scholarly journals Using advanced mass spectrometry techniques to fully characterize atmospheric organic carbon: current capabilities and remaining gaps

2017 ◽  
Vol 200 ◽  
pp. 579-598 ◽  
Author(s):  
G. Isaacman-VanWertz ◽  
P. Massoli ◽  
R. E. O’Brien ◽  
J. B. Nowak ◽  
M. R. Canagaratna ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Structural Information ◽  
Carbon Number ◽  
Chemical Properties ◽  
Oxidation Products ◽  
Particle Phase ◽  
Atmospheric Measurements ◽  
Mass Spectrometers ◽  
Phase Measurements ◽  
New Generation

Organic compounds in the atmosphere vary widely in their molecular composition and chemical properties, so no single instrument can reasonably measure the entire range of ambient compounds. Over the past decade, a new generation of in situ, field-deployable mass spectrometers has dramatically improved our ability to detect, identify, and quantify these organic compounds, but no systematic approach has been developed to assess the extent to which currently available tools capture the entire space of chemical identity and properties that is expected in the atmosphere. Reduced-parameter frameworks that have been developed to describe atmospheric mixtures are exploited here to characterize the range of chemical properties accessed by a suite of instruments. Multiple chemical spaces (e.g. oxidation state of carbon vs. volatility, and oxygen number vs. carbon number) were populated with ions measured by several mass spectrometers, with gas- and particle-phase α-pinene oxidation products serving as the test mixture of organic compounds. Few gaps are observed in the coverage of the parameter spaces by the instruments employed in this work, though the full extent to which comprehensive measurement was achieved is difficult to assess due to uncertainty in the composition of the mixture. Overlaps between individual ions and regions in parameter space were identified, both between gas- and particle-phase measurements, and within each phase. These overlaps were conservatively found to account for little (<10%) of the measured mass. However, challenges in identifying overlaps and in accurately converting molecular formulas into chemical properties (such as volatility or reactivity) highlight a continued need to incorporate structural information into atmospheric measurements.

scholarly journals Elemental composition and clustering behaviour of α-pinene oxidation products for different oxidation conditions

2015 ◽  
Vol 15 (8) ◽  
pp. 4145-4159 ◽  
Author(s):  
A. P. Praplan ◽  
S. Schobesberger ◽  
F. Bianchi ◽  
M. P. Rissanen ◽  
M. Ehn ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Organic Compounds ◽  
Atmospheric Pressure ◽  
Molar Mass ◽  
Oxidation Products ◽  
Neutral Species ◽  
Mass Spectrometers ◽  
Comprehensive Picture ◽  
The Difference ◽  
Chemical Ionisation

Abstract. This study presents the difference between oxidised organic compounds formed by α-pinene oxidation under various conditions in the CLOUD environmental chamber: (1) pure ozonolysis (in the presence of hydrogen as hydroxyl radical (OH) scavenger) and (2) OH oxidation (initiated by nitrous acid (HONO) photolysis by ultraviolet light) in the absence of ozone. We discuss results from three Atmospheric Pressure interface Time-of-Flight (APi-TOF) mass spectrometers measuring simultaneously the composition of naturally charged as well as neutral species (via chemical ionisation with nitrate). Natural chemical ionisation takes place in the CLOUD chamber and organic oxidised compounds form clusters with nitrate, bisulfate, bisulfate/sulfuric acid clusters, ammonium, and dimethylaminium, or get protonated. The results from this study show that this process is selective for various oxidised organic compounds with low molar mass and ions, so that in order to obtain a comprehensive picture of the elemental composition of oxidation products and their clustering behaviour, several instruments must be used. We compare oxidation products containing 10 and 20 carbon atoms and show that highly oxidised organic compounds are formed in the early stages of the oxidation.

scholarly journals Characterization of secondary organic aerosol from heated-cooking-oil emissions: evolution in composition and volatility

2021 ◽  
Vol 21 (6) ◽  
pp. 5137-5149 ◽  
Author(s):  
Manpreet Takhar ◽  
Yunchun Li ◽  
Arthur W. H. Chan
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Carbon Number ◽  
Complex Mixture ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Atmospheric Evolution ◽  
Oxidative Aging ◽  
Cooking Oil

Abstract. Cooking emissions account for a major fraction of urban organic aerosol. It is therefore important to understand the atmospheric evolution in the physical and chemical properties of organic compounds emitted from cooking activities. In this work, we investigate the formation of secondary organic aerosol (SOA) from oxidation of gas-phase organic compounds from heated cooking oil. The chemical composition of cooking SOA is analyzed using thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS). While the particle-phase composition of SOA is a highly complex mixture, we adopt a new method to achieve molecular speciation of the SOA. All the GC-elutable material is classified by the constituent functional groups, allowing us to provide a molecular description of its chemical evolution upon oxidative aging. Our results demonstrate an increase in average oxidation state (from −0.6 to −0.24) and decrease in average carbon number (from 5.2 to 4.9) with increasing photochemical aging of cooking oil, suggesting that fragmentation reactions are key processes in the oxidative aging of cooking emissions within 2 d equivalent of ambient oxidant exposure. Moreover, we estimate that aldehyde precursors from cooking emissions account for a majority of the SOA formation and oxidation products. Overall, our results provide insights into the atmospheric evolution of cooking SOA, a majority of which is derived from gas-phase oxidation of aldehydes.

scholarly journals The importance of sesquiterpene oxidation products for secondary organic aerosol formation in a spring-time hemi-boreal forest

2021 ◽  
Author(s):  
Luis M. F. Barreira ◽  
Arttu Ylisirniö ◽  
Iida Pullinen ◽  
Angela Buchholz ◽  
Zijun Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Field Experiments ◽  
Complex Mixture ◽  
Particle Formation ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase ◽  
Aerosol Formation

Abstract. Secondary organic aerosols (SOA) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to affect significantly the climate and air quality. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. Most of them have focused on a few monoterpenes and isoprene. However, atmospheric SOA particulate mass yields and chemical composition result from a much more complex mixture of oxidation products originating from many BVOCs, including terpenes other than isoprene and monoterpenes. Thus, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas and particle phase atmospheric SOA. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a spring-time hemi-boreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase at some periods, while their gas phase concentrations remained much lower than those of monoterpene products. This can be explained by quick and effective partitioning of sesquiterpene products into the particle phase or their efficient removal by dry deposition. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates the important role of sesquiterpenes in atmospheric chemistry and suggests that the contribution of their products to SOA particles is being underestimated in comparison to the most studied terpenes.

scholarly journals Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

2015 ◽  
Vol 15 (14) ◽  
pp. 7765-7776 ◽  
Author(s):  
F. D. Lopez-Hilfiker ◽  
C. Mohr ◽  
M. Ehn ◽  
F. Rubach ◽  
E. Kleist ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Mass Spectrometer ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Negative Ion ◽  
Ionization Mass ◽  
Particle Phase ◽  
Vapor Pressures ◽  
Aerosol Mass

Abstract. We measured a large suite of gas- and particle-phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas and particle phases, the latter being detected by temperature-programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO–HR-ToF-CIMS are highly correlated with, and explain at least 25–50 % of, the organic aerosol mass measured by an Aerodyne aerosol mass spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from high molecular weight organics and/or oligomers (i.e., multi-phase accretion reaction products). Approximately 50 % of the HR-ToF-CIMS particle-phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption-temperature-based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas-particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the conversion of lower volatility components into the detected higher volatility compounds.

scholarly journals Coupling a gas chromatograph simultaneously to a flame ionization detector and chemical ionization mass spectrometer for isomer-resolved measurements of particle-phase organic compounds

2020 ◽  
Author(s):  
Chenyang Bi ◽  
Jordan E. Krechmer ◽  
Graham O. Frazier ◽  
Wen Xu ◽  
Andrew T. Lambe ◽  
...  
Keyword(s):  
Functional Groups ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Measurement Techniques ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase ◽  
Gas Chromatograph ◽  
New Instrument

Abstract. Atmospheric oxidation products of volatile organic compounds consist of thousands of unique chemicals that have distinctly different physical and chemical properties depending on their detailed structures and functional groups. Measurement techniques that can achieve molecular characterizations with details down to functional groups (i.e., isomer-resolved resolution) are consequently necessary to provide understandings of differences of fate and transport within isomers produced in the oxidation process. We demonstrate a new instrument coupling the thermal desorption aerosol gas chromatograph (TAG), which enables the separation of isomers, with the high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS), which has the capability of classifying unknown compounds by their molecular formulas, and the flame ion detector (FID), which provide a near-universal response to organic compounds. The TAG-CIMS/FID is used to provide isomer-resolved measurements of samples from liquid standard injections and particle-phase organics generated in oxidation flow reactors. By coupling a TAG to a CIMS, the CIMS is enhanced with an additional dimension of information (resolution of individual molecules) at the cost of time resolution (i.e., one sample per hour instead of per minute). We found that isomers are prevalent in sample matrix with an average number of three to five isomers per formula depending on the precursors in the oxidation experiments. Additionally, a multi-reagent ionization mode is investigated in which both zero air and iodide are introduced as reagent ions, to examine the feasibility of extending the use of an individual CIMS to a broader range of analytes with still selective reagent ions. While this approach reduces iodide-adduct ions by a factor of two, [M−H]− and [M+O2]− ions produced from lower-polarity compounds increase by a factor of five to ten, improving their detection by CIMS. The method expands the range of detected chemical species by using two chemical ionization reagents simultaneously, enabled by the pre-separation of analyte molecules before ionization.

scholarly journals Gas-to-particle partitioning of major biogenic oxidation products: a study on freshly formed and aged biogenic SOA

2018 ◽  
Vol 18 (17) ◽  
pp. 12969-12989 ◽  
Author(s):  
Georgios I. Gkatzelis ◽  
Thorsten Hohaus ◽  
Ralf Tillmann ◽  
Iulia Gensch ◽  
Markus Müller ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Transfer Reaction ◽  
Theoretical Calculations ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Particle Phase ◽  
Tof Ms ◽  
Good Agreement

Abstract. Secondary organic aerosols (SOAs) play a key role in climate change and air quality. Determining the fundamental parameters that distribute organic compounds between the phases is essential, as atmospheric lifetime and impacts change drastically between the gas and particle phase. In this work, gas-to-particle partitioning of major biogenic oxidation products was investigated using three different aerosol chemical characterization techniques. The aerosol collection module, the collection thermal desorption unit, and the chemical analysis of aerosols online are different aerosol sampling inlets connected to a proton-transfer reaction time-of-flight mass spectrometer (ACM-PTR-ToF-MS, TD-PTR-ToF-MS, and CHARON-PTR-ToF-MS, respectively, referred to hereafter as ACM, TD, and CHARON). These techniques were deployed at the atmosphere simulation chamber SAPHIR to perform experiments on the SOA formation and aging from different monoterpenes (β-pinene, limonene) and real plant emissions (Pinus sylvestris L.). The saturation mass concentration C* and thus the volatility of the individual ions was determined based on the simultaneous measurement of their signal in the gas and particle phase. A method to identify and exclude ions affected by thermal dissociation during desorption and ionic dissociation in the ionization chamber of the proton-transfer reaction mass spectrometer (PTR-MS) was developed and tested for each technique. Narrow volatility distributions with organic compounds in the semi-volatile (SVOCs – semi-volatile organic compounds) to intermediate-volatility (IVOCs – intermediate-volatility organic compounds) regime were found for all systems studied. Despite significant differences in the aerosol collection and desorption methods of the proton-transfer-reaction (PTR)-based techniques, a comparison of the C* values obtained with different techniques was found to be in good agreement (within 1 order of magnitude) with deviations explained by the different operating conditions of the PTR-MS. The C* of the identified organic compounds were mapped onto the two-dimensional volatility basis set (2D-VBS), and results showed a decrease in C* with increasing oxidation state. For all experiments conducted in this study, identified partitioning organic compounds accounted for 20–30 % of the total organic mass measured from an aerosol mass spectrometer (AMS). Further comparison between observations and theoretical calculations was performed for species found in our experiments that were also identified in previous publications. Theoretical calculations based on the molecular structure of the compounds showed, within the uncertainties ranges, good agreement with the experimental C* for most SVOCs, while IVOCs deviated by up to a factor of 300. These latter differences are discussed in relation to two main processes affecting these systems: (i) possible interferences by thermal and ionic fragmentation of higher molecular-weight compounds, produced by accretion and oligomerization reactions, that fragment in the m∕z range detected by the PTR-MS and (ii) kinetic influences in the distribution between the gas and particle phase with gas-phase condensation, diffusion in the particle phase, and irreversible uptake.

Experimental determination of the partitioning coefficient of β-pinene oxidation products in SOAs

2015 ◽  
Vol 17 (22) ◽  
pp. 14796-14804 ◽  
Author(s):  
Thorsten Hohaus ◽  
Iulia Gensch ◽  
Joel Kimmel ◽  
Douglas R. Worsnop ◽  
Astrid Kiendler-Scharr
Keyword(s):  
Volatile Organic Compounds ◽  
Experimental Determination ◽  
Organic Compounds ◽  
Oxidation Products ◽  
Particle Phase ◽  
Partitioning Coefficient ◽  
Volatile Organic ◽  
Measured Particle

Measured particle phase concentrations of semi-volatile organic compounds exceed those predicted by absorption equilibrium gas-particle partitioning by orders of magnitude.

scholarly journals Characterization of secondary organic aerosol from heated cooking oil emissions: evolution in composition and volatility

2020 ◽  
Author(s):  
Manpreet Takhar ◽  
Yunchun Li ◽  
Arthur W. H. Chan
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Carbon Number ◽  
Complex Mixture ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Atmospheric Evolution ◽  
Oxidative Aging ◽  
Cooking Oil

Abstract. Cooking emissions account for a major fraction of urban organic aerosol. It is therefore important to understand the atmospheric evolution in the physical and chemical properties of organic compounds emitted from cooking activities. In this work, we investigate the formation of secondary organic aerosol (SOA) from oxidation of gas-phase organic compounds from heated cooking oil. The chemical composition of cooking SOA is analyzed using thermal desorption-gas chromatography-mass spectrometry. While the particle-phase composition of SOA is a highly complex mixture, we adopt a new method to achieve molecular speciation of the SOA. All the GC elutable material is classified by the constituent functional groups, allowing us to provide a molecular description of its chemical evolution upon oxidative aging. Our results demonstrate an increase in average oxidation state (from −0.6 to −0.24), and decrease in average carbon number (from 5.2 to 4.9) with increasing photochemical aging of cooking oil, suggesting that fragmentation reactions are key processes in the oxidative aging of cooking emissions within 2 days equivalent of ambient oxidant exposure. Moreover, we estimate that aldehyde precursors from cooking emissions account for a majority of the SOA formation and oxidation products. Overall, our results provide insights into the atmospheric evolution of cooking SOA, a majority of which is derived from gas-phase oxidation of aldehydes.

scholarly journals Chemical characterisation of benzene oxidation products under high- and low-NO<sub><i>x</i></sub> conditions using chemical ionisation mass spectrometry

2021 ◽  
Vol 21 (5) ◽  
pp. 3473-3490
Author(s):  
Michael Priestley ◽  
Thomas J. Bannan ◽  
Michael Le Breton ◽  
Stephen D. Worrall ◽  
Sungah Kang ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
First Generation ◽  
Carbon Number ◽  
Oxidation Products ◽  
Benzene Oxidation ◽  
Volatile Organic ◽  
Cluster 2 ◽  
Chemical Ionisation ◽  
Ionisation Mass

Abstract. Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up a significant fraction of urban volatile organic compound (VOC) emissions that contribute to the formation of secondary organic aerosol (SOA). Benzene is one of the most abundant species emitted from vehicles, biomass burning and industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed at the Jülich Plant Atmosphere Chamber as part of a series of experiments examining benzene oxidation by OH under high- and low-NOx conditions, where a range of organic oxidation products were detected. The nitrate scheme detects many oxidation products with high masses, ranging from intermediate volatile organic compounds (IVOCs) to extremely low volatile organic compounds (ELVOCs), including C12 dimers. In comparison, very few species with C≥6 and O≥8 were detected with the iodide scheme, which detected many more IVOCs and semi-volatile organic compounds (SVOCs) but very few ELVOCs and low volatile organic compounds (LVOCs). A total of 132 and 195 CHO and CHON oxidation products are detected by the iodide ToF-CIMS in the low- and high-NOx experiments respectively. Ring-breaking products make up the dominant fraction of detected signal and 21 and 26 of the products listed in the Master Chemical Mechanism (MCM) were detected. The time series of highly oxidised (O≥6) and ring-retaining oxidation products (C6 and double-bond equivalent = 4) equilibrate quickly, characterised by a square form profile, compared to MCM and ring-breaking products which increase throughout oxidation, exhibiting sawtooth profiles. Under low-NOx conditions, all CHO formulae attributed to radical termination reactions of first-generation benzene products, and first-generation auto-oxidation products are observed. Several N-containing species that are either first-generation benzene products or first-generation auto-oxidation products are also observed under high-NOx conditions. Hierarchical cluster analysis finds four clusters, of which two describe photo-oxidation. Cluster 2 shows a negative dependency on the NO2/NOx ratio, indicating it is sensitive to NO concentration and thus likely to contain NO addition products and alkoxy-derived termination products. This cluster has the highest average carbon oxidation state (OSC‾) and the lowest average carbon number. Where nitrogen is present in a cluster member of cluster 2, the oxygen number is even, as expected for alkoxy-derived products. In contrast, cluster 1 shows no dependency on the NO2/NOx ratio and so is likely to contain more NO2 addition and peroxy-derived termination products. This cluster contains fewer fragmented species, as the average carbon number is higher and OSC‾ lower than cluster 2, and more species with an odd number of oxygen atoms. This suggests that clustering of time series which have features pertaining to distinct chemical regimes, for example, NO2/NOx perturbations, coupled with a priori knowledge, can provide insight into identification of potential functionality.

scholarly journals Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

2015 ◽  
Vol 15 (4) ◽  
pp. 4463-4494 ◽  
Author(s):  
F. D. Lopez-Hilfiker ◽  
C. Mohr ◽  
M. Ehn ◽  
F. Rubach ◽  
E. Kleist ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Mass Spectrometer ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Negative Ion ◽  
Ionization Mass ◽  
Particle Phase ◽  
Vapor Pressures ◽  
Aerosol Mass

Abstract. We measured a large suite of gas and particle phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas and particle phases, the latter being detected upon temperature programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO HR-ToF-CIMS are highly correlated with, and explain at least 25–50% of, the organic aerosol mass measured by an Aerodyne Aerosol Mass Spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from large molecular weight organics and/or oligomers (i.e. multi-phase accretion reaction products). Approximately 50% of the HR-ToF-CIMS particle phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption temperature based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas–particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the conversion of lower volatility components into the detected higher volatility compounds.

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