Abstract: The second derivative differential pulse polarography was developed for the quantitative determination ofactive principles in medicinal herbs(baicalin in Scutellaria baicalensis Georgi, indigo in Baphicacanthus cusia(Nees) Bremek, paeonol in Paeonia suffruticosa Andr.and piperine in Piper longum L.). The group in baicalin, indigo, paeonol and piperine could be reduced to in acidic solution at the dropping mercury electrode, and showed very good second derivative differential pulse polarographic peak at -1.550 V, -1.300 V, -1.630 V and -0.860 V (Vs Ag/AgCl) respectively. The linear relationship between concentration of baicalin, indigo, paeonol, piperine and peak height was obtained in the concentration range of 4.5×10^-5~2.7×10^-4 mol·L^-1, 3.8×10^-5~2.5×10^-4 mol·L^-1, 1.0~6.0×10^-4 mol·L^-1 and 7.0×10^-5~2.5×10^-4 mol·L^-1 and the determination limits were 9.0×10^-8 mol·L^-1, 8.4×10^-9 mol·L^-1, 9.2×10^-9 mol·L^-1 and 8.7×10^-9 mol·L^-1 respectively.fhis method is simple, rapid and sensitive, and the results are accurate.

Key words: Second derivative differential pulse polarography, Baicalin, Indigo, Paeonol, Piperine