Analysis of quinolizidine alkaloids in Sophora flavescens Ait. by capillary electrophoresis with tris(2,2'-bipyridyl) ruthenium (II)-based electrochemiluminescence detection

A capillary electrophoresis method coupled with electrochemiluminescence detection for the analysis of quinolizidine alkaloids was established, especially, oxymatrine (OMT) which could not be measured by previous electrochemiluminescence methods was detected sensitively herein. Complete separation of sophoridine (SR), matrine (MT) and OMT was achieved within 13 min using a background electrolyte of 50mM phosphate buffer at pH 8.4 and a separation voltage of 15 kV. The calibration curves showed a linear range from 2.8 x 10(-8) to 4.4 x 10(-7) M for SR, 2.7 x 10(-8) to 4.4 x 10(-7) M for MT, and 2.5 x 10(-7) to 4.0 x 10(-6)M for OMT, respectively. The relative standard derivations for all analytes were below 3.1%. Good linear relationships were showed with correlation coefficients for all analytes exceeded 0.987. The detection limits were 1.0 nM for SR and MT, and 40 nM for OMT under the optimal conditions, respectively. The developed method was nearly harmless to the human and environment.