix- and electricity-free atmospheric pressure mass spectrometry research.

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, Andrew J.; Shelley, Jacob T.; Walton, Courtney L.

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here in this paper, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-likemore » spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma.« less

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge

DOE PAGES

Schwartz, Andrew J.; Shelley, Jacob T.; Walton, Courtney L.; ...

2016-06-27

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here in this paper, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-likemore » spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma.« less

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

NASA Astrophysics Data System (ADS)

Buchalla, Rainer; Begley, Timothy H.

2006-01-01

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?

Molecular differentiation of five Cinnamomum camphora chemotypes using desorption atmospheric pressure chemical ionization mass spectrometry of raw leaves

PubMed Central

Guo, Xiali; Cui, Meng; Deng, Min; Liu, Xingxing; Huang, Xueyong; Zhang, Xinglei; Luo, Liping

2017-01-01

Five chemotypes, the isoborneol-type, camphora-type, cineole-type, linalool-type and borneol-type of Cinnamomum camphora (L.) Presl have been identified at the molecular level based on the multivariate analysis of mass spectral fingerprints recorded from a total of 750 raw leaf samples (i.e., 150 leaves equally collected for each chemotype) using desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). Both volatile and semi-volatile metabolites of the fresh leaves of C. camphora were simultaneously detected by DAPCI-MS without any sample pretreatment, reducing the analysis time from half a day using conventional methods (e.g., GC-MS) down to 30 s. The pattern recognition results obtained using principal component analysis (PCA) was cross-checked by cluster analysis (CA), showing that the difference visualized by the DAPCI-MS spectral fingerprints was validated with 100% accuracy. The study demonstrates that DAPCI-MS meets the challenging requirements for accurate differentiation of all the five chemotypes of C. camphora leaves, motivating more advanced application of DAPCI-MS in plant science and forestry studies. PMID:28425482

Characterization of nonpolar lipids and selected steroids by using laser-induced acoustic desorption/chemical ionization, atmospheric pressure chemical ionization, and electrospray ionization mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Zhicheng; Daiya, Shivani; Kenttämaa, Hilkka I.

2011-03-01

Laser-induced acoustic desorption (LIAD) combined with ClMn(H2O)+ chemical ionization (CI) was tested for the analysis of nonpolar lipids and selected steroids in a Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR). The nonpolar lipids studied, cholesterol, 5α-cholestane, cholesta-3,5-diene, squalene, and β-carotene, were found to solely form the desired water replacement product (adduct-H2O) upon reaction with the ClMn(H2O)+ ions. The steroids, androsterone, dehydroepiandrosterone (DHEA), estrone, estradiol, and estriol, also form abundant adduct-H2O ions, but less abundant adduct-2H2O ions were also observed. Neither (+)APCI nor (+)ESI can ionize the saturated hydrocarbon lipid, cholestane. APCI successfully ionizes the unsaturated hydrocarbon lipids to form exclusivelymore » the intact protonated analytes. However, it causes extensive fragmentation for cholesterol and the steroids. The worst case is cholesterol that does not produce any stable protonated molecules. On the other hand, ESI cannot ionize any of the hydrocarbon analytes, saturated or unsaturated. However, ESI can be used to protonate the oxygen-containing analytes with substantially less fragmentation than for APCI in all cases except for cholesterol and estrone. In conclusion, LIAD/ClMn(H2O)+ chemical ionization is superior over APCI and ESI for the mass spectrometric characterization of underivatized nonpolar lipids and steroids.« less

Hand-held portable desorption atmospheric pressure chemical ionization ion source for in situ analysis of nitroaromatic explosives.

PubMed

Jjunju, Fred P M; Maher, Simon; Li, Anyin; Syed, Sarfaraz U; Smith, Barry; Heeren, Ron M A; Taylor, Stephen; Cooks, R Graham

2015-10-06

A novel, lightweight (0.6 kg), solvent- and gas-cylinder-free, hand-held ion source based on desorption atmospheric pressure chemical ionization has been developed and deployed for the analysis of nitroaromatic explosives on surfaces in open air, offering portability for in-field analysis. A small, inexpensive, rechargeable lithium polymer battery was used to power the custom-designed circuitry within the device, which generates up to ±5 kV dc voltage to ignite a corona discharge plasma in air for up to 12 h of continuous operation, and allowing positive- and negative-ion mass spectrometry. The generated plasma is pneumatically transported to the surface to be interrogated by ambient air at a rate of 1-3.5 L/min, compressed using a small on-board diaphragm pump. The plasma source allows liquid or solid samples to be examined almost instantaneously without any sample preparation in the open environment. The advantages of low carrier gas and low power consumption (<6 W), as well as zero solvent usage, have aided in developing the field-ready, hand-held device for trigger-based, "near-real-time" sampling/ionization. Individual nitroaromatic explosives (such as 2,4,6-trinitrotoluene) can be easily detected in amounts as low as 5.8 pg with a linear dynamic range of at least 10 (10-100 pg), a relative standard deviation of ca. 7%, and an R(2) value of 0.9986. Direct detection of several nitroaromatic compounds in a complex mixture without prior sample preparation is demonstrated, and their identities are confirmed by tandem mass spectrometry fragmentation patterns.

Tunable Ionization Modes of a Flowing Atmospheric-Pressure Afterglow (FAPA) Ambient Ionization Source.

PubMed

Badal, Sunil P; Michalak, Shawn D; Chan, George C-Y; You, Yi; Shelley, Jacob T

2016-04-05

Plasma-based ambient desorption/ionization sources are versatile in that they enable direct ionization of gaseous samples as well as desorption/ionization of analytes from liquid and solid samples. However, ionization matrix effects, caused by competitive ionization processes, can worsen sensitivity or even inhibit detection all together. The present study is focused on expanding the analytical capabilities of the flowing atmospheric-pressure afterglow (FAPA) source by exploring additional types of ionization chemistry. Specifically, it was found that the abundance and type of reagent ions produced by the FAPA source and, thus, the corresponding ionization pathways of analytes, can be altered by changing the source working conditions. High abundance of proton-transfer reagent ions was observed with relatively high gas flow rates and low discharge currents. Conversely, charge-transfer reagent species were most abundant at low gas flows and high discharge currents. A rather nonpolar model analyte, biphenyl, was found to significantly change ionization pathway based on source operating parameters. Different analyte ions (e.g., MH(+) via proton-transfer and M(+.) via charge-transfer) were formed under unique operating parameters demonstrating two different operating regimes. These tunable ionization modes of the FAPA were used to enable or enhance detection of analytes which traditionally exhibit low-sensitivity in plasma-based ADI-MS analyses. In one example, 2,2'-dichloroquaterphenyl was detected under charge-transfer FAPA conditions, which were difficult or impossible to detect with proton-transfer FAPA or direct analysis in real-time (DART). Overall, this unique mode of operation increases the number and range of detectable analytes and has the potential to lessen ionization matrix effects in ADI-MS analyses.

Fast determination of 3-ethenylpyridine as a marker of environmental tobacco smoke at trace level using direct atmospheric pressure chemical ionization tandem mass spectrometry

NASA Astrophysics Data System (ADS)

Jiang, Cheng-Yong; Sun, Shi-Hao; Zhang, Qi-Dong; Liu, Jun-Hui; Zhang, Jian-Xun; Zong, Yong-Li; Xie, Jian-Ping

2013-03-01

A method with atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS/MS) was developed and applied to direct analysis of Environmental Tobacco Smoke (ETS), using 3-ethenylpyridine (3-EP) as a vapour-phase marker. In this study, the ion source of APCI-MS/MS was modified and direct analysis of gas sample was achieved by the modified instrument. ETS samples were directly introduced, via an atmospheric pressure inlet, into the APCI source. Ionization was carried out in positive-ion APCI mode and 3-EP was identified by both full scan mode and daughter scan mode. Quantification of 3-EP was performed by multiple reaction monitoring (MRM) mode. The calibration curve was obtained in the range of 1-250 ng L-1 with a satisfactory regression coefficient of 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.5 ng L-1 and 1.6 ng L-1, respectively. The precision of the method, calculated as relative standard deviation (RSD), was characterized by repeatability (RSD 3.92%) and reproducibility (RSD 4.81%), respectively. In real-world ETS samples analysis, compared with the conventional GC-MS method, the direct APCI-MS/MS has shown better reliability and practicability in the determination of 3-EP at trace level. The developed method is simple, fast, sensitive and repeatable; furthermore, it could provide an alternative way for the determination of other volatile pollutants in ambient air at low levels.

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

PubMed Central

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

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

High-throughput trace analysis of explosives in water by laser diode thermal desorption/atmospheric pressure chemical ionization-tandem mass spectrometry.

PubMed

Badjagbo, Koffi; Sauvé, Sébastien

2012-07-03

Harmful explosives can accumulate in natural waters in the long term during their testing, usage, storage, and dumping and can pose a health risk to humans and the environment. For the first time, attachment of small anions to neutral molecules in laser diode thermal desorption/atmospheric pressure chemical ionization was systematically investigated for the direct determination of trace nitroaromatics, nitrate esters, and nitramine explosives in water. Using ammonium chloride as an additive improved the instrument response for all the explosives tested and promoted the formation of several characteristic adduct ions. The method performs well achieving good linearity over at least 2 orders of magnitude, with coefficients of determination greater than 0.995. The resulting limits of detection are in the range of 0.009-0.092 μg/L. River water samples were successfully analyzed by the proposed method with accuracy in the range of 96-98% and a response time of 15 s, without any further pretreatment or chromatographic separation.

Gas Chromatography-Tandem Mass Spectrometry of Lignin Pyrolyzates with Dopant-Assisted Atmospheric Pressure Chemical Ionization and Molecular Structure Search with CSI:FingerID

NASA Astrophysics Data System (ADS)

Larson, Evan A.; Hutchinson, Carolyn P.; Lee, Young Jin

2018-06-01

Dopant-assisted atmospheric pressure chemical ionization (dAPCI) is a soft ionization method rarely used for gas chromatography-mass spectrometry (GC-MS). The current study combines GC-dAPCI with tandem mass spectrometry (MS/MS) for analysis of a complex mixture such as lignin pyrolysis analysis. To identify the structures of volatile lignin pyrolysis products, collision-induced dissociation (CID) MS/MS using a quadrupole time-of-flight mass spectrometer (QTOFMS) and pseudo MS/MS through in-source collision-induced dissociation (ISCID) using a single stage TOFMS are utilized. To overcome the lack of MS/MS database, Compound Structure Identification (CSI):FingerID is used to interpret CID spectra and predict best matched structures from PubChem library. With this approach, a total of 59 compounds were positively identified in comparison to only 22 in NIST database search of GC-EI-MS dataset. This study demonstrates the effectiveness of GC-dAPCI-MS/MS to overcome the limitations of traditional GC-EI-MS analysis when EI-MS database is not sufficient. [Figure not available: see fulltext.

Quantitative correlations between collision induced dissociation mass spectrometry coupled with electrospray ionization or atmospheric pressure chemical ionization mass spectrometry - Experiment and theory

NASA Astrophysics Data System (ADS)

Ivanova, Bojidarka; Spiteller, Michael

2018-04-01

The problematic that we consider in this paper treats the quantitative correlation model equations between experimental kinetic and thermodynamic parameters of coupled electrospray ionization (ESI) mass spectrometry (MS) or atmospheric pressure chemical ionization (APCI) mass spectrometry with collision induced dissociation mass spectrometry, accounting for the fact that the physical phenomena and mechanisms of ESI- and APCI-ion formation are completely different. There are described forty two fragment reactions of three analytes under independent ESI- and APCI-measurements. The developed new quantitative models allow us to study correlatively the reaction kinetics and thermodynamics using the methods of mass spectrometry, which complementary application with the methods of the quantum chemistry provide 3D structural information of the analytes. Both static and dynamic quantum chemical computations are carried out. The object of analyses are [2,3-dimethyl-4-(4-methyl-benzoyl)-2,3-di-p-tolyl-cyclobutyl]-p-tolyl-methanone (1) and the polycyclic aromatic hydrocarbons derivatives of dibenzoperylen (2) and tetrabenzo [a,c,fg,op]naphthacene (3), respectively. As far as (1) is known to be a product of [2π+2π] cycloaddition reactions of chalcone (1,3-di-p-tolyl-propenone), however producing cyclic derivatives with different stereo selectivity, so that the study provide crucial data about the capability of mass spectrometry to provide determine the stereo selectivity of the analytes. This work also first provides quantitative treatment of the relations '3D molecular/electronic structures'-'quantum chemical diffusion coefficient'-'mass spectrometric diffusion coefficient', thus extending the capability of the mass spectrometry for determination of the exact 3D structure of the analytes using independent measurements and computations of the diffusion coefficients. The determination of the experimental diffusion parameters is carried out within the 'current monitoring method

Differentiation of dried sea cucumber products from different geographical areas by surface desorption atmospheric pressure chemical ionization mass spectrometry.

PubMed

Wu, Zhongchen; Chen, Huanwen; Wang, Weiling; Jia, Bin; Yang, Tianlin; Zhao, Zhanfeng; Ding, Jianhua; Xiao, Xuxian

2009-10-28

Without any sample pretreatment, mass spectral fingerprints of 486 dried sea cucumber slices were rapidly recorded in the mass range of m/z 50-800 by using surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). A set of 162 individual sea cucumbers (Apostichopus japonicus Selenka) grown up in 3 different geographical regions (Weihai: 59 individuals, 177 slices; Yantai: 53 individuals, 159 slices; Dalian: 50 individuals, 150 slices;) in north China sea were successfully differentiated according to their habitats both by Principal Components Analysis (PCA) and Soft Independent Modeling of Class Analogy (SIMCA) of the mass spectral raw data, demonstrating that DAPCI-MS is a practically convenient tool for high-throughput differentiation of sea cucumber products. It has been found that the difference between the body wall tissue and the epidermal tissue is heavily dependent on the habitats. The experimental data also show that the roughness of the sample surface contributes to the variance of the signal levels in a certain extent, but such variance does not fail the differentiation of the dried sea cucumber samples.

Propagation of atmospheric-pressure ionization waves along the tapered tube

NASA Astrophysics Data System (ADS)

Xia, Yang; Wang, Wenchun; Liu, Dongping; Yan, Wen; Bi, Zhenhua; Ji, Longfei; Niu, Jinhai; Zhao, Yao

2018-02-01

Gas discharge in a small radius dielectric tube may result in atmospheric pressure plasma jets with high energy and density of electrons. In this study, the atmospheric pressure ionization waves (IWs) were generated inside a tapered tube. The propagation behaviors of IWs inside the tube were studied by using a spatially and temporally resolved optical detection system. Our measurements show that both the intensity and velocity of the IWs decrease dramatically when they propagate to the tapered region. After the taper, the velocity, intensity, and electron density of the IWs are improved with the tube inner diameter decreasing from 4.0 to 0.5 mm. Our analysis indicates that the local gas conductivity and surface charges may play a role in the propagation of the IWs under such a geometrical constraint, and the difference in the dynamics of the IWs after the taper can be related to the restriction in the size of IWs.

Determination of imidacloprid, metalaxyl, myclobutanil, propham, and thiabendazole in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

PubMed

Pous, X; Ruíz, M J; Picó, Y; Font, G

2001-09-01

Imidacloprid, metalaxyl, myclobutanil, propham, and thiabendazole have been simultaneously determined in strawberries, oranges, potatoes, pears, and melons by matrix solid-phase dispersion (MSPD) followed by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) in positive-ion mode. The samples were homogenized with C8 bonded silica as MSPD sorbent, placed in a glass column, and eluted with dichloromethane. Chromatographic separation of the compounds was achieved on a reversed-phase LC column using a methanol-ammonium formate (50 mmol L(-1)) gradient as a mobile phase. Samples were screened by monitoring the protonated molecular ion at m/z 256 for imidacloprid, 280 for metalaxyl, 289 for myclobutanil, and 202 for thiabendazole, and the main fragment at m/z 138 for propham. Positive samples were confirmed by multiple-ion monitoring. The repeatability (<20%) and recovery (>57%) of the method were good, and limits of detection (<0.05 mg kg(-1)) were adequate.

Determination of oxygen and nitrogen derivatives of polycyclic aromatic hydrocarbons in fractions of asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization.

PubMed

Nascimento, Paulo Cicero; Gobo, Luciana Assis; Bohrer, Denise; Carvalho, Leandro Machado; Cravo, Margareth Coutinho; Leite, Leni Figueiredo Mathias

2015-12-01

Liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization was used for the determination of polycyclic aromatic hydrocarbon derivatives, the oxygenated polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons, formed in asphalt fractions. Two different methods have been developed for the determination of five oxygenated and seven nitrated polycyclic aromatic hydrocarbons that are characterized by having two or more condensed aromatic rings and present mutagenic and carcinogenic properties. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all compounds. The detection limits of the methods ranged from 0.1 to 57.3 μg/L for nitrated and from 0.1 to 6.6 μg/L for oxygenated derivatives. The limits of quantification were in the range of 4.6-191 μg/L for nitrated and 0.3-8.9 μg/L for oxygenated derivatives. The methods were validated against a diesel particulate extract standard reference material (National Institute of Standards and Technology SRM 1975), and the obtained concentrations (two nitrated derivatives) agreed with the certified values. The methods were applied in the analysis of asphalt samples after their fractionation into asphaltenes and maltenes, according to American Society for Testing and Material D4124, where the maltenic fraction was further separated into its basic, acidic, and neutral parts following the method of Green. Only two nitrated derivatives were found in the asphalt sample, quinoline and 2-nitrofluorene, with concentrations of 9.26 and 2146 mg/kg, respectively, whereas no oxygenated derivatives were detected. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atmospheric Pressure Plasma Induced Sterilization and Chemical Neutralization

NASA Astrophysics Data System (ADS)

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

1998-11-01

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.

Quantitation of triacylglycerols in edible oils by off-line comprehensive two-dimensional liquid chromatography-atmospheric pressure chemical ionization mass spectrometry using a single column.

PubMed

Wei, Fang; Hu, Na; Lv, Xin; Dong, Xu-Yan; Chen, Hong

2015-07-24

In this investigation, off-line comprehensive two-dimensional liquid chromatography-atmospheric pressure chemical ionization mass spectrometry using a single column has been applied for the identification and quantification of triacylglycerols in edible oils. A novel mixed-mode phenyl-hexyl chromatographic column was employed in this off-line two-dimensional separation system. The phenyl-hexyl column combined the features of traditional C18 and silver-ion columns, which could provide hydrophobic interactions with triacylglycerols under acetonitrile conditions and can offer π-π interactions with triacylglycerols under methanol conditions. When compared with traditional off-line comprehensive two-dimensional liquid chromatography employing two different chromatographic columns (C18 and silver-ion column) and using elution solvents comprised of two phases (reversed-phase/normal-phase) for triacylglycerols separation, the novel off-line comprehensive two-dimensional liquid chromatography using a single column can be achieved by simply altering the mobile phase between acetonitrile and methanol, which exhibited a much higher selectivity for the separation of triacylglycerols with great efficiency and rapid speed. In addition, an approach based on the use of response factor with atmospheric pressure chemical ionization mass spectrometry has been developed for triacylglycerols quantification. Due to the differences between saturated and unsaturated acyl chains, the use of response factors significantly improves the quantitation of triacylglycerols. This two-dimensional liquid chromatography-mass spectrometry system was successfully applied for the profiling of triacylglycerols in soybean oils, peanut oils and lord oils. A total of 68 triacylglycerols including 40 triacylglycerols in soybean oils, 50 triacylglycerols in peanut oils and 44 triacylglycerols in lord oils have been identified and quantified. The liquid chromatography-mass spectrometry data were analyzed

Characterization of direct-current atmospheric-pressure discharges useful for ambient desorption/ionization mass spectrometry.

PubMed

Shelley, Jacob T; Wiley, Joshua S; Chan, George C Y; Schilling, Gregory D; Ray, Steven J; Hieftje, Gary M

2009-05-01

Two relatively new ambient ionization sources, direct analysis in real time (DART) and the flowing atmospheric-pressure afterglow (FAPA), use direct current, atmospheric-pressure discharges to produce reagent ions for the direct ionization of a sample. Although at a first glance these two sources appear similar, a fundamental study reveals otherwise. Specifically, DART was found to operate with a corona-to-glow transition (C-G) discharge whereas the FAPA was found to operate with a glow-to-arc transition (G-A) discharge. The characteristics of both discharges were evaluated on the basis of four factors: reagent-ion production, response to a model analyte (ferrocene), infrared (IR) thermography of the gas used for desorption and ionization, and spatial emission characteristics. The G-A discharge produced a greater abundance and a wider variety of reagent ions than the C-G discharge. In addition, the discharges yielded different adducts and signal strengths for ferrocene. It was also found that the gas exiting the discharge chamber reached a maximum of 235 degrees C and 55 degrees C for the G-A and C-G discharges, respectively. Finally, spatially resolved emission maps of both discharges showed clear differences for N(2)(+) and O(I). These findings demonstrate that the discharges used by FAPA and DART are fundamentally different and should have different optimal applications for ambient desorption/ionization mass spectrometry (ADI-MS).

Sensitive determination of RDX, nitroso-RDX metabolites, and other munitions in ground water by solid-phase extraction and isotope dilution liquid chromatography-atmospheric pressure electro-spray [correction of chemical] ionization mass spectrometry.

PubMed

Cassada, D A; Monson, S J; Snow, D D; Spalding, R F

1999-06-04

Recent improvements in the LC-MS interface have increased the sensitivity and selectivity of this instrument in the analysis of polar and thermally-labile aqueous constituents. Determination of RDX, nitroso-RDX metabolites, and other munitions was enhanced using LC-MS with solid-phase extraction, 15N3-RDX internal standard, and electrospray ionization (ESI) in negative ion mode. ESI produced a five-fold increase in detector response over atmospheric pressure chemical ionization (APCI) for the nitramine compounds, while the more energetic APCI produced more than twenty times the ESI response for nitroaromatics. Method detection limits in ESI for nitramines varied from 0.03 microgram l-1 for MNX to 0.05 microgram l-1 for RDX.

Excited level populations and excitation kinetics of nonequilibrium ionizing argon discharge plasma of atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akatsuka, Hiroshi

2009-04-15

Population densities of excited states of argon atoms are theoretically examined for ionizing argon plasma in a state of nonequilibrium under atmospheric pressure from the viewpoint of elementary processes with collisional radiative model. The dependence of excited state populations on the electron and gas temperatures is discussed. Two electron density regimes are found, which are distinguished by the population and depopulation mechanisms for the excited states in problem. When the electron impact excitation frequency for the population or depopulation is lower than the atomic impact one, the electron density of the plasma is considered as low to estimate the populationmore » and depopulation processes. Some remarkable characteristics of population and depopulation mechanisms are found for the low electron density atmospheric plasma, where thermal relaxation by atomic collisions becomes the predominant process within the group of close-energy states in the ionizing plasma of atmospheric pressure, and the excitation temperature is almost the same as the gas temperature. In addition to the collisional relaxation by argon atoms, electron impact excitation from the ground state is also an essential population mechanism. The ratios of population density of the levels pairs, between which exists a large energy gap, include information on the electron collisional kinetics. For high electron density, the effect of atomic collisional relaxation becomes weak. For this case, the excitation mechanism is explained as electron impact ladderlike excitation similar to low-pressure ionizing plasma, since the electron collision becomes the dominant process for the population and depopulation kinetics.« less

Selective ionization of dissolved organic nitrogen by positive ion atmospheric pressure photoionization coupled with Fourier transform ion cyclotron resonance mass spectrometry.

PubMed

Podgorski, David C; McKenna, Amy M; Rodgers, Ryan P; Marshall, Alan G; Cooper, William T

2012-06-05

Dissolved organic nitrogen (DON) comprises a heterogeneous family of organic compounds that includes both well-known biomolecules such as urea or amino acids and more complex, less characterized compounds such as humic and fulvic acids. Typically, DON represents only a small fraction of the total dissolved organic carbon pool and therefore presents inherent problems for chemical analysis and characterization. Here, we demonstrate that DON may be selectively ionized by atmospheric pressure photionization (APPI) and characterized at the molecular level by Fourier transform ion cyclotron resonance mass spectrometry. Unlike electrospray ionization (ESI), APPI ionizes polar and nonpolar compounds, and ionization efficiency is not determined by polarity. APPI is tolerant to salts, due to the thermal treatment inherent to nebulization, and thus avoids salt-adduct formation that can complicate ESI mass spectra. Here, for dissolved organic matter from various aquatic environments, we selectively ionize DON species that are not efficiently ionized by other ionization techniques and demonstrate significant signal-to-noise increase for nitrogen species by use of APPI relative to ESI.

A comparative study of APLI and APCI in IMS at atmospheric pressure to reveal and explain peak broadening effects by the use of APLI.

PubMed

Ihlenborg, Marvin; Raupers, Björn; Gunzer, Frank; Grotemeyer, Jürgen

2015-11-21

The details of the ionization mechanism in atmospheric pressure are still not completely known. In order to obtain further insight into the occurring processes in atmospheric pressure laser ionization (APLI) a comparative study of atmospheric pressure chemical ionization (APCI) and APLI is presented in this paper. This study is carried out using similar experimental condition at atmospheric pressure employing a commercial ion mobility spectrometer (IMS). Two different peak broadening mechanisms can then be assigned, one related to a range of different species generated and detected, and furthermore for the first time a power broadening effect on the signals can be identified.

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

PubMed

Matić, Ivana; Grujić, Svetlana; Jauković, Zorica; Laušević, Mila

2014-10-17

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 (2 g) and time of ultrasonic extraction (3× 10 min). Successful chromatographic separation of hormones (estriol and estrone, 17α- and 17β-estradiol) and four human/animal sterols (epicoprostanol, coprostanol, α-cholestanol and β-cholestanol) that have identical fragmentation reactions was achieved. The developed and optimized method provided high recoveries (73-118%), low limits of detection (0.8-18 ng g(-1)) and quantification (2.5-60 ng g(-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. Copyright © 2014 Elsevier B.V. All rights reserved.

Gas chromatography/atmospheric pressure chemical ionization/mass spectrometry for the analysis of organochlorine pesticides and polychlorinated biphenyls in human serum.

PubMed

Geng, Dawei; Jogsten, Ingrid Ericson; Dunstan, Jody; Hagberg, Jessika; Wang, Thanh; Ruzzin, Jerome; Rabasa-Lhoret, Rémi; van Bavel, Bert

2016-07-01

A method using a novel atmospheric pressure chemical ionization source for coupling gas chromatography (GC/APCI) to triple quadrupole mass spectrometry (MS/MS) for the determination of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) regulated by the Stockholm Convention is presented. One microliter injection of a six-point calibration curve of native PCBs and OCPs, ranging from 0.04 to 300pg/μL, was performed. The relative standard deviation (RSD) of the relative response factors (RRFs) was less than 15% with a coefficient of determination (r(2))>0.995. Meanwhile, two calibration solutions (CS), CS 2 (0.4pg/μL) and CS 3 (4pg/μL) were analyzed to study the repeatability calculated for both area and RRFs. The RSD for RRF ranged from 3.1 to 16% and 3.6 to 5.5% for CS 2 and CS 3, respectively. The limits of detection (LOD) determined by peak-to-peak signal-to-noise ratio (S/N) of 3 were compared between the GC/APCI/MS/MS and a GC coupled to high resolution mass spectrometry (GC/HRMS) system. GC/APCI/MS/MS resulted in lower LOD for most of the compounds, except for PCB#74, cis-chlordane and trans-chlordane. GC/APCI/MS/MS and GC/HRMS were also compared by performing analysis on 75 human serum samples together with eight QA/QC serum samples. The comparison between GC/APCI/MS/MS system and GC/HRMS system for 16 of the targeted compounds was carried out. No statistically significant difference was discovered. Due to increased sensitivity and user friendly operation under atmospheric pressure, GC/APCI/MS/MS is a powerful alternative technique that can easily meet the specification of GC/HRMS. Copyright © 2016 Elsevier B.V. All rights reserved.

Atomic Force Microscopy Thermally-Assisted Microsampling with Atmospheric Pressure Temperature Ramped Thermal Desorption/Ionization-Mass Spectrometry Analysis

DOE PAGES

Hoffmann, William D.; Kertesz, Vilmos; Srijanto, Bernadeta R.; ...

2017-02-20

The use of atomic force microscopy controlled nano-thermal analysis probes for reproducible spatially resolved thermally-assisted sampling of micrometer-sized areas (ca. 11 m 17 m wide 2.4 m deep) from relatively low number average molecular weight (M n < 3000) polydisperse thin films of poly(2-vinylpyridine) (P2VP) is presented. Following sampling, the nano-thermal analysis probes were moved up from the surface and the probe temperature ramped to liberate the sampled materials into the gas phase for atmospheric pressure chemical ionization and mass spectrometric analysis. Furthermore, the procedure and mechanism for material pickup, the sampling reproducibility and sampling size are discussed and themore » oligomer distribution information available from slow temperature ramps versus ballistic temperature jumps is presented. For the M n = 970 P2VP, the Mn and polydispersity index determined from the mass spectrometric data were in line with both the label values from the sample supplier and the value calculated from the simple infusion of a solution of polymer into the commercial atmospheric pressure chemical ionization source on this mass spectrometer. With a P2VP sample of higher Mn (M n = 2070 and 2970), intact oligomers were still observed (as high as m/z 2793 corresponding to the 26-mer), but a significant abundance of thermolysis products were also observed. In addition, the capability for confident identification of the individual oligomers by slowly ramping the probe temperature and collecting data dependent tandem mass spectra was also demonstrated. We also discuss the material type limits to the current sampling and analysis approach as well as possible improvements in nano-thermal analysis probe design to enable smaller area sampling and to enable controlled temperature ramps beyond the present upper limit of about 415°C.« less

Atomic Force Microscopy Thermally-Assisted Microsampling with Atmospheric Pressure Temperature Ramped Thermal Desorption/Ionization-Mass Spectrometry Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffmann, William D.; Kertesz, Vilmos; Srijanto, Bernadeta R.

The use of atomic force microscopy controlled nano-thermal analysis probes for reproducible spatially resolved thermally-assisted sampling of micrometer-sized areas (ca. 11 m 17 m wide 2.4 m deep) from relatively low number average molecular weight (M n < 3000) polydisperse thin films of poly(2-vinylpyridine) (P2VP) is presented. Following sampling, the nano-thermal analysis probes were moved up from the surface and the probe temperature ramped to liberate the sampled materials into the gas phase for atmospheric pressure chemical ionization and mass spectrometric analysis. Furthermore, the procedure and mechanism for material pickup, the sampling reproducibility and sampling size are discussed and themore » oligomer distribution information available from slow temperature ramps versus ballistic temperature jumps is presented. For the M n = 970 P2VP, the Mn and polydispersity index determined from the mass spectrometric data were in line with both the label values from the sample supplier and the value calculated from the simple infusion of a solution of polymer into the commercial atmospheric pressure chemical ionization source on this mass spectrometer. With a P2VP sample of higher Mn (M n = 2070 and 2970), intact oligomers were still observed (as high as m/z 2793 corresponding to the 26-mer), but a significant abundance of thermolysis products were also observed. In addition, the capability for confident identification of the individual oligomers by slowly ramping the probe temperature and collecting data dependent tandem mass spectra was also demonstrated. We also discuss the material type limits to the current sampling and analysis approach as well as possible improvements in nano-thermal analysis probe design to enable smaller area sampling and to enable controlled temperature ramps beyond the present upper limit of about 415°C.« less

Atmospheric Pressure Chemical Ionization Gas Chromatography Mass Spectrometry for the Analysis of Selected Emerging Brominated Flame Retardants in Foods.

PubMed

Lv, Surong; Niu, Yumin; Zhang, Jing; Shao, Bing; Du, Zhenxia

2017-03-10

Emerging brominated flame retardants (eBFRs) other than polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and their derivatives in foods have been in focus in recent years due to their increasing production volumes, indefinite information on toxicities and the lack of data on occurrence in environments, foods as well as humans. In this study, gas chromatography was coupled to an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC-MS/MS) for the analysis of six eBFRs in pork, chicken, egg, milk and fish. A short section of unpacked capillary column coupled to the end of the analytical column was applied to improve the chromatographic behaviors of high boiling point compounds. The method was comprehensively validated with method limit of quantification (mLOQ) lower than 8 pg/g wet weight (w.w.). Samples from Chinese Total Diet study were quantified following the validated APGC-MS/MS method. 2,3,4,5-pentabromo-6-ethylbenzene (PBEB), hexabromobenzene (HBB), pentabromotoluene (PBT) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were most frequently detected in samples. The highest concentration was found in fish with 351.9 pg/g w.w. of PBT. This is the first report on the presence of PBT in food samples with non-ignorable concentrations and detection rate.

Atmospheric Pressure Chemical Ionization Gas Chromatography Mass Spectrometry for the Analysis of Selected Emerging Brominated Flame Retardants in Foods

PubMed Central

Lv, Surong; Niu, Yumin; Zhang, Jing; Shao, Bing; Du, Zhenxia

2017-01-01

Emerging brominated flame retardants (eBFRs) other than polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and their derivatives in foods have been in focus in recent years due to their increasing production volumes, indefinite information on toxicities and the lack of data on occurrence in environments, foods as well as humans. In this study, gas chromatography was coupled to an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC-MS/MS) for the analysis of six eBFRs in pork, chicken, egg, milk and fish. A short section of unpacked capillary column coupled to the end of the analytical column was applied to improve the chromatographic behaviors of high boiling point compounds. The method was comprehensively validated with method limit of quantification (mLOQ) lower than 8 pg/g wet weight (w.w.). Samples from Chinese Total Diet study were quantified following the validated APGC-MS/MS method. 2,3,4,5-pentabromo-6-ethylbenzene (PBEB), hexabromobenzene (HBB), pentabromotoluene (PBT) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were most frequently detected in samples. The highest concentration was found in fish with 351.9 pg/g w.w. of PBT. This is the first report on the presence of PBT in food samples with non-ignorable concentrations and detection rate. PMID:28281659

Atmospheric Pressure Chemical Ionization Gas Chromatography Mass Spectrometry for the Analysis of Selected Emerging Brominated Flame Retardants in Foods

NASA Astrophysics Data System (ADS)

Lv, Surong; Niu, Yumin; Zhang, Jing; Shao, Bing; Du, Zhenxia

2017-03-01

Emerging brominated flame retardants (eBFRs) other than polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and their derivatives in foods have been in focus in recent years due to their increasing production volumes, indefinite information on toxicities and the lack of data on occurrence in environments, foods as well as humans. In this study, gas chromatography was coupled to an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC-MS/MS) for the analysis of six eBFRs in pork, chicken, egg, milk and fish. A short section of unpacked capillary column coupled to the end of the analytical column was applied to improve the chromatographic behaviors of high boiling point compounds. The method was comprehensively validated with method limit of quantification (mLOQ) lower than 8 pg/g wet weight (w.w.). Samples from Chinese Total Diet study were quantified following the validated APGC-MS/MS method. 2,3,4,5-pentabromo-6-ethylbenzene (PBEB), hexabromobenzene (HBB), pentabromotoluene (PBT) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were most frequently detected in samples. The highest concentration was found in fish with 351.9 pg/g w.w. of PBT. This is the first report on the presence of PBT in food samples with non-ignorable concentrations and detection rate.

High pressure xenon ionization detector

DOEpatents

Markey, J.K.

1989-11-14

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

High pressure xenon ionization detector

DOEpatents

Markey, John K.

1989-01-01

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

Triacylglycerols profiling in plant oils important in food industry, dietetics and cosmetics using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Lísa, Miroslav; Holcapek, Michal

2008-07-11

Optimized non-aqueous reversed-phase high-performance liquid chromatography method using acetonitrile-2-propanol gradient elution and the column coupling in the total length of 45 cm has been applied for the high resolution separation of plant oils important in food industry, dietetics and cosmetics. Positive-ion atmospheric pressure chemical ionization mass spectrometry is used for the unambiguous identification and also the reliable quantitation with the response factors approach. Based on the precise determination of individual triacyglycerol concentrations, the calculation of average parameters important in the nutrition is performed, i.e. average carbon number, average double bond number, relative concentrations of essential, saturated, monounsaturated and polyunsaturated fatty acids. Results are reported in the form of both chromatographic fingerprints and tables containing relative concentrations for all triacylglycerols and fatty acids in individual samples. In total, 264 triacylglycerols consisting of 28 fatty acids with the alkyl chain length from 6 to 26 carbon atoms and 0 to 4 double bonds have been identified in 26 industrial important plant oils.

Degradation of the Neonicotinoid Pesticides in the Atmospheric Pressure Ionization Source

NASA Astrophysics Data System (ADS)

Chai, Yunfeng; Chen, Hongping; Liu, Xin; Lu, Chengyin

2018-02-01

During the analysis of neonicotinoid pesticide standards (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) by mass spectrometry, the degradation of these pesticides (M-C=N-R is degraded into M-C=O, M is the skeleton moiety, and R is NO2 or CN) was observed in the atmospheric pressure ionization interfaces (ESI and APCI). In APCI, the degradation of all the five neonicotinoid pesticides studied took place, and the primary mechanism was in-source ion/molecule reaction, in which a molecule of water (confirmed by use of H2 18O) attacked the carbon of the imine group accompanying with loss of NH2R (R=NO2, CN). For the nitroguanidine neonicotinoid pesticides (R=NO2, including thiamethoxam, clothianidin, and imidacloprid), higher auxiliary gas heater temperature also contributed to their degradation in APCI due to in-source pyrolysis. The degradation of the five neonicotinoid pesticides studied in ESI was not significant. In ESI, only the nitroguanidine neonicotinoid pesticides could generate the degradation products through in-source fragmentation mechanism. The degradation of cyanoamidine neonicotinoid pesticides (R=CN, including acetamiprid and thiacloprid) in ESI was not observed. The degradation of neonicotinoid pesticides in the ion source of mass spectrometer renders some adverse consequences, such as difficulty interpreting the full-scan mass spectrum, reducing the sensitivity and accuracy of quantitative analysis, and misleading whether these pesticides have degraded in the real samples. Therefore, a clear understanding of these unusual degradation reactions should facilitate the analysis of neonicotinoid pesticides by atmospheric pressure ionization mass spectrometry.

Degradation of the Neonicotinoid Pesticides in the Atmospheric Pressure Ionization Source.

PubMed

Chai, Yunfeng; Chen, Hongping; Liu, Xin; Lu, Chengyin

2018-02-01

During the analysis of neonicotinoid pesticide standards (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) by mass spectrometry, the degradation of these pesticides (M-C=N-R is degraded into M-C=O, M is the skeleton moiety, and R is NO 2 or CN) was observed in the atmospheric pressure ionization interfaces (ESI and APCI). In APCI, the degradation of all the five neonicotinoid pesticides studied took place, and the primary mechanism was in-source ion/molecule reaction, in which a molecule of water (confirmed by use of H 2 18 O) attacked the carbon of the imine group accompanying with loss of NH 2 R (R=NO 2 , CN). For the nitroguanidine neonicotinoid pesticides (R=NO 2 , including thiamethoxam, clothianidin, and imidacloprid), higher auxiliary gas heater temperature also contributed to their degradation in APCI due to in-source pyrolysis. The degradation of the five neonicotinoid pesticides studied in ESI was not significant. In ESI, only the nitroguanidine neonicotinoid pesticides could generate the degradation products through in-source fragmentation mechanism. The degradation of cyanoamidine neonicotinoid pesticides (R=CN, including acetamiprid and thiacloprid) in ESI was not observed. The degradation of neonicotinoid pesticides in the ion source of mass spectrometer renders some adverse consequences, such as difficulty interpreting the full-scan mass spectrum, reducing the sensitivity and accuracy of quantitative analysis, and misleading whether these pesticides have degraded in the real samples. Therefore, a clear understanding of these unusual degradation reactions should facilitate the analysis of neonicotinoid pesticides by atmospheric pressure ionization mass spectrometry. Graphical Abstract.

Laser Ablation-Aerosol Mass Spectrometry-Chemical Ionization Mass Spectrometry for Ambient Surface Imaging

DOE PAGES

Berry, Jennifer L.; Day, Douglas A.; Elseberg, Tim; ...

2018-02-20

Mass spectrometry imaging is becoming an increasingly common analytical technique due to its ability to provide spatially resolved chemical information. In this paper, we report a novel imaging approach combining laser ablation with two mass spectrometric techniques, aerosol mass spectrometry and chemical ionization mass spectrometry, separately and in parallel. Both mass spectrometric methods provide the fast response, rapid data acquisition, low detection limits, and high-resolution peak separation desirable for imaging complex samples. Additionally, the two techniques provide complementary information with aerosol mass spectrometry providing near universal detection of all aerosol molecules and chemical ionization mass spectrometry with a heated inletmore » providing molecular-level detail of both gases and aerosols. The two techniques operate with atmospheric pressure interfaces and require no matrix addition for ionization, allowing for samples to be investigated in their native state under ambient pressure conditions. We demonstrate the ability of laser ablation-aerosol mass spectrometry-chemical ionization mass spectrometry (LA-AMS-CIMS) to create 2D images of both standard compounds and complex mixtures. Finally, the results suggest that LA-AMS-CIMS, particularly when combined with advanced data analysis methods, could have broad applications in mass spectrometry imaging applications.« less

Laser Ablation-Aerosol Mass Spectrometry-Chemical Ionization Mass Spectrometry for Ambient Surface Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berry, Jennifer L.; Day, Douglas A.; Elseberg, Tim

Mass spectrometry imaging is becoming an increasingly common analytical technique due to its ability to provide spatially resolved chemical information. In this paper, we report a novel imaging approach combining laser ablation with two mass spectrometric techniques, aerosol mass spectrometry and chemical ionization mass spectrometry, separately and in parallel. Both mass spectrometric methods provide the fast response, rapid data acquisition, low detection limits, and high-resolution peak separation desirable for imaging complex samples. Additionally, the two techniques provide complementary information with aerosol mass spectrometry providing near universal detection of all aerosol molecules and chemical ionization mass spectrometry with a heated inletmore » providing molecular-level detail of both gases and aerosols. The two techniques operate with atmospheric pressure interfaces and require no matrix addition for ionization, allowing for samples to be investigated in their native state under ambient pressure conditions. We demonstrate the ability of laser ablation-aerosol mass spectrometry-chemical ionization mass spectrometry (LA-AMS-CIMS) to create 2D images of both standard compounds and complex mixtures. Finally, the results suggest that LA-AMS-CIMS, particularly when combined with advanced data analysis methods, could have broad applications in mass spectrometry imaging applications.« less

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Sewram, V; Nair, J J; Nieuwoudt, T W; Leggott, N L; Shephard, G S

2000-11-03

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.

Feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry in analysis of drugs.

PubMed

Huikko, K; Ostman, P; Sauber, C; Mandel, F; Grigoras, K; Franssila, S; Kotiaho, T; Kostiainen, R

2003-01-01

The feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS) for drug analysis was investigated. It was observed that only compounds with relative high proton affinity are efficiently ionized under AP-DIOS conditions. The limits of detection (LODs) achieved in MS mode with midazolam, propranolol, and angiotensin II were 80 fmol, 20 pmol, and 1 pmol, respectively. In MS/MS mode the LODs for midazolam and propranolol were 10 fmol and 5 pmol, respectively. The good linearity (r(2) > 0.991), linear dynamic range of 3 orders of magnitude, and reasonable repeatability showed that the method is suitable for quantitative analysis. Copyright 2003 John Wiley & Sons, Ltd.

Identification of organic nitrates in the NO3 radical initiated oxidation of alpha-pinene by atmospheric pressure chemical ionization mass spectrometry.

PubMed

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

2010-08-01

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 that can undergo long-range transport, releasing NOx downwind. We report here studies of the reaction of NO3 with alpha-pinene at 1 atm in dry synthetic air (relative humidity approximately 3%) and at 298 K using atmospheric pressure chemical ionization triple quadrupole mass spectrometry (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 GC-MS and by APCI time-of-flight mass spectrometry (APCI-ToF-MS) 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, there was an additional first-generation 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 NOx.

Analysis of aldehydes in beer by gas-diffusion microextraction: characterization by high-performance liquid chromatography-diode-array detection-atmospheric pressure chemical ionization-mass spectrometry.

PubMed

Gonçalves, Luís Moreira; Magalhães, Paulo Jorge; Valente, Inês Maria; Pacheco, João Grosso; Dostálek, Pavel; Sýkora, David; Rodrigues, José António; Barros, Aquiles Araújo

2010-06-11

In this work, a recently developed extraction technique for sample preparation aiming the analysis of volatile and semi-volatile compounds named gas-diffusion microextraction (GDME) is applied in the chromatographic analysis of aldehydes in beer. Aldehydes-namely acetaldehyde (AA), methylpropanal (MA) and furfural (FA)-were simultaneously extracted and derivatized with 2,4-dinitrophenylhydrazine (DNPH), then the derivatives were separated and analyzed by high-performance liquid chromatography with spectrophotometric detection (HPLC-UV). The identity of the eluted compounds was confirmed by high-performance liquid chromatography-atmospheric pressure chemical ionization-mass-spectrometry detection in the negative ion mode (HPLC-APCI-MS). The developed methodology showed good repeatability (ca. 5%) and linearity as well as good limits of detection (AA-12.3, FA-1.5 and MA 5.4microgL(-1)) and quantification (AA-41, FA-4.9 and MA 18microgL(-1)); it also appears to be competitive in terms of speed and cost of analysis. Copyright 2010 Elsevier B.V. All rights reserved.

Characterization of carotenoids and carotenoid esters in red pepper pods (Capsicum annuum L.) by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

PubMed

Schweiggert, Ute; Kammerer, Dietmar R; Carle, Reinhold; Schieber, Andreas

2005-01-01

Carotenoids and carotenoid esters were extracted from red pepper pods (Capsicum annuum L.) without saponification. Among the 42 compounds detected, 4 non-esterified, 11 mono- and 17 diesters were characterized based on their retention times, UV/Vis spectra and their fragmentation patterns in collision-induced dissociation experiments in atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Positive and negative ion mode measurements were used for the characterization of major and minor carotenoids and their esters. Capsanthin esterified with lauric, palmitic and myristic acids represented the predominant compounds in the red pepper extracts. Additionally, three beta-cryptoxanthin and one zeaxanthin monoester were tentatively identified in red pepper pods for the first time. Furthermore, the specific fragmentation patterns of capsanthin-laurate-myristate and capsanthin-myristate-palmitate were used for the distinction of both regioisomers. The results obtained from LC-DAD-APCI-MSn experiments demonstrated that the carotenoid profile of red pepper pods is considerably more complex than considered hitherto. Copyright (c) 2005 John Wiley & Sons, Ltd.

Analysis of vitamin K1 in fruits and vegetables using accelerated solvent extraction and liquid chromatography tandem mass spectrometry with atmospheric pressure chemical ionization.

PubMed

Jäpelt, Rie Bak; Jakobsen, Jette

2016-02-01

The objective of this study was to develop a rapid, sensitive, and specific analytical method to study vitamin K1 in fruits and vegetables. Accelerated solvent extraction and solid phase extraction was used for sample preparation. Quantification was done by liquid chromatography tandem mass spectrometry with atmospheric pressure chemical ionization in selected reaction monitoring mode with deuterium-labeled vitamin K1 as an internal standard. The precision was estimated as the pooled estimate of three replicates performed on three different days for spinach, peas, apples, banana, and beetroot. The repeatability was 5.2% and the internal reproducibility was 6.2%. Recovery was in the range 90-120%. No significant difference was observed between the results obtained by the present method and by a method using the same principle as the CEN-standard i.e. liquid-liquid extraction and post-column zinc reduction with fluorescence detection. Limit of quantification was estimated to 0.05 μg/100g fresh weight. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

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

2014-06-01

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Atmospheric Pressure-Thermal Desorption (AP-TD)/Electrospray Ionization-Mass Spectrometry for the Rapid Analysis of Bacillus Spores

USDA-ARS?s Scientific Manuscript database

A technique is described where an atmospheric pressure-thermal desorption (AP-TD) device and electrospray ionization (ESI)-mass spectrometry are coupled and used for the rapid analysis of Bacillus spores in complex matrices. The resulting AP-TD/ESI-MS technique combines the generation of volatile co...

Investigation and Applications of In-Source Oxidation in Liquid Sampling-Atmospheric Pressure Afterglow Microplasma Ionization (LS-APAG) Source.

PubMed

Xie, Xiaobo; Wang, Zhenpeng; Li, Yafeng; Zhan, Lingpeng; Nie, Zongxiu

2017-06-01

A liquid sampling-atmospheric pressure afterglow microplasma ionization (LS-APAG) source is presented for the first time, which is embedded with both electrospray ionization (ESI) and atmospheric pressure afterglow microplasma ionization (APAG) techniques. This ion source is capable of analyzing compounds with diverse molecule weights and polarities. An unseparated mixture sample was detected as a proof-of-concept, giving complementary information (both polarities and non-polarities) with the two ionization modes. It should also be noted that molecular mass can be quickly identified by ESI with clean and simple spectra, while the structure can be directly studied using APAG with in-source oxidation. The ionization/oxidation mechanism and applications of the LS-APAG source have been further explored in the analysis of nonpolar alkanes and unsaturated fatty acids/esters. A unique [M + O - 3H] + was observed in the case of individual alkanes (C 5 -C 19 ) and complex hydrocarbons mixture under optimized conditions. Moreover, branched alkanes generated significant in-source fragments, which could be further applied to the discrimination of isomeric alkanes. The technique also facilitates facile determination of double bond positions in unsaturated fatty acids/esters due to diagnostic fragments (the acid/ester-containing aldehyde and acid oxidation products) generated by on-line ozonolysis in APAG mode. Finally, some examples of in situ APAG analysis by gas sampling and surface sampling were given as well. Graphical Abstract ᅟ.

Identification of Organic Nitrates in the NO 3 Radical Initiated Oxidation of α-Pinene by Atmospheric Pressure Chemical Ionization Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perraud, Veronique M.; Bruns, Emily A.; Ezell, Michael J.

2010-07-07

The gas-phase reactions of nitrate radicals (NO 3) with biogenic organic compounds are a major sink for these organics during night-time. These reactions form secondary organic aerosols, including organic nitrates that can undergo long-range transport, releasing NO x downwind. We report here studies of the reaction of NO 3 with R-pinene at 1 atm in dry synthetic air(relative humidity ~3%) and at 298K using atmospheric pressure chemical ionization triple quadrupole mass spectrometry (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 productmore » 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, there was an additional first generation 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 x.« less

Stereoselective quantification of methadone and a d(6)-labeled isotopomer using high performance liquid chromatography-atmospheric pressure chemical ionization mass-spectrometry: application to a pharmacokinetic study in a methadone maintained subject.

PubMed

Foster, David J R; Morton, Erin B; Heinkele, Georg; Mürdter, Thomas E; Somogyi, Andrew A

2006-08-01

There is evidence that the apparent oral clearance of rac-methadone is induced during the early phase of methadone maintenance treatment. However, it is not known if this is due to changes in bioavailability or if this phenomenon is stereoselective. This knowledge can be obtained by administering a dose of stable-labeled methadone at selected times during ongoing treatment. Therefore, the authors developed a stereoselective high performance liquid chromatography-atmospheric pressure chemical ionization mass-spectrometry assay for the quantification of the enantiomers of methadone and a d(6)-labeled isotopomer. The compounds were quantified in a single assay after liquid-liquid extraction and stereoselective high performance liquid chromatograph with atmospheric pressure chemical ionization-mass spectrometry detection. The following ions were monitored: m/z 310.15 for unlabeled methadone; m/z 316.15 for methadone-d(6); and m/z 313.15 for the methadone-d(3) (internal standard). Calibration curves ranged from 0.5 to 75 ng/mL for each compound. Extraction recovery was approximately 80% for all analytes, without evidence of differences between the unlabeled and stable-labeled compounds or concentration dependency. Minor ion promotion was observed (<15%) but this was identical for all analytes including the d(3)-labeled internal standard, with peak area ratios in extracted samples identical to control injections. The isotopomers did not alter each others' ionisation, even at 10:1 concentration ratios, and 10-fold diluted samples were within 10% of the nominal concentration. Assay performance was acceptable, with interassay and intra-assay bias and precision <10% for all compounds, including the upper and lower limits of quantitation. In conclusion, the assay was successfully applied to quantify the concentration of the methadone enantiomers of both orally administered unlabeled methadone and an intravenous 5 mg dose of methadone-d(6) in a patient receiving chronic oral

Plasma Ion Sources for Atmospheric Pressure Ionization Mass Spectrometry.

NASA Astrophysics Data System (ADS)

Zhao, Jian-Guo

1994-01-01

Atmospheric pressure ionization (API) sources using direct-current (DC) and radio-frequency (RF) plasma have been developed in this thesis work. These ion sources can provide stable discharge currents of ~ 1 mA, 2-3 orders of magnitude larger than that of the corona discharge, a widely used API source. The plasmas can be generated and maintained in 1 atm of various buffer gases by applying -500 to -1000 V (DC plasma) or 1-15 W with a frequency of 165 kHz (RF plasma) on the needle electrode. These ion sources have been used with liquid injection to detect various organic compounds of pharmaceutical, biotechnological and environmental interest. Key features of these ion sources include soft ionization with the protonated molecule as the largest peak, and superb sensitivity with detection limits in the low picogram or femtomole range and a linear dynamic range over ~4 orders of magnitude. The RF plasma has advantages over the DC plasma in its ability to operate in various buffer gases and to produce a more stable plasma. Factors influencing the performance of the ion sources have been studied, including RF power level, liquid flow rate, chamber temperature, solvent composition, and voltage affecting the collision induced dissociation (CID). Ionization of hydrocarbons by the RF plasma API source was also studied. Soft ionization is generally produced. To obtain high sensitivity, the ion source must be very dry and the needle-to-orifice distance must be small. Nitric oxide was used to enhance the sensitivity. The RF plasma source was then used for the analysis of hydrocarbons in auto emissions. Comparisons between the corona discharge and the RF plasma have been made in terms of discharge current, ion residence time, and the ion source model. The RF plasma source provides larger linear dynamic range and higher sensitivity than the corona discharge, due to its much larger discharge current. The RF plasma was also observed to provide longer ion residence times and was not

Collision-induced dissociation analysis of negative atmospheric ion adducts in atmospheric pressure corona discharge ionization mass spectrometry.

PubMed

Sekimoto, Kanako; Takayama, Mitsuo

2013-05-01

Collision-induced dissociation (CID) experiments were performed on atmospheric ion adducts [M + R](-) formed between various types of organic compounds M and atmospheric negative ions R(-) [such as O2(-), HCO3(-), COO(-)(COOH), NO2(-), NO3(-), and NO3(-)(HNO3)] in negative-ion mode atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. All of the [M + R](-) adducts were fragmented to form deprotonated analytes [M - H](-) and/or atmospheric ions R(-), whose intensities in the CID spectra were dependent on the proton affinities of the [M - H](-) and R(-) fragments. Precursor ions [M + R](-) for which R(-) have higher proton affinities than [M - H](-) formed [M - H](-) as the dominant product. Furthermore, the CID of the adducts with HCO3(-) and NO3(-)(HNO3) led to other product ions such as [M + HO](-) and NO3(-), respectively. The fragmentation behavior of [M + R](-) for each R(-) observed was independent of analyte type (e.g., whether the analyte was aliphatic or aromatic, or possessed certain functional groups).

Rapid Chemical Vapor Infiltration of Silicon Carbide Minicomposites at Atmospheric Pressure.

PubMed

Petroski, Kenneth; Poges, Shannon; Monteleone, Chris; Grady, Joseph; Bhatt, Ram; Suib, Steven L

2018-02-07

The chemical vapor infiltration technique is one of the most popular for the fabrication of the matrix portion of a ceramic matrix composite. This work focuses on tailoring an atmospheric pressure deposition of silicon carbide onto carbon fiber tows using the methyltrichlorosilane (CH 3 SiCl 3 ) and H 2 deposition system at atmospheric pressure to create minicomposites faster than low pressure systems. Adjustment of the flow rate of H 2 bubbled through CH 3 SiCl 3 will improve the uniformity of the deposition as well as infiltrate the substrate more completely as the flow rate is decreased. Low pressure depositions conducted at 50 Torr deposit SiC at a rate of approximately 200 nm*h -1 , while the atmospheric pressure system presented has a deposition rate ranging from 750 nm*h -1 to 3.88 μm*h -1 . The minicomposites fabricated in this study had approximate total porosities of 3 and 6% for 10 and 25 SCCM infiltrations, respectively.

Investigation and Applications of In-Source Oxidation in Liquid Sampling-Atmospheric Pressure Afterglow Microplasma Ionization (LS-APAG) Source

NASA Astrophysics Data System (ADS)

Xie, Xiaobo; Wang, Zhenpeng; Li, Yafeng; Zhan, Lingpeng; Nie, Zongxiu

2017-06-01

A liquid sampling-atmospheric pressure afterglow microplasma ionization (LS-APAG) source is presented for the first time, which is embedded with both electrospray ionization (ESI) and atmospheric pressure afterglow microplasma ionization (APAG) techniques. This ion source is capable of analyzing compounds with diverse molecule weights and polarities. An unseparated mixture sample was detected as a proof-of-concept, giving complementary information (both polarities and non-polarities) with the two ionization modes. It should also be noted that molecular mass can be quickly identified by ESI with clean and simple spectra, while the structure can be directly studied using APAG with in-source oxidation. The ionization/oxidation mechanism and applications of the LS-APAG source have been further explored in the analysis of nonpolar alkanes and unsaturated fatty acids/esters. A unique [M + O - 3H]+ was observed in the case of individual alkanes (C5-C19) and complex hydrocarbons mixture under optimized conditions. Moreover, branched alkanes generated significant in-source fragments, which could be further applied to the discrimination of isomeric alkanes. The technique also facilitates facile determination of double bond positions in unsaturated fatty acids/esters due to diagnostic fragments (the acid/ester-containing aldehyde and acid oxidation products) generated by on-line ozonolysis in APAG mode. Finally, some examples of in situ APAG analysis by gas sampling and surface sampling were given as well. [Figure not available: see fulltext.

Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

NASA Technical Reports Server (NTRS)

Molina, Mario J.

1997-01-01

The objective of this project is to conduct measurements of elementary reaction rate constants and photochemistry parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory.

Optimization and application of atmospheric pressure chemical and photoionization hydrogen-deuterium exchange mass spectrometry for speciation of oxygen-containing compounds.

PubMed

Acter, Thamina; Kim, Donghwi; Ahmed, Arif; Jin, Jang Mi; Yim, Un Hyuk; Shim, Won Joon; Kim, Young Hwan; Kim, Sunghwan

2016-05-01

This paper presents a detailed investigation of the feasibility of optimized positive and negative atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and atmospheric pressure photoionization (APPI) MS coupled to hydrogen-deuterium exchange (HDX) for structural assignment of diverse oxygen-containing compounds. The important parameters for optimization of HDX MS were characterized. The optimized techniques employed in the positive and negative modes showed satisfactory HDX product ions for the model compounds when dichloromethane and toluene were employed as a co-solvent in APCI- and APPI-HDX, respectively. The evaluation of the mass spectra obtained from 38 oxygen-containing compounds demonstrated that the extent of the HDX of the ions was structure-dependent. The combination of information provided by different ionization techniques could be used for better speciation of oxygen-containing compounds. For example, (+) APPI-HDX is sensitive to compounds with alcohol, ketone, or aldehyde substituents, while (-) APPI-HDX is sensitive to compounds with carboxylic functional groups. In addition, the compounds with alcohol can be distinguished from other compounds by the presence of exchanged peaks. The combined information was applied to study chemical compositions of degraded oils. The HDX pattern, double bond equivalent (DBE) distribution, and previously reported oxidation products were combined to predict structures of the compounds produced from oxidation of oil. Overall, this study shows that APCI- and APPI-HDX MS are useful experimental techniques that can be applied for the structural analysis of oxygen-containing compounds.

Identification of organic hydroperoxides and peroxy acids using atmospheric pressure chemical ionization-tandem mass spectrometry (APCI-MS/MS): application to secondary organic aerosol

NASA Astrophysics Data System (ADS)

Zhou, Shouming; Rivera-Rios, Jean C.; Keutsch, Frank N.; Abbatt, Jonathan P. D.

2018-05-01

Molecules with hydroperoxide functional groups are of extreme importance to both the atmospheric and biological chemistry fields. In this work, an analytical method is presented for the identification of organic hydroperoxides and peroxy acids (ROOH) by direct infusion of liquid samples into a positive-ion atmospheric pressure chemical ionization-tandem mass spectrometer ((+)-APCI-MS/MS). Under collisional dissociation conditions, a characteristic neutral loss of 51 Da (arising from loss of H2O2+NH3) from ammonium adducts of the molecular ions ([M + NH4]+) is observed for ROOH standards (i.e. cumene hydroperoxide, isoprene-4-hydroxy-3-hydroperoxide (ISOPOOH), tert-butyl hydroperoxide, 2-butanone peroxide and peracetic acid), as well as the ROOH formed from the reactions of H2O2 with aldehydes (i.e. acetaldehyde, hexanal, glyoxal and methylglyoxal). This new ROOH detection method was applied to methanol extracts of secondary organic aerosol (SOA) material generated from ozonolysis of α-pinene, indicating a number of ROOH molecules in the SOA material. While the full-scan mass spectrum of SOA demonstrates the presence of monomers (m/z = 80-250), dimers (m/z = 250-450) and trimers (m/z = 450-600), the neutral loss scan shows that the ROOH products all have masses less than 300 Da, indicating that ROOH molecules may not contribute significantly to the SOA oligomeric content. We anticipate this method could also be applied to biological systems with considerable value.

Extractive Atmospheric Pressure Photoionization (EAPPI) Mass Spectrometry: Rapid Analysis of Chemicals in Complex Matrices.

PubMed

Liu, Chengyuan; Yang, Jiuzhong; Wang, Jian; Hu, Yonghua; Zhao, Wan; Zhou, Zhongyue; Qi, Fei; Pan, Yang

2016-10-01

Extractive atmospheric pressure photoionization (EAPPI) mass spectrometry was designed for rapid qualitative and quantitative analysis of chemicals in complex matrices. In this method, an ultrasonic nebulization system was applied to sample extraction, nebulization, and vaporization. Mixed with a gaseous dopant, vaporized analytes were ionized through ambient photon-induced ion-molecule reactions, and were mass-analyzed by a high resolution time-of-flight mass spectrometer (TOF-MS). After careful optimization and testing with pure sample solution, EAPPI was successfully applied to the fast screening of capsules, soil, natural products, and viscous compounds. Analysis was completed within a few seconds without the need for preseparation. Moreover, the quantification capability of EAPPI for matrices was evaluated by analyzing six polycyclic aromatic hydrocarbons (PAHs) in soil. The correlation coefficients (R (2) ) for standard curves of all six PAHs were above 0.99, and the detection limits were in the range of 0.16-0.34 ng/mg. In addition, EAPPI could also be used to monitor organic chemical reactions in real time. Graphical Abstract ᅟ.

Ionization asymmetry effects on the properties modulation of atmospheric pressure dielectric barrier discharge sustained by tailored voltage waveforms

NASA Astrophysics Data System (ADS)

Zhang, Z. L.; Nie, Q. Y.; Zhang, X. N.; Wang, Z. B.; Kong, F. R.; Jiang, B. H.; Lim, J. W. M.

2018-04-01

The dielectric barrier discharge (DBD) is a promising technology to generate high density and uniform cold plasmas in atmospheric pressure gases. The effective independent tuning of key plasma parameters is quite important for both application-focused and fundamental studies. In this paper, based on a one-dimensional fluid model with semi-kinetics treatment, numerical studies of ionization asymmetry effects on the properties modulation of atmospheric DBD sustained by tailored voltage waveforms are reported. The driving voltage waveform is characterized by an asymmetric-slope fundamental sinusoidal radio frequency signal superimposing one or more harmonics, and the effects of the number of harmonics, phase shift, as well as the fluctuation of harmonics on the sheath dynamics, impact ionization of electrons and key plasma parameters are investigated. The results have shown that the electron density can exhibit a substantial increase due to the effective electron heating by a spatially asymmetric sheath structure. The strategic modulation of harmonics number and phase shift is capable of raising the electron density significantly (e.g., nearly three times in this case), but without a significant increase in the gas temperature. Moreover, by tailoring the fluctuation of harmonics with a steeper slope, a more profound efficiency in electron impact ionization can be achieved, and thus enhancing the electron density effectively. This method then enables a novel alternative approach to realize the independent control of the key plasma parameters under atmospheric pressure.

Modeling of plasma chemical processes in the artificial ionized layer in the upper atmosphere by the nanosecond corona discharge

NASA Astrophysics Data System (ADS)

Vikharev, A. L.; Gorbachev, A. M.; Ivanov, O. A.; Kolisko, A. L.; Litvak, A. G.

1993-08-01

The plasma chemical processes in the corona discharge formed in air by a series of high voltage pulses of nanosecond duration are investigated experimentally. The experimental conditions (reduced electric field, duration and repetition frequency of the pulses, gas pressure in the chamber) modeled the regime of creation of the artificial ionized layer (AIL) in the upper atmosphere by a nanosecond microwave discharge. It was found that in a nanosecond microwave discharge predominantly generation of ozone occurs, and that the production of nitrogen dioxide is not large. The energy expenditures for the generation of one O 3 molecule were about 15 eV. On the basis of the experimental results the prognosis of the efficiency of ozone generation in AIL was made.

Systematic investigation of ion suppression and enhancement effects of fourteen stable-isotope-labeled internal standards by their native analogues using atmospheric-pressure chemical ionization and electrospray ionization and the relevance for multi-analyte liquid chromatographic/mass spectrometric procedures.

PubMed

Remane, Daniela; Wissenbach, Dirk K; Meyer, Markus R; Maurer, Hans H

2010-04-15

In clinical and forensic toxicology, multi-analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi-analyte procedures, often only a limited number of stable-isotope-labeled internal standards (SIL-ISs) are available. If an SIL-IS is used for quantification of other analytes, it must be excluded that the co-eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL-ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric-pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL-ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix-based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL-ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. 2010 John Wiley & Sons, Ltd.

Determination of patterns of biologically relevant aldehydes in exhaled breath condensate of healthy subjects by liquid chromatography/atmospheric chemical ionization tandem mass spectrometry

PubMed Central

Andreoli, Roberta; Manini, Paola; Corradi, Massimo; Mutti, Antonio; Niessen, Wilfried M. A.

2006-01-01

A method for the simultaneous determination of several classes of aldehydes in exhaled breath condensate (EBC) was developed using liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry (LC/APCI-MS/MS). EBC is a biological matrix obtained by a relatively new, simple and noninvasive technique and provides an indirect assessment of pulmonary status. The measurement of aldehydes in EBC represents a biomarker of the effect of oxidative stress caused by smoke, disease, or strong oxidants like ozone. Malondialdehyde (MDA), acrolein, α,β-unsaturated hydroxylated aldehydes [namely 4-hydroxyhexenal (4-HHE) and 4-hydroxynonenal (4-HNE)], and saturated aldehydes (n-hexanal, n-heptanal and n-nonanal) were measured in EBC after derivatization with 2,4-dinitrophenylhydrazine (DNPH). Atmospheric pressure chemical ionization of the analytes was obtained in positiveion mode for MDA, and in negativeion mode for acrolein, 4-HHE, 4-HNE, and saturated aldehydes. DNPH derivatives were separated on a C18 column using variable proportions of 20 mM aqueous acetic acid and methanol. Linearity was established over 4–5 orders of magnitude and limits of detection were in the 0.3–1.0 nM range. Intra-day and inter-day precision were in the 1.3–9.9% range for all the compounds. MDA, acrolein and n-alkanals were detectable in all EBC samples, whereas the highly reactive 4-HHE and 4-HNE were found in only a few samples. Statistically significant higher concentrations of MDA, acrolein and n-hexanal were found in EBC from smokers. PMID:12661015

Atmospheric Ionization Measurements

NASA Astrophysics Data System (ADS)

Slack, Thomas; Mayes, Riley

2015-04-01

The measurement of atmospheric ionization is a largely unexplored science that potentially holds the key to better understanding many different geophysical phenomena through this new and valuable source of data. Through the LaACES program, which is funded by NASA through the Louisiana Space Consortium, students at Loyola University New Orleans have pursued the goal of measuring high altitude ionization for nearly three years, and were the first to successfully collect ionization data at altitudes over 30,000 feet using a scientific weather balloon flown from the NASA Columbia Scientific Ballooning Facility in Palestine, TX. In order to measure atmospheric ionization, the science team uses a lightweight and highly customized sensor known as a Gerdien condenser. Among other branches of science the data is already being used for, such as the study of aerosol pollution levels in the atmosphere, the data may also be useful in meteorology and seismology. Ionization data might provide another variable with which to predict weather or seismic activity more accurately and further in advance. Thomas Slack and Riley Mayes have served as project managers for the experiment, and have extensive knowledge of the experiment from the ground up. LaSPACE Louisiana Space Consortium.

Characterization of aromatic organosulfur model compounds relevant to fossil fuels by using atmospheric pressure chemical ionization with CS2 and high-resolution tandem mass spectrometry.

PubMed

Tang, Weijuan; Sheng, Huaming; Jin, Chunfen; Riedeman, James S; Kenttämaa, Hilkka I

2016-04-15

The chemistry of desulfurization involved in processing crude oil is greatly dependent on the forms of sulfur in the oil. Sulfur exists in different chemical bonding environments in fossil fuels, including those in thiophenes and benzothiophenes, thiols, sulfides, and disulfides. In this study, the fragmentation behavior of the molecular ions of 17 aromatic organosulfur compounds with various functionalities was systematically investigated by using high-resolution tandem mass spectrometry. Multiple-stage tandem mass spectrometric experiments were carried out using a linear quadrupole ion trap (LQIT) equipped with an atmospheric pressure chemical ionization (APCI) source. (+)APCI/CS2 was used to generate stable dominant molecular ions for all the compounds studied except for three sulfides that also showed abundant fragment ions. The LQIT coupled with an orbitrap mass spectrometer was used for elemental composition analysis, which facilitated the identification of the neutral molecules lost during fragmentation. The characteristic fragment ions generated in MS(2) and MS(3) experiments provide clues for the chemical bonding environment of sulfur atoms in the examined compounds. Upon collision-induced dissociation (CID), the molecular ions can lose the sulfur atom in a variety of ways, including as S (32 Da), HS(•) (33 Da), H2 S (34 Da), CS (44 Da), (•) CHS (45 Da) and CH2 S (46 Da). These neutral fragments are not only indicative of the presence of sulfur, but also of the type of sulfur present in the compound. Generally, losses of HS(•) and H2 S were found to be associated with compounds containing saturated sulfur functionalities, while losses of S, CS and (•) CHS were more common for heteroaromatic sulfur compounds. High-resolution tandem mass spectrometry with APCI/CS2 ionization is a viable approach to determining the types of organosulfur compounds. It can potentially be applied to analysis of complex mixtures, which is beneficial to improving the

Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waltman, Melanie J.

2010-05-01

Explosives detection is a necessary and wide spread field of research. From large shipping containers to airline luggage, numerous items are tested for explosives every day. In the area of trace explosives detection, ion mobility spectrometry (IMS) is the technique employed most often because it is a quick, simple, and accurate way to test many items in a short amount of time. Detection by IMS is based on the difference in drift times of product ions through the drift region of an IMS instrument. The product ions are created when the explosive compounds, introduced to the instrument, are chemically ionizedmore » through interactions with the reactant ions. The identity of the reactant ions determines the outcomes of the ionization process. This research investigated the reactant ions created by various ionization sources and looked into ways to manipulate the chemistry occurring in the sources.« less

Evaluation of the capabilities of atmospheric pressure chemical ionization source coupled to tandem mass spectrometry for the determination of dioxin-like polychlorobiphenyls in complex-matrix food samples.

PubMed

Portolés, T; Sales, C; Abalos, M; Sauló, J; Abad, E

2016-09-21

The use of the novel atmospheric pressure chemical ionization (APCI) source for gas chromatography (GC) coupled to triple quadrupole using tandem mass spectrometry (MS/MS) and its potential for the simultaneous determination of the 12 dioxin-like polychlorobiphenyls (DL-PCBs) in complex food and feed matrices has been evaluated. In first place, ionization and fragmentation behavior of DL-PCBs on the APCI source under charge transfer conditions has been studied followed by their fragmentation in the collision cell. Linearity, repeatability and sensitivity have been studied obtaining instrumental limits of detection and quantification of 0.0025 and 0.005 pg μL(-1) (2.5 and 5 fg on column) respectively for every DL-PCB. Finally, application to real samples has been carried out and DL-PCB congeners (PCB 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189) have been detected in the different samples in the range of 0.40-10000 pg g(-1). GC-(APCI)MS/MS has been proved as a suitable alternative to the traditionally accepted confirmation method based on the use of high resolution mass spectrometry and other triple quadrupole tandem mass spectrometry techniques operating with electron ionization. The development of MS/MS methodologies for the analysis of dioxins and DL-PCBs is nowadays particularly important, since this technique was included as a confirmatory method in the present European Union regulations that establish the requirements for the determination of these compounds in food and feed matrices. Copyright © 2016 Elsevier B.V. All rights reserved.

HO2 measurements at atmospheric concentrations using a chemical ionization mass spectrometry

NASA Astrophysics Data System (ADS)

Albrecht, S.; Novelli, A.; Hofzumahaus, A.; Kang, S.; Baker, Y.; Mentel, T. F.; Fuchs, H.

2017-12-01

Correct and precise measurements of atmospheric radical species are necessary for a better understanding of the oxidative capacity of the atmosphere. Due to the reactivity of radicals, and their consequent low concentrations, direct measurements of these species are particularly challenging and have been proven in the past to be affected by interfering species. Here we present a chemical ionization source coupled to an APi-HR-TOF-MS (Aerodyne Research Inc.), which has a limit of detection for HO2 radicals well below its atmospheric concentrations ( 1 x 108 molecules cm-3). The instrument was calibrated with a well-established and characterized HO2 calibration source in use for the laser induced fluorescence instrument in the Forschungszentrum Jülich. Within the source, a well characterized amount of HO2 radicals is produced after photolysis of water by a mercury lamp. In addition, several experiments were performed in the atmosphere simulation chamber SAPHIR at the Forschungszentrum Jülich to test for potential interferences. Measurements of HO2 radicals were concurrently detected by a laser induced fluorescence instrument allowing for the comparison of measurements within the two different and independent techniques for various atmospheric conditions regarding concentrations of O3, NOx and VOCs. Results from the intercomparison together with the calibration procedure of the instrument and laboratory characterization will be presented.

In-Line Ozonation for Sensitive Air-Monitoring of a Mustard-Gas Simulant by Atmospheric Pressure Chemical Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Okumura, Akihiko

2015-09-01

A highly sensitive method for real-time air-monitoring of mustard gas (bis(2-chloroethyl) sulfide, HD), which is a lethal blister agent, is proposed. Humidified air containing a HD simulant, 2-chloroethyl ethyl sulfide (2CEES), was mixed with ozone and then analyzed by using an atmospheric pressure chemical ionization ion trap tandem mass spectrometer. Mass-spectral ion peaks attributable to protonated molecules of intact, monooxygenated, and dioxygenated 2CEES (MH+, MOH+, and MO2H+, respectively) were observed. As ozone concentration was increased from zero to 30 ppm, the signal intensity of MH+ sharply decreased, that of MOH+ increased once and then decreased, and that of MO2H+ sharply increased until reaching a plateau. The signal intensity of MO2H+ at the plateau was 40 times higher than that of MH+ and 100 times higher than that of MOH+ in the case without in-line ozonation. Twenty-ppm ozone gas was adequate to give a linear calibration curve for 2CEES obtained by detecting the MO2H+ signal in the concentration range up to 60 μg/m3, which is high enough for hygiene management. In the low concentration range lower than 3 μg/m3, which is equal to the short-term exposure limit for HD, calibration plots unexpectedly fell off the linear calibration curve, but 0.6-μg/m3 vapor was actually detected with the signal-to-noise ratio of nine. Ozone was generated from instrumentation air by using a simple and inexpensive home-made generator. 2CEES was ozonated in 1-m extended sampling tube in only 1 s.

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

Lacker, T; Strohschein, S; Albert, K

1999-08-27

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.

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

PubMed

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

2007-11-01

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.

FAST TRACK COMMUNICATION: Effects of Penning ionization on the discharge patterns of atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Li, Qing; Zhu, Wen-Chao; Zhu, Xi-Ming; Pu, Yi-Kang

2010-09-01

Atmospheric pressure plasma jets, generated in a coaxial dielectric barrier discharge configuration, have been investigated with different flowing gases. Discharge patterns in different tube regions were compared in the flowing gases of helium, neon and krypton. To explain the difference of these discharge patterns, a theoretical analysis is presented to reveal the possible basic processes. A comparison of experimental and theoretical results identifies that Penning ionization is mainly responsible for the discharge patterns of helium and neon plasma jets.

Microplasma-based flowing atmospheric-pressure afterglow (FAPA) source for ambient desorption-ionization mass spectrometry.

PubMed

Zeiri, Offer M; Storey, Andrew P; Ray, Steven J; Hieftje, Gary M

2017-02-01

A new direct-current microplasma-based flowing atmospheric pressure afterglow (FAPA) source was developed for use in ambient desorption-ionization mass spectrometry. The annular-shaped microplasma is formed in helium between two concentric stainless-steel capillaries that are separated by an alumina tube. Current-voltage characterization of the source shows that this version of the FAPA operates in the normal glow-discharge regime. A glass surface placed in the path of the helium afterglow reaches temperatures of up to approximately 400 °C; the temperature varies with distance from the source and helium flow rate through the source. Solid, liquid, and vapor samples were examined by means of a time-of-flight mass spectrometer. Results suggest that ionization occurs mainly through protonation, with only a small amount of fragmentation and adduct formation. The mass range of the source was shown to extend up to at least m/z 2722 for singly charged species. Limits of detection for several small organic molecules were in the sub-picomole range. Examination of competitive ionization revealed that signal suppression occurs only at high (mM) concentrations of competing substances. Copyright © 2016 Elsevier B.V. All rights reserved.

Dielectric barrier discharge ionization for liquid chromatography/mass spectrometry.

PubMed

Hayen, Heiko; Michels, Antje; Franzke, Joachim

2009-12-15

An atmospheric pressure microplasma ionization source based on a dielectric barrier discharge with a helium plasma cone outside the electrode region has been developed for liquid chromatography/mass spectrometry (LC/MS). For this purpose, the plasma was realized in a commercial atmospheric pressure ionization source. Dielectric barrier discharge ionization (DBDI) was compared to conventional electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) in the positive ionization mode. Therefore, a heterogeneous compound library was investigated that covered polar compounds such as amino acids, water-soluble vitamins, and nonpolar compounds like polycyclic aromatic hydrocarbons and functionalized hydrocarbons. It turned out that DBDI can be regarded as a soft ionization technique characterized by only minor fragmentation similar to APCI. Mainly protonated molecules were detected. Additionally, molecular ions were observed for polycyclic aromatic hydrocarbons and derivatives thereof. During DBDI, adduct formation with acetonitrile occurred. For aromatic compounds, addition of one to four oxygen atoms and to a smaller extend one nitrogen and oxygen was observed which delivered insight into the complexity of the ionization processes. In general, compounds covering a wider range of polarities can be ionized by DBDI than by ESI. Furthermore, limits of detection compared to APCI are in most cases equal or even better.

Characterization of major and minor alk(en)ylresorcinols from mango (Mangifera indica L.) peels by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

PubMed

Knödler, Matthias; Berardini, Nicolai; Kammerer, Dietmar R; Carle, Reinhold; Schieber, Andreas

2007-01-01

5-Alkyl- and 5-alkenylresorcinols, as well as their hydroxylated derivatives, were extracted from mango (Mangifera indica L.) peels, purified on polyamide and characterized by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APcI-MS) for the first time. Among the 15 compounds analyzed, 3 major and 12 minor C(15)-, C(17)-, and C(19)-substituted resorcinols and related analogues, showing varying degrees of unsaturation, were characterized by their specific fragmentation patterns in collision-induced dissociation experiments. This marks the first report on the occurrence of mono-, di-, and triunsaturated C(15)-homologues, saturated and triunsaturated C(17)-homologues, and mono- and diunsaturated C(19)-homologues in mango peels. Additionally, several hydroxylated C(15)- and C(17)-homologues, also not yet described in mango, and a C(14)-monoene, unique because of its even-numbered side chain, were tentatively identified on the basis of their fragmentation patterns. The results obtained in the present study indicate that HPLC-DAD-APcI-MS(n), combined with the newly developed solid-phase extraction, is a powerful tool for the analysis of alk(en)ylresorcinols and could therefore be used for their determination in various matrices.

Ultra-high performance supercritical fluid chromatography hyphenated to atmospheric pressure chemical ionization high resolution mass spectrometry for the characterization of fast pyrolysis bio-oils.

PubMed

Crepier, Julien; Le Masle, Agnès; Charon, Nadège; Albrieux, Florian; Duchene, Pascal; Heinisch, Sabine

2018-06-01

Extensive characterization of complex mixtures requires the combination of powerful analytical techniques. A Supercritical Fluid Chromatography (SFC) method was previously developed, for the specific case of fast pyrolysis bio oils, as an alternative to gas chromatography (GC and GC × GC) or liquid chromatography (LC and LC × LC), both separation methods being generally used prior to mass spectrometry (MS) for the characterization of such complex matrices. In this study we investigated the potential of SFC hyphenated to high resolution mass spectrometry (SFC-HRMS) for this characterization using Negative ion Atmospheric Pressure Chemical ionization ((-)APCI) for the ionization source. The interface between SFC and (-)APCI/HRMS was optimized from a mix of model compounds with the objective of maximizing the signal to noise ratio. The main studied parameters included both make-up flow-rate and make-up composition. A methodology for the treatment of APCI/HRMS data is proposed. This latter allowed for the identification of molecular formulae. Both SFC-APCI/HRMS method and data processing method were applied to a mixture of 36 model compounds, first analyzed alone and then spiked in a bio-oil. In both cases, 19 compounds could be detected. Among them 9 could be detected in a fast pyrolysis bio-oil by targeted analysis. The whole procedure was applied to the characterization of a bio-oil using helpful representations such as mass-plots, van Krevelen diagrams and heteroatom class distributions. Finally the results were compared with those obtained with a Fourier Transform ion-cyclotron resonance mass spectrometer (FT-ICR/MS). Copyright © 2018 Elsevier B.V. All rights reserved.

Quality classification of Spanish olive oils by untargeted gas chromatography coupled to hybrid quadrupole-time of flight mass spectrometry with atmospheric pressure chemical ionization and metabolomics-based statistical approach.

PubMed

Sales, C; Cervera, M I; Gil, R; Portolés, T; Pitarch, E; Beltran, J

2017-02-01

The novel atmospheric pressure chemical ionization (APCI) source has been used in combination with gas chromatography (GC) coupled to hybrid quadrupole time-of-flight (QTOF) mass spectrometry (MS) for determination of volatile components of olive oil, enhancing its potential for classification of olive oil samples according to their quality using a metabolomics-based approach. The full-spectrum acquisition has allowed the detection of volatile organic compounds (VOCs) in olive oil samples, including Extra Virgin, Virgin and Lampante qualities. A dynamic headspace extraction with cartridge solvent elution was applied. The metabolomics strategy consisted of three different steps: a full mass spectral alignment of GC-MS data using MzMine 2.0, a multivariate analysis using Ez-Info and the creation of the statistical model with combinations of responses for molecular fragments. The model was finally validated using blind samples, obtaining an accuracy in oil classification of 70%, taking the official established method, "PANEL TEST", as reference. Copyright © 2016 Elsevier Ltd. All rights reserved.

The transfer of atmospheric-pressure ionization waves via a metal wire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Yang; Liu, Dongping, E-mail: Dongping.liu@dlnu.edu.cn; School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024

2016-01-15

Our study has shown that the atmospheric-pressure He ionization waves (IWs) may be transferred from one dielectric tube (tube 1) to the other one (tube 2) via a floating metal wire. The propagation of IWs along the two tubes is not affected by the diameter of a floating metal wire, however, their propagation is strongly dependent on the length of a floating metal wire. The propagation of one IW along the tube 1 may result in the second IW propagating reversely inside the tube in vicinity of a floating metal wire, which keeps from their further propagation through the tubemore » 1. After they merge together as one conduction channel inside the tube 1, the transferred plasma bullet starts to propagate along the tube 2. The propagation of transferred plasma bullets along the tube 2 is mainly determined by the capacitance and inductance effects, and their velocity and density can be controlled by the length of a floating metal wire.« less

Diclofenac in municipal wastewater treatment plant: quantification using laser diode thermal desorption--atmospheric pressure chemical ionization--tandem mass spectrometry approach in comparison with an established liquid chromatography-electrospray ionization-tandem mass spectrometry method.

PubMed

Lonappan, Linson; Pulicharla, Rama; Rouissi, Tarek; Brar, Satinder K; Verma, Mausam; Surampalli, Rao Y; Valero, José R

2016-02-12

Diclofenac (DCF), a prevalent non-steroidal anti-inflammatory drug (NSAID) is often detected in wastewater and surface water. Analysis of the pharmaceuticals in complex matrices is often laden with challenges. In this study a reliable, rapid and sensitive method based on laser diode thermal desorption/atmospheric pressure chemical ionization (LDTD/APCI) coupled with tandem mass spectrometry (MS/MS) has been developed for the quantification of DCF in wastewater and wastewater sludge. An established conventional LC-ESI-MS/MS (liquid chromatography-electrospray ionization-tandem mass spectrometry) method was compared with LDTD-APCI-MS/MS approach. The newly developed LDTD-APCI-MS/MS method reduced the analysis time to 12s in lieu of 12 min for LC-ESI-MS/MS method. The method detection limits for LDTD-APCI-MS/MS method were found to be 270 ng L(-1) (LOD) and 1000 ng L(-1) (LOQ). Furthermore, two extraction procedures, ultrasonic assisted extraction (USE) and accelerated solvent extraction (ASE) for the extraction of DCF from wastewater sludge were compared and ASE with 95.6 ± 7% recovery was effective over USE with 86 ± 4% recovery. The fate and partitioning of DCF in wastewater (WW) and wastewater sludge (WWS) in wastewater treatment plant was also monitored at various stages of treatment in Quebec Urban community wastewater treatment plant. DCF exhibited affinity towards WW than WWS with a presence about 60% of DCF in WW in contrary with theoretical prediction (LogKow=4.51). Copyright © 2016 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

1999-05-01

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.

Schinus terebinthifolius scale-up countercurrent chromatography (Part I): High performance countercurrent chromatography fractionation of triterpene acids with off-line detection using atmospheric pressure chemical ionization mass spectrometry.

PubMed

Vieira, Mariana Neves; Costa, Fernanda das Neves; Leitão, Gilda Guimarães; Garrard, Ian; Hewitson, Peter; Ignatova, Svetlana; Winterhalter, Peter; Jerz, Gerold

2015-04-10

'Countercurrent chromatography' (CCC) is an ideal technique for the recovery, purification and isolation of bioactive natural products, due to the liquid nature of the stationary phase, process predictability and the possibility of scale-up from analytical to preparative scale. In this work, a method developed for the fractionation of Schinus terebinthifolius Raddi berries dichloromethane extract was thoroughly optimized to achieve maximal throughput with minimal solvent and time consumption per gram of processed crude extract, using analytical, semi-preparative and preparative 'high performance countercurrent chromatography' (HPCCC) instruments. The method using the biphasic solvent system composed of n-heptane-ethyl acetate-methanol-water (6:1:6:1, v/v/v/v) was volumetrically scaled up to increase sample throughput up to 120 times, while maintaining separation efficiency and time. As a fast and specific detection alternative, the fractions collected from the CCC-separations were injected to an 'atmospheric pressure chemical ionization mass-spectrometer' (APCI-MS/MS) and reconstituted molecular weight MS-chromatograms of the APCI-ionizable compounds from S. terebinthifolius were obtained. This procedure led to the direct isolation of tirucallane type triterpenes such as masticadienonic and 3β-masticadienolic acids. Also oleanonic and moronic acids have been identified for the first time in the species. In summary, this approach can be used for other CCC scale-up processes, enabling MS-target-guided isolation procedures. Copyright © 2015 Elsevier B.V. All rights reserved.

Atmospheric-pressure plasma jet

DOEpatents

Selwyn, Gary S.

1999-01-01

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.

When API Mass Spectrometry Meets Super Atmospheric Pressure Ion Sources

PubMed Central

Chen, Lee Chuin

2015-01-01

In a tutorial paper on the application of free-jet technique for API-MS, John Fenn mentioned that “…for a number of years and a number of reasons, it has been found advantageous in many situations to carry out the ionization process in gas at pressures up to 1000 Torr or more” (Int. J. Mass Spectrom. 200: 459–478, 2000). In fact, the first ESI mass spectrometer constructed by Yamashita and Fenn had a counter-flow curtain gas source at 1050 Torr (ca. 1.4 atm) to sweep away the neutral (J. Phys. Chem. 88: 4451–4459, 1984). For gaseous ionization using electrospray plume, theoretical analysis also shows that “super-atmospheric operation would be more preferable in space-charge-limited situations.”(Int. J. Mass Spectrom. 300: 182–193, 2011). However, electrospray and the corona-based chemical ion source (APCI) in most commercial instrument are basically operated under an atmospheric pressure ambient, perhaps out of the concern of safety, convenience and simplicity in maintenance. Running the ion source at pressure much higher than 1 atm is not so common, but had been done by a number of groups as well as in our laboratory. A brief review on these ion sources will be given in this paper. PMID:26819912

Influence of field emission on the propagation of cylindrical fast ionization wave in atmospheric-pressure nitrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levko, Dmitry; Raja, Laxminarayan L.

2016-04-21

The influence of field emission of electrons from surfaces on the fast ionization wave (FIW) propagation in high-voltage nanosecond pulse discharge in the atmospheric-pressure nitrogen is studied by a one-dimensional Particle-in-Cell Monte Carlo Collisions model. A strong influence of field emission on the FIW dynamics and plasma parameters is obtained. Namely, the accounting for the field emission makes possible the bridging of the cathode–anode gap by rather dense plasma (∼10{sup 13 }cm{sup −3}) in less than 1 ns. This is explained by the generation of runaway electrons from the field emitted electrons. These electrons are able to cross the entire gap pre-ionizingmore » it and promoting the ionization wave propagation. We have found that the propagation of runaway electrons through the gap cannot be accompanied by the streamer propagation, because the runaway electrons align the plasma density gradients. In addition, we have obtained that the field enhancement factor allows controlling the speed of ionization wave propagation.« less

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

PubMed

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-07

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

Quantitative analysis of triacylglycerol regioisomers in fats and oils using reversed-phase high-performance liquid chromatography and atmospheric pressure chemical ionization mass spectrometry.

PubMed

Fauconnot, Laëtitia; Hau, Jörg; Aeschlimann, Jean-Marc; Fay, Laurent-Bernard; Dionisi, Fabiola

2004-01-01

Positional distribution of fatty acyl chains of triacylglycerols (TGs) in vegetable oils and fats (palm oil, cocoa butter) and animal fats (beef, pork and chicken fats) was examined by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to atmospheric pressure chemical ionization using a quadrupole mass spectrometer. Quantification of regioisomers was achieved for TGs containing two different fatty acyl chains (palmitic (P), stearic (S), oleic (O), and/or linoleic (L)). For seven pairs of 'AAB/ABA'-type TGs, namely PPS/PSP, PPO/POP, SSO/SOS, POO/OPO, SOO/OSO, PPL/PLP and LLS/LSL, calibration curves were established on the basis of the difference in relative abundances of the fragment ions produced by preferred losses of the fatty acid from the 1/3-position compared to the 2-position. In practice the positional isomers AAB and ABA yield mass spectra showing a significant difference in relative abundance ratios of the ions AA(+) to AB(+). Statistical analysis of the validation data obtained from analysis of TG standards and spiked oils showed that, under repeatability conditions, least-squares regression can be used to establish calibration curves for all pairs. The regression models show linear behavior that allow the determination of the proportion of each regioisomer in an AAB/ABA pair, within a working range from 10 to 1000 microg/mL and a 95% confidence interval of +/-3% for three replicates. Copyright 2003 John Wiley & Sons, Ltd.

Analysis of trimethoprim, lincomycin, sulfadoxin and tylosin in swine manure using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry.

PubMed

Solliec, Morgan; Massé, Daniel; Sauvé, Sébastien

2014-10-01

A new extraction method coupled to a high throughput sample analysis technique was developed for the determination of four veterinary antibiotics. The analytes belong to different groups of antibiotics such as chemotherapeutics, sulfonamides, lincosamides and macrolides. Trimethoprim (TMP), sulfadoxin (SFX), lincomycin (LCM) and tylosin (TYL) were extracted from lyophilized manure using a sonication extraction. McIlvaine buffer and methanol (MeOH) were used as extraction buffers, followed by cation-exchange solid phase extraction (SPE) for clean-up. Analysis was performed by laser diode thermal desorption-atmospheric pressure chemical-ionization (LDTD-APCI) tandem mass spectrometry (MS/MS) with selected reaction monitoring (SRM) detection. The LDTD is a high throughput sample introduction method that reduces total analysis time to less than 15s per sample, compared to minutes when using traditional liquid chromatography (LC). Various SPE parameters were optimized after sample extraction: the stationary phase, the extraction solvent composition, the quantity of sample extracted and sample pH. LDTD parameters were also optimized: solvent deposition, carrier gas, laser power and corona discharge. The method limit of detection (MLD) ranged from 2.5 to 8.3 µg kg(-1) while the method limit of quantification (MLQ) ranged from 8.3 to 28µgkg(-1). Calibration curves in the manure matrix showed good linearity (R(2)≥ 0.996) for all analytes and the interday and intraday coefficients of variation were below 14%. Recoveries of analytes from manure ranged from 53% to 69%. The method was successfully applied to real manure samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Hydraulic effects in a radiative atmosphere with ionization

NASA Astrophysics Data System (ADS)

Bhat, P.; Brandenburg, A.

2016-03-01

Context. In his 1978 paper, Eugene Parker postulated the need for hydraulic downward motion to explain magnetic flux concentrations at the solar surface. A similar process has also recently been seen in simplified (e.g., isothermal) models of flux concentrations from the negative effective magnetic pressure instability (NEMPI). Aims: We study the effects of partial ionization near the radiative surface on the formation of these magnetic flux concentrations. Methods: We first obtain one-dimensional (1D) equilibrium solutions using either a Kramers-like opacity or the H- opacity. The resulting atmospheres are then used as initial conditions in two-dimensional (2D) models where flows are driven by an imposed gradient force that resembles a localized negative pressure in the form of a blob. To isolate the effects of partial ionization and radiation, we ignore turbulence and convection. Results: Because of partial ionization, an unstable stratification always forms near the surface. We show that the extrema in the specific entropy profiles correspond to the extrema in the degree of ionization. In the 2D models without partial ionization, strong flux concentrations form just above the height where the blob is placed. Interestingly, in models with partial ionization, such flux concentrations always form at the surface well above the blob. This is due to the corresponding negative gradient in specific entropy. Owing to the absence of turbulence, the downflows reach transonic speeds. Conclusions: We demonstrate that, together with density stratification, the imposed source of negative pressure drives the formation of flux concentrations. We find that the inclusion of partial ionization affects the entropy profile dramatically, causing strong flux concentrations to form closer to the surface. We speculate that turbulence effects are needed to limit the strength of flux concentrations and homogenize the specific entropy to a stratification that is close to marginal.

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

NASA Astrophysics Data System (ADS)

Herrmann, Hans W.

1998-11-01

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.

SFC-APLI-(TOF)MS: Hyphenation of Supercritical Fluid Chromatography to Atmospheric Pressure Laser Ionization Mass Spectrometry.

PubMed

Klink, Dennis; Schmitz, Oliver Johannes

2016-01-05

Atmospheric-pressure laser ionization mass spectrometry (APLI-MS) is a powerful method for the analysis of polycyclic aromatic hydrocarbon (PAH) molecules, which are ionized in a selective and highly sensitive way via resonance-enhanced multiphoton ionization. APLI was presented in 2005 and has been hyphenated successfully to chromatographic separation techniques like high performance liquid chromatography (HPLC) and gas chromatography (GC). In order to expand the portfolio of chromatographic couplings to APLI, a new hyphenation setup of APLI and supercritical-fluid chromatography (SFC) was constructed and aim of this work. Here, we demonstrate the first hyphenation of SFC and APLI in a simple designed way with respect to different optimization steps to ensure a sensitive analysis. The new setup permits qualitative and quantitative determination of native and also more polar PAH molecules. As a result of the altered ambient characteristics within the source enclosure, the quantification of 1-hydroxypyrene (1-HP) in human urine is possible without prior derivatization. The limit of detection for 1-HP by SFC-APLI-TOF(MS) was found to be 0.5 μg L(-1), which is lower than the 1-HP concentrations found in exposed persons.

Photochemistry of limonene secondary organic aerosol studied with chemical ionization mass spectrometry

NASA Astrophysics Data System (ADS)

Pan, Xiang

Limonene is one of the most abundant monoterpenes in the atmosphere. Limonene easily reacts with gas-phase oxidants in air such as NO3, ozone and OH. Secondary organic aerosol (SOA) is formed when low vapor pressure products condense into particles. Chemicals in SOA particles can undergo further reactions with oxidants and with solar radiation that significantly change SOA composition over the course of several days. The goal of this work was to characterize radiation induced reaction in SOA. To perform experiments, we have designed and constructed an Atmospheric Pressure Chemical Ionization Mass Spectrometer (APCIMS) coupled to a photochemical cell containing SOA samples. In APCIMS, (H2O)nH 3O+ clusters are generated in a 63Ni source and react with gaseous organic analytes. Most organic chemicals are not fragmented by the ionization process. We have focused our attention on limonene SOA prepared in two different ways. The first type of SOA is produced by oxidation of limonene by ozone; and the second type of SOA is formed by the NO3-induced oxidation of limonene. They model the SOA formed under daytime and nighttime conditions, respectively. Ozone initiated oxidation is the most important chemical sink for limonene both indoors, where it is used for cleaning purposes, and outdoors. Terpenes are primarily oxidized by reactions with NO3 at night time. We generated limonene SOA under different ozone and limonene concentrations. The resulting SOA samples were exposed to wavelength-tunable radiation in the UV-Visible range between 270 nm and 630 nm. The results show that the photodegradation rates strongly depend on radiation wavelengths. Gas phase photodegradation products such as acetone, formaldehyde, acetaldehyde, and acetic acid were shown to have different production rates for SOA formed in different concentration conditions. Even for SOA prepared under the lowest concentrations, the SOA photodegradation was efficient. The conclusion is that exposure of SOA to

Simultaneous determination of triptolide, tripdiolide and tripterine in human urine by high-performance liquid chromatography coupled with ion trap atmospheric-pressure chemical ionization mass spectrometry.

PubMed

Jin, Mi-cong; Chen, Xiao-hong; OuYang, Xiao-kun

2009-03-01

An accurate and selective method for the simultaneous determination of triptolide, tripdiolide and tripterine in human urine using hydrocortisone as an internal standard (IS) by high-performance liquid chromatography coupled with atmospheric-pressure chemical ionization mass spectrometry in negative ion mode has been developed. After triptolide, tripdiolide and tripterine in human urine were extracted with ethyl acetate and cleaned by solid-phase extraction with C(18) cartridges, a satisfactory separation was achieved on an XDB C(18) short column (30 x 2.1 mm i.d., 3 microm) using the mobile phase of acetic acid-ammonium acetate (5 mmol/L, pH = 4.5)-acetonitrile-methanol in gradient elution. Detection was operated by APCI in selected ion monitoring mode. The target ions m/z 359, m/z 375, m/z 449 and m/z 419 were selected for the quantification of triptolide, tripdiolide, tripterine and IS, respectively. The linear range was 1.0-100.0 ng mL(-1), and the limits of quantification in human urine were found to be 0.1-0.5 ng mL(-1) for the three compounds. The precisions (CV%) and accuracies were 6.6-12.9 and 85.1-97.0%, respectively. The developed method could be applied to the determination of triptolide, tripdiolide and tripterine in human urine for diagnosis of the intoxication and for forensic purposes. 2008 John Wiley & Sons, Ltd.

Nanocapillary Atmospheric Pressure Plasma Jet: A Tool for Ultrafine Maskless Surface Modification at Atmospheric Pressure.

PubMed

Motrescu, Iuliana; Nagatsu, Masaaki

2016-05-18

With respect to microsized surface functionalization techniques we proposed the use of a maskless, versatile, simple tool, represented by a nano- or microcapillary atmospheric pressure plasma jet for producing microsized controlled etching, chemical vapor deposition, and chemical modification patterns on polymeric surfaces. In this work we show the possibility of size-controlled surface amination, and we discuss it as a function of different processing parameters. Moreover, we prove the successful connection of labeled sugar chains on the functionalized microscale patterns, indicating the possibility to use ultrafine capillary atmospheric pressure plasma jets as versatile tools for biosensing, tissue engineering, and related biomedical applications.

Controllable growth of shaped graphene domains by atmospheric pressure chemical vapour deposition

NASA Astrophysics Data System (ADS)

Fan, Lili; Li, Zhen; Li, Xiao; Wang, Kunlin; Zhong, Minlin; Wei, Jinquan; Wu, Dehai; Zhu, Hongwei

2011-12-01

Graphene domains in different shapes have been grown on copper substrates via atmospheric pressure chemical vapour deposition by controlling the growth process parameters. Under stabilized conditions, graphene domains tend to be six-fold symmetric hexagons under low flow rate methane with some domains in an irregular hexagonal shape. After further varying the growth duration, methane flow rate, and temperature, graphene domains have developed shapes from hexagon to shovel and dendrite. Two connecting modes, through overlap and merging of adjacent graphene domains, are proposed.Graphene domains in different shapes have been grown on copper substrates via atmospheric pressure chemical vapour deposition by controlling the growth process parameters. Under stabilized conditions, graphene domains tend to be six-fold symmetric hexagons under low flow rate methane with some domains in an irregular hexagonal shape. After further varying the growth duration, methane flow rate, and temperature, graphene domains have developed shapes from hexagon to shovel and dendrite. Two connecting modes, through overlap and merging of adjacent graphene domains, are proposed. Electronic supplementary information (ESI) available: Schematics of CVD setups for graphene growth, Raman spectra and SEM images. See DOI: 10.1039/c1nr11480h

Martian Atmospheric Pressure Static Charge Elimination Tool

NASA Technical Reports Server (NTRS)

Johansen, Michael R.

2014-01-01

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.

An atmospheric pressure ionization source using a high voltage target compared to electrospray ionization for the LC/MS analysis of pharmaceutical compounds.

PubMed

Lubin, Arnaud; De Vries, Ronald; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip

2017-08-05

The type and design of an ionization source can have a significant influence on the performances of a bioanalytical method. It is, therefore, of high interest to evaluate the performances of newly introduced sources to highlight their benefits and limitations in comparison to other well established sources. In this paper, liquid chromatography - mass spectrometry (LC/MS) performances of a new atmospheric pressure ionization (API) source, commercialized as UniSpray, is evaluated. The dynamic range of 24 pharmaceutical and biological compounds is compared between the new API source and electrospray ionization (ESI) for 3 different mobile phase conditions. Matrix effects are also compared with ESI on a refined selection of 19 pharmaceutical and biological compounds in 4 matrices commonly encountered in bioanalysis. A slightly better dynamic range towards lower concentrations was often observed with the new API source. Matrix effects were quite similar between the two sources with a small, but statistically significant, lower percentage of matrix effects observed for the new API source in plasma and bile in the positive ion mode, and bile in negative ion mode for ESI. Finally, the sensitivity of late eluting compounds could be improved on the new API source by post-column addition of water. Copyright © 2017 Elsevier B.V. All rights reserved.

An atmospheric pressure chemical ionization study of the positive and negative ion chemistry of the hydrofluorocarbons 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a) and of perfluoro-n-hexane (FC-72) in air plasma at atmospheric pressure.

PubMed

Marotta, Ester; Paradisi, Cristina; Scorrano, Gianfranco

2004-07-01

A report is given on the ionization/dissociation behavior of the title compounds within air plasmas produced by electrical corona discharges at atmospheric pressure: both positive and negative ions were investigated at different temperatures using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). CHF(2)CH(3) (HFC-152a) undergoes efficient ionic oxidation to C(2)H(5)O(+), in which the oxygen comes from water present in the plasma. In contrast, CF(3)CH(2)F (HFC-134a) does not produce any characteristic positive ion under APCI conditions, its presence within the plasma being revealed only as a neutral ligand in ion-molecule complexes with ions of the background (H(3)O(+) and NO(+)). Analogously, the perfluorocarbon FC-72 (n-C(6)F(14)) does not produce significant positive ions at 30 degrees C: at high temperature, however, it undergoes dissociative ionization to form many product ions including C(3)F(6)(+), C(2)F(4)(+), C(n)F(2n+1)(+) and a few families of oxygen containing cations (C(n)F(2n+1)OH(2)(+), C(n)F(2n)OH(+), C(n)F(2n-1)O(+), C(n)F(2n-1)O(2)H(2)(+), C(n)F(2n-2)O(2)H(+)) which are suggested to derive from C(n)F(2n+1)(+) in a cascade of steps initiated by condensation with water followed by steps of HF elimination and H(2)O addition. Negative ions formed from the fluoroethanes CHF(2)CH(3) and CF(3)CH(2)F (M) include complexes with ions of the background, O(2)(-)(M), O(3)(-)(M) and some higher complexes involving also water, and complexes of the fluoride ion, F(-)(H(2)O), F(-)(M) and higher complexes with both M and H(2)O also together. The interesting product O(2)(-)(HF) is also formed from 1,1-difluoroethane. In contrast to the HFCs, perfluoro-n-hexane gives stable molecular anions, M(-), which at low source temperature or in humidified air are also detected as hydrates, M(-)(H(2)O). In addition, in humidified air F(-)(H(2)O)(n) complexes are also formed. The reactions leading to all major positive and negative product ions are discussed

Comparative study between chemical and atmospheric pressure plasma jet cleaning on glass substrate

NASA Astrophysics Data System (ADS)

Elfa, Rizan Rizon; Ahmad, Mohd Khairul; Fhong, Soon Chin; Sahdan, Mohd Zainizan; Nayan, Nafarizal

2017-01-01

The atmospheric pressure plasma jet with low frequency and argon as working gas is presented in this paper to demonstrate its application for glass substrate clean and modification. The glass substrate clean by atmospheric pressure plasma jet is an efficient method to replace other substrate clean method. A comparative analysis is done in this paper between substrate cleaned by chemical and plasma treatment methods. Water contact angle reading is taken for a different method of substrate clean and period of treatment. Under the plasma treatment, the sample shows low surface adhesion due to having the surface property of super hydrophilic surface 7.26°. This comparative analysis is necessary in the industrial application for cost production due to sufficient time and method of substrate clean.

Desorption atmospheric pressure photoionization.

PubMed

Haapala, Markus; Pól, Jaroslav; Saarela, Ville; Arvola, Ville; Kotiaho, Tapio; Ketola, Raimo A; Franssila, Sami; Kauppila, Tiina J; Kostiainen, Risto

2007-10-15

An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes.

Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae

2017-12-01

Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.

Identification of major xanthones and steroidal saponins in rat urine by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry technology following oral administration of Rhizoma Anemarrhenae decoction.

PubMed

Ma, Chunhui; Wang, Longxing; Tang, Yihong; Fan, Mingsong; Xiao, Hongbin; Huang, Chenggang

2008-10-01

Rhizoma Anemarrhenae (Zhimu in Chinese), the dried rhizome of Anemarrhena asphodeloides Bge. (Fam. Liliaceae), is a well-known traditional Chinese medicinal herb and has been used clinically in China for centuries to cure various diseases. However, like other traditional Chinese medicines, the effective constituents of this medicine, especially the assimilation and metabolites in vivo, which are very important to show their effects, have not been systematically studied. In this paper, solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry technologies were used to study the constituents absorbed into rat urine and their metabolites after oral administration of Rhizoma Anemarrhenae decoction. A total of 11 compounds, including two xanthones, three of their metabolites and six steroidal saponins, were identified in rat urine sample. They were neomangiferin (1), glucuronide and monomethyl conjugate of mangiferin (2), mangiferin (3), monomethyl conjugate of mangiferin (4), dimethyl conjugate of mangiferin (5), timosaponin N or timosaponin E1 (6), timosaponin BII (7), timosaponin BIII (8), anemarrhenasaponin I or anemarrhenasaponin II (9), timosaponin AII (10) and timosaponin AIII (11). The results would efficaciously narrow the potentially active compounds range in Rhizoma Anemarrhenae decoction, and pave a helpful way for follow-up mechanism of action research.

Comparison of free radicals formation induced by cold atmospheric plasma, ultrasound, and ionizing radiation.

PubMed

Rehman, Mati Ur; Jawaid, Paras; Uchiyama, Hidefumi; Kondo, Takashi

2016-09-01

Plasma medicine is increasingly recognized interdisciplinary field combining engineering, physics, biochemistry and life sciences. Plasma is classified into two categories based on the temperature applied, namely "thermal" and "non-thermal" (i.e., cold atmospheric plasma). Non-thermal or cold atmospheric plasma (CAP) is produced by applying high voltage electric field at low pressures and power. The chemical effects of cold atmospheric plasma in aqueous solution are attributed to high voltage discharge and gas flow, which is transported rapidly on the liquid surface. The argon-cold atmospheric plasma (Ar-CAP) induces efficient reactive oxygen species (ROS) in aqueous solutions without thermal decomposition. Their formation has been confirmed by electron paramagnetic resonance (EPR) spin trapping, which is reviewed here. The similarities and differences between the plasma chemistry, sonochemistry, and radiation chemistry are explained. Further, the evidence for free radical formation in the liquid phase and their role in the biological effects induced by cold atmospheric plasma, ultrasound and ionizing radiation are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Comparative study of the flavonoids of some Verbena species cultivated in Egypt by using high-performance liquid chromatography coupled with ultraviolet spectroscopy and atmospheric pressure chemical ionization mass spectrometry.

PubMed

El-Hela, Atef A; Al-Amier, Hussein A; Ibrahim, Taghreed A

2010-10-08

Verbena rigida L., Verbena tenera Spreng. and Verbena venosa L. were investigated for their flavonoid content. Analysis was carried out by high-performance liquid chromatography coupled to diode array UV detection (LC-UV), using different techniques, also using post-column addition of shift reagents, afforded precise structural information about the position of the free hydroxyl groups in the flavonoid nucleus. LC-MS using atmospheric pressure chemical ionization (APCI) in the positive mode provided the molecular weight, the number of hydroxyl groups, the number of sugars and an idea about the substitution pattern of the flavonoid. On-line UV and MS data demonstrated the presence of orientin, vitexin, isovitexin, luteolin, luteolin 7-O-glucoside, apigenin 7-O-glucoside in addition to luteolin, chryseriol and apigenin aglycones in the three Verbena species with different concentrations. Quantitative determination of flavonoid content revealed the presence of 69.84 mg/g dry sample, 88.26 mg/g dry sample and 85.82 mg/g dry sample total flavonoid compounds in V. rigida L., V. tenera Spreng. and V. venosa L., respectively. The method developed for identification is useful for further chromatographic fingerprinting of plant flavonoids. Copyright © 2010 Elsevier B.V. All rights reserved.

Liquid chromatography coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry and post-column addition of metal salt solutions as a powerful tool for the metabolic profiling of Fusarium oxysporum.

PubMed

Cirigliano, Adriana M; Rodriguez, M Alejandra; Gagliano, M Laura; Bertinetti, Brenda V; Godeas, Alicia M; Cabrera, Gabriela M

2016-03-25

Fusarium oxysporum L11 is a non-pathogenic soil-borne fungal strain that yielded an extract that showed antifungal activity against phytopathogens. In this study, reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry (API-QTOF-MS) was applied for the comprehensive profiling of the metabolites from the extract. The employed sources were electrospray (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). Post-column addition of metal solutions of Ca, Cu and Zn(II) was also tested using ESI. A total of 137 compounds were identified or tentatively identified by matching their accurate mass signals, suggested molecular formulae and MS/MS analysis with previously reported data. Some compounds were isolated and identified by NMR. The extract was rich in cyclic peptides like cyclosporins, diketopiperazines and sansalvamides, most of which were new, and are reported here for the first time. The use of post-column addition of metals resulted in a useful strategy for the discrimination of compound classes since specific adducts were observed for the different compound families. This technique also allowed the screening for compounds with metal binding properties. Thus, the applied methodology is a useful choice for the metabolic profiling of extracts and also for the selection of metabolites with potential biological activities related to interactions with metal ions. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of the mycotoxin moniliformin in cultures of Fusarium subglutinans and in naturally contaminated maize by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

PubMed

Sewram, V; Nieuwoudt, T W; Marasas, W F; Shephard, G S; Ritieni, A

1999-07-02

A LC-MS method employing triethylamine as ion-pairing reagent for the determination of moniliformin in culture material and naturally contaminated maize samples is described. Mass spectrometric detection of moniliformin was accomplished following atmospheric pressure chemical ionization to yield the deprotonated molecular ion [M-H]- at m/z 97. The moniliformin response was found to be linear over the injected range 10 ng to 700 ng and a detection limit of 10 ng was attainable at a signal-to-noise (S/N) ratio of 4. Five South African strains of Fusarium subglutinans were grown on maize kernels and moniliformin extracted with an acetonitrile-water (95:5) mixture. Following sample clean up with reversed-phase (C18) solid-phase extraction cartridges, the extracts were subjected to LC-MS analysis. Triethylamine was used as an ion-pair reagent and found to improve the retention characteristics of moniliformin without any detrimental effects to the instrument. Moniliformin concentrations ranged between 130 mg/kg and 1460 mg/kg culture. Application of this method to naturally contaminated maize samples from Transkei showed that it was capable of measuring moniliformin levels down to 10 micrograms/kg in selected moldy maize cobs. This is the first report on the application of LC-MS to the analysis of moniliformin in cultures of F. subglutinans and in naturally contaminated maize.

Analysis of air-, moisture- and solvent-sensitive chemical compounds by mass spectrometry using an inert atmospheric pressure solids analysis probe.

PubMed

Mosely, Jackie A; Stokes, Peter; Parker, David; Dyer, Philip W; Messinis, Antonis M

2018-02-01

A novel method has been developed that enables chemical compounds to be transferred from an inert atmosphere glove box and into the atmospheric pressure ion source of a mass spectrometer whilst retaining a controlled chemical environment. This innovative method is simple and cheap to implement on some commercially available mass spectrometers. We have termed this approach inert atmospheric pressure solids analysis probe ( iASAP) and demonstrate the benefit of this methodology for two air-/moisture-sensitive chemical compounds whose characterisation by mass spectrometry is now possible and easily achieved. The simplicity of the design means that moving between iASAP and standard ASAP is straightforward and quick, providing a highly flexible platform with rapid sample turnaround.

CEC-atmospheric pressure ionization MS of pesticides using a surfactant-bound monolithic column.

PubMed

Gu, Congying; Shamsi, Shahab A

2010-04-01

A surfactant bound poly (11-acrylaminoundecanoic acid-ethylene dimethacrylate) monolithic column was simply prepared by in situ co-polymerization of 11-acrylaminoundecanoic acid and ethylene dimethacrylate with 1-propanol, 1,4-butanediol and water as porogens in 100 microm id fused-silica capillary in one step. This column was used in CEC-atmospheric pressure photoionization (APPI)-MS system for separation and detection of N-methylcarbamates 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 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 was further utilized to optimize the most significant parameters and predict the best sensitivity. Under optimized conditions, S/Ns 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 N-methylcarbamates in spiked apple juice sample after solid phase extraction with recoveries in the range of 65-109%.

Foundations of atmospheric pressure non-equilibrium plasmas

NASA Astrophysics Data System (ADS)

Bruggeman, Peter J.; Iza, Felipe; Brandenburg, Ronny

2017-12-01

Non-equilibrium plasmas have been intensively studied over the past century in the context of material processing, environmental remediation, ozone generation, excimer lamps and plasma display panels. Research on atmospheric pressure non-equilibrium plasmas intensified over the last two decades leading to a large variety of plasma sources that have been developed for an extended application range including chemical conversion, medicine, chemical analysis and disinfection. The fundamental understanding of these discharges is emerging but there remain a lot of unexplained phenomena in these intrinsically complex plasmas. The properties of non-equilibrium plasmas at atmospheric pressure span over a huge range of electron densities as well as heavy particle and electron temperatures. This paper provides an overview of the key underlying processes that are important for the generation and stabilization of atmospheric pressure non-equilibrium plasmas. The unique physical and chemical properties of theses discharges are also summarized.

Flow Tube Studies of Gas Phase Chemical Processes of Atmospheric Importance

NASA Technical Reports Server (NTRS)

Molina, Mario J.

1998-01-01

The objective of this project is to conduct measurements of elementary reaction rate constants and photochemical parameters for processes of importance in the atmosphere. These measurements are being carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere, using the chemical ionization mass spectrometry turbulent flow technique developed in our laboratory. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the third year. Additional details concerning the projects listed in the statement of work were described in our original proposal.

Large area atmospheric-pressure plasma jet

DOEpatents

Selwyn, Gary S.; Henins, Ivars; Babayan, Steve E.; Hicks, Robert F.

2001-01-01

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.

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

PubMed

Takino, Masahiko; Daishima, Shigeki; Nakahara, Taketoshi

2003-01-01

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. Copyright 2003 John Wiley & Sons, Ltd.

Halo-shaped flowing atmospheric pressure afterglow: a heavenly design for simplified sample introduction and improved ionization in ambient mass spectrometry.

PubMed

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

2013-08-06

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, and applied current of 30 mA at 200 V for 6 W 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 450 K) 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.

Revisiting benzene cluster cations for the chemical ionization of dimethyl sulfide and select volatile organic compounds

DOE PAGES

Kim, Michelle J.; Zoerb, Matthew C.; Campbell, Nicole R.; ...

2016-04-05

Here, benzene cluster cations were revisited as a sensitive and selective reagent ion for the chemical ionization of dimethyl sulfide (DMS) and a select group of volatile organic compounds (VOCs). Laboratory characterization was performed using both a new set of compounds (i.e., DMS, β-caryophyllene) as well as previously studied VOCs (i.e., isoprene, α-pinene). Using a field deployable chemical-ionization time-of-flight mass spectrometer (CI-ToFMS), benzene cluster cations demonstrated high sensitivity (> 1 ncps ppt −1) to DMS, isoprene, and α-pinene standards. Parallel measurements conducted using a chemical-ionization quadrupole mass spectrometer, with a much weaker electric field, demonstrated that ion–molecule reactions likely proceed through amore » combination of ligand-switching and direct charge transfer mechanisms. Laboratory tests suggest that benzene cluster cations may be suitable for the selective ionization of sesquiterpenes, where minimal fragmentation (< 25 %) was observed for the detection of β-caryophyllene, a bicyclic sesquiterpene. The in-field stability of benzene cluster cations using CI-ToFMS was examined in the marine boundary layer during the High Wind Gas Exchange Study (HiWinGS). The use of benzene cluster cation chemistry for the selective detection of DMS was validated against an atmospheric pressure ionization mass spectrometer, where measurements from the two instruments were highly correlated ( R 2 > 0.95, 10 s averages) over a wide range of sampling conditions.« less

Laser electrospray mass spectrometry of adsorbed molecules at atmospheric pressure

NASA Astrophysics Data System (ADS)

Brady, John J.; Judge, Elizabeth J.; Simon, Kuriakose; Levis, Robert J.

2010-02-01

Atmospheric pressure mass analysis of solid phase biomolecules is performed using laser electrospray mass spectrometry (LEMS). A non-resonant femtosecond duration laser pulse vaporizes native samples at atmospheric pressure for subsequent electrospray ionization and transfer into a mass spectrometer. LEMS was used to detect a complex molecule (irinotecan HCl), a complex mixture (cold medicine formulation with active ingredients: acetaminophen, dextromethorphan HBr and doxylamine succinate), and a biological building block (deoxyguanosine) deposited on steel surfaces without a matrix molecule.

Ultrapressure liquid chromatography-tandem mass spectrometry assay using atmospheric pressure photoionization (UPLC-APPI-MS/MS) for quantification of 4-methoxydiphenylmethane in pharmacokinetic evaluation.

PubMed

Farhan, Nashid; Fitzpatrick, Sean; Shim, Yun M; Paige, Mikell; Chow, Diana Shu-Lian

2016-09-05

4-Methoxydiphenylmethane (4-MDM), a selective augmenter of Leukotriene A4 Hydrolase (LTA4H), is a new anti-inflammatory compound for potential treatment of chronic obstructive pulmonary disease (COPD). Currently, there is no liquid chromatography tandem mass spectrometric (LC-MS/MS) method for the quantification of 4-MDM. A major barrier for developing the LC-MS/MS method is the inability of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) to ionize 4-MDM due to its hydrophobicity and lack of any functional group for ionization. With the advent of atmospheric pressure photoionization (APPI) technique, many hydrophobic compounds have been demonstrated to ionize by charge transfer reactions. In this study, a highly sensitive ultrapressure liquid chromatography tandem mass spectrometry assay using atmospheric pressure photoionization (UPLC-APPI-MS/MS) for the quantifications of 4-MDM in rat plasma has been developed and validated. 4-MDM was extracted from the plasma by solid phase extraction (SPE) and separated chromatographically using a reverse phase C8 column. The photoionization (PI) was achieved by introducing anisole as a dopant to promote the reaction of charge transfer. The assay with a linear range of 5 (LLOQ)-400ngmL(-1) met the regulatory requirements for accuracy, precision and stability. The validated assay was employed to quantify the plasma concentrations of 4-MDM after an oral dosing in Sprague Dawley (SD) rats. Copyright © 2016 Elsevier B.V. All rights reserved.

Ionization Efficiency in the Dayside Martian Upper Atmosphere

NASA Astrophysics Data System (ADS)

Cui, J.; Wu, X.-S.; Xu, S.-S.; Wang, X.-D.; Wellbrock, A.; Nordheim, T. A.; Cao, Y.-T.; Wang, W.-R.; Sun, W.-Q.; Wu, S.-Q.; Wei, Y.

2018-04-01

Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO2 and O ionization efficiencies tend to be constant from 160 km up to 250 km, with respective median values of 0.19 ± 0.03 and 0.27 ± 0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.

Determination of hexabromocyclododecane by flowing atmospheric pressure afterglow mass spectrometry.

PubMed

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

2014-10-01

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. Copyright © 2014 Elsevier B.V. All rights reserved.

The Protonation Site of para-Dimethylaminobenzoic Acid Using Atmospheric Pressure Ionization Methods

NASA Astrophysics Data System (ADS)

Chai, Yunfeng; Weng, Guofeng; Shen, Shanshan; Sun, Cuirong; Pan, Yuanjiang

2015-04-01

The protonation site of para-dimethylaminobenzoic acid ( p-DMABA) was investigated using atmospheric pressure ionization methods (ESI and APCI) coupled with collision-induced dissociation (CID), nuclear magnetic resonance (NMR), and computational chemistry. Theoretical calculations and NMR experiments indicate that the dimethyl amino group is the preferred site of protonation both in the gas phase and aqueous solution. Protonation of p-DMABA occurs at the nitrogen atom by ESI independent of the solvents and other operation conditions under typical thermodynamic control. However, APCI produces a mixture of the nitrogen- and carbonyl oxygen-protonated p-DMABA when aprotic organic solvents (acetonitrile, acetone, and tetrahydrofuran) are used, exhibiting evident kinetic characteristics of protonation. But using protic organic solvents (methanol, ethanol, and isopropanol) in APCI still leads to the formation of thermodynamically stable N-protonated p-DMABA. These structural assignments were based on the different CID behavior of the N- and O-protonated p-DMABA. The losses of methyl radical and water are the diagnostic fragmentations of the N- and O-protonated p-DMABA, respectively. In addition, the N-protonated p-DMABA is more stable than the O-protonated p-DMABA in CID revealed by energy resolved experiments and theoretical calculations.

Simultaneous determination of organophosphorus pesticides in fruits and vegetables using atmospheric pressure gas chromatography quadrupole-time-of-flight mass spectrometry.

PubMed

Cheng, Zhipeng; Dong, Fengshou; Xu, Jun; Liu, Xingang; Wu, Xiaohu; Chen, Zenglong; Pan, Xinglu; Gan, Jay; Zheng, Yongquan

2017-09-15

This paper describes the application of atmospheric pressure gas chromatography quadrupole-time-of-flight mass spectrometry for the simultaneous determination of organophosphorus pesticides in apple, pear, tomato, cucumber and cabbage. Soft ionization with atmospheric pressure ionization source was compared with traditional electron impact ionization (EI). The sensitivity of GC coupled to atmospheric pressure ionization (APGC) for all the analytes was enhanced by 1.0-8.2 times. The ionization modes with atmospheric pressure ionization source was studied by comparing the charge-transfer and proton-transfer conditions. The optimized QuEChERs method was used to pretreat the samples. The calibration curves were found linear from 10 to 1000μg/L, obtaining correlation coefficients higher than 0.9845. Satisfactory mean recovery values, in the range of 70.0-115.9%, and satisfactory precision, with all RSD r <19.7% and all RSD R values <19.5% at the three fortified concentration levels for all the fifteen OPPs. The results demonstrate the potential of APGC-QTOF-MS for routine quantitative analysis of organophosphorus pesticide in fruits and vegetables. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of model Titan atmospheric components using ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Kojiro, D. R.; Cohen, M. J.; Wernlund, R. F.; Stimac, R. M.; Humphry, D. E.; Takeuchi, N.

1991-01-01

The Gas Chromatograph-Ion Mobility Spectrometer (GC-IMS) was proposed as an analytical technique for the analysis of Titan's atmosphere during the Cassini Mission. The IMS is an atmospheric pressure, chemical detector that produces an identifying spectrum of each chemical species measured. When the IMS is combined with a GC as a GC-IMS, the GC is used to separate the sample into its individual components, or perhaps small groups of components. The IMS is then used to detect, quantify, and identify each sample component. Conventional IMS detection and identification of sample components depends upon a source of energetic radiation, such as beta radiation, which ionizes the atmospheric pressure host gas. This primary ionization initiates a sequence of ion-molecule reactions leading to the formation of sufficiently energetic positive or negative ions, which in turn ionize most constituents in the sample. In conventional IMS, this reaction sequence is dominated by the water cluster ion. However, many of the light hydrocarbons expected in Titan's atmosphere cannot be analyzed by IMS using this mechanism at the concentrations expected. Research at NASA Ames and PCP Inc., has demonstrated IMS analysis of expected Titan atmospheric components, including saturated aliphatic hydrocarbons, using two alternate sample ionizations mechanisms. The sensitivity of the IMS to hydrocarbons such as propane and butane was increased by several orders of magnitude. Both ultra dry (waterless) IMS sample ionization and metastable ionization were successfully used to analyze a model Titan atmospheric gas mixture.

Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets

PubMed Central

Jorabchi, Kaveh; Westphall, Michael S.; Smith, Lloyd M.

2008-01-01

We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted to those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets. PMID:18387311

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

NASA Astrophysics Data System (ADS)

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

2013-03-01

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.

Leidenfrost phenomenon-assisted thermal desorption (LPTD) and its application to open ion sources at atmospheric pressure mass spectrometry.

PubMed

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

2013-03-01

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.

Increasing Polyaromatic Hydrocarbon (PAH) Molecular Coverage during Fossil Oil Analysis by Combining Gas Chromatography and Atmospheric-Pressure Laser Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

PubMed Central

Benigni, Paolo; DeBord, J. Daniel; Thompson, Christopher J.; Gardinali, Piero; Fernandez-Lima, Francisco

2016-01-01

Thousands of chemically distinct compounds are encountered in fossil oil samples that require rapid screening and accurate identification. In the present paper, we show for the first time, the advantages of gas chromatography (GC) separation in combination with atmospheric-pressure laser ionization (APLI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the screening of polyaromatic hydrocarbons (PAHs) in fossil oils. In particular, reference standards of organics in shale oil, petroleum crude oil, and heavy sweet crude oil were characterized by GC-APLI-FT-ICR MS and APLI-FT-ICR MS. Results showed that, while APLI increases the ionization efficiency of PAHs, when compared to other ionization sources, the complexity of the fossil oils reduces the probability of ionizing lower-concentration compounds during direct infusion. When gas chromatography precedes APLI-FT-ICR MS, an increase (more than 2-fold) in the ionization efficiency and an increase in the signal-to-noise ratio of lower-concentration fractions are observed, giving better molecular coverage in the m/z 100–450 range. That is, the use of GC prior to APLI-FT-ICR MS resulted in higher molecular coverage, higher sensitivity, and the ability to separate and characterize molecular isomers, while maintaining the ultrahigh resolution and mass accuracy of the FT-ICR MS separation. PMID:27212790

Determination of 21-hydroxydeflazacort in human plasma by high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry. Application to bioequivalence study.

PubMed

Ifa, D R; Moraes, M E; Moraes, M O; Santagada, V; Caliendo, G; de Nucci, G

2000-03-01

A liquid chromatographic atmospheric pressure chemical ionization tandem mass spectrometric method is described for the determination of 21-hydroxydeflazacort in human plasma using dexamethasone 21-acetate as an internal standard. The procedure requires a single diethyl ether extraction. After evaporation of the solvent under a nitrogen flow, the analytes are reconstituted in the mobile phase, chromatographed on a C18 reversed-phase column and analyzed by mass spectrometry via a heated nebulizer interface where they are detected by multiple reaction monitoring. The method has a chromatographic run time of less than 5 min and a linear calibration curve with a range of 1-400 ng ml(-1) (r>0.999). The between-run precision, based on the relative standard deviation for replicate quality controls, was < or =5.5% (10 ng ml(-1)), 1.0% (50 ng ml(-1)) and 2.7% (200 ng ml(-1)). The between-run accuracy was +/-7.1, 3.8 and 4.8% for the above concentrations, respectively. This method was employed in a bioequivalence study of two DFZ tablet formulations (Denacen from Marjan Industria e Comercio, Brazil, as a test formulation, and Calcort from Merrell Lepetit, Brazil, as a reference formulation) in 24 healthy volunteers of both sexes who received a single 30 mg dose of each formulation. The study was conducted using an open, randomized, two-period crossover design with a 7-day washout interval. The 90% confidence interval (CI) of the individual geometric mean ratio for Denacen/Calcort was 89.8-109.5% for area under the curve AUC(0-24 h) and 80.7-98.5% for Cmax. Since both the 90% CI for AUC(0-24 h) and Cmax were included in the 80-125% interval proposed by the US Food and Drug Administration, Denacen was considered bioequivalent to Calcort according to both the rate and extent of absorption.

Atmospheric Ionizing Radiation (AIR) ER-2 Preflight Analysis

NASA Technical Reports Server (NTRS)

Tai, Hsiang; Wilson, John W.; Maiden, D. L.

1998-01-01

Atmospheric ionizing radiation (AIR) produces chemically active radicals in biological tissues that alter the cell function or result in cell death. The AIR ER-2 flight measurements will enable scientists to study the radiation risk associated with the high-altitude operation of a commercial supersonic transport. The ER-2 radiation measurement flights will follow predetermined, carefully chosen courses to provide an appropriate database matrix which will enable the evaluation of predictive modeling techniques. Explicit scientific results such as dose rate, dose equivalent rate, magnetic cutoff, neutron flux, and air ionization rate associated with those flights are predicted by using the AIR model. Through these flight experiments, we will further increase our knowledge and understanding of the AIR environment and our ability to assess the risk from the associated hazard.

Characterization of non-polar aromatic hydrocarbons in crude oil using atmospheric pressure laser ionization and Fourier transform ion cyclotron resonance mass spectrometry (APLI FT-ICR MS).

PubMed

Schrader, Wolfgang; Panda, Saroj K; Brockmann, Klaus J; Benter, Thorsten

2008-07-01

We report on the successful application of the recently introduced atmospheric pressure laser ionization (APLI) method as a novel tool for the analysis of crude oil and its components. Using Fourier transform ion cyclotron resonance mass spectrometry, unambiguous determination of key compounds in this complex matrix with unprecedented sensitivity is presented.

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

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.

Dominant Overall Chemical Reaction in a Chlorine Trifluoride Silicon Nitrogen System at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Habuka, Hitoshi; Otsuka, Toru; Qu, Wei-Feng

1999-11-01

This study evaluates the overall chemical reaction in a chlorine trifluoride silicon nitrogen system at atmospheric pressure, based on the observation of the dominant chemical species in the gas phase using a quadrupole mass spectra analyzer coupled with a horizontal cold-wall single-wafer epitaxial reactor. Chlorine trifluoride gas etches the silicon surface, producing two major products, silicon tetrafluoride gas and chlorine gas, at room temperature and 530 K. The production of chlorosilanes was not observed in this study. The results obtained in this study indicate that the dominant overall chemical reaction in a chlorine trifluoride silicon nitrogen system is 3Si + 4ClF3 →3SiF4 ↑+ 2Cl2 ↑.

Modeling the Chemical Complexity in Titan's Atmosphere

NASA Astrophysics Data System (ADS)

Vuitton, Veronique; Yelle, Roger; Klippenstein, Stephen J.; Horst, Sarah; Lavvas, Panayotis

2018-06-01

Titan's atmospheric chemistry is extremely complicated because of the multiplicity of chemical as well as physical processes involved. Chemical processes begin with the dissociation and ionization of the most abundant species, N2 and CH4, by a variety of energy sources, i.e. solar UV and X-ray photons, suprathermal electrons (< keV) and ions (H+, O+, < MeV), and cosmic rays. The energetic species produced further react to generate a plethora of gaseous molecules that will eventually become organic aerosols. Thus, molecular growth is driven by gas phase reactions involving radicals as well as positive and negative ions, all possibly in some excited electronic and vibrational state. Heterogeneous chemistry at the surface of the aerosols could also play a significant role. The efficiency and outcome of these reactions depends strongly on the physical characteristics of the atmosphere, namely pressure and temperature, ranging from 1.5×103 to 10-10 mbar and from 70 to 200 K, respectively. Moreover, the distribution of the species is affected by molecular diffusion and winds as well as escape from the top of the atmosphere and condensation in the lower stratosphere.Photochemical and microphysical models are the keystones of our understanding of Titan's atmospheric chemistry. Their main objective is to compute the distribution and nature of minor chemical species (typically containing up to 6 carbon atoms) and haze particles, respectively. Density profiles are compared to the available observations, allowing to identify important processes and to highlight those that remain to be constrained in the laboratory, experimentally and/or theoretically. We argue that positive ion chemistry is at the origin of complex organic molecules, such as benzene, ammonia and hydrogen isocyanide while neutral-neutral radiative association reactions are a significant source of alkanes. We find that negatively charged macromolecules (m/z ~100) attract the abundant positive ions, which

Ionization techniques in capillary electrophoresis-mass spectrometry: principles, design, and application.

PubMed

Hommerson, Paul; Khan, Amjad M; de Jong, Gerhardus J; Somsen, Govert W

2011-01-01

A major step forward in the development and application of capillary electrophoresis (CE) was its coupling to ESI-MS, first reported in 1987. More than two decades later, ESI has remained the principal ionization technique in CE-MS, but a number of other ionization techniques have also been implemented. In this review the state-of-the-art in the employment of soft ionization techniques for CE-MS is presented. First the fundamentals and general challenges of hyphenating conventional CE and microchip electrophoresis with MS are outlined. After elaborating on the characteristics and role of ESI, emphasis is put on alternative ionization techniques including sonic spray ionization (SSI), thermospray ionization (TSI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), matrix-assisted laser desorption ionization (MALDI) and continuous-flow fast atom bombardment (CF-FAB). The principle of each ionization technique is outlined and the experimental set-ups of the CE-MS couplings are described. The strengths and limitations of each ionization technique with respect to CE-MS are discussed and the applicability of the various systems is illustrated by a number of typical examples. Copyright © 2011 Wiley Periodicals, Inc.

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

PubMed Central

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

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

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

PubMed

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

2011-09-19

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 quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards. Prior to LC-MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500 mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d(6) and NDPA-d(14)) were added as surrogate internal standards to the samples. The optimized method was validated at two concentration levels (10 and 100 ng L(-1)) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD<20%). Limits of detection were found to be in the range of 1-8 ng L(-1). The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters. Copyright © 2011 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2014-01-01

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

Atmospheric-pressure electric discharge as an instrument of chemical activation of water solutions

NASA Astrophysics Data System (ADS)

Rybkin, V. V.; Shutov, D. A.

2017-11-01

Results of experimental studies and numerical simulations of physicochemical characteristics of plasmas generated in different types of atmospheric-pressure discharges (pulsed streamer corona, gliding electric arc, dielectric barrier discharge, glow-discharge electrolysis, diaphragmatic discharge, and dc glow discharge) used to initiate various chemical processes in water solutions are analyzed. Typical reactor designs are considered. Data on the power supply characteristics, plasma electron parameters, gas temperatures, and densities of active particles in different types of discharges excited in different gases and their dependences on the external parameters of discharges are presented. The chemical composition of active particles formed in water is described. Possible mechanisms of production and loss of plasma particles are discussed.

Atmospheric-pressure plasma activation and surface characterization on polyethylene membrane separator

NASA Astrophysics Data System (ADS)

Tseng, Yu-Chien; Li, Hsiao-Ling; Huang, Chun

2017-01-01

The surface hydrophilic activation of a polyethylene membrane separator was achieved using an atmospheric-pressure plasma jet. The surface of the atmospheric-pressure-plasma-treated membrane separator was found to be highly hydrophilic realized by adjusting the plasma power input. The variations in membrane separator chemical structure were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Chemical analysis showed newly formed carbonyl-containing groups and high surface concentrations of oxygen-containing species on the atmospheric-pressure-plasma-treated polymeric separator surface. It also showed that surface hydrophilicity primarily increased from the polar component after atmospheric-pressure plasma treatment. The surface and pore structures of the polyethylene membrane separator were examined by scanning electron microscopy, revealing a slight alteration in the pore structure. As a result of the incorporation of polar functionalities by atmospheric-pressure plasma activation, the electrolyte uptake and electrochemical impedance of the atmospheric-pressure-plasma-treated membrane separator improved. The investigational results show that the separator surface can be controlled by atmospheric-pressure plasma surface treatment to tailor the hydrophilicity and enhance the electrochemical performance of lithium ion batteries.

Mechanism of Runaway Electron Generation at Gas Pressures from a Few Atmospheres to Several Tens of Atmospheres

NASA Astrophysics Data System (ADS)

Zubarev, N. M.; Ivanov, S. N.

2018-04-01

The mechanism of runaway electron generation at gas pressures from a few atmospheres to several tens of atmospheres is proposed. According to this mechanism, the electrons pass into the runaway mode in the enhanced field zone that arises between a cathode micropoint—a source of field-emission electrons—and the region of the positive ion space charge accumulated near the cathode in the tails of the developing electron avalanches. As a result, volume gas ionization by runaway electrons begins with a time delay required for the formation of the enhanced field zone. This process determines the delay time of breakdown. The influence of the gas pressure on the formation dynamics of the space charge region is analyzed. At gas pressures of a few atmospheres, the space charge arises due to the avalanche multiplication of the very first field-emission electron, whereas at pressures of several tens of atmospheres, the space charge forms as a result of superposition of many electron avalanches with a relatively small number of charge carriers in each.

Combination of electrospray ionization, atmospheric pressure photoionization and laser desorption ionization Fourier transform ion cyclotronic resonance mass spectrometry for the investigation of complex mixtures - Application to the petroleomic analysis of bio-oils.

PubMed

Hertzog, Jasmine; Carré, Vincent; Le Brech, Yann; Mackay, Colin Logan; Dufour, Anthony; Mašek, Ondřej; Aubriet, Frédéric

2017-05-29

The comprehensive description of complex mixtures such as bio-oils is required to understand and improve the different processes involved during biological, environmental or industrial operation. In this context, we have to consider how different ionization sources can improve a non-targeted approach. Thus, the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been coupled to electrospray ionization (ESI), laser desorption ionization (LDI) and atmospheric pressure photoionization (APPI) to characterize an oak pyrolysis bio-oil. Close to 90% of the all 4500 compound formulae has been attributed to C x H y O z with similar oxygen class compound distribution. Nevertheless, their relative abundance in respect with their double bound equivalent (DBE) value has evidenced significant differences depending on the ion source used. ESI has allowed compounds with low DBE but more oxygen atoms to be ionized. APPI has demonstrated the efficient ionization of less polar compounds (high DBE values and less oxygen atoms). The LDI behavior of bio-oils has been considered intermediate in terms of DBE and oxygen amounts but it has also been demonstrated that a significant part of the features are specifically detected by this ionization method. Thus, the complementarity of three different ionization sources has been successfully demonstrated for the exhaustive characterization by petroleomic approach of a complex mixture. Copyright © 2017 Elsevier B.V. All rights reserved.

Compact cosmic ray detector for unattended atmospheric ionization monitoring

NASA Astrophysics Data System (ADS)

Aplin, K. L.; Harrison, R. G.

2010-12-01

Two vertical cosmic ray telescopes for atmospheric cosmic ray ionization event detection are compared. Counter A, designed for low power remote use, was deployed in the Welsh mountains; its event rate increased with altitude as expected from atmospheric cosmic ray absorption. Independently, Counter B's event rate was found to vary with incoming particle acceptance angle. Simultaneous co-located comparison of both telescopes exposed to atmospheric ionization showed a linear relationship between their event rates.

Enhanced performance for the analysis of prostaglandins and thromboxanes by liquid chromatography-tandem mass spectrometry using a new atmospheric pressure ionization source.

PubMed

Lubin, Arnaud; Geerinckx, Suzy; Bajic, Steve; Cabooter, Deirdre; Augustijns, Patrick; Cuyckens, Filip; Vreeken, Rob J

2016-04-01

Eicosanoids, including prostaglandins and thromboxanes are lipid mediators synthetized from polyunsaturated fatty acids. They play an important role in cell signaling and are often reported as inflammatory markers. LC-MS/MS is the technique of choice for the analysis of these compounds, often in combination with advanced sample preparation techniques. Here we report a head to head comparison between an electrospray ionization source (ESI) and a new atmospheric pressure ionization source (UniSpray). The performance of both interfaces was evaluated in various matrices such as human plasma, pig colon and mouse colon. The UniSpray source shows an increase in method sensitivity up to a factor 5. Equivalent to better linearity and repeatability on various matrices as well as an increase in signal intensity were observed in comparison to ESI. Copyright © 2016 Elsevier B.V. All rights reserved.

Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere

NASA Astrophysics Data System (ADS)

Leenaarts, J.; Carlsson, M.; Hansteen, V.; Rutten, R. J.

2007-10-01

Context: The ionization of hydrogen in the solar chromosphere and transition region does not obey LTE or instantaneous statistical equilibrium because the timescale is long compared with important hydrodynamical timescales, especially of magneto-acoustic shocks. Since the pressure, temperature, and electron density depend sensitively on hydrogen ionization, numerical simulation of the solar atmosphere requires non-equilibrium treatment of all pertinent hydrogen transitions. The same holds for any diagnostic application employing hydrogen lines. Aims: To demonstrate the importance and to quantify the effects of non-equilibrium hydrogen ionization, both on the dynamical structure of the solar atmosphere and on hydrogen line formation, in particular Hα. Methods: We implement an algorithm to compute non-equilibrium hydrogen ionization and its coupling into the MHD equations within an existing radiation MHD code, and perform a two-dimensional simulation of the solar atmosphere from the convection zone to the corona. Results: Analysis of the simulation results and comparison to a companion simulation assuming LTE shows that: a) non-equilibrium computation delivers much smaller variations of the chromospheric hydrogen ionization than for LTE. The ionization is smaller within shocks but subsequently remains high in the cool intershock phases. As a result, the chromospheric temperature variations are much larger than for LTE because in non-equilibrium, hydrogen ionization is a less effective internal energy buffer. The actual shock temperatures are therefore higher and the intershock temperatures lower. b) The chromospheric populations of the hydrogen n = 2 level, which governs the opacity of Hα, are coupled to the ion populations. They are set by the high temperature in shocks and subsequently remain high in the cool intershock phases. c) The temperature structure and the hydrogen level populations differ much between the chromosphere above photospheric magnetic elements

Method development for the determination of 24S-hydroxycholesterol in human plasma without derivatization by high-performance liquid chromatography with tandem mass spectrometry in atmospheric pressure chemical ionization mode.

PubMed

Sugimoto, Hiroshi; Kakehi, Masaaki; Satomi, Yoshinori; Kamiguchi, Hidenori; Jinno, Fumihiro

2015-10-01

We developed a highly sensitive and specific high-performance liquid chromatography with tandem mass spectrometry method with an atmospheric pressure chemical ionization interface to determine 24S-hydroxycholesterol, a major metabolite of cholesterol formed by cytochrome P450 family 46A1, in human plasma without any derivatization step. Phosphate buffered saline including 1% Tween 80 was used as the surrogate matrix for preparation of calibration curves and quality control samples. The saponification process to convert esterified 24S-hydroxycholesterol to free sterols was optimized, followed by liquid-liquid extraction using hexane. Chromatographic separation of 24S-hydroxycholesterol from other isobaric endogenous oxysterols was successfully achieved with gradient mobile phase comprised of 0.1% propionic acid and acetonitrile using L-column2 ODS (2 μm, 2.1 mm id × 150 mm). This assay was capable of determining 24S-hydroxycholesterol in human plasma (200 μL) ranging from 1 to 100 ng/mL with acceptable intra- and inter-day precision and accuracy. The potential risk of in vitro formation of 24S-hydroxycholesterol by oxidation from endogenous cholesterol in human plasma was found to be negligible. The stability of 24S-hydroxycholesterol in relevant solvents and human plasma was confirmed. This method was successfully applied to quantify the plasma concentrations of 24S-hydroxycholesterol in male and female volunteers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterizations of atmospheric pressure low temperature plasma jets and their applications

NASA Astrophysics Data System (ADS)

Karakas, Erdinc

2011-12-01

Atmospheric pressure low temperature plasma jets (APLTPJs) driven by short pulses have recently received great attention because of their potential in biomedical and environmental applications. This potential is due to their user-friendly features, such as low temperature, low risk of arcing, operation at atmospheric pressure, easy handheld operation, and low concentration of ozone generation. Recent experimental observations indicate that an ionization wave exists and propagates along the plasma jet. The plasma jet created by this ionization wave is not a continuous medium but rather consists of a bullet-like-structure known as "Plasma Bullet". More interestingly, these plasma bullets actually have a donut-shaped makeup. The nature of the plasma bullet is especially interesting because it propagates in the ambient air at supersonic velocities without any externally applied electric field. In this dissertation, experimental insights are reported regarding the physical and chemical characteristics of the APLTPJs. The dynamics of the plasma bullet are investigated by means of a high-speed ICCD camera. A plasma bullet propagation model based on the streamer theory is confirmed with adequate explanations. It is also found that a secondary discharge, ignited by the charge accumulation on the dielectric electrode surfaces at the end of the applied voltage, interrupts the plasma bullet propagation due to an opposing current along the ionization channel. The reason for this interesting phenomenon is explained in detail. The plasma bullet comes to an end when the helium mole fraction along the ionization channel, or applied voltage, or both, are less than some critical values. The presence of an inert gas channel in the surrounding air, such as helium or argon, has a critical role in plasma bullet formation and propagation. For this reason, a fluid dynamics study is employed by a commercially available simulation software, COMSOL, based on finite element method. Spatio

Atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry of friction modifier additives analyzed directly from base oil solutions.

PubMed

Widder, Lukas; Brennerb, Josef; Huttera, Herbert

2014-01-01

To develop new products and to apply measures of quality control quick and simple accessibility of additive composition in automo- tive lubrication is important. The aim of this study was to investigate the possibility of analyzing organic friction modifier additives by means of atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry [AP-MALDI-MS] from lubricant solu- tions without the use of additional separation techniques. Analyses of selected friction modifier ethoxylated tallow amines and oleic acid amide were compared using two ionization methods, positive-ion electrospray ionization (ESI) and AP-MALDI, using a LTQ Orbitrap mass spectrometer. Pure additives were characterized from solvent solutions, as well as from synthetic and mineral base oil mixtures. Detected ions of pure additive samples consisted mainly of [M + H]+, but also alkaLi metal adducts [M + Na]+ and [M + K]+ could be seen. Characterizations of blends of both friction modifiers from the base oil mixtures were carried out as well and showed significant inten- sities for several additive peaks. Thus, this work shows a method to directly analyze friction modifier additives used in the automotive industry from an oil blend via the use of AP-MALDI without any further separation steps. The method presented will further simplify the acquisition of data on lubricant composition and additives. Furthermore, it allows the perspective of analyzing additive reaction products directly from formulated oil blends.

Simultaneous determination of eighteen nitro-polyaromatic hydrocarbons in PM2.5 by atmospheric pressure gas chromatography-tandem mass spectrometry.

PubMed

Zhang, Yanhao; Li, Ruijin; Fang, Jing; Wang, Chen; Cai, Zongwei

2018-05-01

A new atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS) was developed to simultaneously separate, identify and quantify 18 nitro-polyaromatic hydrocarbons (NPAHs) in air fine particulate matter (PM 2.5 ). Compared with traditional negative chemical ionization (NCI) or electron impact ionization (EI)-MS/MS methods, APGC-MS/MS equipped with an atmospheric pressure chemical ionization (APCI) source provided better sensitivity and selectivity for NPAHs analysis in PM 2.5 .18 NPAHs were completely separated, and satisfactory linear response (R 2  > 0.99), low instrumental detection limits (0.20-2.18 pg mL -1 ) and method detection limits (0.001-0.015 pg m -3 ) were achieved. Due to the reliable performance of the instrument, only minimal sample pretreatment is needed. It ensured the satisfactory method recovery (70%-120%) and qualified repeatability (RSD: 1.1%-17.2%), which met the requirement of trace analysis of NAPHs in the real environmental PM 2.5 . Using the developed method, the actual PM 2.5 samples collected from Taiyuan, China in both summer and winter were analyzed, and 17 NPAHs but 2-nitrofluorene were detected and quantified. According to the obtained NAPH concentration results, the generation mechanism of NPAHs in PM 2.5 and the effects on NPAHs formation caused by some ambient air pollutants were preliminarily discussed: secondary photochemical reaction might be the dominant source of NPAHs in PM 2.5 collected from Taiyuan in both summer and winter; ambient air pollutants (NO 2 , SO 2 , CO) had more contribution on the NPAHs secondary formation of PM 2.5 in winter. Copyright © 2018 Elsevier Ltd. All rights reserved.

Determination of aldehydes and ketones using derivatization with 2,4-dinitrophenylhydrazine and liquid chromatography-atmospheric pressure photoionization-mass spectrometry.

PubMed

van Leeuwen, Suze M; Hendriksen, Laurens; Karst, Uwe

2004-11-26

Atmospheric pressure photoionization-mass spectrometry (APPI-MS) is used for the analysis of aldehydes and ketones after derivatization with 2,4-dinitrophenylhydrazine (DNPH) and liquid chromatographic separation. In the negative ion mode, the [M - H]- pseudomolecular ions are most abundant for the carbonyls. Compared with the established atmospheric pressure chemical ionization (APCI)-MS, limits of detection are typically lower using similar conditions. Automobile exhaust and cigarette exhaust samples were analyzed with APPI-MS and APCI-MS in combination with an ion trap mass analyzer. Due to improved limits of detection, more of the less abundant long-chain carbonyls are detected with APPI-MS in real samples. While 2,4-dinitrophenylazide, a known reaction product of DNPH with nitrogen dioxide, is detected in APCI-MS due to dissociative electron capture, it is not observed at all in APPI-MS.

Atmospheric-Pressure Chemical Vapor Deposition of Iron Pyrite Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berry, Nicholas; Cheng, Ming; Perkins, Craig L.

2012-10-23

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 bymore » 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.« less

Atmospheric-pressure plasma decontamination/sterilization chamber

DOEpatents

Herrmann, Hans W.; Selwyn, Gary S.

2001-01-01

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.

Is ionizing radiation regulated more stringently than chemical carcinogens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Travis, C.C.; Pack, S.R.; Hattemer-Frey, H.A.

1989-04-01

It is widely believed that United States government agencies regulate exposure to ionizing radiation more stringently than exposure to chemical carcinogens. It is difficult to verify this perception, however, because chemical carcinogens and ionizing radiation are regulated using vastly different strategies. Chemical carcinogens are generally regulated individually. Regulators consider the risk of exposure to one chemical rather than the cumulative radiation exposure from all sources. Moreover, standards for chemical carcinogens are generally set in terms of quantities released or resultant environmental concentrations, while standards for ionizing radiation are set in terms of dose to the human body. Since chemicals andmore » ionizing radiation cannot be compared on the basis of equal dose to the exposed individual, standards regulating chemicals and ionizing radiation cannot be compared directly. It is feasible, however, to compare the two sets of standards on the basis of equal risk to the exposed individual, assuming that standards for chemicals and ionizing radiation are equivalent if estimated risk levels are equitable. This paper compares risk levels associated with current standards for ionizing radiation and chemical carcinogens. The authors do not attempt to determine whether either type of risk is regulated too stringently or not stringently enough but endeavor only to ascertain if ionizing radiation is actually regulated more strictly than chemical carcinogens.« less

Carbon Nanotube Fiber Ionization Mass Spectrometry: A Fundamental Study of a Multi-Walled Carbon Nanotube Functionalized Corona Discharge Pin for Polycyclic Aromatic Hydrocarbons Analysis.

PubMed

Nahan, Keaton S; Alvarez, Noe; Shanov, Vesselin; Vonderheide, Anne

2017-11-01

Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R 2 ) of three target PAHs with phenanthrene internal standard. Graphical Abstract ᅟ.

Carbon Nanotube Fiber Ionization Mass Spectrometry: A Fundamental Study of a Multi-Walled Carbon Nanotube Functionalized Corona Discharge Pin for Polycyclic Aromatic Hydrocarbons Analysis

NASA Astrophysics Data System (ADS)

Nahan, Keaton S.; Alvarez, Noe; Shanov, Vesselin; Vonderheide, Anne

2017-09-01

Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R2) of three target PAHs with phenanthrene internal standard. [Figure not available: see fulltext.

Improving N-Glycan Coverage using HPLC-MS with Electrospray Ionization at Subambient Pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marginean, Ioan; Kronewitter, Scott R.; Moore, Ronald J.

Human serum glycan profiling with mass spectrometry (MS) has been employed to study several disease conditions and is demonstrating promise for e.g. clinical biomarker discovery. However, the poor glycan ionization efficiency and the large dynamic range of glycan concentrations in human sera hinder comprehensive profiling. In particular, large glycans are problematic because they are present at low concentrations and prone to fragmentation. Here we show that the sub-ambient pressure ionization with nanoelectrospray (SPIN)-MS can expand the serum glycome profile when compared with the conventional atmospheric pressure electrospray ionization (ESI)-MS with a heated capillary inlet. Notably, the ions generated by themore » SPIN interface were observed at higher charge states for 50% of the annotated glycans. Out of a total of 130 detected glycans, 34 were only detected with the SPIN-MS, resulting in improved coverage of glycan families as well as of glycans with larger numbers of labile monosaccharides.« less

Improving liquid chromatography-mass spectrometry sensitivity using a subambient pressure ionization with nanoelectrospray (SPIN) interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Keqi; Page, Jason S.; Marginean, Ioan

2011-04-22

In this work the Subambient Pressure Ionization with Nanoelectrospray (SPIN) ion source and interface which operates at ~15-30 Torr is demonstrated to be compatible with gradient reversed-phase liquid chromatography-MS applications, exemplified here with the analysis of complex samples (a protein tryptic digest and a whole cell lysate). A low liquid chromatographic flow rate (100-400 nL/min) allowed stable electrospray to be established while avoiding electrical breakdown. Efforts to increase the operating pressure of the SPIN source relative to previously reported designs prevented solvent freezing and enhanced charged cluster/droplet desolvation. A 5-12-fold improvement in sensitivity relative to a conventional atmospheric pressure nanoelectrospraymore » ionization (ESI) source was obtained for detected peptides.« less

Recent developments in atmospheric pressure photoionization-mass spectrometry.

PubMed

Kauppila, Tiina J; Syage, Jack A; Benter, Thorsten

2017-05-01

Recent developments in atmospheric pressure photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-mass spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient mass spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017. © 2015 Wiley Periodicals, Inc.

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

DOEpatents

Mowry, Curtis Dale; Thornberg, Steven Michael

1999-01-01

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.

Laboratory Studies of Heterogeneous Chemical Processes of Atmospheric Importance

NASA Technical Reports Server (NTRS)

Molina, Mario J.

2004-01-01

The objective of this study is to conduct measurements of chemical kinetics parameters for heterogeneous reactions of importance in the stratosphere and the troposphere. It involves the elucidation of the mechanism of the interaction of HCl vapor with ice surfaces, which is the first step in the heterogeneous chlorine activation processes, as well as the investigation of the atmospheric oxidation mechanism of soot particles emitted by biomass and fossil fuels. The techniques being employed include turbulent flow-chemical ionization mass spectrometry and optical ellipsometry, among others.

Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events

NASA Astrophysics Data System (ADS)

Wolff, E.; Burrows, J.; Kallenrode, M.; von Koenig, M.; Kuenzi, K. F.; Quack, M.

2001-12-01

Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar electrons. Results are presented for well-known solar events, such as July 14, 2000, and are extrapolated to extremely large events, such as Carrington's white light flare in 1859, which from ice cores has been identified ass the largest impulsive NO3 event in the interval 1561 -- 1994 (McCracken et al., 2001).

Ionization Capabilities of Hydronium Ions and High Electric Fields Produced by Atmospheric Pressure Corona Discharge.

PubMed

Sato, Natsuhiko; Sekimoto, Kanako; Takayama, Mitsuo

2016-01-01

Atmospheric pressure corona discharge (APCD) was applied to the ionization of volatile organic compounds. The mass spectra of analytes having aromatic, phenolic, anilinic, basic and aliphatic in nature were obtained by using vapor supply and liquid smear supply methods. The vapor supply method mainly gave protonated analytes [A+H] + caused by proton transfer from hydronium ion H 3 O + , except for benzene, toluene and n -hexane that have lower proton affinity. The use of the liquid smear supply method resulted in the formation of molecular ion A ·+ and/or dehydride analyte [A-H] + , according to the nature of analytes used. The formation of A ·+ without fragment ions could be explained by the electron tunneling via high electric fields 10 8  V/m at the tip of the corona needle. The dehydride analytes [A-H] + observed in the mass spectra of n -hexane, di- and tributylamines may be explained by the hydride abstraction from the alkyl chains by the hydronium ion. The hydronium ion can play the two-roles for analytes, i.e. , the proton donor to form [A+H] + and the hydride acceptor to form [A-H] + .

Ionization Capabilities of Hydronium Ions and High Electric Fields Produced by Atmospheric Pressure Corona Discharge

PubMed Central

Sato, Natsuhiko; Sekimoto, Kanako; Takayama, Mitsuo

2016-01-01

Atmospheric pressure corona discharge (APCD) was applied to the ionization of volatile organic compounds. The mass spectra of analytes having aromatic, phenolic, anilinic, basic and aliphatic in nature were obtained by using vapor supply and liquid smear supply methods. The vapor supply method mainly gave protonated analytes [A+H]+ caused by proton transfer from hydronium ion H3O+, except for benzene, toluene and n-hexane that have lower proton affinity. The use of the liquid smear supply method resulted in the formation of molecular ion A·+ and/or dehydride analyte [A−H]+, according to the nature of analytes used. The formation of A·+ without fragment ions could be explained by the electron tunneling via high electric fields 108 V/m at the tip of the corona needle. The dehydride analytes [A−H]+ observed in the mass spectra of n-hexane, di- and tributylamines may be explained by the hydride abstraction from the alkyl chains by the hydronium ion. The hydronium ion can play the two-roles for analytes, i.e., the proton donor to form [A+H]+ and the hydride acceptor to form [A−H]+. PMID:28616372

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

PubMed

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

2012-01-28

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 CH 4 partial pressure, while the density of domains decreases with increasing growth temperature and is independent of the CH 4 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 cm 2 V -1 s -1 at room temperature.

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)

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

2012-09-01

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.

Non-thermal atmospheric-pressure plasma possible application in wound healing.

PubMed

Haertel, Beate; von Woedtke, Thomas; Weltmann, Klaus-Dieter; Lindequist, Ulrike

2014-11-01

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out.

Non-Thermal Atmospheric-Pressure Plasma Possible Application in Wound Healing

PubMed Central

Haertel, Beate; von Woedtke, Thomas; Weltmann, Klaus-Dieter; Lindequist, Ulrike

2014-01-01

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out. PMID:25489414

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

PubMed

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

2014-05-01

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.

Influence of Dust Loading on Atmospheric Ionizing Radiation on Mars

NASA Technical Reports Server (NTRS)

Norman, Ryan B.; Gronoff, Guillaume; Mertens, Christopher J.

2014-01-01

Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory's Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O'Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays' influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

Atmospheric-pressure ionization and fragmentation of peptides by solution-cathode glow discharge† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02032a Click here for additional data file.

PubMed Central

Schwartz, Andrew J.; Walton, Courtney L.; Williams, Kelsey L.; Hieftje, Gary M.

2016-01-01

Modern “-omics” (e.g., proteomics, glycomics, metabolomics, etc.) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (e.g., 70 mA), electrospray-like spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma. PMID:28451101

Modeling chemical vapor deposition of silicon dioxide in microreactors at atmospheric pressure

NASA Astrophysics Data System (ADS)

Konakov, S. A.; Krzhizhanovskaya, V. V.

2015-01-01

We developed a multiphysics mathematical model for simulation of silicon dioxide Chemical Vapor Deposition (CVD) from tetraethyl orthosilicate (TEOS) and oxygen mixture in a microreactor at atmospheric pressure. Microfluidics is a promising technology with numerous applications in chemical synthesis due to its high heat and mass transfer efficiency and well-controlled flow parameters. Experimental studies of CVD microreactor technology are slow and expensive. Analytical solution of the governing equations is impossible due to the complexity of intertwined non-linear physical and chemical processes. Computer simulation is the most effective tool for design and optimization of microreactors. Our computational fluid dynamics model employs mass, momentum and energy balance equations for a laminar transient flow of a chemically reacting gas mixture at low Reynolds number. Simulation results show the influence of microreactor configuration and process parameters on SiO2 deposition rate and uniformity. We simulated three microreactors with the central channel diameter of 5, 10, 20 micrometers, varying gas flow rate in the range of 5-100 microliters per hour and temperature in the range of 300-800 °C. For each microchannel diameter we found an optimal set of process parameters providing the best quality of deposited material. The model will be used for optimization of the microreactor configuration and technological parameters to facilitate the experimental stage of this research.

Destruction of chemical warfare surrogates using a portable atmospheric pressure plasma jet

NASA Astrophysics Data System (ADS)

Škoro, Nikola; Puač, Nevena; Živković, Suzana; Krstić-Milošević, Dijana; Cvelbar, Uroš; Malović, Gordana; Petrović, Zoran Lj.

2018-01-01

Today's reality is connected with mitigation of threats from the new chemical and biological warfare agents. A novel investigation of cold plasmas in contact with liquids presented in this paper demonstrated that the chemically reactive environment produced by atmospheric pressure plasma jet (APPJ) is potentially capable of rapid destruction of chemical warfare agents in a broad spectrum. The decontamination of three different chemical warfare agent surrogates dissolved in liquid is investigated by using an easily transportable APPJ. The jet is powered by a kHz signal source connected to a low-voltage DC source and with He as working gas. The detailed investigation of electrical properties is performed for various plasmas at different distances from the sample. The measurements of plasma properties in situ are supported by the optical spectrometry measurements, whereas the high performance liquid chromatography measurements before and after the treatment of aqueous solutions of Malathion, Fenitrothion and Dimethyl Methylphosphonate. These solutions are used to evaluate destruction and its efficiency for specific neural agent simulants. The particular removal rates are found to be from 56% up to 96% during 10 min treatment. The data obtained provide basis to evaluate APPJ's efficiency at different operating conditions. The presented results are promising and could be improved with different operating conditions and optimization of the decontamination process.

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

PubMed

DeLacy, Brendan G; Bandy, Alan R

2008-01-01

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.

Low latitude middle atmosphere ionization studies

NASA Technical Reports Server (NTRS)

Bassi, J. P.

1976-01-01

Low latitude middle atmosphere ionization was studied with data obtained from three blunt conductivity probes and one Gerdien condenser. An investigation was conducted into the effects of various ionization sources in the 40 to 65 Km altitude range. An observed enhancement of positive ion conductivity taking place during the night can be explained by an atmsopheric effect, with cosmic rays being the only source of ionization only if the ion-ion recombination coefficient (alpha sub i) is small(10 to the -7 power cu cm/s) and varies greatly with altitude. More generally accepted values of alpha sub i ( approximately equal to 3x10 to the -7 power cu cm/s) require an additional source of ionization peaking at about 65 Km, and corresponding approximately to the integrated effect of an X-ray flux measured on a rocket flown in conjunction with the ionization measurements. The reasonable assumption of an alpha sub i which does not vary with altitude in the 50-70 Km range implies an even greater value alpha sub i and a more intense and harder X-ray spectrum.

Atmospheric Ionizing Radiation and Human Exposure

NASA Technical Reports Server (NTRS)

Wilson, John W.; Mertens, Christopher J.; Goldhagen, Paul; Friedberg, W.; DeAngelis, G.; Clem, J. M.; Copeland, K.; Bidasaria, H. B.

2005-01-01

Atmospheric ionizing radiation is of interest, apart from its main concern of aircraft exposures, because it is a principal source of human exposure to radiations with high linear energy transfer (LET). The ionizing radiations of the lower atmosphere near the Earth s surface tend to be dominated by the terrestrial radioisotopes. especially along the coastal plain and interior low lands, and have only minor contributions from neutrons (11 percent). The world average is substantially larger but the high altitude cities especially have substantial contributions from neutrons (25 to 45 percent). Understanding the world distribution of neutron exposures requires an improved understanding of the latitudinal, longitudinal, altitude and spectral distribution that depends on local terrain and time. These issues are being investigated in a combined experimental and theoretical program. This paper will give an overview of human exposures and describe the development of improved environmental models.

Atmospheric Ionizing Radiation and Human Exposure

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Goldhagen, P.; Friedberg, W.; DeAngelis, G.; Clem, J. M.; Copeland, K.; Bidasaria, H. B.

2004-01-01

Atmospheric ionizing radiation is of interest, apart from its main concern of aircraft exposures, because it is a principal source of human exposure to radiations with high linear energy transfer (LET). The ionizing radiations of the lower atmosphere near the Earth s surface tend to be dominated by the terrestrial radioisotopes especially along the coastal plain and interior low lands and have only minor contributions from neutrons (11 percent). The world average is substantially larger but the high altitude cities especially have substantial contributions from neutrons (25 to 45 percent). Understanding the world distribution of neutron exposures requires an improved understanding of the latitudinal, longitudinal, altitude and spectral distribution that depends on local terrain and time. These issues are being investigated in a combined experimental and theoretical program. This paper will give an overview of human exposures and describe the development of improved environmental models.

A high pressure hollow cathode ionization source for in-situ detection of organic molecules on Mars

NASA Technical Reports Server (NTRS)

Beegle, Luther W.; Kanik, Isik

2001-01-01

We have designed, constructed and characterized a new high-pressure (1-5 Torr) hollow cathode discharge source (HCDSj that can be utilized as an ionizer in a wide variety of mass analyzers. It is able to function under ambient Martian atmospheric conditions without modification.

Fast transient analysis and first-stage collision-induced dissociation with the flowing atmospheric-pressure afterglow ionization source to improve analyte detection and identification.

PubMed

Shelley, Jacob T; Hieftje, Gary M

2010-04-01

The recent development of ambient desorption/ionization mass spectrometry (ADI-MS) has enabled fast, simple analysis of many different sample types. The ADI-MS sources have numerous advantages, including little or no required sample pre-treatment, simple mass spectra, and direct analysis of solids and liquids. However, problems of competitive ionization and limited fragmentation require sample-constituent separation, high mass accuracy, and/or tandem mass spectrometry (MS/MS) to detect, identify, and quantify unknown analytes. To maintain the inherent high throughput of ADI-MS, it is essential for the ion source/mass analyzer combination to measure fast transient signals and provide structural information. In the current study, the flowing atmospheric-pressure afterglow (FAPA) ionization source is coupled with a time-of-flight mass spectrometer (TOF-MS) to analyze fast transient signals (<500 ms FWHM). It was found that gas chromatography (GC) coupled with the FAPA source resulted in a reproducible (<5% RSD) and sensitive (detection limits of <6 fmol for a mixture of herbicides) system with analysis times of ca. 5 min. Introducing analytes to the FAPA in a transient was also shown to significantly reduce matrix effects caused by competitive ionization by minimizing the number and amount of constituents introduced into the ionization source. Additionally, MS/MS with FAPA-TOF-MS, enabling analyte identification, was performed via first-stage collision-induced dissociation (CID). Lastly, molecular and structural information was obtained across a fast transient peak by modulating the conditions that caused the first-stage CID.

Porous tungsten prepared by atmospheric-pressure chemical vapor deposition with WF6 and its characterization

NASA Astrophysics Data System (ADS)

Li, Ying; Yu, Xiaodong; Tan, Chengwen; Wang, Fuchi; Ma, Honglei; Yue, Jintao

2017-05-01

Porous tungsten (W) is used in aeronautic and aerospace engineering, power electronics field and metallurgical industry. In this study, porous W with 98wt% W was prepared on a carbon foam substrate by atmospheric-pressure chemical vapor deposition (CVD) with tungsten fluoride (WF6) as the precursor. The porous W with 78.1346% porosity displayed a pure α-W phase and the uniform surface. The mode pore diameter of porous W is 208.0 µm. In a compression test, the fracture strength of porous W is 20.3 MPa.

Real-time analysis of ambient organic aerosols using aerosol flowing atmospheric-pressure afterglow mass spectrometry (AeroFAPA-MS)

NASA Astrophysics Data System (ADS)

Brüggemann, Martin; Karu, Einar; Stelzer, Torsten; Hoffmann, Thorsten

2015-04-01

Organic aerosol accounts for a major fraction of atmospheric aerosols and has implications on the earth's climate and human health. However, due to the chemical complexity its measurement remains a major challenge for analytical instrumentation.1 Here, we present the development, characterization and application of a new soft ionization technique that allows mass spectrometric real-time detection of organic compounds in ambient aerosols. The aerosol flowing atmospheric-pressure afterglow (AeroFAPA) ion source utilizes a helium glow discharge plasma to produce excited helium species and primary reagent ions. Ionization of the analytes occurs in the afterglow region after thermal desorption and results mainly in intact molecular ions, facilitating the interpretation of the acquired mass spectra. In the past, similar approaches were used to detect pesticides, explosives or illicit drugs on a variety of surfaces.2,3 In contrast, the AeroFAPA source operates 'online' and allows the detection of organic compounds in aerosols without a prior precipitation or sampling step. To our knowledge, this is the first application of an atmospheric-pressure glow discharge ionization technique to ambient aerosol samples. We illustrate that changes in aerosol composition and concentration are detected on the time scale of seconds and in the ng-m-3 range. Additionally, the successful application of AeroFAPA-MS during a field study in a mixed forest region in Central Europe is presented. Several oxidation products of monoterpenes were clearly identified using the possibility to perform tandem MS experiments. The acquired data are in agreement with previous studies and demonstrate that AeroFAPA-MS is a suitable tool for organic aerosol analysis. Furthermore, these results reveal the potential of this technique to enable new insights into aerosol formation, growth and transformation in the atmosphere. References: 1) IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The

Simultaneous extraction of acetylsalicylic acid and salicylic acid from human plasma and simultaneous estimation by liquid chromatography and atmospheric pressure chemical ionization/tandem mass spectrometry detection. Application to a pharmacokinetic study.

PubMed

Nirogi, Ramakrishna; Kandikere, Vishwottam; Mudigonda, Koteshwara; Ajjala, Devender; Suraneni, Ramakrishna; Thoddi, Parthasarathi

2011-01-01

A simple analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in atmospheric chemical ionization mode (APCI) for the simultaneous estimation of acetylsalicylic acid (ASA, CAS 50-78-2) and its active metabolite salicylic acid (SA, CAS 69-72-7) in human plasma has been developed and validated. ASA and SA were analyzed simultaneously despite differences in plasma concentration ranges of ASA and SA after oral administration of ASA. In spite of having different chemical, ionization and chromatographic properties, ASA and SA were extracted simultaneously from the plasma sample using acetonitrile protein precipitation followed by liquid-liquid extraction. The analytes were separated on a reversed phase column with rapid gradient program using mobile phase consisting of ammonium acetate buffer and methanol. The structural analogue diclofenac was used as an internal standard. The multiple reaction monitoring (MRM) transitions m/z 179 --> 137 for ASA, m/z 137 --> 65 for SA and m/z 294 --> 250 for IS were used. The assay exhibited a linear dynamic range of 0.02-10 microg/mL for ASA and 0.1-50 microg/mL for SA. The between-batch precision (%CV) ranged from 2.1 to 7.9% for ASA and from 0.2 to 5.2% for SA. The between-batch accuracy ranged from 95.4 to 96.7% for ASA and from 94.6 to 111.3% for SA. The validated method was successfully applied for the evaluation of pharmacokinetics of ASA after single oral administration of 650 mg test formulation versus two 325 mg reference formulations of ASA in human subjects.

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

NASA Astrophysics Data System (ADS)

Ishikawa, Kenji; Hori, Masaru

2014-08-01

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.

The composition of liquid atmospheric pressure matrix-assisted laser desorption/ionization matrices and its effect on ionization in mass spectrometry.

PubMed

Ryumin, Pavel; Cramer, Rainer

2018-07-12

New liquid atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) matrices that produce predominantly multiply charged ions have been developed and evaluated with respect to their performance for peptide and protein analysis by mass spectrometry (MS). Both the chromophore and the viscous support liquid in these matrices were optimized for highest MS signal intensity, S/N values and maximum charge state. The best performance in both protein and peptide analysis was achieved employing light diols as matrix support liquids (e.g. ethylene glycol and propylene glycol). Investigating the influence of the chromophore, it was found that 2,5-dihydroxybenzoic acid resulted in a higher analyte ion signal intensity for the analysis of small peptides; however, larger molecules (>17 kDa) were undetectable. For larger molecules, a sample preparation based on α-cyano-4-hydroxycinnammic acid as the chromophore was developed and multiply protonated analytes with charge states of more than 50 were detected. Thus, for the first time it was possible to detect with MALDI MS proteins as large as ∼80 kDa with a high number of charge states, i.e. m/z values below 2000. Systematic investigations of various matrix support liquids have revealed a linear dependency between laser threshold energy and surface tension of the liquid MALDI sample. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparative study on ambient ionization methods for direct analysis of navel orange tissues by mass spectrometry.

PubMed

Zhang, Hua; Bibi, Aisha; Lu, Haiyan; Han, Jing; Chen, Huanwen

2017-08-01

It is of sustainable interest to improve the sensitivity and selectivity of the ionization process, especially for direct analysis of complex samples without matrix separation. Herein, four ambient ionization methods including desorption atmospheric pressure chemical ionization (DAPCI), heat-assisted desorption atmospheric pressure chemical ionization (heat-assisted DAPCI), microwave plasma torch (MPT) and internal extractive electrospray ionization (iEESI) were employed for comparative analysis of the navel orange tissue samples by mass spectrometry. The volatile organic compounds (e.g. ethanol, vanillin, leaf alcohol and jasmine lactone) were successfully detected by non-heat-assisted DAPCI-MS, while semi-volatile organic compounds (e.g. 1-nonanol and ethyl nonanoate) together with low abundance of non-volatile organic compounds (e.g. sinensetin and nobiletin) were obtained by heat-assisted DAPCI-MS. Typical nonvolatile organic compounds [e.g. 5-(hydroxymethyl)furfural and glucosan] were sensitively detected with MPT-MS. Compounds of high polarity (e.g. amino acids, alkaloids and sugars) were easily profiled with iEESI-MS. Our data showed that more analytes could be detected when more energy was delivered for the desorption ionization purpose; however, heat-sensitive analytes would not be detected once the energy input exceeded the dissociation barriers of the analytes. For the later cases, soft ionization methods such as iEESI were recommended to sensitively profile the bioanalytes of high polarity. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Demonstration of Laser Induced Acoustic Desoprtion - Chemical Ionization Mass Spectrometry (LIAD-CIMS) for Fragment-Free Measurements of Organic Aerosol Molecular Composition

NASA Astrophysics Data System (ADS)

Browne, E. C.; Abdelhamid, A.; Berry, J.; Alton, M.

2017-12-01

Organic compounds account for a significant portion of fine atmospheric aerosol. Current analytical techniques have provided insights on organic aerosol (OA) sources, composition, and chemical modification pathways. Despite this knowledge, large uncertainties remain and hinder our understanding of aerosol impacts on climate, air quality, and health. Measuring OA composition is challenging due to the complex chemical composition and the wide variation in the properties (e.g., vapor pressure, solubility, reactivity) of organic compounds. In many current measurement techniques, the ability to chemically resolve and quantify OA components is complicated by molecular decomposition, matrix effects, and/or preferential ionization mechanisms. Here, we utilize a novel desorption technique, laser induced acoustic desorption (LIAD), that generates fragment-free, neutral gas-phase molecules. We couple LIAD with a high-resolution chemical ionization mass spectrometer (CIMS) to provide molecular composition OA measurements. Through a series of laboratory experiments, we demonstrate the ability of this technique to measure large, thermally labile species without fragmentation/thermal decomposition. We discuss quantification and detection limits of this technique. We compare LIAD-CIMS measurements with thermal desorption-CIMS measurements using off-line measurements of ambient aerosol collected in Boulder, CO. Lastly, we discuss future development for on-line measurements of OA using LIAD-CIMS.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babij, Michał; Kowalski, Zbigniew W., E-mail: zbigniew.w.kowalski@pwr.wroc.pl; Nitsch, Karol

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 themore » 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.« less

Identification and quantification of astaxanthin esters in shrimp (Pandalus borealis) and in a microalga (Haematococcus pluvialis) by liquid chromatography-mass spectrometry using negative ion atmospheric pressure chemical ionization.

PubMed

Breithaupt, Dietmar E

2004-06-16

Negative ion liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [negative ion LC-(APCI)MS] was used for the identification of astaxanthin esters in extracts of commercial shrimp (Pandalus borealis) and dried microalga (Haematococcus pluvialis) samples. A cleanup step using a normal phase solid phase extraction (SPE) cartridge was applied prior to analysis. Recovery experiments with astaxanthin oleate as model compound proved the applicability of this step (98.5 +/- 7.6%; n = 4). The assignment of astaxanthin esters in negative ion LC-(APCI)MS was based on the detection of the molecular ion (M*-) and the formation of characteristic fragment ions, resulting from the loss of one or two fatty acids. Quantification of individual astaxanthin esters was performed using an astaxanthin calibration curve, which was found to be linear over the required range (1-51 micromol/L; r2 = 0.9996). Detection limits, based on the intensity of M*-, a signal-to-noise ratio of 3:1, and an injection volume of 20 microL, were estimated to be 0.05 microg/mL (free astaxanthin), 0.28 microg/mL (astaxanthin-C16:0), and 0.78 microg/mL (astaxanthin-C16:0/C16:0), respectively. This LC-(APCI)MS method allows for the first time the characterization of native astaxanthin esters in P. borealis and H. pluvialis without using time-consuming isolation steps with subsequent gas chromatographic analyses of fatty acid methyl esters. The results suggest that the pattern of astaxanthin-bound polyunsaturated fatty acids of P. borealis does not reflect the respective fatty acid pattern found in triacylglycerides. Application of the presented LC-(APCI)MS technique in common astaxanthin ester analysis will forestall erroneous xanthophyll ester assignment in natural sources.

Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

NASA Astrophysics Data System (ADS)

Hemawan, Kadek W.; Gou, Huiyang; Hemley, Russell J.

2015-11-01

Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ, and Hα were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm-1 peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit "coral" and "cauliflower-like" morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

Carbon nanotubes synthesized by Ni-assisted atmospheric pressure thermal chemical vapor deposition

NASA Astrophysics Data System (ADS)

Choi, G. S.; Cho, Y. S.; Hong, S. Y.; Park, J. B.; Son, K. H.; Kim, D. J.

2002-03-01

A detailed systematic study on the growth morphology of carbon nanotubes (CNTs) on Si in atmospheric pressure thermal chemical vapor deposition was undertaken. The role of NH3 for vertical alignment of CNTs was investigated. The direct cause for the alignment was a dense distribution of the catalytic metal particles, but that the particles are maintained catalytically active under amorphous carbon deposits was established by NH3. It allows a dense nucleation of the CNTs, and consequently, assists vertical alignment through entanglement and mechanical leaning among the tubes. The CNTs grew in a base growth mode. Since Ni is consumed both by silicide reaction and by capture into the growing tube, the growth stops when Ni is totally depleted. It occurs earlier for smaller particles, and thus a long time of growth results in a thin bottom with poor adhesion.

Atmospheric Photochemistry

NASA Technical Reports Server (NTRS)

Massey, Harrie; Potter, A. E.

1961-01-01

The upper atmosphere offers a vast photochemical laboratory free from solid surfaces, so all reactions take place in the gaseous phase. At 30 km altitude the pressure has fallen to about one-hundredth of that at ground level, and we shall, rather arbitrarily, regard the upper atmosphere as beginning at that height. By a little less than 100 km the pressure has fallen to 10(exp -3) mm Hg and is decreasing by a power of ten for every 15 km increase in altitude. Essentially we are concerned then with the photochemistry of a nitrogen-oxygen mixture under low-pressure conditions in which photo-ionization, as well as photodissociation, plays an important part. Account must also be taken of the presence of rare constituents, such as water vapour and its decomposition products, including particularly hydroxyl, oxides of carbon, methane and, strangely enough, sodium, lithium and calcium. Many curious and unfamiliar reactions occur in the upper atmosphere. Some of them are luminescent, causing the atmosphere to emit a dim light called the airglow. Others, between gaseous ions and neutral molecules, are almost a complete mystery at this time. Similar interesting phenomena must occur in other planetary atmospheres, and they might be predicted if sufficient chemical information were available.

Apparatus and method for enhanced chemical processing in high pressure and atmospheric plasmas produced by high frequency electromagnetic waves

DOEpatents

Efthimion, Philip C.; Helfritch, Dennis J.

1989-11-28

An apparatus and method for creating high temperature plasmas for enhanced chemical processing of gaseous fluids, toxic chemicals, and the like, at a wide range of pressures, especially at atmospheric and high pressures includes an electro-magnetic resonator cavity, preferably a reentrant cavity, and a wave guiding structure which connects an electro-magnetic source to the cavity. The cavity includes an intake port and an exhaust port, each having apertures in the conductive walls of the cavity sufficient for the intake of the gaseous fluids and for the discharge of the processed gaseous fluids. The apertures are sufficiently small to prevent the leakage of the electro-magnetic radiation from the cavity. Gaseous fluid flowing from the direction of the electro-magnetic source through the guiding wave structure and into the cavity acts on the plasma to push it away from the guiding wave structure and the electro-magnetic source. The gaseous fluid flow confines the high temperature plasma inside the cavity and allows complete chemical processing of the gaseous fluids at a wide range of pressures.

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F− reactions

PubMed Central

Tiernan, T. O.; Chang, C.; Cheng, C. C.

1980-01-01

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F− with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F− reagent ion was generated from CF3H or NF3, typically at an ion source pressure of 100 μm. In pure NF3, F− is the major ion formed and constitutes more than 90% of the total ion intensity. While F− is also the major primary ion formed in pure CF3H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)nF− (n = 1−3) ions, which makes CF3H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M − 1)− ion was observed in the F− chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)− ions upon reaction with F−. A weaker (M + F)− ion was also detected in the F− chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F− chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO−, X−, CN−, NO2−, and OR−, respectively. In addition, esters show a very weak (M − 1)− ion (except formates). In the F− chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)− ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F− ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several

Development of a new multi-residue laser diode thermal desorption atmospheric pressure chemical ionization tandem mass spectrometry method for the detection and quantification of pesticides and pharmaceuticals in wastewater samples.

PubMed

Boisvert, Michel; Fayad, Paul B; Sauvé, Sébastien

2012-11-19

A new solid phase extraction (SPE) method coupled to a high throughput sample analysis technique was developed for the simultaneous determination of nine selected emerging contaminants in wastewater (atrazine, desethylatrazine, 17β-estradiol, ethynylestradiol, norethindrone, caffeine, carbamazepine, diclofenac and sulfamethoxazole). We specifically included pharmaceutical compounds from multiple therapeutic classes, as well as pesticides. Sample pre-concentration and clean-up was performed using a mixed-mode SPE cartridge (Strata ABW) having both cation and anion exchange properties, followed by analysis by laser diode thermal desorption atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). The LDTD interface is a new high-throughput sample introduction method, which reduces total analysis time to less than 15s per sample as compared to minutes with traditional liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS). Several SPE parameters were evaluated in order to optimize recovery efficiencies when extracting analytes from wastewater, such as the nature of the stationary phase, the loading flow rate, the extraction pH, the volume and composition of the washing solution and the initial sample volume. The method was successfully applied to real wastewater samples from the primary sedimentation tank of a municipal wastewater treatment plant. Recoveries of target compounds from wastewater ranged from 78% to 106%, the limit of detection ranged from 30 to 122ng L(-1) while the limit of quantification ranged from 90 to 370ng L(-1). Calibration curves in the wastewater matrix showed good linearity (R(2)≥0.991) for all target analytes and the intraday and interday coefficient of variation was below 15%, reflecting a good precision. Copyright © 2012 Elsevier B.V. All rights reserved.

Ionization Processes in the Atmosphere of Titan (Research Note). III. Ionization by High-Z Nuclei Cosmic Rays

NASA Technical Reports Server (NTRS)

Gronoff, G.; Mertens, C.; Lilensten, J.; Desorgher, L.; Fluckiger, E.; Velinov, P.

2011-01-01

Context. The Cassini-Huygens mission has revealed the importance of particle precipitation in the atmosphere of Titan thanks to in-situ measurements. These ionizing particles (electrons, protons, and cosmic rays) have a strong impact on the chemistry, hence must be modeled. Aims. We revisit our computation of ionization in the atmosphere of Titan by cosmic rays. The high-energy high-mass ions are taken into account to improve the precision of the calculation of the ion production profile. Methods. The Badhwahr and O Neill model for cosmic ray spectrum was adapted for the Titan model. We used the TransTitan model coupled with the Planetocosmics model to compute the ion production by cosmic rays. We compared the results with the NAIRAS/HZETRN ionization model used for the first time for a body that differs from the Earth. Results. The cosmic ray ionization is computed for five groups of cosmic rays, depending on their charge and mass: protons, alpha, Z = 8 (oxygen), Z = 14 (silicon), and Z = 26 (iron) nucleus. Protons and alpha particles ionize mainly at 65 km altitude, while the higher mass nucleons ionize at higher altitudes. Nevertheless, the ionization at higher altitude is insufficient to obscure the impact of Saturn s magnetosphere protons at a 500 km altitude. The ionization rate at the peak (altitude: 65 km, for all the different conditions) lies between 30 and 40/cu cm/s. Conclusions. These new computations show for the first time the importance of high Z cosmic rays on the ionization of the Titan atmosphere. The updated full ionization profile shape does not differ significantly from that found in our previous calculations (Paper I: Gronoff et al. 2009, 506, 955) but undergoes a strong increase in intensity below an altitude of 400 km, especially between 200 and 400 km altitude where alpha and heavier particles (in the cosmic ray spectrum) are responsible for 40% of the ionization. The comparison of several models of ionization and cosmic ray spectra (in

Atmospheric pressure MALDI for the noninvasive characterization of carbonaceous ink from Renaissance documents.

PubMed

Grasso, Giuseppe; Calcagno, Marzia; Rapisarda, Alessandro; D'Agata, Roberta; Spoto, Giuseppe

2017-06-01

The analytical methods that are usually applied to determine the compositions of inks from ancient manuscripts usually focus on inorganic components, as in the case of iron gall ink. In this work, we describe the use of atmospheric pressure/matrix-assisted laser desorption ionization-mass spectrometry (AP/MALDI-MS) as a spatially resolved analytical technique for the study of the organic carbonaceous components of inks used in handwritten parts of ancient books for the first time. Large polycyclic aromatic hydrocarbons (L-PAH) were identified in situ in the ink of XVII century handwritten documents. We prove that it is possible to apply MALDI-MS as a suitable microdestructive diagnostic tool for analyzing samples in air at atmospheric pressure, thus simplifying investigations of the organic components of artistic and archaeological objects. The interpretation of the experimental MS results was supported by independent Raman spectroscopic investigations. Graphical abstract Atmospheric pressure/MALDI mass spectrometry detects in situ polycyclic aromatic hydrocarbons in the carbonaceous ink of XVII century manuscripts.

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

NASA Astrophysics Data System (ADS)

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

2008-08-01

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.

Use of capillary gas chromatography with negative ion-chemical ionization mass spectrometry for the determination of perfluorocarbon tracers in the atmosphere.

PubMed

Cooke, K M; Simmonds TPG; Nickless, G; Makepeace, A P

2001-09-01

A sensitive and selective technique for the quantitative measurement of atmospheric perfluorocarbon trace species at the sub part per quadrillion (10(-15)) levels is presented. The method utilizes advances in adsorbent enrichment techniques coupled with benchtop capillary gas chromatography and negative ion-chemical ionization mass spectrometry. The development and enhancement of sampling technology for tracer experiments is described, and the results from background measurements and a preliminary field experiment are presented. The overall precision of the analytical method with respect to the preferred tracer for these atmospheric transport studies, perfluoromethylcyclohexane, was +/-1.7%. The background concentrations of perfluorodimethylcyclobutane, perfluoromethylcyclopentane, and perfluoromethylcyclohexane at a remote coastal location (Mace Head, Ireland, 53 degrees N, 10 degrees W) were found to be 2.5 (+/-0.4), 6.8 (+/-1.0), and 5.2 fL L(-1) (+/-1.3), respectively. Background concentrations within an urban conurbation (Bristol, U.K.) were slightly greater at 3.0 (+/-1.5), 8.1 (+/-1.8), and 6.3 fL L(-1) (+/-1.1), respectively.

Low-Pressure, Field-Ionizing Mass Spectrometer

NASA Technical Reports Server (NTRS)

Hartley, Frank; Smith, Steven

2009-01-01

A small mass spectrometer utilizing a miniature field ionization source is now undergoing development. It is designed for use in a variety of applications in which there are requirements for a lightweight, low-power-consumption instrument that can analyze the masses of a wide variety of molecules and ions. The device can operate without need for a high-vacuum, carrier-gas feed radioactive ionizing source, or thermal ionizer. This mass spectrometer can operate either in the natural vacuum of outer space or on Earth at any ambient pressure below 50 torr (below about 6.7 kPa) - a partial vacuum that can easily be reached by use of a small sampling pump. This mass spectrometer also has a large dynamic range - from singly charged small gas ions to deoxyribonucleic acid (DNA) fragments larger than 104 atomic mass units - with sensitivity adequate for detecting some molecules and ions at relative abundances of less than one part per billion. This instrument (see figure) includes a field ionizer integrated with a rotating-field mass spectrometer (RFMS). The field ionizer effects ionization of a type characterized as "soft" in the art because it does not fragment molecules or initiate avalanche arcing. What makes the "soft" ionization mode possible is that the distance between the ionizing electrodes is less than mean free path for ions at the maximum anticipated operating pressure, so that the ionizer always operates on the non-breakdown side of the applicable Paschen curve (a standard plot of breakdown potential on the ordinate and pressure electrode separation on the abscissa). The field ionizer in this instrument is fabricated by micromachining a submicron-thick membrane out of an electrically nonconductive substrate, coating the membrane on both sides to form electrodes, then micromachining small holes through the electrodes and membrane. Because of the submicron electrode separation, even a potential of only 1 V applied between the electrodes gives rise to an electric

A physics-based model for the ionization of samarium by the MOSC chemical releases in the upper atmosphere

NASA Astrophysics Data System (ADS)

Bernhardt, Paul A.; Siefring, Carl L.; Briczinski, Stanley J.; Viggiano, Albert; Caton, Ronald G.; Pedersen, Todd R.; Holmes, Jeffrey M.; Ard, Shaun; Shuman, Nicholas; Groves, Keith M.

2017-05-01

Atomic samarium has been injected into the neutral atmosphere for production of electron clouds that modify the ionosphere. These electron clouds may be used as high-frequency radio wave reflectors or for control of the electrodynamics of the F region. A self-consistent model for the photochemical reactions of Samarium vapor cloud released into the upper atmosphere has been developed and compared with the Metal Oxide Space Cloud (MOSC) experimental observations. The release initially produces a dense plasma cloud that that is rapidly reduced by dissociative recombination and diffusive expansion. The spectral emissions from the release cover the ultraviolet to the near infrared band with contributions from solar fluorescence of the atomic, molecular, and ionized components of the artificial density cloud. Barium releases in sunlight are more efficient than Samarium releases in sunlight for production of dense ionization clouds. Samarium may be of interest for nighttime releases but the artificial electron cloud is limited by recombination with the samarium oxide ion.

Atmospheric-Pressure Plasma Interaction with Soft Materials as Fundamental Processes in Plasma Medicine.

PubMed

Takenaka, Kosuke; Miyazaki, Atsushi; Uchida, Giichiro; Setsuhara, Yuichi

2015-03-01

Molecular-structure variation of organic materials irradiated with atmospheric pressure He plasma jet have been investigated. Optical emission spectrum in the atmospheric-pressure He plasma jet has been measured. The spectrum shows considerable emissions of He lines, and the emission of O and N radicals attributed to air. Variation in molecular structure of Polyethylene terephthalate (PET) film surface irradiated with the atmospheric-pressure He plasma jet has been observed via X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). These results via XPS and FT-IR indicate that the PET surface irradiated with the atmospheric-pressure He plasma jet was oxidized by chemical and/or physical effect due to irradiation of active species.

Determination of nitrogen monoxide in high purity nitrogen gas with an atmospheric pressure ionization mass spectrometer

NASA Technical Reports Server (NTRS)

Kato, K.

1985-01-01

An atmospheric pressure ionization mass spectrometric (API-MS) method was studied for the determination of residual NO in high purity N2 gas. The API-MS is very sensitive to NO, but the presence of O2 interferes with the NO measurement. Nitrogen gas in cylinders as sample gas was mixed with NO standard gas and/or O2 standard gas, and then introduced into the API-MS. The calibration curves of NO and O2 has linearity in the region of 0 - 2 ppm, but the slopes changed with every cylinder. The effect of O2 on NO+ peak was additive and proportional to O2 concentration in the range of 0 - 0.5 ppm. The increase in NO+ intensity due to O2 was (0.07 - 0.13)%/O2, 1 ppm. Determination of NO and O2 was carried out by the standard addition method to eliminate the influence of variation of slopes. The interference due to O2 was estimated from the product of the O2 concentration and the ratio of slope A to Slope B. Slope A is the change in the NO+ intensity with the O2 concentration. Slope B is the intensity with O2 concentration.

Ionization cross section, pressure shift and isotope shift measurements of osmium

NASA Astrophysics Data System (ADS)

Hirayama, Yoshikazu; Mukai, Momo; Watanabe, Yutaka; Oyaizu, Michihiro; Ahmed, Murad; Kakiguchi, Yutaka; Kimura, Sota; Miyatake, Hiroari; Schury, Peter; Wada, Michiharu; Jeong, Sun-Chan

2017-11-01

In-gas-cell laser resonance ionization spectroscopy of neutral osmium atoms was performed with the use of a two-color two-step laser resonance ionization technique. Saturation curves for the ionization scheme were measured, and the ionization cross section was experimentally determined by solving the rate equations for the ground, intermediate and ionization continuum populations. The pressure shift and pressure broadening in the resonance spectra of the excitation transition were measured. The electronic factor {F}247 for the transition {λ }1=247.7583 nm to the intermediate state was deduced from the measured isotope shifts of stable {}{188,189,{190,192}}Os isotopes. The efficient ionization scheme, pressure shift, nuclear isotope shift and {F}247 are expected to be useful for applications of laser ion sources to unstable nuclei and for nuclear spectroscopy based on laser ionization techniques.

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

NASA Technical Reports Server (NTRS)

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

2002-01-01

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.

Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

DOE PAGES

Gou, Huiyang; Hemley, Russell J.; Hemawan, Kadek W.

2015-11-02

Polycrystalline diamond has been successfully synthesized on silicon substrates at atmospheric pressure using a microwave capillary plasma chemical vapor deposition technique. The CH 4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C 2, Ar, N 2, CH, H β and H α were observed in emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T 2g phonon at 1333 cm -1 peak relative to the Raman features of graphitic carbon. Furthermore, fieldmore » emission scanning electron microscopy (SEM) images reveal that, depending on the on growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.« less

Model atmospheres for cool stars. [varying chemical composition

NASA Technical Reports Server (NTRS)

Johnson, H. R.

1974-01-01

This report contains an extensive series of model atmospheres for cool stars having a wide range in chemical composition. Model atmospheres (temperature, pressure, density, etc.) are tabulated, along with emergent energy flux distributions, limb darkening, and information on convection for selected models. The models are calculated under the usual assumptions of hydrostatic equilibrium, constancy of total energy flux (including transport both by radiation and convection) and local thermodynamic equilibrium. Some molecular and atomic line opacity is accounted for as a straight mean. While cool star atmospheres are regimes of complicated physical conditions, and these atmospheres are necessarily approximate, they should be useful for a number of kinds of spectral and atmospheric analysis.

Laboratory Studies of Heterogeneous Chemical Processes of Atmospheric Importance

NASA Technical Reports Server (NTRS)

Molina, Mario J.

2003-01-01

The objective of this study is to conduct measurements of chemical kinetics parameters for heterogeneous reactions of importance in the stratosphere and the troposphere. It involves the elucidation of the mechanism of the interaction of HC1 vapor with ice surfaces, which is the first step in the heterogeneous chlorine activation processes, as well as the investigation of the atmospheric oxidation mechanism of soot particles emitted by biomass and fossil fuels. The techniques being employed include turbulent flow- chemical ionization mass spectrometry and optical ellipsometry, among others. The next section summarizes our research activities during the first year of the project, and the section that follows consists of the statement of work for the second year.

Influence of Atmospheric Pressure and Composition on LIBS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatch, Jeremy J.; Scott, Jill R.; Effenberger, A. J. Jr.

2014-03-01

Most LIBS experiments are conducted at standard atmospheric pressure in air. However, there are LIBS studies that vary the pressure and composition of the gas. These studies have provided insights into fundamentals of the mechanisms that lead to the emission and methods for improving the quality of LIBS spectra. These atmospheric studies are difficult because the effects of pressure and gas composition and interconnected, making interpretation of the results difficult. The influence of pressures below and above 760 Torr have been explored. Performing LIBS on a surface at reduced pressures (<760 Torr) can result in enhanced spectra due to highermore » resolution, increased intensity, improved signal-to-noise (S/N), and increased ablation. Lower pressures produce increased resolution because the line width in LIBS spectra is predominantly due to Stark and Doppler broadening. Stark broadening is primarily caused from collisions between electrons and atoms, while Doppler broadening is proportional to the plasma temperature. Close examination using a high resolution spectrometer reveals that spectra show significant peak broadening and self-absorption as pressures increase, especially for pressures >760 Torr. During LIBS plasma expansion, energy is lost to the surrounding atmosphere, which reduces the lifetime of the laser plasma. Therefore, reducing the pressure increases the lifetime of the plasma, allowing more light from the laser plasma to be collected; thus, increasing the observed signal intensity. However, if pressures are too low (<10 Torr), then there is a steep drop in LIBS spectral intensity. This loss in intensity is mostly due to a disordered plasma that results from the lack of sufficient atmosphere to provide adequate confinement. At reduced pressures, the plasma expands into a less dense atmosphere, which results in a less dense shock wave. The reduced density in the shock wave results in reduced plasma shielding, allowing more photons to reach the

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

NASA Astrophysics Data System (ADS)

Hamaguchi, Satoshi

2013-07-01

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.

Atmospheric Ionizing Radiation and the High Speed Civil Transport. Chapter 1

NASA Technical Reports Server (NTRS)

Maiden, D. L.; Wilson, J. W.; Jones, I. W.; Goldhagen, P.

2003-01-01

Atmospheric ionizing radiation is produced by extraterrestrial radiations incident on the Earth's atmosphere. These extraterrestrial radiations are of two sources: ever present galactic cosmic rays with origin outside the solar system and transient solar particle events that are at times very intense events associated with solar activity lasting several hours to a few days. Although the galactic radiation penetrating through the atmosphere to the ground is low in intensity, the intensity is more than two orders of magnitude greater at commercial aircraft altitudes. The radiation levels at the higher altitudes of the High Speed Civil Transport (HSCT) are an additional factor of two higher. Ionizing radiation produces chemically active radicals in biological tissues that alter the cell function or result in cell death. Protection standards against low levels of ionizing radiation are based on limitation of excess cancer mortality or limitation of developmental injury resulting in permanent damage to the offspring during pregnancy. The crews of commercial air transport operations are considered as radiation workers by the EPA, the FAA, and the International Commission on Radiological Protection (ICRP). The annual exposures of aircrews depend on the latitudes and altitudes of operation and flight time. Flight hours have significantly increased since deregulation of the airline industry in the 1980's. The FAA estimates annual subsonic aircrew exposures to range from 0.2 to 9.1 mSv compared to 0.5 mSv exposure of the average nuclear power plant worker in the nuclear industry. The commercial aircrews of the HSCT may receive exposures above recently recommended allowable limits for even radiation workers if flying their allowable number of flight hours. An adequate protection philosophy for background exposures in HSCT commercial airtraffic cannot be developed at this time due to current uncertainty in environmental levels. In addition, if a large solar particle event

Space Weather Nowcasting of Atmospheric Ionizing Radiation for Aviation Safety

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Wilson, John W.; Blattnig, Steve R.; Solomon, Stan C.; Wiltberger, J.; Kunches, Joseph; Kress, Brian T.; Murray, John J.

2007-01-01

There is a growing concern for the health and safety of commercial aircrew and passengers due to their exposure to ionizing radiation with high linear energy transfer (LET), particularly at high latitudes. The International Commission of Radiobiological Protection (ICRP), the EPA, and the FAA consider the crews of commercial aircraft as radiation workers. During solar energetic particle (SEP) events, radiation exposure can exceed annual limits, and the number of serious health effects is expected to be quite high if precautions are not taken. There is a need for a capability to monitor the real-time, global background radiations levels, from galactic cosmic rays (GCR), at commercial airline altitudes and to provide analytical input for airline operations decisions for altering flight paths and altitudes for the mitigation and reduction of radiation exposure levels during a SEP event. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model is new initiative to provide a global, real-time radiation dosimetry package for archiving and assessing the biologically harmful radiation exposure levels at commercial airline altitudes. The NAIRAS model brings to bear the best available suite of Sun-Earth observations and models for simulating the atmospheric ionizing radiation environment. Observations are utilized from ground (neutron monitors), from the atmosphere (the METO analysis), and from space (NASA/ACE and NOAA/GOES). Atmospheric observations provide the overhead shielding information and the ground- and space-based observations provide boundary conditions on the GCR and SEP energy flux distributions for transport and dosimetry simulations. Dose rates are calculated using the parametric AIR (Atmospheric Ionizing Radiation) model and the physics-based HZETRN (High Charge and Energy Transport) code. Empirical models of the near-Earth radiation environment (GCR/SEP energy flux distributions and geomagnetic cut-off rigidity) are benchmarked

Dispersive liquid-liquid microextraction for the determination of vitamins D and K in foods by liquid chromatography with diode-array and atmospheric pressure chemical ionization-mass spectrometry detection.

PubMed

Viñas, Pilar; Bravo-Bravo, María; López-García, Ignacio; Hernández-Córdoba, Manuel

2013-10-15

A simple and rapid method was developed using reversed-phase liquid chromatography (LC) with both diode array (DAD) and atmospheric pressure chemical ionization mass spectrometric (APCI-MS) detection, for the simultaneous analysis of the vitamins ergocalciferol (D2), cholecalciferol (D3), phylloquinone (K1), menaquinone-4 (K2) and a synthetic form of vitamin K, menadione (K3). The Taguchi experimental method, an orthogonal array design (OAD), was used to optimize an efficient and clean preconcentration step based on dispersive liquid-liquid microextraction (DLLME). A factorial design was applied with six factors and three levels for each factor, namely, carbon tetrachloride volume, methanol volume, aqueous sample volume, pH of sample, sodium chloride concentration and time of the centrifugation step. The DLLME optimized procedure consisted of rapidly injecting 3 mL of acetonitrile (disperser solvent) containing 150 µL carbon tetrachloride (extraction solvent) into the aqueous sample, thereby forming a cloudy solution. Phase separation was performed by centrifugation, and the sedimented phase was evaporated with nitrogen, reconstituted with 50 µL of acetonitrile, and injected. The LC analyses were carried out using a mobile phase composed of acetonitrile, 2-propanol and water, under gradient elution. Quantification was carried out by the standard additions method. The APCI-MS spectra, in combination with UV spectra, permitted the correct identification of compounds in the food samples. The method was validated according to international guidelines and using a certified reference material. The validated method was applied for the analysis of vitamins D and K in infant foods and several green vegetables. There was little variability in the forms of vitamin K present in vegetables, with the most abundant vitamer in all the samples being phylloquinone, while menadione could not be detected. Conversely, cholecalciferol, which is present in food of animal origin, was

Quantitation of lysergic acid diethylamide in urine using atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry.

PubMed

Cui, Meng; McCooeye, Margaret A; Fraser, Catharine; Mester, Zoltán

2004-12-01

A quantitative method was developed for analysis of lysergic acid diethylamide (LSD) in urine using atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry (AP MALDI-ITMS). Following solid-phase extraction of LSD from urine samples, extracts were analyzed by AP MALDI-ITMS. The identity of LSD was confirmed by fragmentation of the [M + H](+) ion using tandem mass spectrometry. The quantification of LSD was achieved using stable-isotope-labeled LSD (LSD-d(3)) as the internal standard. The [M + H](+) ion fragmented to produce a dominant fragment ion, which was used for a selected reaction monitoring (SRM) method for quantitative analysis of LSD. SRM was compared with selected ion monitoring and produced a wider linear range and lower limit of quantification. For SRM analysis of samples of LSD spiked in urine, the calibration curve was linear in the range of 1-100 ng/mL with a coefficient of determination, r(2), of 0.9917. This assay was used to determine LSD in urine samples and the AP MALDI-MS results were comparable to the HPLC/ ESI-MS results.

Microwave Atmospheric-Pressure Sensor

NASA Technical Reports Server (NTRS)

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

1986-01-01

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.

Atmospheric pressure plasma analysis by modulated molecular beam mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aranda Gonzalvo, Y.; Whitmore, T.D.; Rees, J.A.

Fractional number density measurements for a rf plasma 'needle' operating at atmospheric pressure have been obtained using a molecular beam mass spectrometer (MBMS) system designed for diagnostics of atmospheric plasmas. The MBMS system comprises three differentially pumped stages and a mass/energy analyzer and includes an automated beam-to-background measurement facility in the form of a software-controlled chopper mechanism. The automation of the beam modulation allows the neutral components in the plasma to be rapidly and accurately measured using the mass spectrometer by threshold ionization techniques. Data are reported for plasma generated by a needle plasma source operated using a helium/air mixture.more » In particular, data for the conversion of atmospheric oxygen and nitrogen into nitric oxide are discussed with reference to its significance for medical applications such as disinfecting wounds and dental cavities and for microsurgery.« less

Minimally-Invasive Gene Transfection by Chemical and Physical Interaction of Atmospheric Pressure Plasma Flow

NASA Astrophysics Data System (ADS)

Kaneko, Toshiro

2014-10-01

Non-equilibrium atmospheric pressure plasma irradiated to the living-cell is investigated for medical applications such as gene transfection, which is expected to play an important role in molecular biology, gene therapy, and creation of induced pluripotent stem (iPS) cells. However, the conventional gene transfection using the plasma has some problems that the cell viability is low and the genes cannot be transferred into some specific lipid cells, which is attributed to the unknown mechanism of the gene transfection using the plasma. Therefore, the time-controlled atmospheric pressure plasma flow is generated and irradiated to the living-cell suspended solution for clarifying the transfection mechanism toward developing highly-efficient and minimally- invasive gene transfection system. In this experiment, fluorescent dye YOYO-1 is used as the simulated gene and LIVE/DEAD Stain is simultaneously used for cell viability assay. By the fluorescence image, the transfection efficiency is calculated as the ratio of the number of transferred and surviving cells to total cell count. It is clarified that the transfection efficiency is significantly increased by the short-time (<4 sec) and short-distance (<40 mm) plasma irradiation, and the high transfection efficiency of 53% is realized together with the high cell viability (>90%). This result indicates that the physical effects such as the electric field caused by the charged particles arriving at the surface of the cell membrane, and chemical effects associated with plasma-activated products in solution act synergistically to enhance the cell-membrane transport with low-damage. This work was supported by JSPS KAKENHI Grant Number 24108004.

Beyond Naphthenic Acids: Environmental Screening of Water from Natural Sources and the Athabasca Oil Sands Industry Using Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

PubMed

Barrow, Mark P; Peru, Kerry M; Fahlman, Brian; Hewitt, L Mark; Frank, Richard A; Headley, John V

2015-09-01

There is a growing need for environmental screening of natural waters in the Athabasca region of Alberta, Canada, particularly in the differentiation between anthropogenic and naturally-derived organic compounds associated with weathered bitumen deposits. Previous research has focused primarily upon characterization of naphthenic acids in water samples by negative-ion electrospray ionization methods. Atmospheric pressure photoionization is a much less widely used ionization method, but one that affords the possibility of observing low polarity compounds that cannot be readily observed by electrospray ionization. This study describes the first usage of atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (in both positive-ion and negative-ion modes) to characterize and compare extracts of oil sands process water, river water, and groundwater samples from areas associated with oil sands mining activities. When comparing mass spectra previously obtained by electrospray ionization and data acquired by atmospheric pressure photoionization, there can be a doubling of the number of components detected. In addition to polar compounds that have previously been observed, low-polarity, sulfur-containing compounds and hydrocarbons that do not incorporate a heteroatom were detected. These latter components, which are not amenable to electrospray ionization, have potential for screening efforts within monitoring programs of the oil sands.

Numerical calculation of cosmic ray ionization rate profiles in the middle atmosphere and lower ionosphere with relation to characteristic energy intervals

NASA Astrophysics Data System (ADS)

Velinov, Peter; Asenovski, Simeon; Mateev, Lachezar

2013-04-01

Numerical calculations of galactic cosmic ray (GCR) ionization rate profiles are presented for the middle atmosphere and lower ionosphere altitudes (35-90 km) for the full GCR composition (protons, alpha particles, and groups of heavier nuclei: light L, medium M, heavy H, very heavy VH). This investigation is based on a model developed by Velinov et al. (1974) and Velinov and Mateev (2008), which is further improved in the present paper. Analytical expressions for energy interval contributions are provided. An approximation of the ionization function on three energy intervals is used and for the first time the charge decrease interval for electron capturing (Dorman 2004) is investigated quantitatively. Development in this field of research is important for better understanding the impact of space weather on the atmosphere. GCRs influence the ionization and electric parameters in the atmosphere and also the chemical processes (ozone creation and depletion in the stratosphere) in it. The model results show good agreement with experimental data (Brasseur and Solomon 1986, Rosenberg and Lanzerotti 1979, Van Allen 1952).

Spacecraft Sterilization Using Non-Equilibrium Atmospheric Pressure Plasma

NASA Technical Reports Server (NTRS)

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

2007-01-01

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.

Single photon ionization and chemical ionization combined ion source based on a vacuum ultraviolet lamp for orthogonal acceleration time-of-flight mass spectrometry.

PubMed

Hua, Lei; Wu, Qinghao; Hou, Keyong; Cui, Huapeng; Chen, Ping; Wang, Weiguo; Li, Jinghua; Li, Haiyang

2011-07-01

A novel combined ion source based on a vacuum ultraviolet (VUV) lamp with both single photon ionization (SPI) and chemical ionization (CI) capabilities has been developed for an orthogonal acceleration time-of-flight mass spectrometer (oaTOFMS). The SPI was accomplished using a commercial 10.6 eV krypton discharge lamp with a photon flux of about 10(11) photons s(-1), while the CI was achieved through ion-molecule reactions with O(2)(+) reactant ions generated by photoelectron ionization at medium vacuum pressure (MVP). To achieve high ionization efficiency, the ion source pressure was elevated to 0.3 mbar and the photoionization length was extended to 36 mm. As a result, limits of detection (LODs) down to 3, 4, and 6 ppbv were obtained for benzene, toluene, and p-xylene in MVP-SPI mode, and values of 8 and 10 ppbv were obtained for toluene and chloroform, respectively, in SPI-CI mode. As it is feasible to switch between MVP-SPI mode and SPI-CI mode rapidly, this system is capable of monitoring complex organic mixtures with a wide range of ionization energies (IEs). The analytical capacity of this system was demonstrated by measuring dehydrogenation products of long-chain paraffins to olefins through direct capillary sampling and drinking water disinfection byproducts from chlorine through a membrane interface.

NON-EQUILIBRIUM HELIUM IONIZATION IN AN MHD SIMULATION OF THE SOLAR ATMOSPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golding, Thomas Peter; Carlsson, Mats; Leenaarts, Jorrit, E-mail: thomas.golding@astro.uio.no, E-mail: mats.carlsson@astro.uio.no, E-mail: jorrit.leenaarts@astro.su.se

The ionization state of the gas in the dynamic solar chromosphere can depart strongly from the instantaneous statistical equilibrium commonly assumed in numerical modeling. We improve on earlier simulations of the solar atmosphere that only included non-equilibrium hydrogen ionization by performing a 2D radiation-magnetohydrodynamics simulation featuring non-equilibrium ionization of both hydrogen and helium. The simulation includes the effect of hydrogen Lyα and the EUV radiation from the corona on the ionization and heating of the atmosphere. Details on code implementation are given. We obtain helium ion fractions that are far from their equilibrium values. Comparison with models with local thermodynamicmore » equilibrium (LTE) ionization shows that non-equilibrium helium ionization leads to higher temperatures in wavefronts and lower temperatures in the gas between shocks. Assuming LTE ionization results in a thermostat-like behavior with matter accumulating around the temperatures where the LTE ionization fractions change rapidly. Comparison of DEM curves computed from our models shows that non-equilibrium ionization leads to more radiating material in the temperature range 11–18 kK, compared to models with LTE helium ionization. We conclude that non-equilibrium helium ionization is important for the dynamics and thermal structure of the upper chromosphere and transition region. It might also help resolve the problem that intensities of chromospheric lines computed from current models are smaller than those observed.« less

Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas.

PubMed

Benham, Kevin; Hodyss, Robert; Fernández, Facundo M; Orlando, Thomas M

2016-11-01

We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation. Graphical Abstract ᅟ.

Spectroscopic study of N2(b1Πu, ν = 8) by atmospheric-pressure resonant-enhanced multiphoton ionization and fluorescence detection.

PubMed

Adams, Steven F; Williamson, James M

2013-12-19

A spectroscopic analysis of the strongly perturbed N2(b(1)Πu, ν = 8) state has been conducted, accounting for b(1)Πu(ν = 8) ← X (1)Σg(+)(ν = 0) transitions, for the first time, up to J' = 20. A novel laser spectroscopy technique, using a combination of resonant-enhanced multiphoton ionization and fluorescence detection at atmospheric pressure, avoids the severe effects of perturbation reported in past extreme vacuum ultraviolet absorption experiments that produced weak and unusable spectra for the ν = 8 level. The R, Q, and P branches of the three-photon absorption transition b(1)Πu(ν = 8) ← X(1)Σg(+)(ν = 0) were fit, allowing rotational term energy assignment up to J' = 20 and molecular constants to be determined. Evidence of the previously suspected perturbation in b(1)Πu(ν = 8) is clear in this data, with significant Λ-type doubling at higher J' along with an anomalous negative value determined for the centrifugal distortion coefficient.

Ionization ratios and elemental abundances in the atmosphere of 68 Tauri

NASA Astrophysics Data System (ADS)

Aouina, A.; Monier, R.

2017-12-01

We have derived the ionization ratios of twelve elements in the atmosphere of the star 68 Tauri (HD 27962) using an ATLAS9 model atmosphere with 72 layers computed for the effective temperature and surface gravity of the star. We then computed a grid of synthetic spectra generated by SYNSPEC49 based on an ATLAS9 model atmosphere in order to model one high resolution spectrum secured by one of us (RM) with the échelle spectrograph SOPHIE at Observatoire de Haute Provence. We could determine the abundances of several elements in their dominant ionization stage, including those defining the Am phenomenon. We thus provide new abundance determinations for 68 Tauri using updated accurate atomic data retrieved from the NIST database which extend previous abundance works.

Automatic sampling and analysis of organics and biomolecules by capillary action-supported contactless atmospheric pressure ionization mass spectrometry.

PubMed

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

2013-01-01

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.

An ion-neutral model to investigate chemical ionization mass spectrometry analysis of atmospheric molecules - application to a mixed reagent ion system for hydroperoxides and organic acids

NASA Astrophysics Data System (ADS)

Heikes, Brian G.; Treadaway, Victoria; McNeill, Ashley S.; Silwal, Indira K. C.; O'Sullivan, Daniel W.

2018-04-01

An ion-neutral chemical kinetic model is described and used to simulate the negative ion chemistry occurring within a mixed-reagent ion chemical ionization mass spectrometer (CIMS). The model objective was the establishment of a theoretical basis to understand ambient pressure (variable sample flow and reagent ion carrier gas flow rates), water vapor, ozone and oxides of nitrogen effects on ion cluster sensitivities for hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), formic acid (HFo) and acetic acid (HAc). The model development started with established atmospheric ion chemistry mechanisms, thermodynamic data and reaction rate coefficients. The chemical mechanism was augmented with additional reactions and their reaction rate coefficients specific to the analytes. Some existing reaction rate coefficients were modified to enable the model to match laboratory and field campaign determinations of ion cluster sensitivities as functions of CIMS sample flow rate and ambient humidity. Relative trends in predicted and observed sensitivities are compared as instrument specific factors preclude a direct calculation of instrument sensitivity as a function of sample pressure and humidity. Predicted sensitivity trends and experimental sensitivity trends suggested the model captured the reagent ion and cluster chemistry and reproduced trends in ion cluster sensitivity with sample flow and humidity observed with a CIMS instrument developed for atmospheric peroxide measurements (PCIMSs). The model was further used to investigate the potential for isobaric compounds as interferences in the measurement of the above species. For ambient O3 mixing ratios more than 50 times those of H2O2, O3-(H2O) was predicted to be a significant isobaric interference to the measurement of H2O2 using O2-(H2O2) at m/z 66. O3 and NO give rise to species and cluster ions, CO3-(H2O) and NO3-(H2O), respectively, which interfere in the measurement of CH3OOH using O2-(CH3OOH) at m/z 80. The CO3-(H2O

Chemical investigation of saponins in different parts of Panax notoginseng by pressurized liquid extraction and liquid chromatography-electrospray ionization-tandem mass spectrometry.

PubMed

Wan, Jian-Bo; Zhang, Qing-Wen; Hong, Si-Jia; Li, Peng; Li, Shao-Ping; Wang, Yi-Tao

2012-05-16

A pressurized liquid extraction (PLE) and high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method was developed for the qualitative determination of saponins in different parts of P. notoginseng, including rhizome, root, fibre root, seed, stem, leaf and flower. The samples were extracted using PLE. The analysis was achieved on a Zorbax SB-C18 column with gradient elution of acetonitrile and 8 mM aqueous ammonium acetate as mobile phase. The mass spectrometer was operated in the negative ion mode using the electrospray ionization, and a collision induced dissociation (CID) experiment was also carried out to aid the identification of compounds. Forty one saponins were identified in different parts of P. notoginseng according to the fragmentation patterns and literature reports, among them, 21 saponins were confirmed by comparing the retention time and ESI-MS data with those of standard compounds. The results showed that the chemical characteristics were obviously diverse in different parts of P. notoginseng, which is helpful for pharmacological evaluation and quality control of P. notoginseng.

Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry*

PubMed Central

Inutan, Ellen D.; Trimpin, Sarah

2013-01-01

The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or added heat. This ionization process produces ions having charge states similar to ESI, making the method applicable for high performance mass spectrometers designed for atmospheric pressure ionization. We demonstrate highly sensitive ionization using intermediate pressure MALDI and modified ESI sources. This matrix and vacuum assisted soft ionization method is suitable for the direct surface analysis of biological materials, including tissue, via mass spectrometry. PMID:23242551

The sensibility of SPE induced atmospheric photochemical response to the ionization rate variations.

NASA Astrophysics Data System (ADS)

Krivolutsky, Alexei A.; Kukoleva, Anna; Kuminov, Alexander; Maygkova, Irina

During Solar proton event (SPE) energetic particles affect neutral atmospheric chemistry (Jackman et al. 1990, Krivolutsky A.A. et al. 2001 ets. ). The calculations results for [NO] and [O3] changes have qualitative suitability with observations data from satellites (UARS, HALOE for N.P.), although the simulated result differs in value from observed ones for nitrogen compounds. It seems potential probable reasons for this diversity exist. The sensibility of SPE induced atmospheric response to the ionization rates was investigated. The solar proton fluxes data from two satellites were used for ionization rate calculations by the method Vitt and Jackman (1996): geo-stationary GOES-10 (orbit height ≈ 40000 km) and CORONAS (orbit height is ≈ 400 km) for period of SPE 28.10. 2003. Calculated time integral ion creation during SPE using low and high orbit data differs for 1.5. Differences in ionization rate vertical distribution from GOES and CORONAS were found. Using this different ionization data the atmospherical composition response has been simulated with 1D photochemical model. The corresponding differences are discussed.

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

PubMed

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

2013-03-19

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.

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

PubMed Central

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

2010-01-01

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

Direct analysis of volatile organic compounds in foods by headspace extraction atmospheric pressure chemical ionisation mass spectrometry.

PubMed

Perez-Hurtado, P; Palmer, E; Owen, T; Aldcroft, C; Allen, M H; Jones, J; Creaser, C S; Lindley, M R; Turner, M A; Reynolds, J C

2017-11-30

The rapid screening of volatile organic compounds (VOCs) by direct analysis has potential applications in the areas of food and flavour science. Currently, the technique of choice for VOC analysis is gas chromatography/mass spectrometry (GC/MS). However, the long chromatographic run times and elaborate sample preparation associated with this technique have led a movement towards direct analysis techniques, such as selected ion flow tube mass spectrometry (SIFT-MS), proton transfer reaction mass spectrometry (PTR-MS) and electronic noses. The work presented here describes the design and construction of a Venturi jet-pump-based modification for a compact mass spectrometer which enables the direct introduction of volatiles for qualitative and quantitative analysis. Volatile organic compounds were extracted from the headspace of heated vials into the atmospheric pressure chemical ionization source of a quadrupole mass spectrometer using a Venturi pump. Samples were analysed directly with no prior sample preparation. Principal component analysis (PCA) was used to differentiate between different classes of samples. The interface is shown to be able to routinely detect problem analytes such as fatty acids and biogenic amines without the requirement of a derivatisation step, and is shown to be able to discriminate between four different varieties of cheese with good intra and inter-day reproducibility using an unsupervised PCA model. Quantitative analysis is demonstrated using indole standards with limits of detection and quantification of 0.395 μg/mL and 1.316 μg/mL, respectively. The described methodology can routinely detect highly reactive analytes such as volatile fatty acids and diamines without the need for a derivatisation step or lengthy chromatographic separations. The capability of the system was demonstrated by discriminating between different varieties of cheese and monitoring the spoilage of meats. © 2017 The Authors. Rapid Communications in Mass

Direct analysis of volatile organic compounds in foods by headspace extraction atmospheric pressure chemical ionisation mass spectrometry

PubMed Central

Perez‐Hurtado, P.; Palmer, E.; Owen, T.; Aldcroft, C.; Allen, M.H.; Jones, J.; Creaser, C.S.; Lindley, M.R.; Turner, M.A.

2017-01-01

Rationale The rapid screening of volatile organic compounds (VOCs) by direct analysis has potential applications in the areas of food and flavour science. Currently, the technique of choice for VOC analysis is gas chromatography/mass spectrometry (GC/MS). However, the long chromatographic run times and elaborate sample preparation associated with this technique have led a movement towards direct analysis techniques, such as selected ion flow tube mass spectrometry (SIFT‐MS), proton transfer reaction mass spectrometry (PTR‐MS) and electronic noses. The work presented here describes the design and construction of a Venturi jet‐pump‐based modification for a compact mass spectrometer which enables the direct introduction of volatiles for qualitative and quantitative analysis. Methods Volatile organic compounds were extracted from the headspace of heated vials into the atmospheric pressure chemical ionization source of a quadrupole mass spectrometer using a Venturi pump. Samples were analysed directly with no prior sample preparation. Principal component analysis (PCA) was used to differentiate between different classes of samples. Results The interface is shown to be able to routinely detect problem analytes such as fatty acids and biogenic amines without the requirement of a derivatisation step, and is shown to be able to discriminate between four different varieties of cheese with good intra and inter‐day reproducibility using an unsupervised PCA model. Quantitative analysis is demonstrated using indole standards with limits of detection and quantification of 0.395 μg/mL and 1.316 μg/mL, respectively. Conclusions The described methodology can routinely detect highly reactive analytes such as volatile fatty acids and diamines without the need for a derivatisation step or lengthy chromatographic separations. The capability of the system was demonstrated by discriminating between different varieties of cheese and monitoring the spoilage of meats. PMID

Ionization instability induced striations in low frequency and pulsed He/H2O atmospheric pressure plasmas

NASA Astrophysics Data System (ADS)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

2018-01-01

In previous work [Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016)] and [Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], 1D kinetic particle-in-cell (PIC) simulations of narrow gap (1 to 4 mm), high frequency (27 MHz) or dc-driven, He/2%H2O atmospheric pressure plasmas (APPs) showed an ionization instability resulting in standing striations (spatial oscillations) in the bulk plasma. We developed a steady-state striation theory which showed that the striations are due to non-local electron kinetics. In both the high frequency and dc-driven cases, the equilibrium electron density n0 in the plasma bulk was stationary. In this work, we first conduct 1D PIC simulations of a 1 mm gap He/2%H2O APP, driven by a sinusoidal current at a low frequency of f = 50 kHz such that ω = 2πf is well below the ionization frequency νiz. In this case, n0 varies with time, and we observe a time-varying instability which quasistatically depends on n0(t). At each phase of the rf cycle, the discharge resembles a dc discharge at the same n0. At higher frequencies (200 kHz-1 MHz), ω approaches νiz, and quasistatic equilibrium at each phase breaks down. The discharge is also driven with a 200 kHz, 50% duty cycle square wave pulse with a short rise and fall time of 0.1 μs in an attempt to directly measure the striation growth rate s during the on-cycle before it saturated. However, the spike in current during the rise time leads to a spike in electron temperature Te and hence νiz and s at the beginning of the rise which saturated during the beginning of the on-cycle. To predict the instability growth rate and saturation during and after the current spike, we extend our striation theory to include time-varying n0, Te, νiz, as well as terms for the nonlinear saturation and noise floor of the striation amplitude. The time-varying global model predictions are compared to the PIC simulations, showing reasonable agreement.

Hyphenation of ultra high performance supercritical fluid chromatography with atmospheric pressure chemical ionisation high resolution mass spectrometry: Part 1. Study of the coupling parameters for the analysis of natural non-polar compounds.

PubMed

Duval, Johanna; Colas, Cyril; Pecher, Virginie; Poujol, Marion; Tranchant, Jean-François; Lesellier, Eric

2017-08-04

An analytical method based on Ultra-High-Performance Supercritical Fluid Chromatography (UHPSFC) coupled with Atmospheric Pressure Chemical Ionization - High-resolution mass spectrometry (APCI-Q-TOF-HRMS) was developed for compounds screening from oily samples. The hyphenation was made using a commercial UHPLC device coupled to a CO 2 pump in order to perform the chromatographic analysis. An adaptation of the injection system for compressible fluids was accomplished for this coupling: this modification of the injection sequence was achieved to prevent unusual variations of the injected volume related to the use of a compressible fluid. UHPSFC-HRMS hyphenation was optimized to enhance the response of the varied compounds from a seed extract (anthraquinones, free fatty acids, diacylglycerols, hydroxylated triacylglycerols and triacylglycerols). No split was used prior to the APCI ionization source, allowing introducing all the compounds in the spectrometer, ensuring a better sensitivity for minor compounds. The effects of a mechanical make-up (T-piece) added before this ionization source was discussed in terms of standard deviation of response, response intensity and fragmentation percentage. The location of the T-piece with regards to the backpressure regulator (BPR), the flow rate and the nature of the make-up solvent were studied. Results show that the effects of the studied parameters depend on the nature of the compounds, whereas the make-up addition favours the robustness of the mass response (quantitative aspect). Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of parts per trillion levels of organophosphorus pesticides in groundwater by automated on-line liquid-solid extraction followed by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry using positive and negative ion modes of operation.

PubMed

Lacorte, S; Barceló, D

1996-08-01

Liquid chromatography/atmospheric pressure chemical ionization mass spectrometry with positive and negative ion modes of operations was used for the trace determination of several organophosphorus pesticides, (E)- and (Z)-mevinphos, dichlorvos, azinphos-methyl, azinphosethyl, parathion-methyl, parathion-ethyl, malathion, fenitrothion, fenthion, chlorfenvinphos, and diazinon, in groundwater. This method required only 100 mL of water, and it was combined with a prior automated online liquid-solid extraction step using an OSP-2 autosampler containing C18 cartridges. The limit of quantitation (LOQ) varied between 5 and 37 ng/L in positive ion (PI) mode. Under negative ion (NI) mode of operation, only the parathion group (both parathions and fenitrothion) had a better sensitivity as compared to that in PI mode, with a LOQ of 5-15 ng/L, whereas the rest of pesticides had 2-4 times higher LOQs as compared to those in PI mode. Selected ion monitoring of the group-specific fragment of the organophosphorus pesticides, e.g., [(CH3O)2PO2]- or the [M + H]+ ions, under NI or PI mode, respectively, was used. Sample cone voltage varied from 10 to 130 V. This parameter influenced the transmission and fragmentation of quasi-molecular ions, and it was optimized to achieve identification capabilities with the highest sensitivity. At 20 V, good fragmentation was obtained for most of the studied analytes. The system was used for the certification of a groundwater sample spiked at the nanograms per liter level with organophosphorus pesticides provided by Aquachek.

Determining Atmospheric Pressure Using a Water Barometer

ERIC Educational Resources Information Center

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

2012-01-01

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…

Atmospheric pressure plasma jet's characterization and surface wettability driven by neon transformer

NASA Astrophysics Data System (ADS)

Elfa, R. R.; Nafarizal, N.; Ahmad, M. K.; Sahdan, M. Z.; Soon, C. F.

2017-03-01

Atmospheric pressure plasma driven by Neon transformer power supply argon is presented in this paper. Atmospheric pressure plasma system has attracted researcher interest over low pressure plasma as it provides a flexibility process, cost-efficient, portable device and vacuum-free device. Besides, another golden key of this system is the wide promising application in the field of work cover from industrial and engineering to medical. However, there are still numbers of fundamental investigation that are necessary such as device configuration, gas configuration and its effect. Dielectric barrier discharge which is also known as atmospheric pressure plasma discharge is created when there is gas ionization process occur which enhance the movement of atom and electron and provide energetic particles. These energetic particles can provide modification and cleaning property to the sample surface due to the bombardment of the high reactive ion and radicals to the sample surface. In order to develop atmospheric pressure plasma discharge, a high voltage and high frequency power supply is needed. In this work, we used a neon transformer power supply as the power supply. The flow of the Ar is feed into 10 mm cylinder quartz tube with different treatment time in order to investigate the effect of the plasma discharge. The analysis of each treatment time is presented by optical emission spectroscopy (OES) and water contact angle (WCA) measurement. The increase of gas treatment time shows increases intensity of reactive Ar and reduces the angle of water droplets in water contact angle. Treatment time of 20 s microslide glass surface shows that the plasma needle discharges have modified the sample surface from hydrophilic surface to superhydrophilic surface. Thus, this leads to another interesting application in reducing sample surface adhesion to optimize productivity in the industry of paintings, semiconductor and more.

Clinical Application of Ambient Ionization Mass Spectrometry

PubMed Central

Li, Li-Hua; Hsieh, Hua-Yi; Hsu, Cheng-Chih

2017-01-01

Ambient ionization allows mass spectrometry analysis directly on the sample surface under atmospheric pressure with almost zero sample pretreatment. Since the development of desorption electrospray ionization (DESI) in 2004, many other ambient ionization techniques were developed. Due to their simplicity and low operation cost, rapid and on-site clinical mass spectrometry analysis becomes real. In this review, we will highlight some of the most widely used ambient ionization mass spectrometry approaches and their applications in clinical study. PMID:28337399

Forensic applications of ambient ionization mass spectrometry.

PubMed

Ifa, Demian R; Jackson, Ayanna U; Paglia, Giuseppe; Cooks, R Graham

2009-08-01

This review highlights and critically assesses forensic applications in the developing field of ambient ionization mass spectrometry. Ambient ionization methods permit the ionization of samples outside the mass spectrometer in the ordinary atmosphere, with minimal sample preparation. Several ambient ionization methods have been created since 2004 and they utilize different mechanisms to create ions for mass-spectrometric analysis. Forensic applications of these techniques--to the analysis of toxic industrial compounds, chemical warfare agents, illicit drugs and formulations, explosives, foodstuff, inks, fingerprints, and skin--are reviewed. The minimal sample pretreatment needed is illustrated with examples of analysis from complex matrices (e.g., food) on various substrates (e.g., paper). The low limits of detection achieved by most of the ambient ionization methods for compounds of forensic interest readily offer qualitative confirmation of chemical identity; in some cases quantitative data are also available. The forensic applications of ambient ionization methods are a growing research field and there are still many types of applications which remain to be explored, particularly those involving on-site analysis. Aspects of ambient ionization currently undergoing rapid development include molecular imaging and increased detection specificity through simultaneous chemical reaction and ionization by addition of appropriate chemical reagents.

A new multiplex method for the diagnosis of peroxisomal disorders allowing simultaneous determination of plasma very-long-chain fatty acids, phytanic, pristanic, docosahexaenoic and bile acids by high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.

PubMed

Semeraro, Michela; Rizzo, Cristiano; Boenzi, Sara; Cappa, Marco; Bertini, Enrico; Antonetti, Giacomo; Dionisi-Vici, Carlo

2016-07-01

Peroxisomal disorders (PDs) present with wide phenotypic variability. An appropriate diagnosis requires a complete analysis of peroxisomal metabolites. We developed a multiplex LC-MS/MS method, using atmospheric pressure chemical ionization allowing the simultaneous determination in plasma of very-long-chain fatty acids, phytanic, pristanic, docosahexaenoic acids and di- and tri-hydroxycolestanoic bile acids. Two hundred microliters of plasma extracted with acetonitrile and 200μl extracted with hexane after an acid hydrolysis were combined, evaporated, dissolved in 10μl of methanol and analyzed. The acquisition was in negative-ion mode using multiple reaction monitoring. The method was validated analytically and clinically. Linearity was 0.1-200μmol/l for docosanoic, cis-13-docosenoic, tetracosanoic, cis-15-tetracosenoic and phytanic acids; 0.01-10μmol/l for hexacosanoic acid; 0.02-20μmol/l for di-hydroxycolestanoic, tri-hydroxycolestanoic and pristanic acids; 0.3-300μmol/l for docosahexaenoic acid. Intra-day and inter-day CVs were below 3.88 and 3.98 respectively for all compounds. Samples from patients with known peroxisomal disorders were compared with controls and the method allowed to confirm the diagnosis in all subjects with a 100% sensitivity. The advantage of this multiplex method is to allow in a single chromatographic run the simultaneous determination of a large number of peroxisome biomarkers with a simple preparative phase without derivatization. Copyright © 2016 Elsevier B.V. All rights reserved.

A flowing atmospheric pressure afterglow as an ion source coupled to a differential mobility analyzer for volatile organic compound detection.

PubMed

Bouza, Marcos; Orejas, Jaime; López-Vidal, Silvia; Pisonero, Jorge; Bordel, Nerea; Pereiro, Rosario; Sanz-Medel, Alfredo

2016-05-23

Atmospheric pressure glow discharges have been widely used in the last decade as ion sources in ambient mass spectrometry analyses. Here, an in-house flowing atmospheric pressure afterglow (FAPA) has been developed as an alternative ion source for differential mobility analysis (DMA). The discharge source parameters (inter-electrode distance, current and helium flow rate) determining the atmospheric plasma characteristics have been optimized in terms of DMA spectral simplicity with the highest achievable sensitivity while keeping an adequate plasma stability and so the FAPA working conditions finally selected were: 35 mA, 1 L min(-1) of He and an inter-electrode distance of 8 mm. Room temperature in the DMA proved to be adequate for the coupling and chemical analysis with the FAPA source. Positive and negative ions for different volatile organic compounds were tested and analysed by FAPA-DMA using a Faraday cup as a detector and proper operation in both modes was possible (without changes in FAPA operational parameters). The FAPA ionization source showed simpler ion mobility spectra with narrower peaks and a better, or similar, sensitivity than conventional UV-photoionization for DMA analysis in positive mode. Particularly, the negative mode proved to be a promising field of further research for the FAPA ion source coupled to ion mobility, clearly competitive with other more conventional plasmas such as corona discharge.

Analysis of anabolic steroids in urine by gas chromatography-microchip atmospheric pressure photoionization-mass spectrometry with chlorobenzene as dopant.

PubMed

Hintikka, Laura; Haapala, Markus; Kuuranne, Tiia; Leinonen, Antti; Kostiainen, Risto

2013-10-18

A gas chromatography-microchip atmospheric pressure photoionization-tandem mass spectrometry (GC-μAPPI-MS/MS) method was developed for the analysis of anabolic androgenic steroids in urine as their trimethylsilyl derivatives. The method utilizes a heated nebulizer microchip in atmospheric pressure photoionization mode (μAPPI) with chlorobenzene as dopant, which provides high ionization efficiency by producing abundant radical cations with minimal fragmentation. The performance of GC-μAPPI-MS/MS was evaluated with respect to repeatability, linearity, linear range, and limit of detection (LOD). The results confirmed the potential of the method for doping control analysis of anabolic steroids. Repeatability (RSD<10%), linearity (R(2)≥0.996) and sensitivity (LODs 0.05-0.1ng/mL) were acceptable. Quantitative performance of the method was tested and compared with that of conventional GC-electron ionization-MS, and the results were in good agreement. Copyright © 2013 Elsevier B.V. All rights reserved.

Liquid Sampling-Atmospheric Pressure Glow Discharge (LS-APGD) Ionization Source for Elemental Mass Spectrometry: Preliminary Parametric Evaluation and Figures of Merit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quarles, C. Derrick; Carado, Anthony J.; Barinaga, Charles J.

2012-01-01

A new, low power ionization source for the elemental analysis of aqueous solutions has recently been described. The liquid sampling-atmospheric pressure glow discharge (LS-APGD) source operates at relatively low currents (<20 mA) and solution flow rates (<50 μL min-1), yielding a relatively simple alternative for atomic mass spectrometry applications. The LS-APGD has been interfaced to what is otherwise an organic, LC-MS mass analyzer, the Thermo Scientific Exactive Orbitrap without any modifications; other than removing the electrospray ionization (ESI) source supplied with that instrument. A glow discharge is initiated between the surface of the test solution exiting a glass capillary andmore » a metallic counter electrode mounted at a 90° angle and separated by a distance of ~5 mm. As with any plasma-based ionization source, there are key discharge operation and ion sampling parameters that affect the intensity and composition of the derived mass spectra; including signal-to-background ratios. We describe here a preliminary parametric evaluation of the roles of discharge current, solution flow rate, argon sheath gas flow rate, and ion sampling distance as they apply on this mass analyzer system. A cursive evaluation of potential matrix effects due to the presence of easily ionized elements (EIEs) indicate that sodium concentrations of up to 500 μg mL-1 generally cause suppressions of less than 50%, dependant upon the analyte species. Based on the results of this series of studies, preliminary limits of detection (LOD) have been established through the generation of calibration functions. Whilst solution-based concentrations LOD levels of 0.02 – 2 μg mL-1 3 are not impressive on the surface, the fact that they are determined via discrete 5 μL injections leads to mass-based detection limits at picogram to singlenanogram levels. The overhead costs associated with source operation (10 W d.c. power, solution flow rates of <50 μL min-1, and gas flow rates

Neutralization by a Corona Discharge Ionizer in Nitrogen Atmosphere

NASA Astrophysics Data System (ADS)

Ikeuchi, Toru; Takahashi, Kazunori; Ohkubo, Takahiro; Fujiwara, Tamiya

An electrostatic neutralization of multilayer-loading silicon wafers is demonstrated using a corona discharge ionizer in nitrogen atmosphere, where ac and dc voltages are applied to two needle electrodes for generation of the negative- and positive-charged particles, respectively. We observe a surface potential of the silicon wafer decreases from ±1kV to ±20V within three seconds. Moreover, the density profiles of the charged particles generated by the electrodes are experimentally and theoretically investigated in nitrogen and air atmospheres. Our results show the possibility that the negative-charged particles contributing to the electrostatic neutralization are electrons and negative ions in nitrogen and air atmospheres, respectively.

Influence of hadron and atmospheric models on computation of cosmic ray ionization in the atmosphere-Extension to heavy nuclei

NASA Astrophysics Data System (ADS)

Mishev, A. L.; Velinov, P. I. Y.

2014-12-01

In the last few years an essential progress in development of physical models for cosmic ray induced ionization in the atmosphere is achieved. The majority of these models are full target, i.e. based on Monte Carlo simulation of an electromagnetic-muon-nucleon cascade in the atmosphere. Basically, the contribution of proton nuclei is highlighted, i.e. the contribution of primary cosmic ray α-particles and heavy nuclei to the atmospheric ionization is neglected or scaled to protons. The development of cosmic ray induced atmospheric cascade is sensitive to the energy and mass of the primary cosmic ray particle. The largest uncertainties in Monte Carlo simulations of a cascade in the Earth atmosphere are due to assumed hadron interaction models, the so-called hadron generators. In the work presented here we compare the ionization yield functions Y for primary cosmic ray nuclei, such as α-particles, Oxygen and Iron nuclei, assuming different hadron interaction models. The computations are fulfilled with the CORSIKA 6.9 code using GHEISHA 2002, FLUKA 2011, UrQMD hadron generators for energy below 80 GeV/nucleon and QGSJET II for energy above 80 GeV/nucleon. The observed difference between hadron generators is widely discussed. The influence of different atmospheric parametrizations, namely US standard atmosphere, US standard atmosphere winter and summer profiles on ion production rate is studied. Assuming realistic primary cosmic ray mass composition, the ion production rate is obtained at several rigidity cut-offs - from 1 GV (high latitudes) to 15 GV (equatorial latitudes) using various hadron generators. The computations are compared with experimental data. A conclusion concerning the consistency of the hadron generators is stated.

Analysis of nitrogen-based explosives with desorption atmospheric pressure photoionization mass spectrometry.

PubMed

Kauppila, T J; Flink, A; Pukkila, J; Ketola, R A

2016-02-28

Fast methods that allow the in situ analysis of explosives from a variety of surfaces are needed in crime scene investigations and home-land security. Here, the feasibility of the ambient mass spectrometry technique desorption atmospheric pressure photoionization (DAPPI) in the analysis of the most common nitrogen-based explosives is studied. DAPPI and desorption electrospray ionization (DESI) were compared in the direct analysis of trinitrotoluene (TNT), trinitrophenol (picric acid), octogen (HMX), cyclonite (RDX), pentaerythritol tetranitrate (PETN), and nitroglycerin (NG). The effect of different additives in DAPPI dopant and in DESI spray solvent on the ionization efficiency was tested, as well as the suitability of DAPPI to detect explosives from a variety of surfaces. The analytes showed ions only in negative ion mode. With negative DAPPI, TNT and picric acid formed deprotonated molecules with all dopant systems, while RDX, HMX, PETN and NG were ionized by adduct formation. The formation of adducts was enhanced by addition of chloroform, formic acid, acetic acid or nitric acid to the DAPPI dopant. DAPPI was more sensitive than DESI for TNT, while DESI was more sensitive for HMX and picric acid. DAPPI could become an important method for the direct analysis of nitroaromatics from a variety of surfaces. For compounds that are thermally labile, or that have very low vapor pressure, however, DESI is better suited. Copyright © 2016 John Wiley & Sons, Ltd.

Open Port Probe Sampling Interface for the Direct Coupling of Biocompatible Solid-Phase Microextraction to Atmospheric Pressure Ionization Mass Spectrometry.

PubMed

Gómez-Ríos, Germán Augusto; Liu, Chang; Tascon, Marcos; Reyes-Garcés, Nathaly; Arnold, Don W; Covey, Thomas R; Pawliszyn, Janusz

2017-04-04

In recent years, the direct coupling of solid phase microextraction (SPME) and mass spectrometry (MS) has shown its great potential to improve limits of quantitation, accelerate analysis throughput, and diminish potential matrix effects when compared to direct injection to MS. In this study, we introduce the open port probe (OPP) as a robust interface to couple biocompatible SPME (Bio-SPME) fibers to MS systems for direct electrospray ionization. The presented design consisted of minimal alterations to the front-end of the instrument and provided better sensitivity, simplicity, speed, wider compound coverage, and high-throughput in comparison to the LC-MS based approach. Quantitative determination of clenbuterol, fentanyl, and buprenorphine was successfully achieved in human urine. Despite the use of short extraction/desorption times (5 min/5 s), limits of quantitation below the minimum required performance levels (MRPL) set by the world antidoping agency (WADA) were obtained with good accuracy (≥90%) and linearity (R 2 > 0.99) over the range evaluated for all analytes using sample volumes of 300 μL. In-line technologies such as multiple reaction monitoring with multistage fragmentation (MRM 3 ) and differential mobility spectrometry (DMS) were used to enhance the selectivity of the method without compromising analysis speed. On the basis of calculations, once coupled to high throughput, this method can potentially yield preparation times as low as 15 s per sample based on the 96-well plate format. Our results demonstrated that Bio-SPME-OPP-MS efficiently integrates sampling/sample cleanup and atmospheric pressure ionization, making it an advantageous configuration for several bioanalytical applications, including doping in sports, in vivo tissue sampling, and therapeutic drug monitoring.

Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source.

PubMed

Orejas, Jaime; Pfeuffer, Kevin P; Ray, Steven J; Pisonero, Jorge; Sanz-Medel, Alfredo; Hieftje, Gary M

2014-11-01

Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected.

Ionization of NO at high temperature

NASA Technical Reports Server (NTRS)

Hansen, C. Frederick

1991-01-01

Space vehicles flying through the atmosphere at high speed are known to excite a complex set of chemical reactions in the atmospheric gases, ranging from simple vibrational excitation to dissociation, atom exchange, electronic excitation, ionization, and charge exchange. Simple arguments are developed for the temperature dependence of the reactions leading to ionization of NO, including the effect of vibrational electronic thermal nonequilibrium. NO ionization is the most important source of electrons at intermediate temperatures and at higher temperatures provides the trigger electrons that ionize atoms. Based on these arguments, recommendations are made for formulae which fit observed experimental results, and which include a dependence on both a heavy particle temperature and different vibration electron temperatures. In addition, these expressions will presumably provide the most reliable extrapolation of experimental results to much higher temperatures.

Overview of Atmospheric Ionizing Radiation (AIR)

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Maiden, D. L.; Goldhagen, P.; Tai, H.; Shinn, J. L.

2003-01-01

The SuperSonic Transport (SST) development program within the US was based at the Langley Research Center as was the Apollo radiation testing facility (Space Radiation Effects Laboratory) with associated radiation research groups. It was natural for the issues of the SST to be first recognized by this unique combination of research programs. With a re-examination of the technologies for commercial supersonic flight and the possible development of a High Speed Civil Transport (HSCT), the remaining issues of the SST required resolution. It was the progress of SST radiation exposure research program founded by T. Foelsche at the Langley Research Center and the identified remaining issues after that project over twenty-five years ago which became the launch point of the current atmospheric ionizing radiation (AIR) research project. Added emphasis to the need for reassessment of atmospheric radiation resulted from the major lowering of the recommended occupational exposure limits, the inclusion of aircrew as radiation workers, and the recognition of civil aircrew as a major source of occupational exposures. Furthermore, the work of Ferenc Hajnal of the Environmental Measurements Laboratory brought greater focus to the uncertainties in the neutron flux at high altitudes. A re-examination of the issues involved was committed at the Langley Research Center and by the National Council on Radiation Protection (NCRP). As a result of the NCRP review, a new flight package was assembled and flown during solar minimum at which time the galactic cosmic radiation is at a maximum (June 1997). The present workshop is the initial analysis of the new data from that flight. The present paper is an overview of the status of knowledge of atmospheric ionizing radiations. We will re-examine the exposures of the world population and examine the context of aircrew exposures with implications for the results of the present research. A condensed version of this report was given at the 1998

Characterization of Dust-Plasma Interactions In Non-Thermal Plasmas Under Low Pressure and the Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Bilik, Narula

difficulties in maintaining an APGD is ensuring its uniformity over large discharge volume. By examining past atmospheric pressure plasma reactor designs and looking into the details of the atmospheric pressure gas breakdown mechanism, three design features are proposed to ensure the APGD uniformity. These include the use of a dielectric barrier and the RF driving frequency, as well as a pre-ionization technique achieved by having a non-uniform gap spacing in a capacitively-coupled concentric cylinder reactor. The resulting APGD reactor operates stably in the abnormal glow regime using either helium or argon as the carrier gas. Diethylzinc (DEZ) and oxygen precursors are injected into the APGD to form zinc oxide nanocrystals. The physical and optical properties of these nanocrystals are characterized, and the system parameters that impact the nanoparticle size and deposition rate are identified.

Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

NASA Astrophysics Data System (ADS)

Williams, Thomas Scott

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

A comparative study on the analytical utility of atmospheric and low-pressure MALDI sources for the mass spectrometric characterization of peptides.

PubMed

Moskovets, Eugene; Misharin, Alexander; Laiko, Viktor; Doroshenko, Vladimir

2016-07-15

A comparative MS study was conducted on the analytical performance of two matrix-assisted laser desorption/ionization (MALDI) sources that operated at either low pressure (∼1Torr) or at atmospheric pressure. In both cases, the MALDI sources were attached to a linear ion trap mass spectrometer equipped with a two-stage ion funnel. The obtained results indicate that the limits of detection, in the analysis of identical peptide samples, were much lower with the source that was operated slightly below the 1-Torr pressure. In the low-pressure (LP) MALDI source, ion signals were observed at a laser fluence that was considerably lower than the one determining the appearance of ion signals in the atmospheric pressure (AP) MALDI source. When the near-threshold laser fluences were used to record MALDI MS spectra at 1-Torr and 750-Torr pressures, the level of chemical noise at the 1-Torr pressure was much lower compared to that at AP. The dependency of the analyte ion signals on the accelerating field which dragged the ions from the MALDI plate to the MS analyzer are presented for the LP and AP MALDI sources. The study indicates that the laser fluence, background gas pressure, and field accelerating the ions away from a MALDI plate were the main parameters which determined the ion yield, signal-to-noise (S/N) ratios, the fragmentation of the analyte ions, and adduct formation in the LP and AP MALDI MS methods. The presented results can be helpful for a deeper insight into the mechanisms responsible for the ion formation in MALDI. Copyright © 2016 Elsevier Inc. All rights reserved.

Electrode Configurations in Atmospheric Pressure Plasma Jets

NASA Astrophysics Data System (ADS)

Lietz, Amanda M.; Kushner, Mark J.

2016-09-01

Atmospheric pressure plasma jets (APPJs) are being studied for emerging medical applications including cancer treatment and wound healing. APPJs typically consist of a dielectric tube through which a rare gas flows, sometimes with an O2 or H2O impurity. In this paper, we present results from a computational study of APPJs using nonPDPSIM, a 2-D plasma hydrodynamics model, with the goal of providing insights on how the placement of electrodes can influence the production of reactive species. Gas consisting of He/O2 = 99.5/0.5 is flowed through a capillary tube at 2 slpm into humid air, and a pulsed DC voltage is applied. An APPJ with two external ring electrodes will be compared with one having a powered electrode inside and a ground electrode on the outside. The consequences on ionization wave propagation and the production of reactive oxygen and nitrogen species (RONS) will be discussed. Changing the electrode configuration can concentrate the power deposition in volumes having different gas composition, resulting in different RONS production. An internal electrode can result in increased production of NOx and HNOx by increasing propagation of the ionization wave through the He dominated plume to outside of the tube where humid air is diffusing into the plume. Work supported by US DOE Office of Fusion Energy Science and the National Science Foundation.

Examination of fluctuations in atmospheric pressure related to migraine.

PubMed

Okuma, Hirohisa; Okuma, Yumiko; Kitagawa, Yasuhisa

2015-01-01

Japan has four seasons and many chances of low atmospheric pressure or approaches of typhoon, therefore it has been empirically known that the fluctuation of weather induces migraine in people. Generally, its mechanism has been interpreted as follows: physical loading, attributed by atmospheric pressure to human bodies, compresses or dilates human blood vessels, which leads to abnormality in blood flow and induces migraine. We report our examination of the stage in which migraine tends to be induced focusing on the variation of atmospheric pressure. Subjects were 34 patients with migraine, who were treated in our hospital. The patients included 31 females and three males, whose mean age was 32 ± 6.7. 22 patients had migraine with aura and 12 patients had migraine without aura. All of patients with migraine maintained a headache diary to record atmospheric pressures when they developed a migraine. The standard atmospheric pressure was defined as 1013 hPa, and with this value as the criterion, we investigated slight fluctuations in the atmospheric pressure when they developed a migraine. It was found that the atmospheric pressure when the patients developed a migraine was within 1003-1007 hPa in the approach of low atmospheric pressure and that the patients developed a migraine when the atmospheric pressure decreased by 6-10 hPa, slightly less than the standard atmospheric pressure. Small decreases of 6-10 hPa relative to the standard atmospheric pressure of 1013 hPa induced migraine attacks most frequently in patients with migraine.

Preparation and characterization of epitaxial MgO thin film by atmospheric-pressure metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Zeng, J. M.; Wang, H.; Shang, S. X.; Wang, Z.; Wang, M.

1996-12-01

Magnesium oxide (MgO) thin films have been prepared on Si(100), {SiO2(100) }/{Si} and {Pt(111) }/{Si} substrates by atmospheric-pressure metalorganic chemical vapor deposition (AP-MOCVD) for the first time. The relationship between the temperature of substrates ( Ts) and crystallographic orientations was also investigated. Magnesium acetylacetonate [Mg(CH 2COCH 2COCH 3) 2] was used as the metalorganic source. The relatively low temperature of substrates is about 480°C and the MgO thin films obtained were uniform, dense and well-ordered single crystal. X-ray diffraction experiments provided evidence that the MgO thin films on Si(100) ( Ts ≈ 400-680°C), {SiO2}/{Si} and {Pt}/{Si} were fully textured with (100) orientation. The deliquescent character of MgO thin films was also studied.

Direct olive oil analysis by mass spectrometry: A comparison of different ambient ionization methods.

PubMed

Lara-Ortega, Felipe J; Beneito-Cambra, Miriam; Robles-Molina, José; García-Reyes, Juan F; Gilbert-López, Bienvenida; Molina-Díaz, Antonio

2018-04-01

Analytical methods based on ambient ionization mass spectrometry (AIMS) combine the classic outstanding performance of mass spectrometry in terms of sensitivity and selectivity along with convenient features related to the lack of sample workup required. In this work, the performance of different mass spectrometry-based methods has been assessed for the direct analyses of virgin olive oil for quality purposes. Two sets of experiments have been setup: (1) direct analysis of untreated olive oil using AIMS methods such as Low-Temperature Plasma Mass Spectrometry (LTP-MS) or paper spray mass spectrometry (PS-MS); or alternatively (2) the use of atmospheric pressure ionization (API) mass spectrometry by direct infusion of a diluted sample through either atmospheric pressure chemical ionization (APCI) or electrospray (ESI) ionization sources. The second strategy involved a minimum sample work-up consisting of a simple olive oil dilution (from 1:10 to 1:1000) with appropriate solvents, which originated critical carry over effects in ESI, making unreliable its use in routine; thus, ESI required the use of a liquid-liquid extraction to shift the measurement towards a specific part of the composition of the edible oil (i.e. polyphenol rich fraction or lipid/fatty acid profile). On the other hand, LTP-MS enabled direct undiluted mass analysis of olive oil. The use of PS-MS provided additional advantages such as an extended ionization coverage/molecular weight range (compared to LTP-MS) and the possibility to increase the ionization efficiency towards nonpolar compounds such as squalene through the formation of Ag + adducts with carbon-carbon double bounds, an attractive feature to discriminate between oils with different degree of unsaturation. Copyright © 2017 Elsevier B.V. All rights reserved.

Continuous Growth of Hexagonal Graphene and Boron Nitride In-Plane Heterostructures by Atmospheric Pressure Chemical Vapor Deposition

PubMed Central

Han, Gang Hee; Rodríguez-Manzo, Julio A.; Lee, Chan-Woo; Kybert, Nicholas J.; Lerner, Mitchell B.; Qi, Zhengqing John; Dattoli, Eric N.; Rappe, Andrew M.; Drndic, Marija; Charlie Johnson, A. T.

2013-01-01

Graphene-boron nitride monolayer heterostructures contain adjacent electrically active and insulating regions in a continuous, single-atom thick layer. To date structures were grown at low pressure, resulting in irregular shapes and edge direction, so studies of the graphene-boron nitride interface were restricted to microscopy of nano-domains. Here we report templated growth of single crystalline hexagonal boron nitride directly from the oriented edge of hexagonal graphene flakes by atmospheric pressure chemical vapor deposition, and physical property measurements that inform the design of in-plane hybrid electronics. Ribbons of boron nitride monolayer were grown from the edge of a graphene template and inherited its crystallographic orientation. The relative sharpness of the interface was tuned through control of growth conditions. Frequent tearing at the graphene-boron nitride interface was observed, so density functional theory was used to determine that the nitrogen-terminated interface was prone to instability during cool down. The electronic functionality of monolayer heterostructures was demonstrated through fabrication of field effect transistors with boron nitride as an in-plane gate dielectric. PMID:24182310

Continuous growth of hexagonal graphene and boron nitride in-plane heterostructures by atmospheric pressure chemical vapor deposition.

PubMed

Han, Gang Hee; Rodríguez-Manzo, Julio A; Lee, Chan-Woo; Kybert, Nicholas J; Lerner, Mitchell B; Qi, Zhengqing John; Dattoli, Eric N; Rappe, Andrew M; Drndic, Marija; Johnson, A T Charlie

2013-11-26

Graphene-boron nitride monolayer heterostructures contain adjacent electrically active and insulating regions in a continuous, single-atom thick layer. To date structures were grown at low pressure, resulting in irregular shapes and edge direction, so studies of the graphene-boron nitride interface were restricted to the microscopy of nanodomains. Here we report templated growth of single crystalline hexagonal boron nitride directly from the oriented edge of hexagonal graphene flakes by atmospheric pressure chemical vapor deposition, and physical property measurements that inform the design of in-plane hybrid electronics. Ribbons of boron nitride monolayer were grown from the edge of a graphene template and inherited its crystallographic orientation. The relative sharpness of the interface was tuned through control of growth conditions. Frequent tearing at the graphene-boron nitride interface was observed, so density functional theory was used to determine that the nitrogen-terminated interface was prone to instability during cool down. The electronic functionality of monolayer heterostructures was demonstrated through fabrication of field effect transistors with boron nitride as an in-plane gate dielectric.

Comparison of electrospray ionization and atmospheric pressure photoionization liquid chromatography mass spectrometry methods for analysis of ergot alkaloids from endophyte-infected sleepygrass (Achnatherum robustum).

PubMed

Jarmusch, Alan K; Musso, Ashleigh M; Shymanovich, Tatsiana; Jarmusch, Scott A; Weavil, Miranda J; Lovin, Mary E; Ehrmann, Brandie M; Saari, Susanna; Nichols, David E; Faeth, Stanley H; Cech, Nadja B

2016-01-05

Ergot alkaloids are mycotoxins with an array of biological effects. With this study, we investigated for the first time the application of atmospheric pressure photoionization (APPI) as an ionization method for LC-MS analysis of ergot alkaloids, and compared its performance to that of the more established technique of electrospray ionization (ESI). Samples of the grass Achnatherum robustum infected with the ergot producing Epichloë fungus were extracted using cold methanol and subjected to reserved-phase HPLC-ESI-MS and HPLC-APPI-MS analysis. The ergot alkaloids ergonovine and lysergic acid amide were detected in these samples, and quantified via external calibration. Validation parameters were recorded in accordance with ICH guidelines. A triple quadrupole MS operated in multiple reaction monitoring yielded the lowest detection limits. The performance of APPI and ESI methods was comparable. Both methods were subject to very little matrix interference, with percent recoveries ranging from 82% to 100%. As determined with HPLC-APPI-MS quantification, lysergic acid amide and ergonovine were extracted from an A. robustum sample infected with the Epichloë fungus at concentrations of 1.143±0.051 ppm and 0.2822±0.0071 ppm, respectively. There was no statistically significant difference between these concentrations and those determined using ESI for the same samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparison of Ambient and Atmospheric Pressure Ion Sources for Cystic Fibrosis Exhaled Breath Condensate Ion Mobility-Mass Spectrometry Metabolomics

NASA Astrophysics Data System (ADS)

Zang, Xiaoling; Pérez, José J.; Jones, Christina M.; Monge, María Eugenia; McCarty, Nael A.; Stecenko, Arlene A.; Fernández, Facundo M.

2017-08-01

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The vast majority of the mortality is due to progressive lung disease. Targeted and untargeted CF breath metabolomics investigations via exhaled breath condensate (EBC) analyses have the potential to expose metabolic alterations associated with CF pathology and aid in assessing the effectiveness of CF therapies. Here, transmission-mode direct analysis in real time traveling wave ion mobility spectrometry time-of-flight mass spectrometry (TM-DART-TWIMS-TOF MS) was tested as a high-throughput alternative to conventional direct infusion (DI) electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) methods, and a critical comparison of the three ionization methods was conducted. EBC was chosen as the noninvasive surrogate for airway sampling over expectorated sputum as EBC can be collected in all CF subjects regardless of age and lung disease severity. When using pooled EBC collected from a healthy control, ESI detected the most metabolites, APCI a log order less, and TM-DART the least. TM-DART-TWIMS-TOF MS was used to profile metabolites in EBC samples from five healthy controls and four CF patients, finding that a panel of three discriminant EBC metabolites, some of which had been previously detected by other methods, differentiated these two classes with excellent cross-validated accuracy.

An Atmospheric Pressure Ping-Pong "Ballometer"

ERIC Educational Resources Information Center

Kazachkov, Alexander; Kryuchkov, Dmitriy; Willis, Courtney; Moore, John C.

2006-01-01

Classroom experiments on atmospheric pressure focus largely on demonstrating its existence, often in a most impressive way. A series of amusing physics demonstrations is widely known and practiced by educators teaching the topic. However, measuring the value of atmospheric pressure(P[subscript atm]) is generally done in a rather mundane way,…

Collison nebulizer as a new soft ionization source for mass spectrometry

NASA Astrophysics Data System (ADS)

Pervukhin, V. V.; Sheven', D. G.; Kolomiets, Yu. N.

2016-08-01

We have proposed that a Collison-type nebulizer be used as an ionization source for mass spectrometry with ionization under atmospheric pressure. This source does not require the use of electric voltage, radioactive sources, heaters, or liquid pumps. It has been shown that the number of ions produced by the 63Ni radioactive source is three to four times larger than the number of ions produced by acoustic ionization sources. We have considered the possibility of using a Collison-type nebulizer in combination with a vortex focusing system as an ion source for extractive ionization of compounds under atmospheric pressure. The ionization of volatile substances in crossflows of a charged aerosol and an analyte (for model compounds of the amine class, viz., diethylaniline, triamylamine, and cocaine) has been investigated. It has been shown that the limit of detecting cocaine vapor by this method is on the level of 4.6 × 10-14 g/cm3.

Shuttle Orbiter Atmospheric Revitalization Pressure Control Subsystem

NASA Technical Reports Server (NTRS)

Walleshauser, J. J.; Ord, G. R.; Prince, R. N.

1982-01-01

The Atmospheric Revitalization Pressure Control Subsystem (ARPCS) provides oxygen partial pressure and total pressure control for the habitable atmosphere of the Shuttle for either a one atmosphere environment or an emergency 8 PSIA mode. It consists of a Supply Panel, Control Panel, Cabin Pressure Relief Valves and Electronic Controllers. The panels control and monitor the oxygen and nitrogen supplies. The cabin pressure relief valves protect the habitable environment from overpressurization. Electronic controllers provide proper mixing of the two gases. This paper describes the ARPCS, addresses the changes in hardware that have occurred since the inception of the program; the performance of this subsystem during STS-1 and STS-2; and discusses future operation modes.

The applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research

NASA Technical Reports Server (NTRS)

Fegley, Bruce, Jr.

1990-01-01

A review of the applications of chemical thermodynamics and chemical kinetics to planetary atmospheres research during the past four decades is presented with an emphasis on chemical equilibrium models and thermochemical kinetics. Several current problems in planetary atmospheres research such as the origin of the atmospheres of the terrestrial planets, atmosphere-surface interactions on Venus and Mars, deep mixing in the atmospheres of the gas giant planets, and the origin of the atmospheres of outer planet satellites all require laboratory data on the kinetics of thermochemical reactions for their solution.

Processing materials inside an atmospheric-pressure radiofrequency nonthermal plasma discharge

DOEpatents

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

2006-04-11

Apparatus for the processing of materials involving placing a material either placed between an radio-frequency electrode and a ground electrode, or which is itself one of the electrodes. This is done in atmospheric pressure conditions. The apparatus effectively etches or cleans substrates, such as silicon wafers, or provides cleaning of spools and drums, and uses a gas containing an inert gas and a chemically reactive gas.

The potential of organic (electrospray- and atmospheric pressure chemical ionisation) mass spectrometric techniques coupled to liquid-phase separation for speciation analysis.

PubMed

Rosenberg, Erwin

2003-06-06

The use of mass spectrometry based on atmospheric pressure ionisation techniques (atmospheric pressure chemical ionisation, APCI, and electrospray ionisation, ESI) for speciation analysis is reviewed with emphasis on the literature published in and after 1999. This report accounts for the increasing interest that atmospheric pressure ionisation techniques, and in particular ESI, have found in the past years for qualitative and quantitative speciation analysis. In contrast to element-selective detectors, organic mass spectrometric techniques provide information on the intact metal species which can be used for the identification of unknown species (particularly with MS-MS detection) or the confirmation of the actual presence of species in a given sample. Due to the complexity of real samples, it is inevitable in all but the simplest cases to couple atmospheric pressure MS detection to a separation technique. Separation in the liquid phase (capillary electrophoresis or liquid chromatography in reversed phase, ion chromatographic or size-exclusion mode) is particularly suitable since the available techniques cover a very wide range of analyte polarities and molecular mass. Moreover, derivatisation can normally be avoided in liquid-phase separation. Particularly in complex environmental or biological samples, separation in one dimension is not sufficient for obtaining adequate resolution for all relevant species. In this case, multi-dimensional separation, based on orthogonal separation techniques, has proven successful. ESI-MS is also often used in parallel with inductively coupled plasma MS detection. This review is structured in two parts. In the first, the fundamentals of atmospheric pressure ionisation techniques are briefly reviewed. The second part of the review discusses recent applications including redox species, use of ESI-MS for structural elucidation of metal complexes, characterisation and quantification of small organometallic species with relevance to

Spontaneous Charge Separation and Sublimation Processes are Ubiquitous in Nature and in Ionization Processes in Mass Spectrometry

NASA Astrophysics Data System (ADS)

Trimpin, Sarah; Lu, I.-Chung; Rauschenbach, Stephan; Hoang, Khoa; Wang, Beixi; Chubatyi, Nicholas D.; Zhang, Wen-Jing; Inutan, Ellen D.; Pophristic, Milan; Sidorenko, Alexander; McEwen, Charles N.

2018-02-01

Ionization processes have been discovered by which small and large as well as volatile and nonvolatile compounds are converted to gas-phase ions when associated with a matrix and exposed to sub-atmospheric pressure. Here, we discuss experiments further defining these simple and unexpected processes. Charge separation is found to be a common process for small molecule chemicals, solids and liquids, passed through an inlet tube from a higher to a lower pressure region, with and without heat applied. This charge separation process produces positively- and negatively-charged particles with widely different efficiencies depending on the compound and its physical state. Circumstantial evidence is presented suggesting that in the new ionization process, charged particles carry analyte into the gas phase, and desolvation of these particles produce the bare ions similar to electrospray ionization, except that solid particles appear likely to be involved. This mechanistic proposition is in agreement with previous theoretical work related to ion emission from ice.

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

PubMed

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

2014-04-07

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.

Assessing the sensitivity of benzene cluster cation chemical ionization mass spectrometry toward a wide array of biogenic volatile organic compounds

NASA Astrophysics Data System (ADS)

Lavi, Avi; Vermeuel, Michael; Novak, Gordon; Bertram, Timothy

2017-04-01

Chemical ionization mass spectrometry is a real-time, sensitive and selective measurement technique for the detection of volatile organic compounds (VOCs). The benefits of CIMS technology make it highly suitable for field measurements that requires fast (10Hz and higher) response rates, such as the study of surface-atmosphere exchange processes by the eddy covariance method. The use of benzene cluster cations as a regent ion was previously demonstrated as a sensitive and selective method for the detection of select biogenic VOCs (e.g. isoprene, monoterpenes and sesquiterpenes) [Kim et al., 2016; Leibrock and Huey, 2000]. Quantitative analysis of atmospheric trace gases necessitates calibration for each analyte as a function of atmospheric conditions. We describe a custom designed calibration system, based on liquid evaporation, for determination of the sensitivity of the benzene-CIMS to a wide range of organic compounds at atmospherically relevant mixing ratios (<200 ppt). We report on the effect of atmospheric water vapor and oxygen concentrations on instrument response for isoprene and a wide range of monoterpenes and sesquiterpenes. To gain mechanistic insight into the ion-molecule reactions and the role of water vapor and oxygen, we compare our measured sensitivities with a computational analysis of the charge distribution between the analyte, reagent ion and water molecules in the gas phase. These parameters provide insight on the ionization mechanism and provide parameters for quantification of organic molecules measured during field campaigns. References Kim, M. J., M. C. Zoerb, N. R. Campbell, K. J. Zimmermann, B. W. Blomquist, B. J. Huebert, and T. H. Bertram (2016), Revisiting benzene cluster cations for the chemical ionization of dimethyl sulfide and select volatile organic compounds, Atmos Meas Tech, 9(4), 1473-1484, doi:10.5194/amt-9-1473-2016. Leibrock, E., and L. G. Huey (2000), Ion chemistry for the detection of isoprene and other volatile organic

Tantalum Etching with an Atmospheric Pressure Plasma Jet

NASA Astrophysics Data System (ADS)

Teslow, Hilary; Herrmann, Hans; Rosocha, Louis

2002-10-01

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.

Laboratory Studies of Homogeneous and Heterogeneous Chemical Processes of Importance in the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Molina, Mario J.

2003-01-01

The objective of this study was to conduct measurements of chemical kinetics parameters for reactions of importance in the stratosphere and upper troposphere, and to study the interaction of trace gases with ice surfaces in order to elucidate the mechanism of heterogeneous chlorine activation processes, using both a theoretical and an experimental approach. The measurements were carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere. The main experimental technique employed was turbulent flow-chemical ionization mass spectrometry, which is particularly well suited for investigations of radical-radical reactions.

Fe(+) chemical ionization of peptides.

PubMed

Speir, J P; Gorman, G S; Amster, I J

1993-02-01

Laser-desorbed peptide neutral molecules were allowed to react with Fe(+) in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe(+) ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne(+). Prior to reaction with laser-desorbed peptide molecules, Fe(+) ions undergo 20-100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe(+) ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe(+)] and fragment ions that result from the loss of small, stable molecules, such as H2O, CO, and CO2, from the metal ion-peptide complex.

Detection of transient radical cations in electron transfer-initiated Diels-Alder reactions by electrospray ionization mass spectrometry.

PubMed

Fürmeier, Sven; Metzger, Jürgen O

2004-11-10

The coupling of a simple microreactor to an atmospheric pressure ion source, such as electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), allows the investigation of reactions in solution by mass spectrometry. The tris(p-bromophenyl)aminium hexachloroantimonate (1(*)(+)SbCl(6)(-))-initiated reactions of phenylvinylsulfide (2) and cyclopentadiene (3) and of trans-anethole (5) and isoprene (6) and the dimerization of 1,3-cyclohexadiene (8) to give the respective Diels-Alder products were studied. These preparatively interesting reactions proceed as radical cation chain reactions via the transient radical cations of the respective dienophiles and of the respective Diels-Alder addition products. These radical cations could be detected directly and characterized unambiguously in the reacting solution by ESI-MS-MS. The identity was confirmed by comparison with MS-MS spectra of the authentic radical cations obtained by APCI-MS and by CID experiments of the corresponding molecular ions generated by EI-MS. In addition, substrates and products could be monitored easily in the reacting solution by APCI-MS.

Analytical instruments, ionization sources, and ionization methods

DOEpatents

Atkinson, David A.; Mottishaw, Paul

2006-04-11

Methods and apparatus for simultaneous vaporization and ionization of a sample in a spectrometer prior to introducing the sample into the drift tube of the analyzer are disclosed. The apparatus includes a vaporization/ionization source having an electrically conductive conduit configured to receive sample particulate which is conveyed to a discharge end of the conduit. Positioned proximate to the discharge end of the conduit is an electrically conductive reference device. The conduit and the reference device act as electrodes and have an electrical potential maintained between them sufficient to cause a corona effect, which will cause at least partial simultaneous ionization and vaporization of the sample particulate. The electrical potential can be maintained to establish a continuous corona, or can be held slightly below the breakdown potential such that arrival of particulate at the point of proximity of the electrodes disrupts the potential, causing arcing and the corona effect. The electrical potential can also be varied to cause periodic arcing between the electrodes such that particulate passing through the arc is simultaneously vaporized and ionized. The invention further includes a spectrometer containing the source. The invention is particularly useful for ion mobility spectrometers and atmospheric pressure ionization mass spectrometers.

A high-resolution time-of-flight chemical ionization mass spectrometer utilizing hydronium ions (H3O+ ToF-CIMS) for measurements of volatile organic compounds in the atmosphere

NASA Astrophysics Data System (ADS)

Yuan, Bin; Koss, Abigail; Warneke, Carsten; Gilman, Jessica B.; Lerner, Brian M.; Stark, Harald; de Gouw, Joost A.

2016-07-01

Proton transfer reactions between hydronium ions (H3O+) and volatile organic compounds (VOCs) provide a fast and highly sensitive technique for VOC measurements, leading to extensive use of proton-transfer-reaction mass spectrometry (PTR-MS) in atmospheric research. Based on the same ionization approach, we describe the development of a high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) utilizing H3O+ as the reagent ion. The new H3O+ ToF-CIMS has sensitivities of 100-1000 cps ppb-1 (ion counts per second per part-per-billion mixing ratio of VOC) and detection limits of 20-600 ppt at 3σ for a 1 s integration time for simultaneous measurements of many VOC species of atmospheric relevance. The ToF analyzer with mass resolution (m/Δm) of up to 6000 allows the separation of isobaric masses, as shown in previous studies using similar ToF-MS. While radio frequency (RF)-only quadrupole ion guides provide better overall ion transmission than ion lens system, low-mass cutoff of RF-only quadrupole causes H3O+ ions to be transmitted less efficiently than heavier masses, which leads to unusual humidity dependence of reagent ions and difficulty obtaining a humidity-independent parameter for normalization. The humidity dependence of the instrument was characterized for various VOC species and the behaviors for different species can be explained by compound-specific properties that affect the ion chemistry (e.g., proton affinity and dipole moment). The new H3O+ ToF-CIMS was successfully deployed on the NOAA WP-3D research aircraft for the SONGNEX campaign in spring of 2015. The measured mixing ratios of several aromatics from the H3O+ ToF-CIMS agreed within ±10 % with independent gas chromatography measurements from whole air samples. Initial results from the SONGNEX measurements demonstrate that the H3O+ ToF-CIMS data set will be valuable for the identification and characterization of emissions from various sources, investigation of secondary

Highly ionized physical vapor deposition plasma source working at very low pressure

NASA Astrophysics Data System (ADS)

Stranak, V.; Herrendorf, A.-P.; Drache, S.; Cada, M.; Hubicka, Z.; Tichy, M.; Hippler, R.

2012-04-01

Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti+ and Ti++ peaks are observed in the mass scan spectra). This corresponds well with high plasma density ne ˜ 1018 m-3, measured during the HiPIMS pulse.

Atmospheric-pressure-plasma-enhanced fabrication of nonfouling nanocoatings for 316 stainless steel biomaterial interfaces

NASA Astrophysics Data System (ADS)

Huang, Chun; Lin, Jin-He; Li, Chi-Heng; Yu, I.-Chun; Chen, Ting-Lun

2018-03-01

Atmospheric-pressure plasma, which was generated with electrical RF power, was fed to a tetramethyldisiloxane/argon gas mixture to prepare bioinert organosilicon coatings for 316 stainless steel. The surface characteristics of atmospheric-pressure-plasma-deposited nanocoatings were evaluated as a function of RF plasma power, precursor gas flow, and plasma working distance. After surface deposition, the chemical features, elemental compositions, and surface morphologies of the organosilicon nanocoatings were examined. It was found that RF plasma power and plasma working distance are the essential factors that affect the formation of plasma-deposited nanocoatings. Fourier transform infrared spectroscopy spectra indicate that the atmospheric-pressure-plasma-deposited nanocoatings formed showed inorganic features. Atomic force microscopy analysis showed the surface roughness variation of the plasma-deposited nanocoating at different RF plasma powers and plasma working distances during surface treatment. From these surface analyses, it was found that the plasma-deposited organosilicon nanocoatings under specific operational conditions have relatively hydrophobic and inorganic characteristics, which are essential for producing an anti-biofouling interface on 316 stainless steel. The experimental results also show that atmospheric-pressure-plasma-deposited nanocoatings have potential use as a cell-resistant layer on 316 stainless steel.

Mass spectrometer characterization of halogen gases in air at atmospheric pressure.

PubMed

Ivey, Michelle M; Foster, Krishna L

2005-03-01

We have developed a new interface for a commercial ion trap mass spectrometer equipped with APCI capable of real-time measurements of gaseous compounds with limits of detection on the order of pptv. The new interface has been tested using the detection of Br2 and Cl2 over synthetic seawater ice at atmospheric pressure as a model system. A mechanical pump is used to draw gaseous mixtures through a glass manifold into the corona discharge area, where the molecules are ionized. Analysis of bromine and chlorine in dry air show that ion intensity is affected by the pumping rate and the position of the glass manifold. The mass spectrometer signals for Br2 are linear in the 0.1-10.6 ppbv range, and the estimated 3sigma detection limit is 20 pptv. The MS signals for Cl2 are linear in the 0.2-25 ppbv range, and the estimated 3sigma detection limit is 1 ppbv. This new interface advances the field of analytical chemistry by introducing a practical modification to a commercially available ion trap mass spectrometer that expands the available methods for performing highly specific and sensitive measurements of gases in air at atmospheric pressure.

Means of introducing an analyte into liquid sampling atmospheric pressure glow discharge

DOEpatents

Marcus, R. Kenneth; Quarles, Jr., Charles Derrick; Russo, Richard E.; Koppenaal, David W.; Barinaga, Charles J.; Carado, Anthony J.

2017-01-03

A liquid sampling, atmospheric pressure, glow discharge (LS-APGD) device as well as systems that incorporate the device and methods for using the device and systems are described. The LS-APGD includes a hollow capillary for delivering an electrolyte solution to a glow discharge space. The device also includes a counter electrode in the form of a second hollow capillary that can deliver the analyte into the glow discharge space. A voltage across the electrolyte solution and the counter electrode creates the microplasma within the glow discharge space that interacts with the analyte to move it to a higher energy state (vaporization, excitation, and/or ionization of the analyte).

Application of high-resolution time-of-flight chemical ionization mass spectrometry measurements to estimate volatility distributions of α-pinene and naphthalene oxidation products

DOE PAGES

Chhabra, P. S.; Lambe, A. T.; Canagaratna, M. R.; ...

2015-01-05

Recent developments in high-resolution time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made it possible to directly detect atmospheric organic compounds in real time with high sensitivity and with little or no fragmentation, including low-volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, using ions identified by high-resolution spectra from an HR-ToF-CIMS with acetate reagent ion chemistry, we develop an algorithm to estimate the vapor pressures of measured organic acids. The algorithm uses identified ion formulas and calculated double bond equivalencies, information unavailable in quadrupole CIMS technology, as constraints for the number of possible oxygen-containing functionalmore » groups. The algorithm is tested with acetate chemical ionization mass spectrometry (acetate-CIMS) spectra of O 3 and OH oxidation products of α-pinene and naphthalene formed in a flow reactor with integrated OH exposures ranged from 1.2 × 10 11 to 9.7 × 10 11 molec s cm −3, corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. The predicted condensed-phase secondary organic aerosol (SOA) average acid yields and O/C and H/C ratios agree within uncertainties with previous chamber and flow reactor measurements and ambient CIMS results. Furthermore, while acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allendorf, Mark D.; Sopko, J.F.; Houf, William G.

2006-11-01

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 accuratemore » 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

Following the Ions through a Mass Spectrometer with Atmospheric Pressure Interface: Simulation of Complete Ion Trajectories from Ion Source to Mass Analyzer.

PubMed

Zhou, Xiaoyu; Ouyang, Zheng

2016-07-19

Ion trajectory simulation is an important and useful tool in instrumentation development for mass spectrometry. Accurate simulation of the ion motion through the mass spectrometer with atmospheric pressure ionization source has been extremely challenging, due to the complexity in gas hydrodynamic flow field across a wide pressure range as well as the computational burden. In this study, we developed a method of generating the gas flow field for an entire mass spectrometer with an atmospheric pressure interface. In combination with the electric force, for the first time simulation of ion trajectories from an atmospheric pressure ion source to a mass analyzer in vacuum has been enabled. A stage-by-stage ion repopulation method has also been implemented for the simulation, which helped to avoid an intolerable computational burden for simulations at high pressure regions while it allowed statistically meaningful results obtained for the mass analyzer. It has been demonstrated to be suitable to identify a joint point for combining the high and low pressure fields solved individually. Experimental characterization has also been done to validate the new method for simulation. Good agreement was obtained between simulated and experimental results for ion transfer though an atmospheric pressure interface with a curtain gas.

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

NASA Astrophysics Data System (ADS)

Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.

2013-02-01

Results are presented from experimental studies of decomposition of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N2: O2: H2O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C6H5CH3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.

Application of Atmospheric Pressure Photoionization H/D-exchange Mass Spectrometry for Speciation of Sulfur-containing Compounds.

PubMed

Acter, Thamina; Kim, Donghwi; Ahmed, Arif; Ha, Ji-Hyoung; Kim, Sunghwan

2017-08-01

Herein we report the observation of atmospheric pressure in-source hydrogen-deuterium exchange (HDX) of thiol group for the first time. The HDX for thiol group was optimized for positive atmospheric pressure photoionization (APPI) mass spectrometry (MS). The optimized HDX-MS was applied for 31 model compounds (thiols, thiophenes, and sulfides) to demonstrate that exchanged peaks were observed only for thiols. The optimized method has been successfully applied to the isolated fractions of sulfur-rich oil samples. The exchange of one and two thiol hydrogens with deuterium was observed in the thiol fraction; no HDX was observed in the other fractions. Thus, the results presented in this study demonstrate that the HDX-MS method using APPI ionization source can be effective for speciation of sulfur compounds. This method has the potential to be used to access corrosion problems caused by thiol-containing compounds. Graphical Abstract ᅟ.

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

NASA Astrophysics Data System (ADS)

Yui, Hiroharu; Banno, Motohiro

2018-01-01

In this article, we review the development of scientific instruments for obtaining information on the evolution of physical properties and chemical species of solution plasma (SP). When a pulsed high voltage is applied between electrodes immersed in an aqueous solution, SP is formed in water vapor bubbles transiently generated in the solution under atmospheric pressure. To clarify how SP emerges in water vapor bubbles and is sustained in solutions, an instrument with micrometer spatial resolution and nanosecond temporal resolution is required. To meet these requirements, a microscopic system with a custom-made optical discharge cell was newly developed, where the working distance between the SP and the microscopic objective lens was minimized. A hollow electrode equipped in the discharge cell also enabled us to control the chemical composition in water vapor bubbles. To study the spatial and temporal evolutions of chemical species in micrometer and nano- to microsecond regions, a streak camera with a spectrometer and a CCD detector with a time-gated electronic device were combined with the microscope system. The developed instrument is expected to contribute to providing a new means of developing new schemes for chemical reactions and material syntheses.

Mycotoxin Decontamination of Food: Cold Atmospheric Pressure Plasma versus "Classic" Decontamination.

PubMed

Hojnik, Nataša; Cvelbar, Uroš; Tavčar-Kalcher, Gabrijela; Walsh, James L; Križaj, Igor

2017-04-28

Mycotoxins are secondary metabolites produced by several filamentous fungi, which frequently contaminate our food, and can result in human diseases affecting vital systems such as the nervous and immune systems. They can also trigger various forms of cancer. Intensive food production is contributing to incorrect handling, transport and storage of the food, resulting in increased levels of mycotoxin contamination. Mycotoxins are structurally very diverse molecules necessitating versatile food decontamination approaches, which are grouped into physical, chemical and biological techniques. In this review, a new and promising approach involving the use of cold atmospheric pressure plasma is considered, which may overcome multiple weaknesses associated with the classical methods. In addition to its mycotoxin destruction efficiency, cold atmospheric pressure plasma is cost effective, ecologically neutral and has a negligible effect on the quality of food products following treatment in comparison to classical methods.

Non-equilibrium synergistic effects in atmospheric pressure plasmas.

PubMed

Guo, Heng; Zhang, Xiao-Ning; Chen, Jian; Li, He-Ping; Ostrikov, Kostya Ken

2018-03-19

Non-equilibrium is one of the important features of an atmospheric gas discharge plasma. It involves complicated physical-chemical processes and plays a key role in various actual plasma processing. In this report, a novel complete non-equilibrium model is developed to reveal the non-equilibrium synergistic effects for the atmospheric-pressure low-temperature plasmas (AP-LTPs). It combines a thermal-chemical non-equilibrium fluid model for the quasi-neutral plasma region and a simplified sheath model for the electrode sheath region. The free-burning argon arc is selected as a model system because both the electrical-thermal-chemical equilibrium and non-equilibrium regions are involved simultaneously in this arc plasma system. The modeling results indicate for the first time that it is the strong and synergistic interactions among the mass, momentum and energy transfer processes that determine the self-consistent non-equilibrium characteristics of the AP-LTPs. An energy transfer process related to the non-uniform spatial distributions of the electron-to-heavy-particle temperature ratio has also been discovered for the first time. It has a significant influence for self-consistently predicting the transition region between the "hot" and "cold" equilibrium regions of an AP-LTP system. The modeling results would provide an instructive guidance for predicting and possibly controlling the non-equilibrium particle-energy transportation process in various AP-LTPs in future.

Rapid sample classification using an open port sampling interface coupled with liquid introduction atmospheric pressure ionization mass spectrometry

DOE PAGES

Van Berkel, Gary J.; Kertesz, Vilmos

2016-11-15

An “Open Access”-like mass spectrometric platform to fully utilize the simplicity of the manual open port sampling interface for rapid characterization of unprocessed samples by liquid introduction atmospheric pressure ionization mass spectrometry has been lacking. The in-house developed integrated software with a simple, small and relatively low-cost mass spectrometry system introduced here fills this void. Software was developed to operate the mass spectrometer, to collect and process mass spectrometric data files, to build a database and to classify samples using such a database. These tasks were accomplished via the vendorprovided software libraries. Sample classification based on spectral comparison utilized themore » spectral contrast angle method. As a result, using the developed software platform near real-time sample classification is exemplified using a series of commercially available blue ink rollerball pens and vegetable oils. In the case of the inks, full scan positive and negative ion ESI mass spectra were both used for database generation and sample classification. For the vegetable oils, full scan positive ion mode APCI mass spectra were recorded. The overall accuracy of the employed spectral contrast angle statistical model was 95.3% and 98% in case of the inks and oils, respectively, using leave-one-out cross-validation. In conclusion, this work illustrates that an open port sampling interface/mass spectrometer combination, with appropriate instrument control and data processing software, is a viable direct liquid extraction sampling and analysis system suitable for the non-expert user and near real-time sample classification via database matching.« less

Rapid sample classification using an open port sampling interface coupled with liquid introduction atmospheric pressure ionization mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Berkel, Gary J.; Kertesz, Vilmos

An “Open Access”-like mass spectrometric platform to fully utilize the simplicity of the manual open port sampling interface for rapid characterization of unprocessed samples by liquid introduction atmospheric pressure ionization mass spectrometry has been lacking. The in-house developed integrated software with a simple, small and relatively low-cost mass spectrometry system introduced here fills this void. Software was developed to operate the mass spectrometer, to collect and process mass spectrometric data files, to build a database and to classify samples using such a database. These tasks were accomplished via the vendorprovided software libraries. Sample classification based on spectral comparison utilized themore » spectral contrast angle method. As a result, using the developed software platform near real-time sample classification is exemplified using a series of commercially available blue ink rollerball pens and vegetable oils. In the case of the inks, full scan positive and negative ion ESI mass spectra were both used for database generation and sample classification. For the vegetable oils, full scan positive ion mode APCI mass spectra were recorded. The overall accuracy of the employed spectral contrast angle statistical model was 95.3% and 98% in case of the inks and oils, respectively, using leave-one-out cross-validation. In conclusion, this work illustrates that an open port sampling interface/mass spectrometer combination, with appropriate instrument control and data processing software, is a viable direct liquid extraction sampling and analysis system suitable for the non-expert user and near real-time sample classification via database matching.« less

Chemical protection against ionizing radiation. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Livesey, J.C.; Reed, D.J.; Adamson, L.F.

1984-08-01

The scientific literature on radiation-protective drugs is reviewed. Emphasis is placed on the mechanisms involved in determining the sensitivity of biological material to ionizing radiation and mechanisms of chemical radioprotection. In Section I, the types of radiation are described and the effects of ionizing radiation on biological systems are reviewed. The effects of ionizing radiation are briefly contrasted with the effects of non-ionizing radiation. Section II reviews the contributions of various natural factors which influence the inherent radiosensitivity of biological systems. Inlcuded in the list of these factors are water, oxygen, thiols, vitamins and antioxidants. Brief attention is given tomore » the model describing competition between oxygen and natural radioprotective substances (principally, thiols) in determining the net cellular radiosensitivity. Several theories of the mechanism(s) of action of radioprotective drugs are described in Section III. These mechanisms include the production of hypoxia, detoxication of radiochemical reactive species, stabilization of the radiobiological target and the enhancement of damage repair processes. Section IV describes the current strategies for the treatment of radiation injury. Likely areas in which fruitful research might be performed are described in Section V. 495 references.« less

Steroid hormone profiles of urban and tidal rivers using LC/MS/MS equipped with electrospray ionization and atmospheric pressure photoionization sources.

PubMed

Yamamoto, Atsushi; Kakutani, Naoya; Yamamoto, Kohji; Kamiura, Toshikazu; Miyakoda, Hidekazu

2006-07-01

A highly sensitive and uncomplicated method of analyzing steroidal hormones in river and estuarine water samples was developed using a liquid chromatography tandem mass spectrometer equipped with an electrospray ionization (ESI) source and atmospheric pressure photoionization (APPI) source. Steroidal hormones included not only estrogen but also androgen and conjugates of these two. APPI displayed greater sensitivity than ESI for most of the unconjugated steroids examined, with very high sensitivity for testosterone and 4-androstene-3,17-dione in particular. For conjugated hormones, in contrast, ESI was more effective. The method developed was applied to the determination of hormones in the rivers of Osaka City and their estuaries, where the hormones detected were affected by the effluent from municipal wastewater treatment plants (WWTPs), and hormone concentration values were comparable to those reported in previous studies of such effluent. Because of the two-way flow and stagnancy of streams and watercourses, continuous input of steroidal hormones from WWTPs seems to bring about local accumulation. Levels of androgen were 1 order of magnitude lower than those of estrogen. Estrone, estrone 3-sulfate, and 4-androstene-3,17-dione were detected in almost all water samples, with maxima of 51, 5.1, and 6.4 ng L(-1), respectively.

Atmospheric Ionizing Radiation (AIR) Project Review

NASA Technical Reports Server (NTRS)

Singleterry, R. C., Jr.; Wilson, J. W.; Whitehead, A. H.; Goldhagen, P. E.

1999-01-01

The National Council on Radiation Protection and Measurement (NCRP) and the National Academy of Science (NAS) established that the uncertainty in the data and models associated with the high-altitude radiation environment could and should be reduced. In response, the National Aeronautics and Space Administration (NASA) and the U.S. Department of Energy Environmental Measurements Laboratory (EML) created the Atmospheric Ionizing Radiation (AIR) Project under the auspices of the High Speed Research (HSR) Program Office at the Langley Research Center. NASA's HSR Program was developed to address the potential of a second-generation supersonic transport. A critical element focussed on the environmental issues, including the threat to crew and passengers posed by atmospheric radiation. Various international investigators were solicited to contribute instruments to fly on an ER-2 aircraft at altitudes similar to those proposed for the High Speed Civil Transport (HSCT). A list of participating investigators, their institutions, and instruments with quantities measured is presented. The flight series took place at solar minimum (radiation maximum) with northern, southern, and east/west flights. The investigators analyzed their data and presented preliminary results at the AIR Workshop in March, 1998. A review of these results are included.

Development of a particle-trap preconcentration-soft ionization mass spectrometric technique for the quantification of mercury halides in air.

PubMed

Deeds, Daniel A; Ghoshdastidar, Avik; Raofie, Farhad; Guérette, Élise-Andrée; Tessier, Alain; Ariya, Parisa A

2015-01-01

Measurement of oxidized mercury, Hg(II), in the atmosphere poses a significant analytical challenge as Hg(II) is present at ultra-trace concentrations (picograms per cubic meter air). Current technologies are sufficiently sensitive to measure the total Hg present as Hg(II) but cannot determine the chemical speciation of Hg(II). We detail here the development of a soft ionization mass spectrometric technique coupled with preconcentration onto nano- or microparticle-based traps prior to analysis for the measurement of mercury halides in air. The current methodology has comparable detection limits (4-11 pg m(-3)) to previously developed techniques for the measurement of total inorganic mercury in air while allowing for the identification of HgX2 in collected samples. Both mercury chloride and mercury bromide have been sporadically detected in Montreal urban and indoor air using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). We discuss limitations and advantages of the current technique and discuss potential avenues for future research including quantitative trace measurements of a larger range of mercury compounds.

Electrodynamic balance-mass spectrometry of single particles as a new platform for atmospheric chemistry research

NASA Astrophysics Data System (ADS)

Birdsall, Adam W.; Krieger, Ulrich K.; Keutsch, Frank N.

2018-01-01

New analytical techniques are needed to improve our understanding of the intertwined physical and chemical processes that affect the composition of aerosol particles in the Earth's atmosphere, such as gas-particle partitioning and homogenous or heterogeneous chemistry, and their ultimate relation to air quality and climate. We describe a new laboratory setup that couples an electrodynamic balance (EDB) to a mass spectrometer (MS). The EDB stores a single laboratory-generated particle in an electric field under atmospheric conditions for an arbitrarily long length of time. The particle is then transferred via gas flow to an ionization region that vaporizes and ionizes the analyte molecules before MS measurement. We demonstrate the feasibility of the technique by tracking evaporation of polyethylene glycol molecules and finding agreement with a kinetic model. Fitting data to the kinetic model also allows determination of vapor pressures to within a factor of 2. This EDB-MS system can be used to study fundamental chemical and physical processes involving particles that are difficult to isolate and study with other techniques. The results of such measurements can be used to improve our understanding of atmospheric particles.

Computational studies of atmospherically-relevant chemical reactions in water clusters and on liquid water and ice surfaces.

PubMed

Gerber, R Benny; Varner, Mychel E; Hammerich, Audrey D; Riikonen, Sampsa; Murdachaew, Garold; Shemesh, Dorit; Finlayson-Pitts, Barbara J

2015-02-17

CONSPECTUS: Reactions on water and ice surfaces and in other aqueous media are ubiquitous in the atmosphere, but the microscopic mechanisms of most of these processes are as yet unknown. This Account examines recent progress in atomistic simulations of such reactions and the insights provided into mechanisms and interpretation of experiments. Illustrative examples are discussed. The main computational approaches employed are classical trajectory simulations using interaction potentials derived from quantum chemical methods. This comprises both ab initio molecular dynamics (AIMD) and semiempirical molecular dynamics (SEMD), the latter referring to semiempirical quantum chemical methods. Presented examples are as follows: (i) Reaction of the (NO(+))(NO3(-)) ion pair with a water cluster to produce the atmospherically important HONO and HNO3. The simulations show that a cluster with four water molecules describes the reaction. This provides a hydrogen-bonding network supporting the transition state. The reaction is triggered by thermal structural fluctuations, and ultrafast changes in atomic partial charges play a key role. This is an example where a reaction in a small cluster can provide a model for a corresponding bulk process. The results support the proposed mechanism for production of HONO by hydrolysis of NO2 (N2O4). (ii) The reactions of gaseous HCl with N2O4 and N2O5 on liquid water surfaces. Ionization of HCl at the water/air interface is followed by nucleophilic attack of Cl(-) on N2O4 or N2O5. Both reactions proceed by an SN2 mechanism. The products are ClNO and ClNO2, precursors of atmospheric atomic chlorine. Because this mechanism cannot result from a cluster too small for HCl ionization, an extended water film model was simulated. The results explain ClNO formation experiments. Predicted ClNO2 formation is less efficient. (iii) Ionization of acids at ice surfaces. No ionization is found on ideal crystalline surfaces, but the process is efficient on

Experimental investigation on large-area dielectric barrier discharge in atmospheric nitrogen and air assisted by the ultraviolet lamp.

PubMed

Zhang, Yan; Gu, Biao; Wang, Wenchun; Wang, Dezhen; Peng, Xuwen

2009-04-01

In this paper, ultraviolet radiation produced by the ultraviolet lamp is employed to supply pre-ionization for the dielectric barrier discharge in N(2) or air at atmospheric pressure. The effect of the ultraviolet pre-ionization on improving the uniformity of the dielectric barrier discharge is investigated experimentally. The atmospheric pressure glow discharge of the large area (270 mm x 120 mm) is obtained successfully via the ultraviolet pre-ionization in atmospheric DBD in N(2) when the gas gap decrease to 3mm. Based on the emission spectra, the mechanism which ultraviolet pre-ionization improves the uniformity of the dielectric barrier discharge is discussed.

Clouds Composition in Super-Earth Atmospheres: Chemical Equilibrium Calculations

NASA Astrophysics Data System (ADS)

Kempton, Eliza M.-R.; Mbarek, Rostom

2015-12-01

Attempts to determine the composition of super-Earth atmospheres have so far been plagued by the presence of clouds. Yet the theoretical framework to understand these clouds is still in its infancy. For the super-Earth archetype GJ 1214b, KCl, Na2S, and ZnS have been proposed as condensates that would form under the condition of chemical equilibrium, if the planet’s atmosphere has a bulk composition near solar. Condensation chemistry calculations have not been presented for a wider range of atmospheric bulk composition that is to be expected for super-Earth exoplanets. Here we provide a theoretical context for the formation of super-Earth clouds in atmospheres of varied composition by determining which condensates are likely to form, under the assumption of chemical equilibrium. We model super-Earth atmospheres assuming they are formed by degassing of volatiles from a solid planetary core of chondritic material. Given the atomic makeup of these atmospheres, we minimize the global Gibbs free energy of over 550 gases and condensates to obtain the molecular composition of the atmospheres over a temperature range of 350-3,000 K. Clouds should form along the temperature-pressure boundaries where the condensed species appear in our calculations. The super-Earth atmospheres that we study range from highly reducing to oxidizing and have carbon to oxygen (C:O) ratios that are both sub-solar and super-solar, thereby spanning a diverse range of atmospheric composition that is appropriate for low-mass exoplanets. Some condensates appear across all of our models. However, the majority of condensed species appear only over specific ranges of H:O and C:O ratios. We find that for GJ 1214b, KCl is the primary cloud-forming condensate at solar composition, in agreement with previous work. However, for oxidizing atmospheres, where H:O is less than unity, K2SO4 clouds form instead. For carbon-rich atmospheres with super-solar C:O ratios, graphite clouds additionally appear. At

Advanced PIC-MCC simulation for the investigation of step-ionization effect in intermediate-pressure capacitively coupled plasmas

NASA Astrophysics Data System (ADS)

Kim, Jin Seok; Hur, Min Young; Kim, Chang Ho; Kim, Ho Jun; Lee, Hae June

2018-03-01

A two-dimensional parallelized particle-in-cell simulation has been developed to simulate a capacitively coupled plasma reactor. The parallelization using graphics processing units is applied to resolve the heavy computational load. It is found that the step-ionization plays an important role in the intermediate gas pressure of a few Torr. Without the step-ionization, the average electron density decreases while the effective electron temperature increases with the increase of gas pressure at a fixed power. With the step-ionization, however, the average electron density increases while the effective electron temperature decreases with the increase of gas pressure. The cases with the step-ionization agree well with the tendency of experimental measurement. The electron energy distribution functions show that the population of electrons having intermediate energy from 4.2 to 12 eV is relaxed by the step-ionization. Also, it was observed that the power consumption by the electrons is increasing with the increase of gas pressure by the step-ionization process, while the power consumption by the ions decreases with the increase of gas pressure.

Mass spectrometry imaging for visualizing organic analytes in food.

PubMed

Handberg, Eric; Chingin, Konstantin; Wang, Nannan; Dai, Ximo; Chen, Huanwen

2015-01-01

The demand for rapid chemical imaging of food products steadily increases. Mass spectrometry (MS) is featured by excellent molecular specificity of analysis and is, therefore, a very attractive method for chemical profiling. MS for food imaging has increased significantly over the past decade, aided by the emergence of various ambient ionization techniques that allow direct and rapid analysis in ambient environment. In this article, the current status of food imaging with MSI is reviewed. The described approaches include matrix-assisted laser desorption/ionization (MALDI), but emphasize desorption atmospheric pressure photoionization (DAPPI), electrospray-assisted laser desorption/ionization (ELDI), probe electrospray ionization (PESI), surface desorption atmospheric pressure chemical ionization (SDAPCI), and laser ablation flowing atmospheric pressure afterglow (LA-FAPA). The methods are compared with regard to spatial resolution; analysis speed and time; limit of detection; and technical aspects. The performance of each method is illustrated with the description of a related application. Specific requirements in food imaging are discussed. © 2014 Wiley Periodicals, Inc.

A high temperature and atmospheric pressure experimental and detailed chemical kinetic modelling study of 2-methyl furan oxidation

PubMed Central

Somers, Kieran P.; Simmie, John M.; Gillespie, Fiona; Burke, Ultan; Connolly, Jessica; Metcalfe, Wayne K.; Battin-Leclerc, Frédérique; Dirrenberger, Patricia; Herbinet, Olivier; Glaude, Pierre-Alexandre; Curran, Henry J.

2013-01-01

An experimental ignition delay time study for the promising biofuel 2-methyl furan (2MF) was performed at equivalence ratios of 0.5, 1.0 and 2.0 for mixtures of 1% fuel in argon in the temperature range 1200–1800 K at atmospheric pressure. Laminar burning velocities were determined using the heat-flux method for mixtures of 2MF in air at equivalence ratios of 0.55–1.65, initial temperatures of 298–398 K and atmospheric pressure. A detailed chemical kinetic mechanism consisting of 2059 reactions and 391 species has been constructed to describe the oxidation of 2MF and is used to simulate experiment. Accurate reproduction of the experimental data has been obtained over all conditions with the developed mechanism. Rate of production and sensitivity analyses have been carried out to identify important consumption pathways of the fuel and key kinetic parameters under these conditions. The reactions of hydrogen atom with the fuel are highlighted as important under all experimental conditions studied, with abstraction by the hydrogen atom promoting reactivity and hydrogen atom addition to the furan ring inhibiting reactivity. This work, to the authors knowledge, is the first to combine theoretical and experimental work to describe the oxidation of any of the alkylated furans. The mechanism developed herein to describe 2MF combustion should also function as a sub-mechanism to describe the oxidation of 2,5-dimethyl furan whilst also providing key insights into the oxidation of this similar biofuel candidate. PMID:23814505

Solid-phase extraction combined with high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry analysis of pesticides in water: method performance and application in a reconnaissance survey of residues in drinking water in Greater Cairo, Egypt.

PubMed

Potter, Thomas L; Mohamed, Mahmoud A; Ali, Hannah

2007-01-24

Monitoring of water resources for pesticide residues is often needed to ensure that pesticide use does not adversely impact the quality of public water supplies or the environment. In many rural areas and throughout much of the developing world, monitoring is often constrained by lack of testing facilities; thus, collection of samples and shipment to centralized laboratories for analysis is required. The portability, ease of use, and potential to enhance analyte stability make solid-phase extraction (SPE) an attractive technique for handling water samples prior to their shipment. We describe performance of an SPE method targeting a structurally diverse mixture of 25 current-use pesticides and two common degradates in samples of raw and filtered drinking water collected in Greater Cairo, Egypt. SPE was completed in a field laboratory in Egypt, and cartridges were shipped to the United States for elution and high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry analysis. Quantitative and reproducible recovery of 23 of 27 compounds (average = 96%; percent relative standard deviation = 21%) from matrix spikes (1 microg L-1 per component) prepared in the field and from deionized water fortified similarly in the analytical laboratory was obtained. Concurrent analysis of unspiked samples identified four parent compounds and one degradate in drinking water samples. No significant differences were observed between raw and filtered samples. Residue levels in all cases were below drinking water and "harm to aquatic-life" thresholds, indicating that human and ecological risks of pesticide contamination were relatively small; however, the study was limited in scale and scope. Further monitoring is needed to define spatial and temporal variation in residue concentrations. The study has demonstrated the feasibility of performing studies of this type using SPE to extract and preserve samples in the field. The approach should be broadly

Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

PubMed

Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

2016-05-05

Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

Double-Layered Atmospheric Pressure Plasma Jet

NASA Astrophysics Data System (ADS)

Choi, Jaegu; Matsuo, Keita; Yoshida, Hidekazu; Namihira, Takao; Katsuki, Sunao; Akiyama, Hidenori

2009-08-01

In this paper, we present a double-layered atmospheric pressure plasma jet (DLAPPJ) that is expected to improve conventional single-layered atmospheric pressure plasma jets. With the additional introduction of nitrogen gas into the outer nozzle between the inner and outer tubes, the plasma plume is boosted, resulting in a brighter and longer plasma torch, which may have more radicals and which may broaden the application range of atmospheric pressure plasma jets. The characteristics of the proposed device were investigated with the measurement of the visible torch length, wettability tests and optical emission spectroscopy. The results obtained imply that the DLAPPJ can be used for target-based plasma treatments, that is, (a) oxidation-related applications, such as surface treatment, biological decontamination and apoptosis induction, and (b) nitrification-related applications such as NO generation for wound healing and surface modification, by controlling radicals in plasmas.

Collaborative Research: Atmospheric Pressure Microplasma Chemistry-Photon Synergies Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graves, David

Combining the effects of low temperature, atmospheric pressure microplasmas and microplasma photon sources shows greatly expanded range of applications of each of them. The plasma sources create active chemical species and these can be activated further by addition of photons and associated photochemistry. There are many ways to combine the effects of plasma chemistry and photochemistry, especially if there are multiple phases present. The project combines construction of appropriate test experimental systems, various spectroscopic diagnostics and mathematical modeling.

Direct atmospheric pressure chemical ionisation ion trap mass spectrometry for aroma analysis: Speed, sensitivity and resolution of isobaric compounds

NASA Astrophysics Data System (ADS)

Jublot, Lionel; Linforth, Robert S. T.; Taylor, Andrew J.

2005-06-01

Atmospheric pressure chemical ionisation (APCI) sources were developed for real time analysis of volatile release from foods using an ion trap (IT) mass spectrometer (MS). Key objectives were spectral simplicity (minimal fragmentation), response time and signal to noise ratio. The benefits of APCI-IT-MS were assessed by comparing the performance for in vivo and headspace analyses with that obtained using APCI coupled to a quadrupole mass analyser. Using MS-MS, direct APCI-IT-MS was able to differentiate mixtures of some C6 and terpene isobaric aroma compounds. Resolution could be achieved for some compounds by monitoring specific secondary ions. Direct resolution was also achieved with two of the three isobaric compounds released from chocolate with time as the sample was eaten.

Chemical kinetics and modeling of planetary atmospheres

NASA Technical Reports Server (NTRS)

Yung, Yuk L.

1990-01-01

A unified overview is presented for chemical kinetics and chemical modeling in planetary atmospheres. The recent major advances in the understanding of the chemistry of the terrestrial atmosphere make the study of planets more interesting and relevant. A deeper understanding suggests that the important chemical cycles have a universal character that connects the different planets and ultimately link together the origin and evolution of the solar system. The completeness (or incompleteness) of the data base for chemical kinetics in planetary atmospheres will always be judged by comparison with that for the terrestrial atmosphere. In the latter case, the chemistry of H, O, N, and Cl species is well understood. S chemistry is poorly understood. In the atmospheres of Jovian planets and Titan, the C-H chemistry of simple species (containing 2 or less C atoms) is fairly well understood. The chemistry of higher hydrocarbons and the C-N, P-N chemistry is much less understood. In the atmosphere of Venus, the dominant chemistry is that of chlorine and sulfur, and very little is known about C1-S coupled chemistry. A new frontier for chemical kinetics both in the Earth and planetary atmospheres is the study of heterogeneous reactions. The formation of the ozone hole on Earth, the ubiquitous photochemical haze on Venus and in the Jovian planets and Titan all testify to the importance of heterogeneous reactions. It remains a challenge to connect the gas phase chemistry to the production of aerosols.

Atmospheric Pressure Photoionization Tandem Mass Spectrometry of Androgens in Prostate Cancer

PubMed Central

Lih, Fred Bjørn; Titus, Mark A.; Mohler, James L.; Tomer, Kenneth B.

2010-01-01

Androgen deprivation therapy is the most common treatment option for advanced prostate cancer. Almost all prostate cancers recur during androgen deprivation therapy, and new evidence suggests that androgen receptor activation persists despite castrate levels of circulating androgens. Quantitation of tissue levels of androgens is critical to understanding the mechanism of recurrence of prostate cancer during androgen deprivation therapy. A liquid chromatography atmospheric pressure photoionization tandem mass spectrometric method was developed for quantitation of tissue levels of androgens. Quantitation of the saturated keto-steroids dihydrotestosterone and 5-α-androstanedione required detection of a novel parent ion, [M + 15]+. The nature of this parent ion was explored and the method applied to prostate tissue and cell culture with comparison to results achieved using electrospray ionization. PMID:20560527

Comparison of various liquid chromatographic methods involving UV and atmospheric pressure chemical ionization mass spectrometric detection for the efficient trace analysis of phenylurea herbicides in various types of water samples.

PubMed

van der Heeft, E; Dijkman, E; Baumann, R A; Hogendoorn, E A

2000-05-19

The performance of mass spectrometric (MS) detection and UV detection in combination with reversed-phase liquid chromatography without and with the use of coupled column RPLC (LC-LC) has been compared for the trace analysis of phenylurea herbicides in environmental waters. The selected samples of this comparative study originated from an inter-laboratory study. For both detection modes, a 50 mm x 4.6 mm I.D. column and a 100 mm x 4.6 mm I.D. column packed with 3 microm C18 were used as the first (C-1) and second (C-2) column, respectively. Atmospheric pressure chemical ionization mass spectrometry was performed on a magnetic sector instrument. The LC-LC-MS analysis was carried out on-line by means of direct large volume (11.7 ml) injection (LVI). The performance of both on-line (LVI, 4 ml of sample) and off-line LC-LC-UV (244 nm) analysis was investigated. The latter procedure consisted of a solid-phase extraction (SPE) of 250 ml of water sample on a 500 mg C18 cartridge. The comparative study showed that LC-LC-MS is more selective then LC-LC-UV and, in most cases, more sensitive. The LVI-LC-LC-MS approach combines direct quantification and confirmation of most of the analytes down to a level of 0.01 microg/l in water samples in less then 30 min. As regards LC-LC-UV, the off-line method appeared to be a more viable approach in comparison with the on-line procedure. This method allows the screening of phenylurea's in various types of water samples down to a level of at least 0.05 microg/l. On-line analysis with LVI provided marginal sensitivity (limits of detection of about 0.1 microg/l) and selectivity was sometimes less in case of surface water samples. Both the on-line LVI-LC-LC-MS method and the LC-LC-UV method using off-line SPE were validated by analysing a series of real-life reference samples. These samples were part of an inter-laboratory test and contained residues of herbicides ranging from 0.02 to 0.8 microg/l. Beside good correlation between the methods

Ionization processes in combined high-voltage nanosecond - laser discharges in inert gas

NASA Astrophysics Data System (ADS)

Starikovskiy, Andrey; Shneider, Mikhail; PU Team

2016-09-01

Remote control of plasmas induced by laser radiation in the atmosphere is one of the challenging issues of free space communication, long-distance energy transmission, remote sensing of the atmosphere, and standoff detection of trace gases and bio-threat species. Sequences of laser pulses, as demonstrated by an extensive earlier work, offer an advantageous tool providing access to the control of air-plasma dynamics and optical interactions. The avalanche ionization induced in a pre-ionized region by infrared laser pulses where investigated. Pre-ionization was created by an ionization wave, initiated by high-voltage nanosecond pulse. Then, behind the front of ionization wave extra avalanche ionization was initiated by the focused infrared laser pulse. The experiment was carried out in argon. It is shown that the gas pre-ionization inhibits the laser spark generation under low pressure conditions.

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).

PubMed

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

2007-04-01

The sn position of fatty acids in seed oil lipids affects physiological function in pharmaceutical and dietary applications. In 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 fatty acid-enriched rape seed oil were analyzed by reversed-phase high performance liquid chromatography coupled with online atmospheric-pressure chemical ionization ion-trap mass spectrometry. The transformation of summer rape with thioesterase and 3-ketoacyl-[ACP]-synthase genes of Cuphea lanceolata led to increased expression of 1.5% (w/w) caprylic acid (8:0), 6.7% (w/w) capric acid (10:0), 0.9% (w/w) lauric acid (12:0), and 0.2% (w/w) myristic acid (14:0). In contrast, linoleic (18:2n6) and alpha-linolenic acid (18:3n3) levels decreased compared with the original seed oil. The TAG sn position distribution of fatty acids was also modified. The original oil included eleven unique TAG species whereas the transgenic oil contained sixty. Twenty species were common to both oils. The transgenic oil included trioctadecenoyl-glycerol (18:1/18:1/18:1) and trioctadecatrienoyl-glycerol (18:3/18:3/18:3) whereas the native oil included only the latter. The transgenic TAG were dominated by combinations of caprylic, capric, lauric, myrisitic, palmitic (16:0), stearic (18:0), oleic (18:1n9), linoleic, arachidic (20:0), behenic (22:0), and lignoceric acids (24:0), which accounted for 52% of the total fat. In the original TAG palmitic, stearic, oleic, and linoleic acids accounted for 50% of the total fat. Medium-chain triacylglycerols with capric and lauric acids combined with stearic, oleic, linoleic, alpha-linolenic, arachidic, and gondoic acids (20:1n9) accounted for 25% of the transgenic oil. The medium-chain fatty acids were mainly integrated into the sn-1/3 position combined with the essential linoleic and alpha-linolenic acids at the sn-2 position. Eight species

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

NASA Astrophysics Data System (ADS)

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

2012-06-01

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.

Improving uniformity of atmospheric-pressure dielectric barrier discharges using dual frequency excitation

NASA Astrophysics Data System (ADS)

Liu, Y.; Peeters, F. J. J.; Starostin, S. A.; van de Sanden, M. C. M.; de Vries, H. W.

2018-01-01

This letter reports a novel approach to improve the uniformity of atmospheric-pressure dielectric barrier discharges using a dual-frequency excitation consisting of a low frequency (LF) at 200 kHz and a radio frequency (RF) at 13.56 MHz. It is shown that due to the periodic oscillation of the RF electric field, the electron acceleration and thus the gas ionization is temporally modulated, i.e. enhanced and suppressed during each RF cycle. As a result, the discharge development is slowed down with a lower amplitude and a longer duration of the LF discharge current. Hence, the RF electric field facilitates improved stability and uniformity simultaneously allowing a higher input power.

The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

NASA Astrophysics Data System (ADS)

Lavi, Avi; Vermeuel, Michael P.; Novak, Gordon A.; Bertram, Timothy H.

2018-06-01

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and α-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (< 100 pptv). In addition, we determine the dependence of CI-ToFMS sensitivity on the reagent ion neutral delivery concentration and water vapor concentration. We show that isoprene is primarily detected as an adduct (C5H8 ṡ C6H6+) with a sensitivity ranging between 4 and 10 ncps ppt-1, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C10H16+) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt-1 for SH between 7 and 14 g kg-1, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C15H24+) with an average sensitivity, across the four measured compounds, of 9.6 ± 2.3 ncps ppt-1, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere-atmosphere interactions.

Ionizing Electrons on the Martian Nightside: Structure and Variability

NASA Astrophysics Data System (ADS)

Lillis, Robert J.; Mitchell, David L.; Steckiewicz, Morgane; Brain, David; Xu, Shaosui; Weber, Tristan; Halekas, Jasper; Connerney, Jack; Espley, Jared; Benna, Mehdi; Elrod, Meredith; Thiemann, Edward; Eparvier, Frank

2018-05-01

The precipitation of suprathermal electrons is the dominant external source of energy deposition and ionization in the Martian nightside upper atmosphere and ionosphere. We investigate the spatial patterns and variability of ionizing electrons from 115 to 600 km altitude on the Martian nightside, using CO2 electron impact ionization frequency (EIIF) as our metric, examining more than 3 years of data collected in situ by the Mars Atmosphere and Volatile EvolutioN spacecraft. We characterize the behavior of EIIF with respect to altitude, solar zenith angle, solar wind pressure, and the geometry and strength of crustal magnetic fields. EIIF has a complex and correlated dependence on these factors, but we find that it generally increases with altitude and solar wind pressure, decreases with crustal magnetic field strength and does not depend detectably on solar zenith angle past 115°. The dependence is governed by (a) energy degradation and backscatter by collisions with atmospheric neutrals below 220 km and (b) magnetic field topology that permits or retards electron access to certain regions. This field topology is dynamic and varies with solar wind conditions, allowing greater electron access at higher altitudes where crustal fields are weaker and also for higher solar wind pressures, which result in stronger draped magnetic fields that push closed crustal magnetic field loops to lower altitudes. This multidimensional electron flux behavior can in the future be parameterized in an empirical model for use as input to global simulations of the nightside upper atmosphere, which currently do not account for this important source of energy.

Influence of ionization on the Gupta and on the Park chemical models

NASA Astrophysics Data System (ADS)

Morsa, Luigi; Zuppardi, Gennaro

2014-12-01

This study is an extension of former works by the present authors, in which the influence of the chemical models by Gupta and by Park was evaluated on thermo-fluid-dynamic parameters in the flow field, including transport coefficients, related characteristic numbers and heat flux on two current capsules (EXPERT and Orion) during the high altitude re-entry path. The results verified that the models, even computing different air compositions in the flow field, compute only slight different compositions on the capsule surface, therefore the difference in the heat flux is not very relevant. In the above mentioned studies, ionization was neglected because the velocities of the capsules (about 5000 m/s for EXPERT and about 7600 m/s for Orion) were not high enough to activate meaningful ionization. The aim of the present work is to evaluate the incidence of ionization, linked to the chemical models by Gupta and by Park, on both heat flux and thermo fluid-dynamic parameters. The present computer tests were carried out by a direct simulation Monte Carlo code (DS2V) in the velocity interval 7600-12000 m/s, considering only the Orion capsule at an altitude of 85 km. The results verified what already found namely when ionization is not considered, the chemical models compute only a slight different gas composition in the core of the shock wave and practically the same composition on the surface therefore the same heat flux. On the opposite, the results verified that when ionization is considered, the chemical models compute different compositions in the whole shock layer and on the surface therefore different heat flux. The analysis of the results relies on a qualitative and a quantitative evaluation of the effects of ionization on both chemical models. The main result of the study is that when ionization is taken into account, the Park model is more reactive than the Gupta model; consequently, the heat flux computed by Park is lower than the one computed by Gupta; using the

Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a mass-to-structure (MTS) Search Engine with integral isotope pattern ranking.

PubMed

Liao, Wenta; Draper, William M

2013-02-21

The mass-to-structure or MTS Search Engine is an Access 2010 database containing theoretical molecular mass information for 19,438 compounds assembled from common sources such as the Merck Index, pesticide and pharmaceutical compilations, and chemical catalogues. This database, which contains no experimental mass spectral data, was developed as an aid to identification of compounds in atmospheric pressure ionization (API)-LC-MS. This paper describes a powerful upgrade to this database, a fully integrated utility for filtering or ranking candidates based on isotope ratios and patterns. The new MTS Search Engine is applied here to the identification of volatile and semivolatile compounds including pesticides, nitrosoamines and other pollutants. Methane and isobutane chemical ionization (CI) GC-MS spectra were obtained from unit mass resolution mass spectrometers to determine MH(+) masses and isotope ratios. Isotopes were measured accurately with errors of <4% and <6%, respectively, for A + 1 and A + 2 peaks. Deconvolution of interfering isotope clusters (e.g., M(+) and [M - H](+)) was required for accurate determination of the A + 1 isotope in halogenated compounds. Integrating the isotope data greatly improved the speed and accuracy of the database identifications. The database accurately identified unknowns from isobutane CI spectra in 100% of cases where as many as 40 candidates satisfied the mass tolerance. The paper describes the development and basic operation of the new MTS Search Engine and details performance testing with over 50 model compounds.

IR/THz Double Resonance Spectroscopy Approach for Remote Chemical Detection at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Tanner, Elizabeth A.; Phillips, Dane J.; De Lucia, Frank C.; Everitt, Henry O.

2013-06-01

A remote sensing methodology based on infrared/terahertz (IR/THz) double resonance (DR) spectroscopy is shown to overcome limitations traditionally associated with either IR or THz spectroscopic approaches for detecting trace gases in an atmosphere. The applicability of IR/THz DR spectroscopy is explored by estimating the IR and THz power requirements for detecting a 100 part-per-million-meter cloud of methyl fluoride, methyl chloride, or methyl bromide at ranges up to 1km in three atmospheric windows below 0.3 THz. These prototypical molecules are used to ascertain the dependence of the DR signal-to-noise ratio on IR and THz beam power. A line-tunable CO_2 laser with 100 ps pulse duration generates a DR signature in four rotational transitions on a time scale commensurate with collisional relaxations caused by atmospheric N_2 and O_2. A continuous wave THz beam is frequency tuned to probe one of these rotational transitions so that laser-induced absorption variations in the analyte cloud are detected as temporal power fluctuations synchronized with the laser pulses. A combination of molecule-specific physics and scenario-dependent atmospheric conditions are used to predict the signal-to-noise ratio (SNR) for detecting an analyte as a function of cloud column density. A methodology is presented by which the optimal IR/THz pump/probe frequencies are identified. These estimates show the potential for low concentration chemical detection in a challenging atmospheric scenario with currently available or near term hardware components.

Comprehensive chemical comparison of fuel composition and aerosol particles emitted from a ship diesel engine by gas chromatography atmospheric pressure chemical ionisation ultra-high resolution mass spectrometry with improved data processing routines.

PubMed

Rüger, Christopher P; Schwemer, Theo; Sklorz, Martin; O'Connor, Peter B; Barrow, Mark P; Zimmermann, Ralf

2017-02-01

The analysis of petrochemical materials and particulate matter originating from combustion sources remains a challenging task for instrumental analytical techniques. A detailed chemical characterisation is essential for addressing health and environmental effects. Sophisticated instrumentation, such as mass spectrometry coupled with chromatographic separation, is capable of a comprehensive characterisation, but needs advanced data processing methods. In this study, we present an improved data processing routine for the mass chromatogram obtained from gas chromatography hyphenated to atmospheric pressure chemical ionisation and ultra high resolution mass spectrometry. The focus of the investigation was the primary combustion aerosol samples, i.e. particulate matter extracts, as well as the corresponding fossil fuels fed to the engine. We demonstrate that utilisation of the entire transient and chromatographic information results in advantages including minimisation of ionisation artefacts and a reliable peak assignment. A comprehensive comparison of the aerosol and the feed fuel was performed by applying intensity weighted average values, compound class distribution and principle component analysis. Certain differences between the aerosol generated with the two feed fuels, diesel fuel and heavy fuel oil, as well as between the aerosol and the feed were revealed. For the aerosol from heavy fuel oil, oxidised species from the CHN and CHS class precursors of the feed were predominant, whereas the CHO x class is predominant in the combustion aerosol from light fuel oil. Furthermore, the complexity of the aerosol increases significantly compared to the feed and incorporating a higher chemical space. Coupling of atmospheric pressure chemical ionisation to gas chromatography was found to be a useful additional approach for characterisation of a combustion aerosol, especially with an automated utilisation of the information from the ultra-high resolution mass spectrometer

Atmospheric pressure matrix-assisted laser desorption ionization as a plume diagnostic tool in laser evaporation methods

NASA Astrophysics Data System (ADS)

Callahan, John H.; Galicia, Marsha C.; Vertes, Akos

2002-09-01

Laser evaporation techniques, including matrix-assisted pulsed laser evaporation (MAPLE), are attracting increasing attention due to their ability to deposit thin layers of undegraded synthetic and biopolymers. Laser evaporation methods can be implemented in reflection geometry with the laser and the substrate positioned on the same side of the target. In some applications (e.g. direct write, DW), however, transmission geometry is used, i.e. the thin target is placed between the laser and the substrate. In this case, the laser pulse perforates the target and transfers some target material to the substrate. In order to optimize evaporation processes it is important to know the composition of the target plume and the material deposited from the plume. We used a recently introduced analytical method, atmospheric pressure matrix-assisted laser desorption ionization (AP-MALDI) to characterize the ionic components of the plume both in reflection and in transmission geometry. This technique can also be used to directly probe materials deposited on surfaces (such as glass slides) by laser evaporation methods. The test compound (small peptides, e.g. Angiotensin I, ATI or Substance P) was mixed with a MALDI matrix (α-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA) or 2,5-dihydroxybenzoic acid (DHB)) and applied to the stainless steel (reflection geometry) or transparent conducting (transmission geometry) target holder. In addition to the classical dried droplet method, we also used electrospray target deposition to gain better control of crystallite size, thickness and homogeneity. The target was mounted in front of the inlet orifice of an ion trap mass spectrometer (IT-MS) that sampled the ionic components of the plume generated by a nitrogen laser. We studied the effect of several parameters, such as, the orifice to target distance, illumination geometry, extracting voltage distribution and sample preparation on the generated ions. Various analyte-matrix and

Unusual neurological syndrome induced by atmospheric pressure change.

PubMed

Ptak, Judy A; Yazinski, Nancy A; Block, Clay A; Buckey, Jay C

2013-05-01

We describe a case of a 46-yr-old female who developed hypertension, tachycardia, dysarthria, and leg weakness provoked by pressure changes associated with flying. Typically during the landing phase of flight, she would feel dizzy and note that she had difficulty with speech and leg weakness. After the flight the leg weakness persisted for several days. The symptoms were mitigated when she took a combined alpha-beta blocker (labetalol) prior to the flight. To determine if these symptoms were related to atmospheric pressure change, she was referred for testing in a hyperbaric chamber. She was exposed to elevated atmospheric pressure (maximum 1.2 ATA) while her heart rate and blood pressure were monitored. Within 1 min she developed tachycardia and hypertension. She also quickly developed slurred speech, left arm and leg weakness, and sensory changes in her left leg. She was returned to sea level pressure and her symptoms gradually improved. A full neurological workup has revealed no explanation for these findings. She has no air collections, cysts, or other anatomic findings that could be sensitive to atmospheric pressure change. The pattern is most consistent with a vascular event stimulated by altitude exposure. This case suggests that atmospheric pressure change can produce neurological symptoms, although the mechanism is unknown.

Inactivation of virus in solution by cold atmospheric pressure plasma: identification of chemical inactivation pathways

NASA Astrophysics Data System (ADS)

Aboubakr, Hamada A.; Gangal, Urvashi; Youssef, Mohammed M.; Goyal, Sagar M.; Bruggeman, Peter J.

2016-05-01

Cold atmospheric pressure plasma (CAP) inactivates bacteria and virus through in situ production of reactive oxygen and nitrogen species (RONS). While the bactericidal and virucidal efficiency of plasmas is well established, there is limited knowledge about the chemistry leading to the pathogen inactivation. This article describes a chemical analysis of the CAP reactive chemistry involved in the inactivation of feline calicivirus. We used a remote radio frequency CAP produced in varying gas mixtures leading to different plasma-induced chemistries. A study of the effects of selected scavengers complemented with positive control measurements of relevant RONS reveal two distinctive pathways based on singlet oxygen and peroxynitrous acid. The first mechanism is favored in the presence of oxygen and the second in the presence of air when a significant pH reduction is induced in the solution by the plasma. Additionally, smaller effects of the H2O2, O3 and \\text{NO}2- produced were also found. Identification of singlet oxygen-mediated 2-imidazolone/2-oxo-His (His  +14 Da)—an oxidative modification of His 262 comprising the capsid protein of feline calicivirus links the plasma induced singlet oxygen chemistry to viral inactivation.

Fragmentation pathways and structural characterization of organophosphorus compounds related to the Chemical Weapons Convention by electron ionization and electrospray ionization tandem mass spectrometry.

PubMed

Hosseini, Seyed Esmaeil; Saeidian, Hamid; Amozadeh, Ali; Naseri, Mohammad Taghi; Babri, Mehran

2016-12-30

For unambiguous identification of Chemical Weapons Convention (CWC)-related chemicals in environmental samples, the availability of mass spectra, interpretation skills and rapid microsynthesis of suspected chemicals are essential requirements. For the first time, the electron ionization single quadrupole and electrospray ionization tandem mass spectra of a series of O-alkyl N-[bis(dimethylamino)methylidene]-P-methylphosphonamidates (Scheme 1, cpd 4) were studied for CWC verification purposes. O-Alkyl N-[bis(dimethylamino)methylidene]-P-methylphosphonamidates were prepared through a microsynthetic method and were analyzed using electron ionization and electrospray ionization mass spectrometry with gas and liquid chromatography, respectively, as MS-inlet systems. General EI and ESI fragmentation pathways were proposed and discussed, and collision-induced dissociation studies of the protonated derivatives of these compounds were performed to confirm proposed fragment ion structures by analyzing mass spectra of deuterated analogs. Mass spectrometric studies revealed some interesting fragmentation pathways during the ionization process, such as McLafferty rearrangement, hydrogen rearrangement and a previously unknown intramolecular electrophilic aromatic substitution reaction. The EI and ESI fragmentation routes of the synthesized compounds 4 were investigated with the aim of detecting and identifying CWC-related chemicals during on-site inspection and/or off-site analysis and toxic chemical destruction monitoring. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Mycotoxin Decontamination of Food: Cold Atmospheric Pressure Plasma versus “Classic” Decontamination

PubMed Central

Hojnik, Nataša; Cvelbar, Uroš; Tavčar-Kalcher, Gabrijela; Walsh, James L.; Križaj, Igor

2017-01-01

Mycotoxins are secondary metabolites produced by several filamentous fungi, which frequently contaminate our food, and can result in human diseases affecting vital systems such as the nervous and immune systems. They can also trigger various forms of cancer. Intensive food production is contributing to incorrect handling, transport and storage of the food, resulting in increased levels of mycotoxin contamination. Mycotoxins are structurally very diverse molecules necessitating versatile food decontamination approaches, which are grouped into physical, chemical and biological techniques. In this review, a new and promising approach involving the use of cold atmospheric pressure plasma is considered, which may overcome multiple weaknesses associated with the classical methods. In addition to its mycotoxin destruction efficiency, cold atmospheric pressure plasma is cost effective, ecologically neutral and has a negligible effect on the quality of food products following treatment in comparison to classical methods. PMID:28452957

GoAmazon 2014/15 Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, JN

2016-04-01

The Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) deployment to the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility T3 site in Manacapuru, Brazil, was motivated by two main scientific objectives of the Green Ocean Amazon (GoAmazon) 2014/15 field campaign. 1) Study the interactions between anthropogenic and biogenic emissions by determining important molecular species in ambient nanoparticles. To address this, TDCIMS data will be combined with coincident measurements such as gas-phase sulfuric acid to determine the contribution of sulfuric acid condensation to nucleation and growth. We can then compare that result to TDCIMS-derived nanoparticle composition tomore » determine the fraction of growth that can be attributed to the uptake of organic compounds. The molecular composition of sampled particles will also be used to attribute specific chemical species and mechanisms to growth, such as the condensation of low-volatility species or the oligomerization of α-dicarbonyl compounds. 2) Determine the source of new ambient nanoparticles in the Amazon. The hypothesis prior to measurements was that potassium salts formed from the evaporation of primary particles emitted by fungal spores can provide a unique and important pathway for new particle production in the Amazon basin. To explore this hypothesis, the TDCIMS recorded the mass spectra of sampled ambient particles using a protonated water cluster Chemical Ionization Mass Spectrometer (CIMS). Laboratory tests performed using potassium salts show that the TDCIMS can detect potassium with high sensitivity with this technique.« less

Chemical Composition of the Atmosphere

NASA Astrophysics Data System (ADS)

Schlager, Hans; Grewe, Volker; Roiger, Anke

Atmospheric trace gases have an important impact on Earth's radiative budget, the oxidative or cleansing ability of the atmosphere, the formation, growth and properties of aerosols, air quality, and human health. During recent years, the coupling between atmospheric chemistry and climate has received particular attention. Therefore, research is now focused on the composition and processes in the upper troposphere and lower stratosphere, a key region in this respect. In this chapter the chemical composition of the atmosphere is addressed and selected examples of significant advances in this field are presented.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnoult, G.; Belmonte, T.; Henrion, G.

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 aremore » submitted to high compressive stress. When it is relaxed, 'nestlike structures' made of nanoribbons are synthesized.« less

Reduced Lung Cancer Mortality With Lower Atmospheric Pressure.

PubMed

Merrill, Ray M; Frutos, Aaron

2018-01-01

Research has shown that higher altitude is associated with lower risk of lung cancer and improved survival among patients. The current study assessed the influence of county-level atmospheric pressure (a measure reflecting both altitude and temperature) on age-adjusted lung cancer mortality rates in the contiguous United States, with 2 forms of spatial regression. Ordinary least squares regression and geographically weighted regression models were used to evaluate the impact of climate and other selected variables on lung cancer mortality, based on 2974 counties. Atmospheric pressure was significantly positively associated with lung cancer mortality, after controlling for sunlight, precipitation, PM2.5 (µg/m 3 ), current smoker, and other selected variables. Positive county-level β coefficient estimates ( P < .05) for atmospheric pressure were observed throughout the United States, higher in the eastern half of the country. The spatial regression models showed that atmospheric pressure is positively associated with age-adjusted lung cancer mortality rates, after controlling for other selected variables.

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

Treesearch

J. M. Roberts; P. Veres; C. Warneke; J. A. Neuman; R. A. Washenfelder; S. S. Brown; M. Baasandorj; J. B. Burkholder; I. R. Burling; T. J. Johnson; R. J. Yokelson; J. de Gouw

2010-01-01

A negative-ion proton transfer chemical ionization mass spectrometric technique (NI-PT-CIMS), using acetate as the reagent ion, was applied to the measurement of volatile inorganic acids of atmospheric interest: hydrochloric (HCl), nitrous (HONO), nitric 5 (HNO3), and isocyanic (HNCO) acids. Gas phase calibrations through the sampling inlet showed the method to be...

Application of diffuse discharges of atmospheric pressure formed by runaway electrons for modification of copper and stainless steel surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarasenko, V. F., E-mail: VFT@loi.hcei.tsc.ru; Shulepov, M. A.; Erofeev, M. V.

The results of studies devoted to the influence of a runaway electron pre-ionized diffuse discharge (REP DD) formed in air and nitrogen at atmospheric pressure on the surface of copper and stainless steel are presented. Nanosecond high-voltage pulses were used to obtain REP DD in different gases at high pressures in a chamber with a flat anode and a cathode possessing a small radius of curvature. This mode of discharge was implemented owing to the generation of runaway electrons and X-rays. The conditions under which the surface of copper and stainless steel was cleaned from carbon and oxidized are described.

Miniature flowing atmospheric-pressure afterglow ion source for facile interfacing of CE with MS.

PubMed

Jecklin, Matthias C; Schmid, Stefan; Urban, Pawel L; Amantonico, Andrea; Zenobi, Renato

2010-10-01

Here, we present a miniaturized version of the flowing atmospheric-pressure afterglow (miniFAPA) ion source and use it for sheathless coupling of CE with MS. The simple design of the CE-miniFAPA-MS interface makes it easy to separate the electric potentials used for CE and for ionization. A pneumatically assisted nebulization of the CE effluent transfers the analytes from the liquid phase into the gas phase before they are ionized by interacting with reactive species produced by the FAPA. An important advantage of this interface is its high stability during operation: optimization of five different parameters indicated that the interface is not sensitive to minor deviations from the optimum values. Other advantages include ease of construction and maintenance, as well as relatively low cost. Samples with complex matrices, such as yeast extract, soil extract and urine, spiked with the test compounds, were successfully analyzed using the CE-miniFAPA-MS setup.

The major influence of the atmosphere on intracranial pressure: an observational study

NASA Astrophysics Data System (ADS)