SYNTHESIS AND CHARACTERIZATION OF MgO/ZnO NANOCOMPOSITE MODIFIED CARBON PASTE ELECTRODE FOR THE DETERMINATION OF CADMIUM AND LEAD IN MILK

Abstract

Magnesium oxide/zinc oxide nanocomposite was synthesized using hydrothermal methods from Mg(NO3)2.6H2O and Zn(NO3)2.6H2O precursor salts. The morphology, structure and composition of the nanocomposite were characterized by employing FTIR, SEM, XRD and Uv-vis spectroscopy. The SEM image showed a uniform distribution of nanosheet of ZnO and irregular shape of MgO nanoparticles. Also the XRD and the EDX result showed that the synthesis nanocomposite was purely MgO/ZnO. An electrochemical property of MgO/ZnO composite modified carbon paste electrode (CPE) was studied using cyclic voltammetry in the presence of 2 M potassium ferrocynide +0.1 M KCl. The MgO/ZnO modified CPE highly reversible than the bare CPE and single system modified CPE. The active surface area of carbon paste electrode was significantly improved with 1.7 fold by the nanocomposite. The modified CPE optimized condition was found to be pH 4.5, deposition potential was -0.6 and - 0.9V for Pb and Cd ions, respectively, deposition time 90s and 400 ppm concentration for both metals. Under the optimized conditions, MgO/ZnO modified CPE was utilized for the determination of Lead and Cadmium in milk samples using anodic stripping voltammetry. The sensor exhibited 100 – 800 ppm linear range; the sensitivity of Cd and Pb was 0.817 and 0.797 respectively and detection limit for both metal ions was 0.45µg/L for Cd and 0.142µg/L for Pb. Besides, compared with CPE, MgO/ZnO modified CPE exhibited well-defined and separate peaks for Cd and Pb. The modified CPE electrode was also applied for the determination of the two metals in milk; the obtained result was less than the maximum allowed limits. The modified CPE electrode displayed good sensitivity and selectivity for Pb and Cd detection. Therefore, MgO/ZnO nanocomposite modified CPE could be a potential candidate for the determination of trace heavy metals and holding great promise for routine analysis.