Radical cations from nitrone spin-traps: Reaction with water to give OH adducts

Exposure of dilute solutions of three widely used nitrone spin-traps in dry Freon matrices (CFCl3) at 77 K to ionising radiation gave corresponding radical cations, characterised by their EPR spectra. On melting, these radical-cations were stable and good liquid-phase EPR spectra were obtained, together with spectra for chloride ion adducts. When solutions containing water were used, the same cations were detected at 77 K. However, on melting, isotropic spectra characteristic of the (OH)-O-. radical adducts were obtained in high yield. These results are discussed in terms of the use of nitrone spin-traps to detect (OH)-O-. radicals, especially in biological systems.