Nonaqueous capillary electrophoresis for rapid and sensitive determination of fangchinoline and tetrandrine in Radix Stephaniae tetrandrae and its medicinal preparations

A simple, rapid, and sensitive non‐aqueous capillary electrophoresis procedure with head‐column field‐amplified sample stacking concentration for the analysis of fangchinoline and tetrandrine is established. Optimum separation and stacking conditions were obtained when the sample was injected at 8 kV for 50 s after preliminary pressure injection of ethanol (16.9 kPa) for 0.6 s and separated with the buffer containing 50 mM ammonium acetate, 0.5% (v/v) acetic acid, and 50% (v/v) acetonitrile in methanol medium at 24 kV applied voltage. The analytes were detected by UV at 214 nm. The two bisbenzylisoquinoline alkaloids can be separated within 6 min and quantified with high sensitivity. The detection limits were 0.30 ng mL–1 for fangchinoline and 0.34 ng mL–1 for tetrandrine, which indicated that the sensitivities were at least 1000‐fold enhanced over those reported in the literature as obtained by UV detection. The method was applied to the analysis of fangchinoline and tetrandrine in Radix Stephaniae tetrandrae and its medicinal preparations with good results.