scholarly journals A new aerosol flow reactor to study secondary organic aerosol

2019 ◽  
Vol 12 (8) ◽  
pp. 4519-4541 ◽  
Author(s):  
Kelly L. Pereira ◽  
Grazia Rovelli ◽  
Young C. Song ◽  
Alfred W. Mayhew ◽  
Jonathan P. Reid ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Chemical Composition ◽  
Relative Humidity ◽  
Single Particle ◽  
Physical State ◽  
Flow Reactor ◽  
Organic Aerosol ◽  
Physiochemical Properties ◽  
Formation Conditions

Abstract. Gas-particle equilibrium partitioning is a fundamental concept used to describe the growth and loss of secondary organic aerosol (SOA). However, recent literature has suggested that gas-particle partitioning may be kinetically limited, preventing volatilization from the aerosol phase as a result of the physical state of the aerosol (e.g. glassy, viscous). Experimental measurements of diffusion constants within viscous aerosol are limited and do not represent the complex chemical composition observed in SOA (i.e. multicomponent mixtures). Motivated by the need to address fundamental questions regarding the effect of the physical state and chemical composition of a particle on gas-particle partitioning, we present the design and operation of a newly built 0.3 m3 continuous-flow reactor (CFR), which can be used as a tool to gain considerable insights into the composition and physical state of SOA. The CFR was used to generate SOA from the photo-oxidation of α-pinene, limonene, β-caryophyllene and toluene under different experimental conditions (i.e. relative humidity, VOC and VOC∕NOx ratios). Up to 102 mg of SOA mass was collected per experiment, allowing the use of highly accurate compositional- and single-particle analysis techniques, which are not usually accessible due to the large quantity of organic aerosol mass required for analysis. A suite of offline analytical techniques was used to determine the chemical composition and physical state of the generated SOA, including attenuated total reflectance infrared spectroscopy; carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis; 1H and 1H-13C nuclear magnetic resonance spectroscopy (NMR); ultra-performance liquid chromatography ultra-high-resolution mass spectrometry (UHRMS); high-performance liquid chromatography ion-trap mass spectrometry (HPLC-ITMS); and an electrodynamic balance (EDB). The oxygen-to-carbon (O∕C) and hydrogen-to-carbon (H∕C) ratios of generated SOA samples (determined using a CHNS elemental analyser) displayed good agreement with literature values and were consistent with the characteristic Van Krevelen diagram trajectory, with an observed slope of −0.41. The elemental composition of two SOA samples formed in separate replicate experiments displayed excellent reproducibility, with the O∕C and H∕C ratios of the SOA samples observed to be within error of the analytical instrumentation (instrument accuracy ±0.15 % to a reference standard). The ability to use a highly accurate CHNS elemental analyser to determine the elemental composition of the SOA samples allowed us to evaluate the accuracy of reported SOA elemental compositions using UHRMS (a commonly used technique). In all of the experiments investigated, the SOA O∕C ratios obtained for each SOA sample using UHRMS were lower than the O∕C ratios obtained from the CHNS analyser (the more accurate and non-selective technique). The average difference in the ΔO∕C ratios ranged from 19 % to 45 % depending on the SOA precursor and formation conditions. α-pinene SOA standards were generated from the collected SOA mass using semi-preparative HPLC-ITMS coupled to an automated fraction collector, followed by 1H NMR spectroscopy. Up to 35.8±1.6 % (propagated error of the uncertainty in the slope of the calibrations graphs) of α-pinene SOA was quantified using this method; a considerable improvement from most previous studies. Single aerosol droplets were generated from the collected SOA samples and trapped within an EDB at different temperatures and relative humidities to investigate the dynamic changes in their physiochemical properties. The volatilization of organic components from toluene and β-caryophyllene SOA particles at 0 % relative humidity was found to be kinetically limited, owing to particle viscosity. The unconventional use of a newly built CFR, combined with comprehensive offline chemical characterization and single-particle measurements, offers a unique approach to further our understanding of the relationship between SOA formation conditions, chemical composition and physiochemical properties.

scholarly journals Novel Aerosol Flow Reactor to Study Secondary Organic Aerosol

2019 ◽  
Author(s):  
Kelly L. Pereira ◽  
Grazia Rovelli ◽  
Young C. Song ◽  
Alfred W. Mayhew ◽  
Jonathan P. Reid ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Chemical Composition ◽  
Relative Humidity ◽  
Single Particle ◽  
Physical State ◽  
Flow Reactor ◽  
Organic Aerosol ◽  
Physiochemical Properties ◽  
Formation Conditions

Abstract. Gas-particle equilibrium partitioning is a fundamental concept used to describe the growth and loss of secondary organic aerosol (SOA). However, recent literature has suggested that gas-particle partitioning may be kinetically limited, preventing volatilization from the aerosol phase as a result of the physical state of the aerosol (e.g. glassy, viscous). Experimental measurements of diffusion constants within viscous aerosol are limited and do not represent the complex chemical composition observed in SOA (i.e. multicomponent mixtures). Motivated by the need to address fundamental questions regarding the effect of the physical state and chemical composition of a particle on gas-particle partitioning, we present the design and operation of a newly built 0.3 m3 continuous flow reactor (CFR) which can be used as a tool to gain considerable insights into the composition and physical state of SOA. The CFR was used to generate SOA mass from the photo-oxidation of α-pinene, limonene, β-caryophyllene and toluene under different experimental conditions (i.e. relative humidity, VOC and VOC/NOx ratios). Up to 102 mg of SOA mass was collected per experiment, allowing the use of highly accurate compositional and single particle analysis techniques which are not usually accessible, due to the large quantity of organic aerosol mass required for analysis. A suite of offline analytical techniques was used to determine the chemical composition and physical state of the generated SOA, including: attenuated total reflectance infra-red spectroscopy, CHNS elemental analyser, 1H and 1H-13C nuclear magnetic resonance spectroscopy (NMR), ultra-performance liquid chromatography ultra-high resolution mass spectrometry (UHRMS), high performance liquid chromatography ion-trap mass spectrometry (HPLC-ITMS) and an electrodynamic balance (EDB). The oxygen-to-carbon (O/C) and hydrogen-to-carbon (H/C) ratios of generated SOA samples (determined using a CHNS elemental analyser) displayed very good agreement with literature values and were consistent with the characteristic Van Krevelen diagram trajectory, with an observed slope of −0.41. The elemental composition of two SOA samples formed in separate replicate experiments displayed excellent reproducibility, with the O/C and H/C ratios of the SOA samples observed to be within error of the analytical instrumentation (instrument accuracy ±0.15 % to a reference standard). The ability to use a highly accurate CHNS elemental analyser to determine the elemental composition of the SOA samples, allowed us to evaluate the accuracy of reported SOA elemental compositions using UHRMS (a commonly used technique). In all of the experiments investigated, the SOA O/C ratios obtained for each SOA sample using UHRMS were lower than the O/C ratios obtained from the CHNS analyser (the more accurate and non-selective technique). The average difference in the ∆O/C ratios ranged from 19 to 45 % depending on the SOA precursor and formation conditions. α-pinene SOA standards were generated from the collected SOA mass using semi-preparative HPLC-ITMS coupled to an automated fraction collector, followed by 1H NMR spectroscopy. Up to 35.8 ± 1.6 % (propagated error of the uncertainty in the slope of the calibrations graphs) of α-pinene SOA was quantified using this method; a considerable improvement from most previous studies. Single aerosol droplets were generated from the collected SOA samples and trapped within an EDB at different temperatures and relative humidities to investigate the dynamic changes in their physiochemical properties. The volatilisation of organic components from toluene and β-caryophyllene SOA particles at 0 % relative humidity was found to be kinetically limited, owing to particle viscosity. The unconventional use of a newly-built CFR combined with comprehensive offline chemical characterisation and single particle measurements, offers a unique approach to further our understanding of the relationship/s between SOA formation conditions, chemical composition and physiochemical properties.

scholarly journals Urban organic aerosol composition in Eastern China differs from North to South: Molecular insight from a liquid chromatography-Orbitrap mass spectrometry study

2019 ◽  
Author(s):  
Kai Wang ◽  
Ru-Jin Huang ◽  
Martin Brüggemann ◽  
Yun Zhang ◽  
Lu Yang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Eastern China ◽  
Organic Aerosol ◽  
Photochemical Oxidation ◽  
Lower Latitude ◽  
Molecular Formula ◽  
Aerosol Composition ◽  
Orbitrap Mass Spectrometry ◽  
Low Degrees

Abstract. Particulate air pollution in China is influencing human health, ecosystem and 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 ≤ 2.5 μm (PM2.5) were collected in January 2014 in three cities located in Northeast, East and Southeast China, i.e., Changchun, Shanghai and Guangzhou, respectively. Organic aerosol (OA) in the PM2.5 samples was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution Orbitrap mass spectrometry in both negative mode (ESI−) and positive mode electrospray ionization (ESI+). After a non-target screening including molecular formula assignments, compounds were classified into five groups based on their elemental composition, i.e., CHO, CHON, CHN, CHOS and CHONS. The CHO, CHON and CHN compounds present the dominant signal abundances of 81–99.7 % in the mass spectra and the majority of these compounds were assigned to mono- and polyaromatics, suggesting that anthropogenic emissions are a large source of urban OA in all three cities. However, the chemical characteristics of these compounds varied among different cities. The degree of aromaticity and the number of polyaromatic compounds were significantly higher in samples from Changchun, which could be attributed to the large emissions from residential heating (i.e., coal combustion) during winter time in Northeast China. Moreover, the ESI− analysis showed higher H / C and O / C ratios for organic compounds in Shanghai and Guangzhou compared to samples from Changchun, indicating that OA in lower latitude regions of China experiences more intense photochemical oxidation processes. The majority of sulfur-containing compounds (CHOS and CHONS) in all cities were assigned to aliphatic compounds with low degrees of unsaturation and aromaticity. Again, samples from Shanghai and Guangzhou exhibit a larger chemical similarity but largely differ from those from Changchun.

ADSORPTION LIQUID CHROMATOGRAPHY OF ETHANOL ELUATE OF ETHANOL EXTRACT OF GREEN WALNUTS+LEAVES (LUGLANS REGIA L., NUT FAMILY - LUGLANDACEAC) (Message VI)

2021 ◽  
Vol 7 (2) ◽  
pp. 17-22
Author(s):  
V. Platonov ◽  
Aleksandr Hadarcev ◽  
G. Suhih ◽  
M. Volochaeva ◽  
I. Dunaeva
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Chemical Composition ◽  
Carboxylic Acids ◽  
Phthalic Acid ◽  
Ethanol Extract ◽  
X Ray ◽  
Chromatography Mass Spectrometry ◽  
Column Adsorption ◽  
Structural Formulas

The aim of the study was to perform column adsorption liquid chromatography in order to obtain ethanol eluate, after preliminary sequential elution of ethanol extract with solvents in the order of their polarity: n–hexane, toluene, chloroform, acetone; to study in detail the chemical composition of this eluate by chromatography-mass spectrometry and X-ray fluorescence spectroscopy, with the intensification of compounds determining the composition of eluate, obtaining their masses -spectra, structural formulas, determination of the nature of trace elements. Materials and methods of research. A detailed study of the chemical composition of acetone eluate of ethanol extract of walnuts+ leaves was carried out using column adsorption liquid chromatography, chromato-mass spectrometry and X-ray fluorescence analysis. The results and their discussion. The features of the chemical composition of ethanol eluate of the product of column adsorption liquid chromatography of ethanol extract were studied, the qualitative composition and quantitative content of compounds identified in the first one were established by chromatography-mass spectrometry. Mass spectra and structural formulas were obtained for 31 individual eluate compounds. Ethanol eluate is characterized by the following indicators of structural and group composition (mass. % of eluate): esters of phthalic acid - 52.14, silicon and sulfur-containing compounds, respectively - 20.19 and 6.43, hydrocarbons - 15.38, glycosides - 2.21, alcohols - 1.92, carboxylic acids - 1.07, sterols - 0.89. It is assumed that the pharmacological effect of ethanol eluate is mainly determined by a set of free carboxylic acids, as well as phthalic acid, formed as a result of biochemical and hydrological transesterification of its esters containing compounds, alcohols, glycosides and sterols. Organosilicon compounds during hydrolysis give silica in the size of nanoparticles, which play the role of carriers of the above compounds to various organs of a living organism, as well as drainage of blood vessels from the products of cell metabolism, for example, cholesterol, various fats, etc. A comparative characteristic of the chemical composition of all ethanol extract eluates was carried out, the effectiveness of column adsorption liquid chromatography was shown.

scholarly journals Secondary Organic Aerosol from Atmospheric Photooxidation of Indole

2017 ◽  
Author(s):  
Julia Montoya ◽  
Jeremy R. Horne ◽  
Mallory L. Hinks ◽  
Lauren T. Fleming ◽  
Veronique Perraud ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Air Quality ◽  
Chemical Composition ◽  
High Resolution ◽  
Secondary Organic Aerosol ◽  
High Resolution Mass Spectrometry ◽  
Organic Aerosol ◽  
Scanning Mobility Particle Sizer ◽  
High Resolution Mass ◽  
Resolution Mass

Abstract. Indole is a heterocyclic compound emitted by various plant species under stressed conditions or during flowering events. The formation, optical properties, and chemical composition of secondary organic aerosol (SOA) formed by low-NOx photooxidation of indole were investigated. The SOA yield (1.1 ± 0.3) was estimated from measuring the particle mass concentration with a scanning mobility particle sizer (SMPS) and correcting it for the wall loss effects. The SOA particles were collected on filters and analysed offline with UV-Vis spectrophotometry to measure the mass absorption coefficient (MAC) of the bulk sample. The samples were visibly brown and had MAC values of ~7 m2/g at λ = 300 nm and ~2 m2/g at λ = 400 nm, comparable to strongly absorbing brown carbon emitted from biomass burning. The chemical composition of SOA was examined with several mass spectrometry methods. The direct analysis in real time mass spectrometry (DART-MS) and nanospray desorption electrospray high resolution mass spectrometry (nano-DESI-HRMS) were used to provide information about the overall distribution of SOA compounds. High performance liquid chromatography, coupled to photodiode array spectrophotometry and high resolution mass spectrometry (HPLC-PDA-HRMS) was used to identify chromophoric compounds. Indole derivatives, such as tryptanthrin, indirubin, indigo dye, and indoxyl red were found to contribute significantly to the visible absorption spectrum of indole SOA. The potential effect of indole SOA on air quality was explored with the airshed model, which found elevated concentrations of indole SOA during the afternoon hours contributing considerably to the total organic aerosol under selected scenarios. Because of its high MAC values, indole SOA can contribute to decreased visibility and poor air quality.

scholarly journals Effect of oxidant concentration, exposure time, and seed particles on secondary organic aerosol chemical composition and yield

2015 ◽  
Vol 15 (6) ◽  
pp. 3063-3075 ◽  
Author(s):  
A. T. Lambe ◽  
P. S. Chhabra ◽  
T. B. Onasch ◽  
W. H. Brune ◽  
J. F. Hunter ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Short Exposure ◽  
Heterogeneous Oxidation ◽  
Seed Particles ◽  
Aerosol Mass ◽  
Environmental Chambers

Abstract. We performed a systematic intercomparison study of the chemistry and yields of secondary organic aerosol (SOA) generated from OH oxidation of a common set of gas-phase precursors in a Potential Aerosol Mass (PAM) continuous flow reactor and several environmental chambers. In the flow reactor, SOA precursors were oxidized using OH concentrations ranging from 2.0 × 108 to 2.2 × 1010 molec cm−3 over exposure times of 100 s. In the environmental chambers, precursors were oxidized using OH concentrations ranging from 2 × 106 to 2 × 107 molec cm−3 over exposure times of several hours. The OH concentration in the chamber experiments is close to that found in the atmosphere, but the integrated OH exposure in the flow reactor can simulate atmospheric exposure times of multiple days compared to chamber exposure times of only a day or so. In most cases, for a specific SOA type the most-oxidized chamber SOA and the least-oxidized flow reactor SOA have similar mass spectra, oxygen-to-carbon and hydrogen-to-carbon ratios, and carbon oxidation states at integrated OH exposures between approximately 1 × 1011 and 2 × 1011 molec cm−3 s, or about 1–2 days of equivalent atmospheric oxidation. This observation suggests that in the range of available OH exposure overlap for the flow reactor and chambers, SOA elemental composition as measured by an aerosol mass spectrometer is similar whether the precursor is exposed to low OH concentrations over long exposure times or high OH concentrations over short exposure times. This similarity in turn suggests that both in the flow reactor and in chambers, SOA chemical composition at low OH exposure is governed primarily by gas-phase OH oxidation of the precursors rather than heterogeneous oxidation of the condensed particles. In general, SOA yields measured in the flow reactor are lower than measured in chambers for the range of equivalent OH exposures that can be measured in both the flow reactor and chambers. The influence of sulfate seed particles on isoprene SOA yield measurements was examined in the flow reactor. The studies show that seed particles increase the yield of SOA produced in flow reactors by a factor of 3 to 5 and may also account in part for higher SOA yields obtained in the chambers, where seed particles are routinely used.

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