Study of electrochemical determination of capsaicin and dihydrocapsaicin at carbon paste electrodes modified by β-cyclodextrin

In this work, we showed electrochemical evidences that alpha-, beta-, and gamma-cyclodextrins (CDs) form inclusion complex in a solution with capsaicin (CP). The electrochemical behavior of CP was evaluated on carbon paste electrodes modified with CDs. The modified electrodes exhibited a markedly enhanced Faradic current compared with the naked electrode. Our results show that CP accumulates at the surface of the modified electrodes. The electrode modified with beta-CD presented best behavior. Consequently, the analytical performance was examined with this electrode. The sensitivity further improves of determination of CP on beta-CD electrode at low pH and at low amounts of beta-CD. The range of linearity for CP quantification was between 1.6 and 61 mu mol L-1. LOD and LOQ were the best for CP at 0.062 and 0.200 mu mol L-1, respectively. Square wave voltammetry was then used to study CP and dihydrocapsaicin (DHCP) at electrodes modified with beta-CD. Voltammograms of both capsaicinoids showed peaks at the same potential. However, the current is notably larger for DHCP and the voltammograms were distinct for each capasicinoid. The linearity range for CP was between 1.3 and 9.3 mu mol L-1 , while the LOD was 0.2102 mu mol L-1 , and the LOQ was 0.7 mu mol L-1 . For DHPC, the linearity range was 0.69-6.7 mu mol L-1 , LOD was 0.09041 mu mol L-1 , and LOQ was 0.301 mu mol L-1 . No analyte preconcentration was required. Tabasco sauce was then analyzed using this method and the result was equivalent to those obtained with high performance liquid chromatography.