Electrochemical evaluation and adsorptive stripping voltammetric determination of capsaicin or dihydrocapsaicin on a disposable pencil graphite electrode

Capsaicin and dihydrocapsaicin are the two most abundant capsaicinoids in peppers, which are responsible for about 90% of the spiciness. A detailed study of the electrochemical properties of these compounds at pencil graphite (PG) electrode was carried out in the pH range 1.0-12.0 in aqueous solutions. The compounds underwent irreversible oxidation at PG electrode, which was an adsorption-controlled process with two protons and two electrons. The voltammetric data indicated that their oxidation proceeded via an ECE mechanism. Using the square-wave adsorptive stripping voltammetry with accumulation at a fixed potential of −0.1 V for 120 s, both of them yielded a well-defined voltammetric response at +0.31 V (vs. Ag/AgCl) in Britton-Robinson buffer, pH 9.0. Capsaicin and dihydrocapsaicin could be determined with detection limits of 1.12 ng mL−1 (3.7×10−9 M) and 0.28 ng mL−1 (9.1×10−10 M), respectively. The practical applicability of this methodology was tested in commercial Turkish pepper products. The concentration of total capsaicinoids was determined using capsaicin as standard.