title: Quantitative aspects of ESR and spin trapping of hydroxyl radicals and hydrogen atoms in gamma-irradiated aqueous solutions.
abstract: The efficiency of 5,5-dimethylpyrroline-1-N-oxide (DMPO) and alpha-(4-pyridyl-1-oxide)-N-tert.-butylnitrone (POBN) to spin trap hydroxyl radicals and hydrogen atoms, respectively, was studied in gamma-irradiated solutions where the radical yields are accurately known. The effects of dose, spin trap concentration, and pH and of the stability of the spin adducts on the spin-trapping efficiency were investigated. In degassed or N2-saturated solutions the spin-trapping efficiencies were 35% for DMPO and hydroxyl radicals and 14% for POBN and hydrogen atoms. The low spin-trapping efficiencies were shown not to be due to the instability of the DMPO-OH and POBN-H spin adducts or to the effects of H2O2 or O2. The low spin-trapping efficiency of DMPO may be explained by the reaction of hydroxyl radicals to abstract hydrogen from the DMPO molecule to produce carbon radicals as well as addition to the N = C double bond to form nitroxide radicals. For POBN the low spin-trapping efficiency for hydrogen atoms is explained in terms of addition reactions of hydrogen atoms to the aromatic ring and the pyridinium and nitrone oxygens.
mesh_terms: D003037:Cobalt Radioisotopes; D003497:Cyclic N-Oxides / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005720:Gamma Rays; D006859:Hydrogen; D006878:Hydroxides; D017665:Hydroxyl Radical; D009589:Nitrogen Oxides / Q000528:radiation effects; D011725:Pyridines; D012996:Solutions; D013113:Spin Labels; D014867:Water / Q000528:radiation effects
chemical_list: D003037:Cobalt Radioisotopes; D003497:Cyclic N-Oxides; D005609:Free Radicals; D006878:Hydroxides; D009589:Nitrogen Oxides; D011725:Pyridines; D012996:Solutions; D013113:Spin Labels; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; D014867:Water; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D006859:Hydrogen