Use of a phosphorylated spin trap to discriminate between the hydroxyl radical and other oxidising species

The spin-trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) is shown to provide a simple method to distinguish free-radical reactions which lead to the production of (.)OH from those which proceed via one-electron transfer followed by hydration or nucleophilic substitution of another adduct, In the first case, only an (.)OH adduct is detected; in the latter, signals from the hydroxyl adduct (labelled with (17)O when H(2) (17)O is-employed) are accompanied by a second signal believed:to result via internal trapping of a radical formed from an intermediate radical cation, This provides a potentially useful mechanistic probe, for example for use in biochemical systems.