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.
