Simultaneous determination of flavonoids and phenolic acids in Chinese herbal tea by beta-cyclodextrin based capillary zone electrophoresis

Kaempferol, apigenin, rutin, quercetin, luteolin and ferulic acid are separated and detected in Chinese herbal tea using capillary zone electrophoresis coupled to amperometric detection. The phosphate running buffer also contains ß-cyclodextrin (ß-CD), which assists in separation and gives excellent separations within 20 min and detection limits as low as 10 ng mL^-1 (S/N = 3). The effects of working electrode potential, pH and concentration of running buffer, concentration of ß-CD, separation voltage and injection time were investigated. The method was applied to analyze tea samples with recoveries in the range of 90. 0 to 107. 0%. The method offers high separation efficiency, short analysis time, small sample consumption, and good repeatability.