Electrochemical determination of capsaicin in pharmaceutical and pepper sauce samples by TiO₂ nanoparticles modified epoxy-graphite electrode

Capsaicin, a lipophilic alkaloid, is responsible for the main reason of hotness in chili peppers. The presented research focuses on the development of an electrochemical sensor based on epoxy-graphite composite with the modification of Titanium dioxide (TiO₂) nanoparticles for the quantification of capsaicin. The measurements were carried out in glycine buffer at pH 2.5 using the cyclic voltammetry technique.

It is observed that carbon based electrodes lead to fouling effect in the cyclic voltammetric measurements of capsaicin. This fouling results in unstable baselines with decreasing oxidation peak current. In order to overcome this problem, extensive search of electrode modifiers, mainly of nano-technological origin, has been made. From this we observed good behavior in TiO₂ modified electrode. TiO₂ nanoparticles were incorporated into the sensor by adding the nanoparticles into the mixture of epoxy graphite composite during the fabrication of the sensor.

When performing the calibration of the developed sensors, two linear concentration ranges were obtained from 6 to 75 μM (R = 0.99) and 12 to 138 µM; the detection limit was estimated as 5.34 µM and 11.3 μM capsaicin for 1st and 2nd oxidation peak, respectively. The main advantage of the developed sensor is its repeatability with a relative standard deviation (RSD) value of 2.5% after 10 repeated measurements. To the best of our knowledge, our proposed sensor is the first sensor to be developed which does not show fouling effect with capsaicin, this is accomplished through the use of chemical cleaning of the electrode surface which simply involved rinsing the surface in specific media (50% ethanol). This voltammetric sensing platform has successfully been applied to quantify capsaicin in various real samples such as sauce and pharmaceuticals.