Determination of polar constituents in scrophulariae radix by micellar electrokinetic capillary chromatography

A rapid method for simultaneous determination of three marker constituents, 2-(3-hydroxy-4-methoxyphenyl) ethyl 1-O-[alpha-1-arabinopyranosyl (1 --> 6)]-feruloyl (1 --> 4)-alpha-L-rhamnopyranosyl (1 --> 3)-beta-D-glucopyranoside (SN-A), harpagoside (SN-B) and cinnamic acid (SN-C) in Scrophulariae Radix by micellar electrokinetic capillary chromatography was developed. In this study, the effects of analytical conditions, including buffer pH, buffer electrolyte, temperature, applied voltage and organic modifier concentration, on separations were studied. The optimal chromatographic conditions were obtained with a buffer composed of 20 mM sodium tetraborate and sodium dihydrogen phosphate containing 100 mM sodium cholate and 10% acetonitrile at pH 7.5. Propylparaben was used as an internal standard and analytes were detected at 280 nm. The linear calibration range of SN-A, SN-B and SN-C were 20.0-320.0 mu g/ml (r=O.9994), 9.6-153.6 mu g/ml (r=0.9994) and 1.6-25.6 mu g/ml (r=0.9996), respectively. The recoveries of these markers were SN-A: 103.5 +/- 0.4%, SN-B: 102.4 +/- 2.9% and SN-C: 102.4 +/- 1.9%. The relative standard deviations of the three marker substances for intraday and interday analyses were 0.55-1.71% and 1.36-3.83%, respectively.