Electrochemical Reduction of Isatin-monohydrazone on Mercury Electrode

Electrochemical behaviour of isatin monohydrazone (IM) on a hanging mercury drop electrode in the Britton-Robinson (B-R) buffer solution of pH = 2.00–9.00 has been investigated using square-wave voltammetry (SWV) and cyclic voltammetry (CV) techniques. In the pH range of 2.00–5.00, the voltammogram of IM exhibited a single cathodic irreversible peak. When the pH value exceeds 5.00, a new cathodic irreversible peak was also seen. According to the voltammetric data, a plausible electrode reaction mechanism of IM was proposed. The first reduction peak of IM is resulted from the reduction of =N–NH– group with consumption of 2e–/2H+. Also, its second cathodic peak is formed by the participation of 2e–/2H+ for the reduction of –N=N– group on its tautomeric form

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 exhib¬ited 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 3.0×10-8 M to 6.0×10-7 M with a detection limit of 2.2×10-8 M. It was also found that the novel 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