Determination of hypaphorine and oligomeric stilbenes in the root of Caragana sinica by capillary electrophoresis with electrochemical detection

Capillary electrophoresis with electrochemical detection (CE-ED) was employed for the determination of hypaphorine (an alkaloid) and four oligomeric stilbenes (including pallidol, kobophenol A, miyabenol C and (+)-α-viniferin) in Radix seu Cortex Caraganae Sinicae, the root of Caragana sinica (Bucʹhoz) Rehd. The effects of several important factors were investigated to find optimum conditions. The working electrode was a 300 μm diameter carbon disc electrode positioned opposite the outlet of capillary. The five analytes could be well separated within 12 min in a 40 cm length capillary at the separation voltage of 12 kV in a 100 mmol l−1 borate buffer (pH 10.0). The response was linear over about three orders of magnitude for all investigated compounds with detection limits (S/N=3) ranging from 0.0385 to 0.111 mg l−1. This proposed method has also been successfully applied to analyze the root of other Caragana plants.