A Newly Developed Electrocatalytic Oxidation and Voltammetric Determination of Curcumin at the Surface of PdNp-graphite Electrode by an Aqueous Solution Process with Al3+

Abstract

In the first stage, the palladium nanoparticles (PdNps)-coated graphite electrode (PdNp/GE) has been prepared. Scanning electron microscopy (SEM) technique showed that the palladium nanoparticles were uniformly distributed with an average particle diameter of 60-75 nm. And then, a novel-modified electrode has been developed by the physical deposition of Al 3+ ions on palladium nanoparticles (PdNps)- coated graphite electrode (Al 3+ /PdNp/GE). This modified electrode was characterized by square-wave voltammetry (SWV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The sensitivities of PdNp/GE and Al 3+ /PdNp/GE electrodes were tested with dopamine. Al 3+ /PdNp/GE exhib- ited a catalytic activity for curcumin oxidation. The square-wave voltammogram of curcumin in phos- phate buffer (pH = 2) gave an anodic peak at 0.56 V. The anodic peak current of curcumin was found to be linearly related to its concentration in the range of 3.0 × 10 -8 M to 6.0 × 10 -7 M with a detection limit of 2.2 10 -8 M. It was also found that the novel Al 3+ /PdNp/GE electrode had the best sensitivity when com- pared to glassy carbon electrode (GCE), hanging mercury drop electrode (HMDE) and glassy carbon elec- trode electropolymerized with acid chrome blue K (poly-ACBK/GCE), used for the determination of cur- cumin. The curcumin was detected in marketed spices sample of turmeric powder. Pure turmeric powder had the highest curcumin concentration, averaging 4.317 ± 0.175 % by weight.