The polarographic catalytic wave of vitamin P in the presence of persulfate was studied by linear potential scan polarography and cyclic voltammetry. Vitamin P yielded a single reduction wave in acidic aqueous solution, which was ascribed to a 2e Ψ , 2H Ψ reduction of the carbonyl group in the C-4 position. Actually, the carbonyl group CAO first underwent a 1e Ψ , 1H Ψ reduction to form a neutral free radical, and the further 1e Ψ , 1H Ψ reduction of the free radical was simultaneous with its following chemical reactions. When S 2 O 8 2Ψ was present, the free radical of vitamin P was oxidized by both S 2 O 8 2Ψ and its reduction intermediate, the sulfate radical anion SO 4
β’Ψ , to regenerate the original, which resulted in the production of a polarographic catalytic wave of vitamin P.
Based on this catalytic wave, a novel method for the determination of vitamin P was proposed. In 0.02 M tartaric acid-sodium tartrate (pH 3.3) buffer containing 5.0 Ψ 10 Ψ3 M K 2 S 2 O 8 , the peak potential of the catalytic wave was Ψ1.42 V (vs SCE) and the peak current was rectilinear to the vitamin P concentration in the range of 8.0 Ψ 10 Ψ9 -1.0 Ψ 10 Ψ6 M (r β«Ψβ¬ 0.9994, n β«Ψβ¬ 13). The catalytic wave of 2.0 Ψ 10 Ψ7 M vitamin P enhanced the polarographic current 70 times compared with the corresponding reduction wave. The detection limit was 2.0 Ψ 10 Ψ9 M, and the relative standard deviation at the 2.0 Ψ 10 Ψ7 M level was 0.7% (n β«Ψβ¬ 15). The proposed method was used for the determination of vitamin P content in the pharmaceutical preparation of tablets and the medicinal plant Sophora japonica L. without previous separation.