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

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 Al3+ ions on palladium nanoparticles (PdNps)coated graphite electrode (Al3+/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 Al3+/PdNp/GE electrodes were tested with dopamine. Al3+ /PdNp/GE exhibited a catalytic activity for curcumin oxidation. The square-wave voltammogram of curcumin in phosphate 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 x 10(-8) M to 6.0 x 10(-7) M with a detection limit of 2.2. 10(-8) M. It was also found that the novel Al3+/PdNp/GE electrode had the best sensitivity when compared to glassy carbon electrode (GCE), hanging mercury drop electrode (HMDE) and glassy carbon electrode electropolymerized with acid chrome blue K (poly-ACBK/GCE), used for the determination of curcumin. 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.