Quick and sensitive determination of flavonoids by capillary electrophoresis-potential gradient detection.

A capillary electrophoresis (CE)-potential gradient detection (PGD) method was developed for quick and sensitive determinations of puerarin, farrerol and baicalin. The flavonoids were baseline separated in 1.9 min with a buffer comprised of 20 mM tris(hydroxymethyl)aminomethane (Tris) and 3 mM HCl at pH 8.69. The analysis time is, to the best of our knowledge, the shortest for the CE analysis of flavonoids. The association constants, determined by affinity CE, suggested an ion-dipole or ion-induced dipole interaction between Tris and flavonoid molecules. The detection limits, in the range of 0.068 and 0.116 mg L(-1), were lower than the early reported UV and chemiluminescence detection techniques. A solvent-extraction method was coupled to CE to determine baicalin in a Chinese herbal preparation Scutellaria Baicalensis Georgi. The concentration of baicalin in the sample was determined to be 5.1%. Validation of the method suggested its applicability in real sample analysis.