Simultaneous Determination of Pb(II) and Cd(II) by Electrochemical Method Using ZnO/ErGO-modified Electrode

Some heavy metals such as Pb, Cd, Hg and As are extremely hazardous to the human beings because of their non-biodegradable nature even at very low levels of exposure. Besides the standard methods such as Inductively Coupled Plasma (ICP)-Mass Spectrometry and ICP-Optical Emission Spectrometry, the other methods with fast, accurate and cheap requirements also need to be developed to detect these toxic heavy metals ions in aquatic sources. Recently the application of porous materials in the anodic stripping voltammetry has gained a great attention owing to high selectivity, sensitive and low cost. In the present study, a glassy carbon electrode (GCE) modified by ZnO- electrochemically reduced graphene oxide (ZnO/ErGO) was used for the electrochemical detection of Pd(II) and Cd(II). It is found that the surface area of ZnO/ErGO-GCE is 0.130 cm2 much larger than that of the bare GCE (0.083 cm2).The charge transfer resistance decreases significantly from 3212 Ω for the bare GCE to 924 Ω for ZnO/ErGO-GCE. These results manifest a fast electron transfer ratio of kinetics for the ZnO/ErGO-modified electrode. ZnO/ErGO-GCE exhibits excellent electrochemical performance towards the detection of Pb(II) and Cd(II) compared with ErGO-GCE and bare GCE. The peak current has a linear relationship with the Cd(II) and Pb(II) concentration in the 2.5–200 µM range. The limit of detection for Cd(II) and Pb(II) is 1.69 and 0.45 ppb, respectively. In addition, the electrochemical sensor exhibits excellent selectivity, stability, and repeatability in experimental studies, and it opens up great potential for detecting a trace amount of metals.