Identification and determination of active anthraquinones in Chinese teas by micellar electrokinetic capillary chromatography

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Abstract
The simultaneous determination of emodin, aloe‐emodin and rhein, in Semen Cassiae, Qinghai Wild Dahuang tea, Ningxia Juemingzi tea, Lanzhou Juemingzi tea and Surong Juemingzi tea, has been investigated by micellar electrokinetic capillary chromatography for the first time. With an electrolyte containing 15 mm borax, 30 mm SDS, 10% (v/v) ethanol, at pH 9.60 and 20 kV applied voltage, the three analytes were completely separated within 12 min. The effects of the concentration of borax, electrolyte pH, the concentrations of SDS and organic modifier and the applied voltage on electropheoretic behavior and separation were studied. The linear calibration range was 4–120 µg/mL (r = 0.9921) for emodin, 10–200 µg/mL (r = 0.9970) for aloe‐emodin and 2–100 µg/mL (r = 0.9971) for rhein, respectively. Under the optimum conditions, the relative standard deviation (RSD) values (n = 6) of the migration time and the peak area of each peak was 0.59–0.80% and 1.30–3.22%, respectively. The contents of the analytes in Rheum, Qinghai Wild Dahuang tea, Semen Cassiae and three other kinds of teas were easily determined with recoveries ranging from 95.3 to 104.4%. Copyright © 2003 John Wiley & Sons, Ltd.