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Radical identification by liquid chromatography/thermospray mass spectrometry
H Iwahashi1, C E Parker, R P Mason
1Laboratory of Molecular Biophysics, National Institute of Environmental Health Science, Research Triangle Park, NC 27709.
Rapid Communications in Mass Spectrometry : RCM
|September 1, 1990
Summary
Researchers detected radical adducts using liquid chromatography with electron paramagnetic resonance or mass spectrometry. They identified specific adducts from hydroxyl, methanol, and ethanol radicals in a Fenton system, characterizing their structures.
Area of Science:
- Analytical Chemistry
- Free Radical Chemistry
- Spectroscopy
Background:
- The Fenton system is a common method for generating hydroxyl radicals.
- Spin trapping agents like DMPO are used to detect short-lived radicals.
- Characterizing radical species is crucial for understanding reaction mechanisms.
Purpose of the Study:
- To detect and characterize radical adducts formed in the Fenton system using DMPO.
- To differentiate between hydroxyl, methanol-derived, and ethanol-derived radicals.
- To elucidate the structure of detected radical adducts.
Main Methods:
- Liquid chromatography coupled with electron paramagnetic resonance (LC/EPR).
- Liquid chromatography coupled with thermospray mass spectrometry (LC/TSP-MS).
- Use of deuterated alcohols (CD3OH, CD3CD2OH, CD3CH2OH, CH3CD2OH) for structural elucidation.
Main Results:
- One DMPO adduct detected for hydroxyl and methanol-derived radicals; two adducts for ethanol-derived radicals.
- LC/TSP-MS identified adducts with specific quasi-molecular ions ([M+H]+ at m/z 146/160, M+ at m/z 130).
- Deuteration studies confirmed the formation of carbon-centered radicals and identified two diastereomeric adducts with the alpha-hydroxyethyl radical.
Conclusions:
- DMPO successfully traps hydroxyl, methanol-derived, and ethanol-derived radicals in the Fenton system.
- LC/EPR and LC/TSP-MS are effective techniques for identifying and characterizing radical adducts.
- The study elucidates the formation of carbon-centered radicals and specific diastereomeric adducts from ethanol.