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The present work is a comprehensive review of the whole field of atmospheric chemistry, with particular reference to the composition and dynamics of the chemosphere, airglow, ionosphere, air pollution, and the atmospheres of other... more
The present work is a comprehensive review of the whole field of atmospheric chemistry, with particular reference to the composition and dynamics of the chemosphere, airglow, ionosphere, air pollution, and the atmospheres of other planets. The properties of the earth's atmosphere as a photochemical system are described along with those of the sun as a light source for photolysis. Experimental
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Selected ion flow tube mass spectrometry (SIFT‐MS) is now recognized as the most versatile analytical technique for the identification and quantification of trace gases down to the parts‐per‐trillion by volume, pptv, range. This statement... more
Selected ion flow tube mass spectrometry (SIFT‐MS) is now recognized as the most versatile analytical technique for the identification and quantification of trace gases down to the parts‐per‐trillion by volume, pptv, range. This statement is supported by the wide reach of its applications, from real‐time analysis, obviating sample collection of very humid exhaled breath, to its adoption in industrial scenarios for air quality monitoring. This review touches on the recent extensions to the underpinning ion chemistry kinetics library and the alternative challenge of using nitrogen carrier gas instead of helium. The addition of reagent anions in the Voice200 series of SIFT‐MS instruments has enhanced the analytical capability, thus allowing analyses of volatile trace compounds in humid air that cannot be analyzed using reagent cations alone, as clarified by outlining the anion chemistry involved. Case studies are reviewed of breath analysis and bacterial culture volatile organic compound (VOC), emissions, environmental applications such as air, water, and soil analysis, workplace safety such as transport container fumigants, airborne contamination in semiconductor fabrication, food flavor and spoilage, drugs contamination and VOC emissions from packaging to demonstrate the stated qualities and uniqueness of the new generation SIFT‐MS instrumentation. Finally, some advancements that can be made to improve the analytical capability and reach of SIFT‐MS are mentioned.
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We report a fast, sensitive, real-time method to measure monobromamine, monochloramine and dichloramine using selected ion flow tube mass spectrometry (SIFT-MS). Relative rate coefficients and product distributions are reported for the... more
We report a fast, sensitive, real-time method to measure monobromamine, monochloramine and dichloramine using selected ion flow tube mass spectrometry (SIFT-MS). Relative rate coefficients and product distributions are reported for the reagent ions H3O+ and O2 +. Rapid reactions with the haloamines were observed with H3O+ and O2 + but no fast reaction was found with NO+. A slow reaction between NO+ and dichloramine was observed. We demonstrate the feasibility of determining these compounds in a single human breath for which the limit of detection is approaching 10 parts per billion (ppb). We also report preliminary measurements of these compounds in the breath of individuals where the concentrations of bromamine and chloramine ranged from 10 to 150 ppb.
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Chapter 8 Recently, we have seen a rapid development in direct introduction mass spectrometry (DIMS). Among the DIMS instruments mentioned are: atmosphericpressure chemical ionization (APCI), proton-transfer-reaction mass spectrometry... more
Chapter 8 Recently, we have seen a rapid development in direct introduction mass spectrometry (DIMS). Among the DIMS instruments mentioned are: atmosphericpressure chemical ionization (APCI), proton-transfer-reaction mass spectrometry (PTR-MS), selected ion-flow-tube mass spectrometry (SIFT-MS), ion-molecule reaction mass spectrometry (IMR-MS), direct analysis in real time (DART) and desorption electrospray ionization (DESI). These technologies are also compared for applications to ambient mass spectrometry. Finally, selected examples of applications for the technologies are given, including research monitoring of volatile organic compounds (VOCs) in the applications to food-quality control, flavor release, process monitoring, environmental and medical sciences.
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The distribution of unimolecular lifetimes of ion-molecule complexes formed in association reactions has been measured by ion cyclotron double-resonance. The mean unimolecular lifetimes of (H(sub 2)C(sub 6)N(sub 2)(sup +))(sup *) and... more
The distribution of unimolecular lifetimes of ion-molecule complexes formed in association reactions has been measured by ion cyclotron double-resonance. The mean unimolecular lifetimes of (H(sub 2)C(sub 6)N(sub 2)(sup +))(sup *) and (CH(sub 3)CN.CH(sub 3)(sup +))(sup *) were determined to be 180 (micro)s and 140 (micro)s respectively. A theoretical examination of the distribution of lifetimes of (CH(sub 3)CN.CH(sub 3)(sup +))(sup *) was conducted using a RRKM model. The RRKM distribution, when modified by experimental constraints, was found to be a good approximation of the experimentally determined lifetime distribution. The lifetimes for unimolecular dissociation and radiative relaxation, and the absolute efficiency of collisional relaxation are also reported.
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Es werden Geschwindigkeitskonstanten der Löschung der 253,7 nm‐Fluoreszenz sowie Quantenausbeuten der Lumineszenzemission während der Hg‐sensibilisierten Photolyse für folgende Alkohole bestimmt: Methanol, Äthanol, Propanol, Isopropanol,... more
Es werden Geschwindigkeitskonstanten der Löschung der 253,7 nm‐Fluoreszenz sowie Quantenausbeuten der Lumineszenzemission während der Hg‐sensibilisierten Photolyse für folgende Alkohole bestimmt: Methanol, Äthanol, Propanol, Isopropanol, n‐Butanol, Isobutanol, sek.‐, tert.‐Butanol und tert.‐Amylalkohol.
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Rate coefficients are reported for a number of proton-transfer reactions with formic acid. These reactions can be represented by the general equation �������������������������� XH++HCOOH → (HCOOH)H+ +X : (X = CH4, H2O, N2, CO, HCN, HCHO,... more
Rate coefficients are reported for a number of proton-transfer reactions with formic acid. These reactions can be represented by the general equation �������������������������� XH++HCOOH → (HCOOH)H+ +X : (X = CH4, H2O, N2, CO, HCN, HCHO, CH3OH and H2S). Reasonable agreement was obtained between our observed results and predictions based on the average-dipole-orientation (ADO) model except that ADO theory may slightly underestimate the collision rate.
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Trap and analyse methods have been successful for analyzing these species but the rapid chemistry of their production and loss drives the need for measurements on the minute time scale. Mass spectrometric methods have the advantage of... more
Trap and analyse methods have been successful for analyzing these species but the rapid chemistry of their production and loss drives the need for measurements on the minute time scale. Mass spectrometric methods have the advantage of wide applicability to the hydrocarbons and the carbonyl compounds with fast time response. However, since this is fundamentally a mass measurement, these methods often cannot distinguish between structural isomers on the basis of the parent ion alone. This is a particular problem for the carbonyl compounds such as methacrolein and methylvinyl ketone produced from the oxidation of isoprene as the aldehyde and ketone have the same mass.
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Odors from wastewater treatment plants (WWTPs) have frequently been attributed primarily to hydrogen sulfide (H2S). Low-to-medium cost hydrogen sulfide sensors have been utilized as odor indicators. However, other odorous species are... more
Odors from wastewater treatment plants (WWTPs) have frequently been attributed primarily to hydrogen sulfide (H2S). Low-to-medium cost hydrogen sulfide sensors have been utilized as odor indicators. However, other odorous species are usually present that may have lower odor thresholds than hydrogen sulfide. Hydrogen sulfide is not always present in odorous environments and the correlation of hydrogen sulfide to odor at a treatment facility is inconsistent. Such factors determine hydrogen sulfide an inconsistent indicator and more sophisticated measurement techniques are required to accurately predict odor intensity from complex gaseous mixes. In this paper, the performance of a direct mass spectrometric technique, selected ion flow tube mass spectrometry (SIFT-MS), is evaluated for analysis of odors from diverse sources at a modern WWTP. The soft chemical ionization employed in SIFT-MS provides detection and quantification of a wide range of potential odorants to below, or close to,...
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The Nutrition Section of the Mozambican Ministry of Health recently implemented a low-cost, rapid field tool for assessing the quality of household diets. Such tools can play an important part in targeting development assistance in... more
The Nutrition Section of the Mozambican Ministry of Health recently implemented a low-cost, rapid field tool for assessing the quality of household diets. Such tools can play an important part in targeting development assistance in countries where resources are scarce. This paper evaluates how well the tool performs at describing household dietary intakes in northern Mozambique and explores ways to improve it. The food-group classification and scoring system that form the core of the tool were applied to household data (n = 1,140) collected in a previous quantitative diet study in Nampula and Cabo Delgado Provinces. Using mean intakes as a criterion, the diet assessment tool performed well on all nutrients studied, except vitamin A. Those classified by the tool into the top group of diet quality had the highest mean intakes of energy, protein, and iron as well as the highest mean scores on the Mozambican Diet Quality Index, whereas those classified in the bottom group had the lowest...
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ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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In the ion-molecule reaction between HC3N(+) and HC3N, the lifetime of the collision complex (H2C6N2+)-asterisk was long enough that ion cyclotron double-resonance techniques could be used to probe the distribution of the lifetimes of the... more
In the ion-molecule reaction between HC3N(+) and HC3N, the lifetime of the collision complex (H2C6N2+)-asterisk was long enough that ion cyclotron double-resonance techniques could be used to probe the distribution of the lifetimes of the collision complex. The mean lifetime of the collision complex at room temperature was measured as 180 microsec with a distribution ranging from 60 to 260
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The analysis of volatile biomarkers of disease in breath is attractive because breath analysis is non-invasive and quick, and allows for repeated sampling. Challenges faced in the development of breath analysis include developing... more
The analysis of volatile biomarkers of disease in breath is attractive because breath analysis is non-invasive and quick, and allows for repeated sampling. Challenges faced in the development of breath analysis include developing techniques that can measure analytes at very low concentrations, gaining an understanding of the exhalation physiology of individual volatiles, and determining the relationship between the proposed biomarker
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We report selected ion flow tube measurements of reaction rate coefficients and branching ratios for the reactions of H3O+, O2+ and NO+ with the small hydrocarbons CH4, C2H2, C2H4, C2H6, C3H4 (allene and propyne), C3H6, c-C3H6, C3H8,... more
We report selected ion flow tube measurements of reaction rate coefficients and branching ratios for the reactions of H3O+, O2+ and NO+ with the small hydrocarbons CH4, C2H2, C2H4, C2H6, C3H4 (allene and propyne), C3H6, c-C3H6, C3H8, C4H2, C4H8 and n,i-C4H10. The relevance of these measurements to quantitative selected ion flow tube mass spectrometry (SIFT-MS) is discussed. An application of
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... Murray J. McEwan,*J***s Cara L. McConnell,+ Colin G. Freeman,+ and Vincent G. Anicich'** Department of Chemistry, University of Canterbury ... is in apparent contrast to the much higher-pressure selected ion flow tube... more
... Murray J. McEwan,*J***s Cara L. McConnell,+ Colin G. Freeman,+ and Vincent G. Anicich'** Department of Chemistry, University of Canterbury ... is in apparent contrast to the much higher-pressure selected ion flow tube (SIFT) observations of Adams and Smith,s who observed a ...
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Ion cyclotron mass spectrometry is used here to study the reactions between HC3N(+) and HC3N and between HC5N(+) and HC3N at pressures from 1 x 10 to the -7th to 0.001 Torr. The former reaction has both a bimolecular reaction path and a... more
Ion cyclotron mass spectrometry is used here to study the reactions between HC3N(+) and HC3N and between HC5N(+) and HC3N at pressures from 1 x 10 to the -7th to 0.001 Torr. The former reaction has both a bimolecular reaction path and a termolecular reaction path. The overall bimolecular reaction rate coefficient is 1.3 x 10 to the -19 cu cm/s. The primary product HC5N(+) represents 90 percent of the product ions, while HC6N2(+) and H2C6N2(+) each represent 5 percent. The termolecular association rate coefficient is 3.7 x 10 to the -24th cm exp 6/s, with He as the third body. The mean lifetime of the collision is 180 microsec. HC5N(+) reacts with HC3N to form the adduct ion H2C8N2(+) through both bimolecular and termolecular reactions. The bimolecular rate coefficient is 5.0 x 10 to the -10th cu cm/s and the termolecular one is 1.2 x 10 to the -22nd cm exp 6/s, with HC3N as the third body.
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... J. Mass Spectrom. Ion Processes 1995, 149/50, 251. [CrossRef]. (8) Fairley, DA; Scott, GBI;Freeman, CG; Maclagan, RGAR; McEwan, MJ J. Chem. Soc., Faraday Trans. 1996, 92, 1305. ... 11) McIntosh, BJ; Adams, NG; Smith, D. Chem. Phys.... more
... J. Mass Spectrom. Ion Processes 1995, 149/50, 251. [CrossRef]. (8) Fairley, DA; Scott, GBI;Freeman, CG; Maclagan, RGAR; McEwan, MJ J. Chem. Soc., Faraday Trans. 1996, 92, 1305. ... 11) McIntosh, BJ; Adams, NG; Smith, D. Chem. Phys. Lett. 1988, 148, 142. ...