Selective Electrochemical Detection of Toxic Heavy Metals at Ultra Trace Levels using Natural Clay-Modified- Electrode

Abstract

Clay-modified platinum electrodes (CMEs) were prepared using naturally occurring Jordanian
silicates, kaolinite and montmorillonite. Modified electrodes, which prepared using spin-coating
procedures, were used for the selective and sensitive determination of Cu2+ and Hg2+ at ultra trace
levels. Prior to clay deposition onto Pt surface, the extent of uptake of different organic and inorganic
compounds were tested for kaolinite; the adsorption parameters for Cu2+ and Hg2+ were described
using the popular Langmuir isotherm. The results of these analyses, using linear regression
procedures, were also disclosed in the study. The shapes of Cu2+ and Hg2+ adsorption isotherms were
of “L2” and “L1” types indicating a favorable uptake of cations and a high electrochemical function of
the modified electrode. Cyclic voltammetry and differential pulse voltammetry, combined with anodic
stripping voltammetry, were employed for the qualitative and quantitative analysis of the tested
cations. The modified electrodes showed a remarkable selectivity and sensitivity for Cu2+ and Hg2+
ions in natural water. Using montmorillonite-modified platinum electrodes, very low detection limits
for cations were reached, 2.0×10-7 and 3.0×10-9 mol L-1 for Hg2+ and Cu2+, respectively. The earlier
detections limits were much lower than those reported in literature.