Microchip electrophoretic separation and fluorescence detection of chelerythrine and sanguinarine in medicinal plants

A new method has been developed for separation of chelerythrine and sanguinarine in medicinal plants used in traditional Chinese medicine (TCM). The separation is achieved by microchip electrophoresis (CE) using laser-induced fluorescence detection. The CE separation is achieved by using a hydro-organic medium as the electrolyte buffer. The experimental results are consistent with the prediction by theory in terms of resolution and migration speed because of the low Joule heat generated in microchip CE. In addition, formamide was found to have a potential for separation of molecules with similar chemical structures. Based on these findings, a run buffer containing 50% formamide was used to separate chelerythrine (CHE) and sanguinarine (SAN). The influencing factors, such as solvent of run buffer, pH of buffer, separation distance, and separation voltage, were optimized. Baseline separation of chelerythrine and sanguinarine was achieved within 120 s under an electrical voltage of 1.8 kV. Good linearity was observed in the concentration range of 0.15-550 μg mL(-1) (r=0.9993) for CHE and in the range of 0.3-600 μg mL(-1) (r=0.9998) for SAN. A low limit of detection (LOD) was achieved because of the high sensitivity achieved by laser-induced fluorescence detection (i.e. 5.0 ng mL(-1) and 2.0 ng mL(-1) for CHE and SAN, respectively). The contents of CHE are found to be 641.8±7.5 and 134.0±2.3 mg/kg in extracts of Macleaya cordata and Chelidonium majus, respectively, with good recovery of above 99%. The corresponding values for SAN found in these Chinese herbal extracts are 681.8±7.9 mg/kg and 890.5±8.9 mg/kg, respectively.