Rapid separation and determination of structurally related anthraquinones in Rhubarb by pressurized capillary electrochromatography

A pressurized capillary electrochromatography (pCEC) with monolithic column has been developed for the rapid separation and determination of five structurally related anthraquinones in Rhubarb. The possibility of rapid separation resulted from the unique pore structure with high permeability and favorable mass transfer characteristics of the monolithic stationary phase. The effect factors such as organic modifier, acidity and concentration of running buffer, separation voltage were investigated to acquire the optimum condition. In the 220 nm wavelengths, the five anthraquinones could be baseline-separated rapidly within 5 min with the separation voltage of −20 kV in 10 mmol/L phosphate buffer (pH 6.2) containing 65% acetonitrile. The calibration graphs of rhein, aloe-emodin, emodin chrysophanol and physcion were linear by plotting the peak area against the analytes concentration over the range of 0.2–65, 0.1–30, 0.1–55, 0.5–30 and 0.5–55 μg/mL, respectively. The detection limits of five anthraquinones were ranged from 0.06 to 0.2 μg/mL and the recoveries of Rhubarb samples were about 81.3–86.4% (R.S.D. ≤ 5.2%). This proposed method was successfully applied to determination of the five analytes in Rhubarb with satisfactory results.