Enass M. Ghoneim

Simultaneous determination of cadmium (II), lead (II), copper (II) and mercury (II) by square-wave anodic stripping voltammetry at a montmorillonite-calcium modified carbon paste electrode

A simple and efficient montmorillonite-calcium modified carbon paste electrode (MMT-Ca modified CPE) was constructed for simultaneous trace determination of Cd(II), Pb(II), Cu(II) and Hg(II). The MMT-Ca modified CPE significantly enhances the voltammetric stripping peak current magnitudes of the investigated metal ions compared to the bare CPE due to the large cation-exchange capacity and the strong adsorptive property of montmorillonite-Ca clay. A fully validated simple, sensitive, selective and precise square-wave anodic stripping voltammetric method was developed for the simultaneous trace determination of Cd(II), Pb(II), Cu(II) and Hg(II) in various water samples using a fabricated 10% (w/w) MMT-Ca modified CPE. The achieved limits of detection of Cd(II) 0.54 µg L−1, Pb(II) 0.30 µg L−1, Cu(II) 0.75 µg L−1 and Hg(II) 1.05 µg L−1 indicating the high sensitivity of the described SW-AS voltammetry method for the assay of these metal ions in aqueous solutions. The method was successfully applied for analysis of tap water, bottled natural water and seawater samples.

Adsorptive stripping voltammetric determination of the anti-inflammatory drug tolmetin in bulk form, pharmaceutical formulation and human serum

The electro-reduction of tolmetin at the hanging mercury drop electrode was studied in different supporting electrolytes using cyclic voltammetry and square-wave stripping voltammetry techniques. Voltammograms of tolmetin exhibited a single well-defined 2-electron irreversible cathodic peak in media of pH < 4, which may be attributed to reduction of the >C=O double bond of the analyte molecule. Adsorption of tolmetin onto the surface of the hanging mercury electrode was identified and each adsorbed tolmetin molecule was found to occupy an area of 0.23 nm2. A square-wave adsorptive cathodic stripping voltammetric procedure was described for the direct determination of tolmetin in bulk form and pharmaceutical formulation (Rumatol® capsules) with a limit of quantitation of 2 × 10−9 M and a mean percentage recovery of 98.35 ± 1.21% to 99.57 ± 1.23. Moreover, the described procedure was successfully applied for the direct assay of tolmetin in spiked human serum without pretreatment or extraction prior to the analysis while a quantitation limit of 5 × 10−9 M tolmetin was achieved.