Flow-injection amperometric determination of yohimbine alkaloid in dietary supplements using a boron-doped diamond electrode

A simple, rapid and sensitive flow-injection method for the amperometric determination of the alkaloid yohimbine using a boron-doped diamond electrode has been developed. Best conditions for flow-injection analysis were a detection potential of +1.20 V (vs. Ag/AgCl) and a flow rate of 1.4 mL min−1 with an injection volume of 100 μL in Britton–Robinson buffer solution at pH 7 as a carrier. The current response of yohimbine was proportional in the concentration range from 0.3 to 100 μM with two linear segments (0.3–10 and 10–100 μM) and a low detection limit of 0.15 μM (0.053 mg L−1) as well as good repeatability (relative standard deviation of 4.5% for n = 10) were achieved. The sampling frequency was calculated about 70 injections h−1. The practical analytical usefulness of the developed procedure was successfully demonstrated in the determination of yohimbine in dietary supplements with good recoveries (94–98% and 92–95%) for Pausinystalia yohimbe and Rauvolfia serpentina, respectively.