The electrochemical behaviour of the anticancer herbal drug emodin was investigated by cyclic voltammetry (CV) at glassy carbon electrode. In 0.05 M NH3-NH4Cl (50% ethanol, pH 7.2) buffer solution, a pair of quasi-reversible redox peaks at potentials of E-p1 = -0.688 V and E-p2 = -0.628 V and one irreversible anodic peak, which was a typical anodic peak of emodin, at E-p3 = -0.235 V appeared at a scan rate of 100 mV/s. The irreversible anodic peak currents are linearly related to the emodin concentrations in a range from 8.9 x 10(-8) M to 7.8 x 10(-6) M with a pre-concentration time of 80 s under -0.620 V. Using the established method without pretreatment and pre-separation, emodin in herbal drug was determined with satisfactory results. Moreover, the electrode process dynamics parameters were also investigated by electrochemical techniques. (c) 2006 Elsevier Ltd. All fights reserved.