Separation and determination of rutin and quercetin in the flowers of Sophora japonica L. by capillary electrophoresis with electrochemical detection

Capillary electropkoresis with amperometric detection has been evaluated for the simultaneous determination of rutin and quercetin. The cyclic voltammogram, hydrodynamic voltommogram, and the effects of pH, concentration of buffer and sodium doclecyl sulfate (SDS), and amount of organic modifier on the separation and the detection were studied. The optimized conditions were: defection potential 1.2 V, separation at 12 kV, 5 s at 15 kV for sample injection, running electrolyte 20 mmol L-1 borate buffer, pH 8.8, containing 40 mmol L-1 SDS and 10% acetonitrile. The defection limit of the method was low, 0.001 and 0.0005 mg mL(-1), for rutin and quercetin, respectively; the linear ranges were wide - 0.005 - 0.5 and 0.005 0.4 mg mL(-1), respectively. The variations in peak current and migration time for eight consecutive injections of a standard solution containing 0.1 mg mL(-1) of each compound were 4.78 and 3.63%, and 6.50 and 2.59% for rutin and quercetin, respectively. The levels of the two compounds in traditional Chinese herbal drugs were easily determined.