CE-electrochemiluminescence with ionic liquid for the facile separation and determination of diester-diterpenoid aconitum alkaloids in traditional Chinese herbal medicine

A CE-electrochemiluminescence(CE-ECL) detection system, CE/tris(2,2'-bipyridyl) ruthenium(II)ECL with ionic liquid, was established for the determination of diester-diterpenoid aconitum alkaloids (aconitine (AC), mesaconitine (MA) and hypaconitine (HA)) in traditional Chinese herbal medicine. Running buffer containing 25 mM borax-20 mM 1-ethyl-3-methylimidazolium tetrafluoroborate at pH 9.15 was used, which resulted in significant changes in separation and obvious enhancement in ECL intensity for AC, MA and HA with similar structures. End-column detection was achieved in 50 mM phosphate buffer with 5 mM Ru(bpy)(3)(2+) (pH 9.15) at applied detection voltage of 1.20 V when the distance between the Pt working electrode and outlet of capillary (50 cm x 25 mu m id) was set at 150 mu m. One single quantitative analysis of three alkaloids was achieved at a separation voltage of 15 kV within 10 min. Moreover, two extraction processes (ethanol extraction and ethyl ether extraction after basification) were investigated. The result showed that ethanol extraction process has higher extraction efficiency than ethyl ether extraction process. Under the optimized conditions, the detection limits of AC, MA and HA were 5.62 x 10(-8), 2.78 x 10(-8) and 3.50 x 10(-9) mol/L (S/N = 3), respectively. The method was successfully applied to determine the amounts of AC, MA and HA in the aconitum herbal samples.