Determination of Dendrobine in Dendrobium Nobile Lindl by Capillary Electrophoresis Coupled with Electrochemiluminescence

After the sample was extracted with ethanol, the extract was injected to the capillary for capillary electrophoresis (CE) separation by electric sampling for 10 s with the injection voltage of 10 kV. The running buffer solution for CE was 10 mmol·L^-1 PBS (pH 5.13) and the separation voltage was 15 kV. The dendrobine after CE separation reacted with 5 mmol·L^-1 Ru(bpy)₃²⁺ solution (in 70 mmol·L^-1 PBS with pH 8.10) in electrochemiluminescence (ECL) detection cell, resulting the ECL intensity of Ru(bpy)₃²⁺ increaced at the detection potential of 1.17 V (vs. Ag/AgCl). Linear relationship was found between the peak area of ECL signal with the mass concentration of dendrobine in the range of 1.0-100 mg·L^-1, with detection limit (3S/N)of 0.045 mg·L^-1. The proposed method was applied to the determination of dendrobine in Dendrobium nobile Lindl, giving recovery rates obtained by standard addition method in the range of 92.0%-105% and RSDs (n=5) were in the range of 2.5%-5.1%.