On the detection of oxidized and highly oxidized organic molecules by CHARON PTR-MS via ammonium adduct ionization

2020 ◽  
Author(s):  
Markus Müller ◽  
Felix Piel ◽  
Armin Wisthaler
Keyword(s):  
Mass Spectrometry ◽  
Functional Groups ◽  
Organic Molecules ◽  
Organic Aerosol ◽  
Proton Transfer Reaction ◽  
Protonated Form ◽  
Ionization Mass ◽  
Single Digit ◽  
Target Analytes ◽  
Ammonium Adduct

<p>Oxidized and highly oxidized organic molecules are important target analytes in atmospheric air samples. In recent years, several chemical ionization mass spectrometry (CIMS) methods have been developed for detecting these target analytes in real time and at ultra-trace levels. One of these CIMS techniques is proton-transfer-reaction mass spectrometry (PTR-MS), which, in combination with the so-called CHARON inlet, measures oxidized and highly oxidized organic molecules in the atmosphere in the gaseous and particulate state. PTR-MS typically uses hydronium ions (H<sub>3</sub>O<sup>+</sup>) as reagent ions for detecting organic analytes in their protonated form, [A+H<sup>+</sup>]. H<sub>3</sub>O<sup>+</sup> ions react with all oxidized organics at unit efficiency, meaning that PTR-MS universally detects these target analytes, with little dependency of the signal response on their oxidation state. A drawback of PTR-MS operation in the H<sub>3</sub>O<sup>+ </sup>mode is that oxidized functional groups are often ejected upon protonation.</p><p>Herein, we present the results obtained when a CHARON PTR-MS analyzer was operated with ammonium (NH<sub>4</sub><sup>+</sup>) ions as CI reagent ions. We studied the instrumental response to a set of oxidized and highly oxidized compounds including hydroxy, carboxy and peroxy functional groups. We found that fragmentation was greatly suppressed, with ammonium adducts, [A+NH<sub>4</sub>]<sup>+</sup>, being the main analyte ions formed. The ionization efficiency ranged from 10 to 80% of the collisional limit, meaning that the NH<sub>4</sub><sup>+</sup> mode is less quantitative than the H<sub>3</sub>O<sup>+</sup> mode. The performance and advantages of ammonium adduct ionization are demonstrated on two application examples: i) secondary organic aerosol generated in the laboratory from the ozonolysis of limonene, with a particular focus on the detection of peroxides and dimers, and (ii) ambient organic aerosol in Innsbruck, Austria, which was characterized at the molecular level at single digit ng m<sup>-</sup>³ mass concentrations.</p>

scholarly journals Insights into organic-aerosol sources via a novel laser-desorption/ionization mass spectrometry technique applied to one year of PM<sub>10</sub> samples from nine sites in central Europe

2017 ◽  
Author(s):  
Kaspar R. Daellenbach ◽  
Imad El-Haddad ◽  
Lassi Karvonen ◽  
Athanasia Vlachou ◽  
Joel C. Corbin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Central Europe ◽  
Internal Standard ◽  
Laser Desorption ◽  
Organic Aerosol ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Laser Desorption Ionization ◽  
Desorption Ionization ◽  
Wood Burning

Abstract. We assess the benefits of offline laser-desorption/ionization mass spectrometry (LDI-MS) in understanding ambient particulate matter (PM) sources. The technique was optimized for measuring PM collected on quartz-fiber filters using silver nitrate as an internal standard for m/z calibration. This is the first application of this technique to samples collected at nine sites in central Europe throughout the entire year 2013 (819 samples). Different PM sources were identified by positive matrix factorization (PMF) including also concomitant measurements (such as NOx, levoglucosan, and temperature). By comparison to reference mass spectral signatures from laboratory wood burning experiments as well as samples from a traffic tunnel, three biomass-burning factors and two traffic factors were identified. The wood-burning factors could be linked to the burning conditions; the factors related to inefficient burns had a larger impact on air quality in southern Alpine valleys than in northern Switzerland. The traffic factors were identified as primary tailpipe exhaust and most possibly aged/secondary traffic emissions, respectively. The latter attribution was supported by radiocarbon analyses of both the organic and elemental carbon. Besides these sources, also factors related to secondary organic aerosol were separated. The contribution of the wood burning emissions based on LDI-PMF correlates well with that based on AMS-PMF analyses, while the comparison between the two techniques for other components is more complex.

scholarly journals Identifying precursors and aqueous organic aerosol formation pathways during the SOAS campaign

2016 ◽  
Vol 16 (22) ◽  
pp. 14409-14420 ◽  
Author(s):  
Neha Sareen ◽  
Annmarie G. Carlton ◽  
Jason D. Surratt ◽  
Avram Gold ◽  
Ben Lee ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Negative Ion ◽  
Anthropogenic Sources ◽  
Ionization Mass ◽  
Aqueous Mixtures ◽  
Aerosol Formation

Abstract. Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized, low-volatility organic aerosol and, in some cases, light-absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, and health. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented, forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols), leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify additional precursors and products that may be atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere into water at Brent, Alabama, during the 2013 Southern Oxidant and Aerosol Study (SOAS). Hydroxyl (OH⚫) radical oxidation experiments were conducted with the aqueous mixtures collected from SOAS to better understand the formation of SOA through gas-phase followed by aqueous-phase chemistry. Total aqueous-phase organic carbon concentrations for these mixtures ranged from 92 to 179 µM-C, relevant for cloud and fog waters. Aqueous OH-reactive compounds were primarily observed as odd ions in the positive ion mode by electrospray ionization mass spectrometry (ESI-MS). Ultra high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) spectra and tandem MS (MS–MS) fragmentation of these ions were consistent with the presence of carbonyls and tetrols. Products were observed in the negative ion mode and included pyruvate and oxalate, which were confirmed by ion chromatography. Pyruvate and oxalate have been found in the particle phase in many locations (as salts and complexes). Thus, formation of pyruvate/oxalate suggests the potential for aqueous processing of these ambient mixtures to form SOAAQ.

scholarly journals OH-chemistry of non-methane organic gases (NMOG) emitted from laboratory and ambient biomass burning smoke: evaluating the influence of furans and oxygenated aromatics on ozone and secondary NMOG formation

2019 ◽  
Author(s):  
Matthew M. Coggon ◽  
Christoper Y. Lim ◽  
Abigail R. Koss ◽  
Kanako Sekimoto ◽  
Bin Yuan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Maleic Anhydride ◽  
Biomass Burning ◽  
Time Of Flight ◽  
Proton Transfer Reaction ◽  
Box Model ◽  
Chemical Mechanism ◽  
Ionization Mass ◽  
Organic Gases ◽  
Tof Ms

Abstract. Chamber oxidation experiments conducted at the Fire Sciences Laboratory in 2016 are evaluated to identify important chemical processes contributing to the OH chemistry of biomass burning non-methane organic gases (NMOG). Based on the decay of primary carbon measured by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), it is confirmed that furans and oxygenated aromatics are among the NMOG emitted from western United States fuel types with the highest reactivities towards OH. The oxidation processes and formation of secondary NMOG masses measured by PTR-ToF-MS and iodide clustering time-of-flight chemical ionization mass spectrometry (I-CIMS) is interpreted using a box model employing a modified version of the Master Chemical Mechanism (v. 3.3.1) that includes the OH oxidation of furan, 2-methylfuran, 2,5-dimethylfuran, furfural, 5-methylfurfural, and guaiacol. The model supports the assignment of major PTR-ToF-MS and I-CIMS signals to a series of anhydrides and hydroxy furanones formed primarily through furan chemistry. This mechanism is applied to a Lagrangian box model used previously to model a real biomass burning plume. The updated mechanism reproduces the decay of furans and oxygenated aromatics and the formation of secondary NMOG, such as maleic anhydride. Based on model simulations conducted with and without furans, it is estimated that furans contributed up to 10 % of ozone and over 90 % of maleic anhydride formed within the first 4 hours of oxidation. It is shown that maleic anhydride is present in a biomass burning plume transported over several days, which demonstrates the utility of anhydrides as tracers for aged biomass burning plumes.

scholarly journals Simultaneous Aerosol Mass Spectrometry and Chemical Ionisation Mass Spectrometry measurements during a biomass burning event in the UK: Insights into nitrate chemistry

2017 ◽  
Author(s):  
Ernesto Reyes-Villegas ◽  
Michael Priestley ◽  
Yu-Chieh Ting ◽  
Sophie Haslett ◽  
Thomas Bannan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Black Carbon ◽  
Source Apportionment ◽  
Organic Aerosol ◽  
Organic Nitrate ◽  
Ionization Mass ◽  
Night Time ◽  
Aerosol Mass ◽  
Pollutant Concentrations ◽  
The Uk

Abstract. Over the past decade, there has been an increasing interest in short-term events that negatively affect air quality such as bonfires and fireworks. High aerosol and gas concentrations generated from public bonfires/fireworks were measured in order to understand the night-time chemical processes and their atmospheric implications. Nitrate chemistry was observed during the bonfire night with nitrogen containing compounds in both gas and aerosol phase and further N2O5 and ClNO2 concentrations, which depleted early next morning due to photolysis of NO3 radicals, ceasing production. Particulate organic nitrate (PON) concentrations of 2.8 μg.m−3 were estimated using the m/z 46:30 ratios from AMS measurements, according to previously published methods. ME-2 source apportionment was performed to determine organic aerosol concentrations from different sources after modifying the fragmentation table and it was possible to identify two PON factors representing primary (pPON_ME2) and secondary (sPON_ME2) contributions. A slight improvement in the agreement between the source apportionment of the AMS and a collocated AE-31 Aethalometer was observed after modifying the prescribed fragmentation in the AMS organic spectrum (the fragmentation table) to determine PON sources, which resulted in an r2 = 0.865 between BBOA and babs_470wb compared to an r2 = 0.819 obtained without the modification. Correlations between OA sources and measurements made using Time of Flight Chemical Ionization Mass Spectrometry with an iodide adduct ion were performed in order to determine possible gas tracers to be used in future ME-2 analyses to constrain solutions. During bonfire night, high correlations (r2) were observed between BBOA and methacrylic acid (0.915), Acrylic acid (0.901), nitrous acid (0.864), propionic acid, (0.851) and Hydrogen cyanide (0.755). A series of oxygenated species, chlorine compounds as well as cresol showed good correlations with sPON_ME2 and the low volatility oxygenated organic aerosol (LVOOA) factor during an episode with low pollutant concentrations. Further analysis of pPON_ME2 and sPON_ME2 was performed in order to determine whether these PON sources absorb light near the UV region using an Aethalometer. This hypothesis was tested by doing multilinear regressions between babs_470wb and BBOA, sPON_ME2 and pPON_ME2. Our results suggest that sPON_ME2 does not absorb light at 470 nm while pPON_ME2 and LVOOA absorb light at 470 nm over that of black carbon. This may inform black carbon (BC) source apportionment studies from Aethalometer measurements, through investigation of the brown carbon contribution to babs_470wb.

scholarly journals Insights into organic-aerosol sources via a novel laser-desorption/ionization mass spectrometry technique applied to one year of PM<sub>10</sub> samples from nine sites in central Europe

2018 ◽  
Vol 18 (3) ◽  
pp. 2155-2174 ◽  
Author(s):  
Kaspar R. Daellenbach ◽  
Imad El-Haddad ◽  
Lassi Karvonen ◽  
Athanasia Vlachou ◽  
Joel C. Corbin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Central Europe ◽  
Internal Standard ◽  
Laser Desorption ◽  
Organic Aerosol ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Laser Desorption Ionization ◽  
Desorption Ionization ◽  
Wood Burning

Abstract. We assess the benefits of offline laser-desorption/ionization mass spectrometry in understanding ambient particulate matter (PM) sources. The technique was optimized for measuring PM collected on quartz-fiber filters using silver nitrate as an internal standard for m∕z calibration. This is the first application of this technique to samples collected at nine sites in central Europe throughout the entire year of 2013 (819 samples). Different PM sources were identified by positive matrix factorization (PMF) including also concomitant measurements (such as NOx, levoglucosan, and temperature). By comparison to reference mass spectral signatures from laboratory wood burning experiments as well as samples from a traffic tunnel, three biomass burning factors and two traffic factors were identified. The wood burning factors could be linked to the burning conditions; the factors related to inefficient burns had a larger impact on air quality in southern Alpine valleys than in northern Switzerland. The traffic factors were identified as primary tailpipe exhaust and most possibly aged/secondary traffic emissions. The latter attribution was supported by radiocarbon analyses of both the organic and elemental carbon. Besides these sources, factors related to secondary organic aerosol were also separated. The contribution of the wood burning emissions based on LDI-PMF (laser-desorption/ionization PMF) correlates well with that based on AMS-PMF (aerosol mass spectrometer PMF) analyses, while the comparison between the two techniques for other components is more complex.

scholarly journals Assessing the impact of anthropogenic pollution on isoprene-derived secondary organic aerosol formation in PM<sub>2.5</sub> collected from the Birmingham, Alabama ground site during the 2013 Southern Oxidant and Aerosol Study

2016 ◽  
Author(s):  
W. Rattanavaraha ◽  
K. Chu ◽  
S. H. Budisulistiorini ◽  
M. Riva ◽  
Y.-H. Lin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Secondary Organic Aerosol ◽  
Anthropogenic Pollution ◽  
Organic Aerosol ◽  
Limiting Factor ◽  
Ionization Mass ◽  
Aerosol Formation ◽  
Anthropogenic Pollutants ◽  
Aerosol Acidity ◽  
The Impact

Abstract. In the southeastern U.S., substantial emissions of isoprene from deciduous trees undergo atmospheric oxidation to form secondary organic aerosol (SOA) that contributes to fine particulate matter (PM2.5). Laboratory studies have revealed that anthropogenic pollutants, such as sulfur dioxide (SO2), oxides of nitrogen (NOx), and aerosol acidity, can enhance SOA formation from the hydroxyl radical (OH)-initiated oxidation of isoprene; however, the mechanisms by which specific pollutants enhance isoprene SOA in ambient PM2.5 remain unclear. As one aspect of an investigation to examine how anthropogenic pollutants influence isoprene-derived SOA formation, high-volume PM2.5 filter samples were collected at the Birmingham, Alabama (BHM) ground site during the 2013 Southern Oxidant and Aerosol Study (SOAS). Sample extracts were analyzed by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) with prior trimethylsilylation and ultra performance liquid chromatography coupled to an electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR QTOFMS) to identify known isoprene SOA tracers. Tracers quantified using both surrogate and authentic standards were compared with collocated gas- and particle-phase data as well as meteorological data provided by the Southeastern Aerosol Research and Characterization (SEARCH) network to assess the impact of anthropogenic pollution on isoprene-derived SOA formation. Results of this study reveal that isoprene-derived SOA tracers contribute a substantial mass fraction of organic matter (OM) (~7 to ~20%). Isoprene-derived SOA tracers correlated with sulfate (SO42-) (r2 = 0.34, n = 117), but not with NOx. Moderate correlation between methacrylic acid epoxide and hydroxymethyl-methyl-α-lactone (MAE/HMML)-derived SOA tracers and nitrate radical production (P[NO3]) (r2 = 0.57, n = 40) were observed during nighttime, suggesting a potential role of NO3 radical in forming this SOA type. However, the nighttime correlation of these tracers with nitrogen dioxide (NO2) (r2 = 0.26, n = 40) was weaker. Ozone (O3) correlated strongly with MAE/HMML-derived tracers (r2 = 0.72, n = 30) and moderately with 2-methyltetrols (r2 = 0.34, n = 15) during daytime only, suggesting that a fraction of SOA formation could occur from isoprene ozonolysis in urban areas. No correlation was observed between aerosol pH and isoprene-derived SOA. Lack of correlation between aerosol acidity and isoprene-derived SOA indicates that acidity is not a limiting factor for isoprene SOA formation at the BHM site as aerosols were acidic enough to promote multiphase chemistry of isoprene-derived epoxides throughout the duration of the study. All in all, these results confirm the reports that anthropogenic pollutants enhance isoprene-derived SOA formation.

scholarly journals Formation of Highly Oxygenated Low-Volatility Products from Cresol Oxidation

2016 ◽  
Author(s):  
Rebecca H. Schwantes ◽  
Katherine A. Schilling ◽  
Renee C. McVay ◽  
Hanna Lignell ◽  
Matthew M. Coggon ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Ring Opening ◽  
Chemical Ionization ◽  
First Generation ◽  
Direct Analysis ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase

Abstract. Hydroxyl radical (OH) oxidation of toluene produces the ring-retaining products cresol and benzaldehyde, and the ring-opening products bicyclic intermediate compounds and epoxides. Here, first- and later-generation OH oxidation products from cresol and benzaldehyde are identified in laboratory chamber experiments. For benzaldehyde, first-generation ring-retaining products are identified, but later-generation products are not detected. For cresol, low-volatility (saturation mass concentration, C* ~ 3.5 × 104–7.7 × 10−3 μg m−3) first- and later-generation ring-retaining products are identified. Subsequent OH addition to the aromatic ring of o-cresol leads to compounds such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones and dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes. These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real time mass spectrometry (DART-MS). Our data suggest that the yield of trihydroxy toluene from dihydroxy toluene is substantial. While an exact yield cannot be reported as authentic standards are unavailable, we find that a yield for trihydroxy toluene from dihydroxy toluene of ~ 0.7 (equal to the yield of dihydroxy toluene from o-cresol) is consistent with experimental results for o-cresol oxidation under low-NO conditions. These results suggest that even though the cresol pathway accounts for only ~ 20 % of the oxidation products of toluene, it is the source of a significant fraction (~ 20–40 %) of toluene secondary organic aerosol (SOA) due to the formation of low-volatility products.

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