Application of spin trapping techniques to detect reactive intermediates and radical species in the gas phase
Abstract
Peroxy radicals (HO2 and RO2) play a substantial role in the formation of tropospheric ozone and in controlling the atmospheric oxidation capacity. RO2 can undergo unimolecular H-migration followed by O2-addition, resulting in the formation of more oxidized peroxy radicals and highly oxygenated organic molecules (HOMs), which can contribute to the formation of secondary organic aerosol (SOA). While several methods are currently available for probing concentrations of peroxy radicals, the understanding of unimolecular H-shift reactions of RO2 radicals is still incomplete, partially due to the lack of reliable measurement techniques of individual radical species.
In this work, we use radical-addition reactions, also known as spin trapping techniques, followed by detection of the formed complexes with chemical ionization mass spectrometry (CIMS) to detect reactive intermediates and radical species including peroxy radicals. Several spin traps, including DMPO (5,5-dimethyl-1-pyrroline-N-oxide), were utilized to form covalently bound adducts with radical species. These adducts, detected with high-resolution time-of-flight CIMS in two positive ionization modes (NH4+ CIMS and H3O+ CIMS), show little to none fragmentation, have unique mass defects and can therefore be clearly separated from other detected compounds in the mass-spectrum. We further highlight both analytical and technical challenges accompanied with the implementation of reactive intermediates detection scheme along this route.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A43Q3125Z
- Keywords:
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- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE