Determination of Sub – Parts per Billion Levels of Copper in Complex Matrices by Adsorptive String Voltammery on a Mercury Electrode

The voltammetric characteristics of Cu(II)-SSA complex at the mercury electrode were investigated. An analytical method that based on the adsorptive accumulation of Cu(II)-SSA complex followed by the reduction of the complexed copper was developed for copper determination in complex matrices in presence of the large amount of foreign ions. Adsorptive voltammetry determinations showed that the Cu(II)-SSA complex behaves irreversibly exchanging two electrons on the hanging mercury drop electrode (HMDE). Factor affecting on the complextion, accumulation, and stripping steps were studied and a procedure was developed. The instrumental parameters in the measurement step were also tested. The optimum conditions of pH, SSA concentration, accumulation potential and accumulation time were studied. Under optimal conditions (pH= 12.9 glycin Buffer, 7×10 M SSA and accumulation potential -100 mV vs. Ag/AgCl), a linear calibration graph in the range 1.25 μg L to 42.5 μg L and a detection limit of 0.8 μg L were obtained. The average relative standard deviation (RSD) for seven determinations was calculated as 7%, 5.5% and 3% for the concentrations between 3, 15 and 23 μg L. The effect of foreign ions and surfactants on the peak height of Cu(II)-SSA complex was evaluated. The method was applied for the determination of the copper in different real samples such as crude oil, crude oil tank button sludge, wastewater and tap water samples. The accuracy of the results was checked by ICP.