Measurement of atmospheric amines and ammonia using the high resolution time-of-flight chemical ionization mass spectrometry

2015 ◽  
Vol 102 ◽  
pp. 249-259 ◽  
Author(s):  
Jun Zheng ◽  
Yan Ma ◽  
Mindong Chen ◽  
Qi Zhang ◽  
Lin Wang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Chemical Ionization ◽  
Time Of Flight ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Resolution Time

scholarly journals Aqueous-phase photooxidation of levoglucosan – a mechanistic study using Aerosol Time of Flight Chemical Ionization Mass Spectrometry (Aerosol-ToF-CIMS)

2014 ◽  
Vol 14 (7) ◽  
pp. 8819-8850 ◽  
Author(s):  
R. Zhao ◽  
E. L. Mungall ◽  
A. K. Y. Lee ◽  
D. Aljawhary ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Phase ◽  
Chemical Ionization ◽  
Time Of Flight ◽  
Charge Ratio ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Ambient Atmosphere

Abstract. Levoglucosan (LG) is a widely employed tracer for biomass burning (BB). Recent studies have shown that LG can react rapidly with hydroxyl (OH) radicals in the aqueous phase, despite many mass balance receptor models assuming it to be inert during atmospheric transport. In the current study, aqueous-phase photooxidation of LG by OH radicals was performed in the laboratory. The reaction kinetics and products were monitored by Aerosol Time of Flight Chemical Ionization Mass Spectrometry (Aerosol-ToF-CIMS). Approximately 50 reaction products were detected by the Aerosol-ToF-CIMS during the photooxidation experiments, representing one of the most detailed product studies yet performed. By following the evolution of mass defects of product peaks, unique trends of adding oxygen (+O) and removing hydrogen (−2H) were observed among the products detected, providing useful information to determine potential reaction mechanisms and sequences. As well, bond scission reactions take place, leading to reaction intermediates with lower carbon numbers. We introduce a data analysis framework where the average oxidation state (OSc) is plotted against a novel molecular property: double bond equivalence to carbon ratio (DBE / #C). The trajectory of LG photooxidation on this plot suggests formation of poly-carbonyl intermediates and their subsequent conversion to carboxylic acids as a general reaction trend. We also determined the rate constant of LG with OH radicals at room temperature to be 1.08 ± 0.16 × 109 M−1 s−1. By coupling an Aerosol Mass Spectrometer (AMS) to the system, we observed a rapid decay of the mass fraction of organic signals at mass-to-charge ratio 60 (f60), corresponding closely to the LG decay monitored by the Aerosol-ToF-CIMS. The trajectory of LG photooxidation on a f44–f60 correlation plot matched closely to literature field measurement data. This implies that aqueous-phase photooxidation might be partially contributing to aging of BB particles in the ambient atmosphere.

scholarly journals Aqueous-phase photooxidation of levoglucosan – a mechanistic study using aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS)

2014 ◽  
Vol 14 (18) ◽  
pp. 9695-9706 ◽  
Author(s):  
R. Zhao ◽  
E. L. Mungall ◽  
A. K. Y. Lee ◽  
D. Aljawhary ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometry ◽  
Aqueous Phase ◽  
Chemical Ionization ◽  
Time Of Flight ◽  
Charge Ratio ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Ambient Atmosphere

Abstract. Levoglucosan (LG) is a widely employed tracer for biomass burning (BB). Recent studies have shown that LG can react rapidly with hydroxyl (OH) radicals in the aqueous phase despite many mass balance receptor models assuming it to be inert during atmospheric transport. In the current study, aqueous-phase photooxidation of LG by OH radicals was performed in the laboratory. The reaction kinetics and products were monitored by aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS). Approximately 50 reaction products were detected by the Aerosol ToF-CIMS during the photooxidation experiments, representing one of the most detailed product studies yet performed. By following the evolution of mass defects of product peaks, unique trends of adding oxygen (+O) and removing hydrogen (−2H) were observed among the products detected, providing useful information for determining potential reaction mechanisms and sequences. Additionally, bond-scission reactions take place, leading to reaction intermediates with lower carbon numbers. We introduce a data analysis framework where the average oxidation state (OSc) is plotted against a novel molecular property: double-bond-equivalence-to-carbon ratio (DBE/#C). The trajectory of LG photooxidation on this plot suggests formation of polycarbonyl intermediates and their subsequent conversion to carboxylic acids as a general reaction trend. We also determined the rate constant of LG with OH radicals at room temperature to be 1.08 ± 0.16 × 109 M−1 s−1. By coupling an aerosol mass spectrometer (AMS) to the system, we observed a rapid decay of the mass fraction of organic signals at mass-to-charge ratio 60 (f60), corresponding closely to the LG decay monitored by the Aerosol ToF-CIMS. The trajectory of LG photooxidation on a f44–f60 correlation plot matched closely to literature field measurement data. This implies that aqueous-phase photooxidation might be partially contributing to aging of BB particles in the ambient atmosphere.

scholarly journals Application of high resolution Chemical Ionization Mass Spectrometry (CI-ToFMS) to study SOA composition: focus on formation of oxygenated species via aqueous phase processing

2013 ◽  
Vol 6 (4) ◽  
pp. 6147-6186 ◽  
Author(s):  
D. Aljawhary ◽  
A. K. Y. Lee ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Compounds ◽  
Chemical Ionization ◽  
Water Clusters ◽  
Chemical Change ◽  
Organic Aerosol ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass

Abstract. This paper demonstrates the capabilities of Chemical Ionization Mass Spectrometry (CIMS) to study secondary organic aerosol (SOA) composition with a high resolution (HR) time-of-flight mass analyzer (aerosol-CI-ToFMS). In particular, by studying aqueous oxidation of Water Soluble Organic Compounds (WSOC) extracted from α-pinene ozonolysis SOA, we assess the capabilities of three common CIMS reagent ions: (a) protonated water clusters (H2O)nH+, (b) acetate CH3C(O)O− and (c) iodide water clusters I(H2O)n− to monitor SOA composition. As well, we report the relative sensitivity of these reagent ions to a wide range of common organic aerosol constituents. We find that (H2O)nH+ is more selective to the detection of less oxidized species, so that the range of O/C and OSC (carbon oxidation state) in the SOA spectra is considerably lower than those measured using CH3C(O)O− and I(H2O)n−. Specifically, (H2O)nH+ ionizes organic compounds with OSC ≤ 1.3, whereas CH3C(O)O− and I(H2O)n− both ionize highly oxygenated organics with OSC up to 4 with I(H2O)n− being more selective towards multi-functional organic compounds. In the bulk O/C and H/C space, i.e. in a Van Krevelen plot, there is a remarkable agreement in both absolute magnitude and oxidation trajectory between CI-ToFMS data and those from a high resolution aerosol mass spectrometer (HR-AMS). This indicates that the CI-ToFMS data captures much of the chemical change occurring in the particle and that gas phase species, which are not detected by the HR-AMS, do not dominate the overall ion signal. Finally, the data illustrate the capability of aerosol-CI-ToFMS to monitor specific chemical change, including the fragmentation and functionalization reactions that occur during organic oxidation, and the oxidative conversion of dimeric SOA species into monomers. Overall, aerosol-CI-ToFMS is a valuable, selective complement to some common SOA characterization methods, such as AMS and spectroscopic techniques. Both laboratory and ambient SOA samples can be analyzed using the techniques illustrated in the paper.

scholarly journals High-resolution chemical ionization mass spectrometry (ToF-CIMS): application to study SOA composition and processing

2013 ◽  
Vol 6 (11) ◽  
pp. 3211-3224 ◽  
Author(s):  
D. Aljawhary ◽  
A. K. Y. Lee ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Compounds ◽  
Chemical Ionization ◽  
Water Clusters ◽  
Chemical Change ◽  
Organic Aerosol ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass

Abstract. This paper demonstrates the capabilities of chemical ionization mass spectrometry (CIMS) to study secondary organic aerosol (SOA) composition with a high-resolution (HR) time-of-flight mass analyzer (aerosol-ToF-CIMS). In particular, by studying aqueous oxidation of water-soluble organic compounds (WSOC) extracted from α-pinene ozonolysis SOA, we assess the capabilities of three common CIMS reagent ions: (a) protonated water clusters (H2O)nH+, (b) acetate CH3C(O)O− and (c) iodide water clusters I(H2O)n− to monitor SOA composition. Furthermore, we report the relative sensitivity of these reagent ions to a wide range of common organic aerosol constituents. We find that (H2O)nH+ is more selective to the detection of less oxidized species, so that the range of O / C and OSC (carbon oxidation state) in the SOA spectra is considerably lower than those measured using CH3C(O)O− and I(H2O)n−. Specifically, (H2O)nH+ ionizes organic compounds with OSC ≤ 1.3, whereas CH3C(O)O− and I(H2O)n− both ionize highly oxygenated organics with OSC up to 4 with I(H2O)n− being more selective towards multi-functional organic compounds. In the bulk O / C and H / C space (in a Van Krevelen plot), there is a remarkable agreement in both absolute magnitude and oxidation trajectory between ToF-CIMS data and those from a high-resolution aerosol mass spectrometer (HR-AMS). Despite not using a sensitivity-weighted response for the ToF-CIMS data, the CIMS approach appears to capture much of the chemical change occurring. As demonstrated by the calibration experiments with standards, this is likely because there is not a large variability in sensitivities from one highly oxygenated species to another, particularly for the CH3C(O)O− and I(H2O)n− reagent ions. Finally, the data illustrate the capability of aerosol-ToF-CIMS to monitor specific chemical change, including the fragmentation and functionalization reactions that occur during organic oxidation, and the oxidative conversion of dimeric SOA species into monomers. Overall, aerosol-ToF-CIMS is a valuable, selective complement to some common SOA characterization methods, such as AMS and spectroscopic techniques. Both laboratory and ambient SOA samples can be analyzed using the techniques illustrated in the paper.

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

2015 ◽  
Vol 8 (1) ◽  
pp. 1-18 ◽  
Author(s):  
P. S. Chhabra ◽  
A. T. Lambe ◽  
M. R. Canagaratna ◽  
H. Stark ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Acids ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Oxidation Products ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Ion Chemistry

Abstract. 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 functional groups. The algorithm is tested with acetate chemical ionization mass spectrometry (acetate-CIMS) spectra of O3 and OH oxidation products of α-pinene and naphthalene formed in a flow reactor with integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 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. 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.

scholarly journals A new technique for the direct detection of HO<sub>2</sub> radicals using bromide chemical ionization mass spectrometry (Br-CIMS): initial characterization

2016 ◽  
Author(s):  
Javier Sanchez ◽  
David J. Tanner ◽  
Dexian Chen ◽  
Lewis G. Huey ◽  
Nga L. Ng
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Chemical Ionization ◽  
Direct Detection ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Detection Scheme ◽  
Mixing Ratios ◽  
Direct Technique

Abstract. Hydroperoxy radicals (HO2) play an important part in tropospheric photochemistry, yet photochemical models do not capture ambient HO2 mixing ratios consistently. This is likely due to a combination of uncharacterized chemical pathways and measurement limitations. The indirect nature of current HO2 measurements introduces challenges in accurately measuring HO2, therefore a direct technique would help constrain HOx chemistry in the atmosphere. In this work we evaluate the feasibility of using chemical ionization mass spectrometry (CIMS) and propose a direct HO2 detection scheme using bromide as a reagent ion. Ambient observations were made with a high resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) in Atlanta over the month of June 2015 to demonstrate the capability of this direct measurement technique. Observations displayed expected diurnal profiles, reaching daytime median values of ~ 7 ppt between 1 p.m. and 3 p.m. local time. The HO2 diurnal was found to be dictated by morning-time vehicular NOx emissions and shows a slow decrease into the evening. Measurement sensitivities of 4.95 ± 1.00 Hz/ppt per 106 bromide ion counts (79Br) were observed. The relatively low baseline allowed for 3σ lower detection limits of 0.7 ppt for 1 minute integration times. Mass spectra of ambient measurements showed the 79BrHO2− peak was the major component of the signal at nominal mass-to-charge 112, suggesting high selectivity for HO2 at this mass-to-charge. More importantly, this demonstrates that high resolution instrumentation is not necessary to conduct these measurements.

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