Electrochemical Investigation of Coenzyme Q10 on Silver Electrode in Ethanol Aqueous Solution and Its Determination Using Differential Pulse Voltammetry

The electrochemistry reduction of coenzyme Q10 (CoQ10) on silver electrodes has been investigated in mixed solvent containing 95 vol. % ethanol and 5 vol. % water. A combination of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) is employed to explore the mechanism of redox processes of CoQ10 in the presence and absence of oxygen, respectively. It has been proved that the redox reaction of CoQ10 is highly dependent on the oxygen in the solution compared with that of CoQ0, which may be attributed to the isoprenoid side chain effect of CoQ10. Moreover, the effects of experimental variables such as electrolyte component, pH, temperature, and sonication time on the amperometric and potentiometric responses of CoQ10 are presented. The differential pulse voltammetry method has been developed for the quantification of the CoQ10 in the complex samples. Under the optimum conditions, the method is linear over the concentration range of 1.00 × 10−7 to 1.00 × 10−3 mol/L (8.63 × 10−2 to 8.63 × 102 mg/kg). The limit of detection (3σ/k) is 3.33 × 10−8 mol/L (2.88 × 10−2 mg/kg). The recoveries of the spiked samples are between 91% and 108%. The presented method can be applied to the analysis of CoQ10 in real samples without any pretreatment.