Determination of gambogic acid in Gamboge by non-aqueous capillary electrophoresis

Gambogic acid (GA), a kind of caged xanthones, has low solubility in water. A non-aqueous capillary electrophoresis (NACE) was established for the determination of GA in Gamboge based on the optimized conditions. The effect of 20% -60% methanol or acetonitrile spiked in running solution was investigated. The effects of compositions, concentration, pH, additives like β-cyclodextrin in running buffer were thoroughly studied. Applied voltage and applied temperature were also observed. Optimal electrophoretic conditions were as follows: 20 mmol/L sodium borohydride solution (pH 9.86) containing 40% (v/v) acetonitrile, 10 mmol/L β-cyclodextrin as running buffer, applied voltage of 10 kV, capillary temperature of 30°c and detection wavelength of 280 nm. The calibration curve had good linearity in the range of 2-2 000 mg/L with the correlation coefficient of 0.999 6. The limit of quantification (S/N = 3) of the method was 2 mg/L. The quantifications of GA in Gamboge from different producing places including Vietnam, Thailand, Burma, India were 1.67-472.40 mg/g with the RSD (n=3) of 1.12% -2.60%. The content of Gamboge from Vietnam is obviously low while the others are high. The recoveries of GA spiked in real samples ranged from 95.2% to 105.6%. The method of NACE is simple, efficient and of good reproducibility, can be served as a novel reference to identify and control the quality of Gamboge.