A new method for the determination of oxygen solubilities by EPR

Free radicals dissolved in oxygen-containing solutions give rise to EPR spectra characterized by very broad lines due to Heisenberg spin exchange. In the method herein proposed oxygen is consumed at a constant rate, within the cavity of an EPR spectrometer, by alkyl radicals generatedin situ by thermal decomposition of an aliphatic azo compound in the presence of a nitroxide probe. The effect of decreasing the oxygen concentration is to reduce the width, and therefore to increase the height of the spectral lines of the nitroxide, which reach a maximum when oxygen has been completely consumed. From the knowledge of the rate of generation of the alkyl radicals, the oxygen solubility in a given solvent can be easily determined.