Simultaneous determination of effective components in Gualou Guizhi granules using microemulsion electrokinetic chromatography coupled with large volume sample stacking

Abstract

A method using microemulsion electrokinetic chromatography (MEEKC) coupled with large volume sample stacking was developed for the quantitative analysis of five compounds, namely liquiritin, glycyrrhizin, cinnamic acid, gallic acid and protocatechuic acid in Gualou Guizhi granules. The effect of the microemulsion components, such as the oil phase, surfactant and cosurfactant on the resolution of the analytes was studied. The baseline separation of the five analytes was achieved within 10 min by using a microemulsion buffer containing 0.5% (w/v, 17 mmol L⁻¹) sodium dodecyl sulfate, 5.0% (v/v) butan-1-ol, 0.5% (v/v) ethyl acetate and 94.5% (v/v) 5 mmol L⁻¹ borate–10 mmol L⁻¹ phosphate buffer (pH 9.0). After combining with on-line preconcentration via large volume sample stacking (LVSS), the detection limits (defined as S/N = 3) for the analytes could be as low as 0.05 μg mL⁻¹. MEEKC-LVSS was successfully applied to the determination of four analytes in Gualou Guizhi granules; the recoveries ranged from 94.51% to 97.53%, and good reproducibilities were obtained with relative standard deviations (RSDs) less than 5%.