Fig. 3. (A) EPR spectrum of K₂S₂O₈–Na₂SO₃–DMPO. (B) (a) EPR spectrum of DMPO–0.1 M Na₂SO₃ in a cyclic potential scan from 0 to 1.5 V. (b) EPR spectrum of DMPO–0.1 M Na₂SO₃–0.01 M K₂S₂O₈. (c) EPR spectrum of DMPO–0.1 M Na₂SO₃–0.01 M K₂S₂O₈ in a cyclic potential scan from 0 to 1.5 V.