Determination of isoflavones in red clover by capillary electrophoresis with electrochemical detection

Capillary electrophoresis with electrochemical detection (CE-ED) was employed to analyze isoflavones in red clover (Trifolium pratense). The effects of potential of working electrode, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Operated in a wall-jet configuration, a 300 μm diameter carbon-disk electrode was used as the working electrode, which exhibits a good response at + 0.85 V (versus saturated calomel electrode) for the analytes. The analytes could be separated in a 50 mmol/l borate buffer (pH 9.5) within 25 min. The response was linear over three orders of magnitude with detection limit (S/N = 3) ranging from 2 × 10− 5 mg/ml to 5 × 10− 5 mg/ml for the analytes. This method has been used for the determination of daidzein, genistein and biochanin A in red clover with satisfactory results.