Determination of gallic acid and salidroside in Rhodiola and its preparation by capillary electrophoresis

A new, simple, and rapid capillary electrophoresis (CE) method employing hexadimethrine bromide (HDB) as electroosmotic flow (EOF) modifier was developed for the identification and quantitative determination of two pharmaceutically active constituents—gallic acid (GA) and salidroside (S)—in extracts of Rhodiola root and its medicinal preparation. The optimum separation was achieved at pH 11.00 with the use of 10 mM borate buffer containing 0.001% (w/v) of HDB. The applied voltage was ∼15 kV and the capillary temperature was kept constant at 25°C. m-Phthalic acid was used as an internal standard for quantification. The calibration dependences exhibited good linearity for the ratios of the concentrations of standard samples and internal standard and the ratios of the peak area of samples and internal standard over the concentration range from 24 to 1200 μg/mL for GA and 2.4 to 72 μg/mL for S. The correlation coefficients were 0.9999 and 0.9997, and the detection limits of the CE method corresponding to a signal-to-noise ratio of three were 6 and 2 μg/mL for GA and S, respectively. The relative standard deviations of the relative migration time and the relative peak area of samples were 0.5 and 4.0% for GA and 1.9 and 5.3% for S. The effects of buffer pH and the concentration of HDB on the resolution were studied systematically. The contents of these two active compounds in Rhodiola root and its preparation were successfully determined over 6 min with satisfactory repeatability and recovery.