Separation and determination of tetrandrine and fangchinoline in herbal medicines by flow injection-micellar electrokinetic capillary chromatography with internal standard method

A simple, rapid and precision flow injection-micellar electrokinetic capillary chromatography (FI-MEKC) system with trimethoprim as internal standard (IS) for automated quantitative analysis of tetrandrine (TET) and fangchinoline (FAN) in various herbal medicines was demonstrated. The real sample throughput was 19–40 samples per hour using the background electrolyte (BGE) containing 15 mM acetic acid–15 mM sodium acetate–3% (v/v) polyoxyethylene sorbitan monolaurate (Tween 20)–5% (v/v) methanol at pH 5.5. The method resulted in excellent linearity, with correlation coefficient of regression equation of 0.9996 and 0.9991 for TET and FAN, respectively. Recoveries were in the range 95–109% and 92–106% for TET and FAN, respectively.