An improved method for the quantitation of flavonoids in Herba Leonuri by capillary electrophoresis.

A capillary electrophoresis system coupled with wall-jet amperometric detection was used to determine five flavonoids (kaempferol, rutin, hyperoside, quercitrin, quercetin) in Herba Leonuri. Several important effect factors, such as the pH and concentration of running buffer, separation voltage, injection time, and detection potential, were investigated to acquire the optimum conditions. With 50 mmoL/L Na(2)B(4)O(7)-100 mmoL/L NaH(2)PO(4) buffer (pH=7.50) as the running buffer, the five flavonoids were baseline separated within 15 min in a 60 cm length capillary at a separation voltage of 15 kV. The relationship between peak currents and analyte concentrations was linear over about 2 orders of magnitude, with detection limits (S/N = 3) ranging from 0.03 to 0.08 microg/mL for all analytes. The use of this method for the quantitation of the above flavonoids present in the real sample of Herba Leonuri was reported.