Detection of the formyl radical by EPR spin-trapping and mass spectrometry

Publication date: Available online 4 January 2018
Source:Free Radical Biology and Medicine
Author(s): Norbert A. Bauer, Enamul Hoque, Manfred Wolf, Karin Kleigrewe, Thomas Hofmann
For the first time we here present the unambiguous identification of the formyl radical (^●CHO) by EPR (Electron Paramagnetic Resonance) spectroscopy and mass spectrometry (MS) using DMPO (5,5-dimethyl-1-pyrroline N-oxide) as spin trap at ambient temperature without using any catalysator(s). The ^●CHO was continuously generated by UV photolysis in closed anoxic environment from pure formaldehyde (HCHO) in aqueous solution. The isotropic hyperfine structure constants of ^●CHO were determined as aN = 15.72G and aH = 21.27G. The signals were deconvoluted and split by simulation in their single adduct components: DMPO-CHO, DMPO-H and DMPO-OH. We verified our results at first using MNP (2-methyl-2-nitroso-propane) as spin trap with known literature data and then mass spectroscopy. Similarly the MNP adduct components MNP-CHO, MNP-H as well as its own adduct, the MNP-2-methyl-2-propyl (MNP-MP) were deconvoluted. Due to the low signal intensities, we had to accumulate single measurements for both spin traps. Using MS we got the exact mass of the reduced ^●CHO adduct independently confirming the result of EPR detection of formyl radical.

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