Search results for "Mass spectrum"

Urban organic aerosol composition in eastern China differs from north to south:Molecular insight from a liquid chromatography-mass spectrometry (Orbi…

2021

Air pollution by particulate matter in China affects human health, the ecosystem and the climate. However, the chemical composition of particulate aerosol, especially of the organic fraction, is still not well understood. In this study, particulate aerosol samples with a diameter of ≤2.5 µm (PM2.5) were collected in January 2014 in three cities located in northeast, east and southeast China, namely Changchun, Shanghai and Guangzhou. Organic aerosol (OA) in the PM2.5 samples was analyzed by an ultrahigh-performance liquid chromatograph (UHPLC) coupled to a high-resolution Orbitrap mass spectrometer in both negative mode (ESI-) and positive mode electrospray ionization (ESI+). After non-targe…

Unambiguous identification of esters as oligomers in secondary organic aerosol formed from cyclohexene and cyclohexene/α-pinene ozonolysis

2007

Abstract. The build-up of oligomeric compounds during secondary organic aerosol (SOA) formation is subject of atmospheric research since several years. New particle formation and especially the SOA mass yield might be influenced significantly by oligomer formation. However, the chemical nature of observed oligomers and their formation pathways are still unclear. In this paper, the structural characterization of certain dimeric compounds (esters) formed during the ozonolysis of cyclohexene and cyclohexene/α-pinene mixtures are presented. The identification is based on the comparison of the mass spectra and the retention times (LC) of the oligomeric products with synthesized reference compoun…

Seasonal variations in aerosol particle composition at the puy-de-Dôme research station in France

2011

Detailed investigations of the chemical and microphysical properties of atmospheric aerosol particles were performed at the puy-de-Dôme (pdD) research station (1465 m) in autumn (September and October 2008), winter (February and March 2009), and summer (June 2010) using a compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS). Over the three campaigns, the average mass concentrations of the non-refractory submicron particles ranged from 10 μg m<sup>−3</sup> up to 27 μg m<sup>−3</sup>. Highest nitrate and ammonium mass concentrations were measured during the winter and during periods when marine modified airmasses were arriving at the site, wh…

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and…

2010

Abstract. Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l.) during the Cloud and Aerosol Characterization Experiment (CLACE 6) in February and March 2007. During mixed phase cloud events ice crystals from 5–20 μm were separated from larger ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI). During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The …

Observation of an Excited $B^{\pm}_c$ Meson State with the ATLAS Detector

2014

A search for excited states of the B±c meson is performed using 4.9 fb-1 of 7 TeV and 19.2 fb-1 of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay B±c→J/ψπ±. The state appears in the m(Bc±π+π-)-m(Bc±)-2m(π±) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842±4±5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the B±c meson, B±c(2S).

Studies in organic mass spectrometry.VIII. The electron impact mass spectra of 2,4-substituted-3-diazo-5-phenylpyrroles

1990

The electron impact mass spectra (75 eV) of the β-diazopyrroles always show the molecular ions and undergo as the main fragmentation process the elimination of nitrogen followed by ring opening reactions leading to benzonitrile either as neutral or charged species. The peaks at 26 amu below the molecular ions, which are a general feature of these spectra, are due to the presence of the corresponding pyrroles which are formed by reductive reactions during the vaporization process of the samples.

Elektronenstoß-induzierte massenspektrometrische Fragmentierung von 2,2′-Bisindolylmethoxy- und Trisindolyl-methanen

1986

Mass spectra of halogenated esters: 8. Methyl esters of 2,3-dichloro-, bromochloro- and dibromopropenoic acids

1988

The mass spectral fragmentation of methyl esters of E and Z isomers of 2,3-dichloro-, 2-bromo-3-chloro-, 3-bromo-2-chIoro- and 2,3-dibromopropenoic acids have been investigated. The M+˙ peak is shown with all isomers, the [M − OCH3]+, [M − X]+, [M − OCH3 − CO]+, [M − OCH3 − CO − X]+˙ and [M − OCH3 − CO − X − X]+ ions constituting abundant peaks in all spectra. The results, particularly from the bromochloro isomers, show that a halogen atom is eliminated from the 3- rather than the 2- position and from the Z rather than the E isomer. Bromine as a bulky atom is preferentially lost.

Determination of carbosulfan and its metabolites in oranges by liquid chromatography ion-trap triple-stage mass spectrometry.

2005

Liquid chromatography ion-trap mass spectrometry LC-MSn has been successfully applied to identify and confirm carbosulfan and seven of its metabolites in oranges after pressurized liquid extraction (PLE) with dichloromethane. Mass spectra of carbosulfan and its metabolites were investigated using multiple stages of mass spectrometry. Although interpretation of the fragmentation pathways, based on mass spectra, enables structural elucidation and identification of these compounds, the proposed fragmentation pathways and ion structures need verification by exact mass measurements. The analytical method--PLE and LC-MS3 --was validated: limits of quantification (LOQ) ranged from 0.01 to 0.07 mg …

Studies in organic mass spectrometry. Part 24† Electron ionization mass spectra of some aryl(2-nitrobenzo[b]thiophen-3-yl)amines

1999

The main fragmentation routes of eighteen title compounds and of three 5-chloro derivatives have been investigated with the aid of linked scan (B/E = constant) spectrometry, accurate mass measurements and deuterium labelling. Copyright © 1999 John Wiley & Sons, Ltd.