Abstract
The pH dependence of the apparent rate constant kT ap for trapping by four nitrones was examined. In each case, kinetic curves were obtained after treatment of EPR spectra of the spin adduct formed using both singular value decomposition and pseudo-inverse deconvolution methods. Modelling these curves led to evaluate kT ap at various pH values. Analysis of the pH dependence of kT ap permitted the determination of the rate constants for the spin trapping of and of separately. Whatever the nitrone, our results clearly show that the EPR signals of the nitrone/superoxide spin adducts observed in aqueous media were essentially due to the trapping of the protonated species