A new electrochemical sensor based on oxidized capsaicin/multi-walled carbon nanotubes/glassy carbon electrode for the quantification of dopamine, epinephrine, and xanthurenic, ascorbic and uric acids

Capsaicin (CAP) was used as a redox mediator and added to multi-walled carbon nanotubes (MWCNT) modified glassy carbon electrode (GCE), to be used in the quantitation of xanthurenic (XA), ascorbic (AA) and uric (UA) acids, along with the neurotransmitters dopamine (DA) and epinephrine (EP), one at a time, using cyclic voltammetry and chronoamperometry, in buffered aqueous solutions, pH 7.0. The presence, after oxidation of CAP on MWCNT/GCE, of two reversible redox systems, which can be understood through the formation of a reversible surface-confined quinone systems, is important for the redox catalysis. The obtained analytical curves for XA, AA, DA, EP and UA showed linear ranges, between 10 and 95, 5–75, 5–115, 50–1150 and 5–70 μmol L−1, respectively. The detection limits were 8.76, 1.95, 1.80, 7.20 and 1.56 μmol L−1 for XA, AA, DA, EP and UA, respectively. This oxidized CAP-based platform is reported for the first time and is able to detect the analytes at a micromolar level. •A versatile developed sensor is based on the oxidation of capsaicin on MWCNT, without any surface fouling.•The sensor is able to detect dopamine, epinephrine, xanthurenic, ascorbic and uric acids at a micromolar level.•Xanthurenic acid was quantified, for the first time, using amperometry.•The sensor is easily prepared and has high sensitivity and a short analysis time.