SYNTHESIS AND CHARACTERIZATION OF POLYANILINE/NiO NANOCOMPOSITE FOR ELECTROCHEMICAL DETERMINATION OF DOPAMINE

Abstract

Al2O3 nanoporous was synthesized by using sol-gel method from aluminum nitrate nano hydrate precursor solution. On the other hand, Fe3O4 nanoparticles and Al2O3/Fe3O4 nanocomposite were synthesized by co-precipitate method using ferric chloride hexa hydrate, ferrous chloride tetrahydrate and aluminum nitrate nanohydrate. The prepared metal oxides and their composite structure and composition were characterized by XRD, UV-Vis, SEM-EDX and FTIR. In addition to this, the electrochemical behaviors of bare carbon paste electrode (CPE) and modified by the produced nanocomposite were characterized by cyclic voltammetry in the presence of 2 mM K3Fe (CN)6/0.1 M KCl. The results show that Al2O3/Fe3O4 nanocomposite was the highest electroactive substrate compared to Al2O3 and Fe3O4. This is most probably due to the synergistc effect of the high absorption capacity of Fe3O4 and electrocatalytic properties of Al2O3. Further more,the Fe3O4/Al2O3 nanocomposite modified CPE was optimized for the determination of Pb and Cd in standard solutions and in milk sample using anodic stripping voltammetry. The optimal experimental conditions were pH = 4.5 (Sodium acetate buffer as supporting electrolyte), deposition time 120 seconds, concentration 400 ppm for both metal ions and deposition potential of -0.6 V and -0.9 V for Pb and Cd metal ions respectively. Fe3O4/Al2O3/CPE sensor exhibited a linear range 10 µg/L to 100 µg/L for both metal ions, detection limit of 0.46 µg/L for cadmium and 0.36 µg/L for lead with high sensitivity. Besides, the nanocomposite modified CPE was applied to determine the level of Pb and Cd in milk sample collected from Haramaya University Dairy farm. The concentration of Pb and Cd was found to be below the detection limit so by spiking there concentration was estimated to be the higher recovery values around 98.16% and 99.25% for Pb and Cd respectively. The results reveals that Fe3O4/Al2O3/CPE can be a good candidate for the detection of toxic heavy metals in various environmental and food samples.