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Updated: May 17, 2025

Electron Spin Resonance Micro-imaging of Live Species for Oxygen Mapping
Published on: August 26, 2010
EPR Spectra and Electron Spin Relaxation of O2
Sandra S Eaton1, Gareth R Eaton1
1Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80210 USA.
Abstract:
It has been known from the pioneering and approximately simultaneous work of Freed and Frankel, Hausser and Deguchi (1959 -1960) that collisions with O2 in fluid solutions broaden the electron paramagnetic resonance (EPR) spectra of free radicals. Freed showed Hausser the effect of degassing solutions on the hyperfine of DPPH. Hausser and Deguchi published spectra illustrating the effect. The effect of O2 on CW EPR spectra and on relaxation times have been applied to the problem of measuring O2 concentration in vivo. Various aspects of the effect of O2 on biological EPR and on the biological systems have been studied. A large literature has developed about in vivo O2 measurements using nitroxyl radicals, triarylmethyl radicals (trityl, TAM), carbon particles, and analogues of lithium phthalocyanine (LiPc). All of these measurements correctly assume that the O2 electron spin relaxation time is short relative to the relaxation time of the sensor molecules. There has been no prior review of the EPR spectra and electron spin relaxation of O2 in the gas phase, dissolved in fluid solution, and in frozen solutions. A summary of the relevant literature is presented here as a resource for the O2 measurement community.
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