Differential Pulse Anodic Stripping Voltammetric Determination of Cadmium(II) withN-p-Chlorophenyl-cinnamohydroxamic Acid Modified Carbon Paste Electrode

Abstract

A sensitive voltammetric method has been developed for the determination of cadmium(II) utilizing a carbon paste electrode modified with N-p-chlorophenylcinnamohydroxamic acid. The analyte was accumulated at the modified electrode surface (via complexation) under open circuit and precisely controlled convective condition. It was then quantified electrochemically by differential pulse anodic stripping voltammetry in a different nondeaerated electrolyte solution following medium exchange. Detailed experiments were conducted to establish the optimal carbon paste composition, pH and concentration of accumulation and stripping solutions, preconcentration time, bulk cadmium(II) concentration, and instrumental parameters. Two good linearities were obtained between the voltammetric current and cadmium concentration employing different preconcentration times. One was acquired in the concentration range 2.00×10−7–3.20×10−6 M Cd(II) (r=0.999) and the other from 4.00×10−8 to 1.60×10−7 M Cd(II) (r=0.999) with 1 min and 2 min preconcentration time, respectively. The detection limit was found to be 9.80×10−9 M (1.1 ppb) Cd(II) with 2 min preconcentration time. For a series of six determinations of Cd(II) at 1×10−6 M and 8×10−8 M levels relative standard deviations of 2.6% and 5.5%, respectively, were achieved. Electrochemical cleaning was used to regenerate the surface rapidly and reproducibly; and this allows the use of a single modified electrode surface in multiple analytical determinations over several weeks. Many common metal ions had little or no effect on the determination of cadmium(II). The method was verified by the determination of trace cadmium(II) in municipal and mineral waters.