Simultaneous determination of tetrandrine and fangchinoline in herbal medicine Stephania tetrandra S. Moore by liquid chromatography with electrochemical detection.

A simple and selective method was developed for the simultaneous determination of tetrandrine and fangchinoline in herbal medicine by HPLC with electrochemical detection (ECD) on a bare glassy carbon electrode. The HPLC separation and ECD conditions have been optimized. The separation was carried out on a WondaSil C18-WR column (4.6 mm × 250 mm, 5 μm), with the mobile phase of acetonitrile-ammonium acetate buffer (pH 6.5; 40 mM) (32:68, v/v) using an isocratic elution at the flow rate of 0.5 mL/min. The electrochemical detection potential was set at +0.9 V. The obtained LODs for tetrandrine and fangchinoline were 0.26 and 0.27 μmol/L, respectively. The method was successfully applied to the analysis of tetrandrine and fangchinoline contents in Stephania tetrandra S. Moore. It has been demonstrated that the LC-ECD method is an excellent technique for analysis of the herbal medicine. The mean recoveries were in the range of 95-105%, while the precision expressed as repetition of peak area was lower than 2.7%.