Determination of nanomolar concentrations of cadmium by anodic-stripping voltammetry at a carbon paste electrode modified with zirconium phosphated amorphous silica

A carbon paste electrode modified with zirconium phosphated-silica was used for the determination of cadmium. The measurements were carried out in three steps including an open circuit accumulation, subsequent electrolysis of accumulated cadmium at the carbon paste electrode, and differential pulse voltammetric determination. The effects of several experimental variables such as carbon paste composition, pH of solution at the accumulation step, pH and concentration of supporting electrolyte, electrolysis potential, accumulation time and electrolysis time were studied. The resulting electrode demonstrated linear response over a wide range of Cd(II) concentration (3–1400 ng mL−1) with an accumulation time of 120 s. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The prepared electrode was used for determination of cadmium in some artificial synthetic samples, and very good recovery results were obtained over a wide concentration range of cadmium.