Polarographic determination of diazepam with its parallel catalytic wave in the presence of persulfate.

A new method for the determination of diazepam was proposed based on its polarographic catalytic wave in the presence of persulfate. In 0.20 M NaAc-HAc (pH 4.7)-1.0 x 10(-2) M K(2)S(2)O(8) supporting electrolyte, the reduction wave of diazepam with peak potential -0.89 V (versus SCE) was catalyzed, producing a parallel catalytic wave. The peak current of the catalytic wave was 15 times higher than that of the corresponding reduction wave for 4.0 x 10(-6) M diazepam, and was rectilinear to diazepam concentration in the range of 5.6 x 10(-8) to 8.9 x 10(-6) and 8.8 x 10(-6) to 2.0 x 10(-4) M. The detection limit was 9.6 x 10(-9) M. The mechanism of the parallel catalytic wave of diazepam was discussed.