scholarly journals Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase

2020 ◽  
Author(s):  
Alexander Zaytsev ◽  
Martin Breitenlechner ◽  
Anna Novelli ◽  
Hendrik Fuchs ◽  
Daniel A. Knopf ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Ionization ◽  
Laboratory Experiments ◽  
Spin Trapping ◽  
Chemical Ionization Mass Spectrometry ◽  
Integration Time ◽  
Ionization Mass ◽  
Peroxy Radicals ◽  
Chemical Derivatization ◽  
Criegee Intermediates

Abstract. Short-lived highly reactive atmospheric species, such as organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), play an important role in controlling the oxidative removal and transformation of many natural and anthropogenic trace gases in the atmosphere. Direct speciated measurements of these components are extremely helpful for understanding their atmospheric fate and impact. We describe the development of an online method for measurements of SCIs and RO2 in laboratory experiments using chemical derivatization and spin trapping techniques combined with H3O+ and NH4+ chemical ionization mass spectrometry (CIMS). Using chemical derivatization agents with low proton affinity, such as electron-poor carbonyls, we scavenge all SCIs produced from a wide range of alkenes without depleting CIMS reagent ions. Comparison between our measurements and results from numeric modelling, using a modified version of the Master Chemical Mechanism, shows that the method can be used for quantification of SCIs in laboratory experiments with detection limit of 1.4 × 107 molecule cm-3 for 30 s integration time with the instrumentation used in this study. We show that spin traps are highly reactive towards atmospheric radicals and form stable adducts with them by studying the gas-phase kinetics of their reaction with hydroxyl radical (OH). We also demonstrate that spin trap adducts with SCIs and RO2 can be simultaneously probed and quantified under laboratory conditions with detection limit of 1.6 × 108 molecule cm-3 for 30  s integration time for RO2 species with the instrumentation used in this study. Spin trapping prevents radical secondary reactions and cycling, which ensures that measurements are not biased by chemical interferences, and can be implemented for detecting RO2 species in the ambient atmosphere.

scholarly journals Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase

2021 ◽  
Vol 14 (3) ◽  
pp. 2501-2513
Author(s):  
Alexander Zaytsev ◽  
Martin Breitenlechner ◽  
Anna Novelli ◽  
Hendrik Fuchs ◽  
Daniel A. Knopf ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Ionization ◽  
Laboratory Experiments ◽  
Spin Trapping ◽  
Integration Time ◽  
Ionization Mass ◽  
Peroxy Radicals ◽  
Chemical Derivatization ◽  
Spin Traps ◽  
Criegee Intermediates

Abstract. Short-lived highly reactive atmospheric species, such as organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), play an important role in controlling the oxidative removal and transformation of many natural and anthropogenic trace gases in the atmosphere. Direct speciated measurements of these components are extremely helpful for understanding their atmospheric fate and impact. We describe the development of an online method for measurements of SCIs and RO2 in laboratory experiments using chemical derivatization and spin trapping techniques combined with H3O+ and NH4+ chemical ionization mass spectrometry (CIMS). Using chemical derivatization agents with low proton affinity, such as electron-poor carbonyls, we scavenge all SCIs produced from a wide range of alkenes without depleting CIMS reagent ions. Comparison between our measurements and results from numeric modeling, using a modified version of the Master Chemical Mechanism, shows that the method can be used for the quantification of SCIs in laboratory experiments with a detection limit of 1.4×107 molecule cm−3 for an integration time of 30 s with the instrumentation used in this study. We show that spin traps are highly reactive towards atmospheric radicals and form stable adducts with them by studying the gas-phase kinetics of the reaction of spin traps with the hydroxyl radical (OH). We also demonstrate that spin trap adducts with SCIs and RO2 can be simultaneously probed and quantified under laboratory conditions with a detection limit of 1.6×108 molecule cm−3 for an integration time of 30 s for RO2 species with the instrumentation used in this study. Spin trapping prevents radical secondary reactions and cycling, ensuring that measurements are not biased by chemical interferences, and it can be implemented for detecting RO2 species in laboratory studies and potentially in the ambient atmosphere.

scholarly journals Chemical ionization mass spectrometry (CIMS) may not measure all gas-phase sulfuric acid if base molecules are present

2010 ◽  
Vol 10 (12) ◽  
pp. 30539-30568
Author(s):  
T. Kurtén ◽  
T. Petäjä ◽  
J. Smith ◽  
I. K. Ortega ◽  
M. Sipilä ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Gas Phase ◽  
Chemical Ionization ◽  
Measurement Data ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Proton Affinities ◽  
Reaction Thermodynamics

Abstract. The state-of-the art method for measuring atmospheric gas-phase sulfuric acid is chemical ionization mass spectrometry (CIMS) based on nitrate reagent ions. Using computed proton affinities and reaction thermodynamics for the relevant charging reactions, we show that in the presence of strong bases such as amines, which tend to cluster with the sulfuric acid molecules, a significant fraction of the total gas-phase sulfuric acid may not be measured by a CIMS instrument. If this is the case, this effect has to be taken into account in the interpretation of atmospheric sulfuric acid measurement data, as well as in intercomparison of different CIMS instruments, which likely have different susceptibilities to amine-sulfuric acid clustering.

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 ◽  
Vol 9 (8) ◽  
pp. 3851-3861 ◽  
Author(s):  
Javier Sanchez ◽  
David J. Tanner ◽  
Dexian Chen ◽  
L. Gregory Huey ◽  
Nga L. Ng
Keyword(s):  
Mass Spectrometry ◽  
Chemical Ionization ◽  
Direct Detection ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Integration Time ◽  
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 ∼ 5 ppt between 2 and 3 p.m. local time. The HO2 diurnal profile was found to be influenced by morning-time vehicular NOx emissions and shows a slow decrease into the evening, likely from non-photolytic production, among other factors. Measurement sensitivities of approximately 5.1 ± 1.0 cps ppt−1 for a bromide ion (79Br−) count rate of 106 cps were observed. The relatively low instrument background allowed for a 3σ lower detection limit of 0.7 ppt for a 1 min integration time. 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 these measurements can be achieved using instruments with only unit mass resolution capability.

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