Development of flow injection method for indirect copper determination with amperometric detection in drinking water samples

Abstract

A gas-diffusion flow injection method with amperometric detection for indirect copper determination on a silver electrode is developed. The flow through system is equipped with two injection valves and a gas-diffusion unit. In the first step, a signal of cyanide solution was recorded. In the following step a signal of cyanide in the presence of copper was measured. Interferences (Cd(II), Co(II), Ag(I), Ni(II), Fe(III), Hg(II) and Zn(II)) were investigated and successfully removed. The calibration graph is linear in the range 1-90 μmol dm-3 of copper, correlation coefficient is 0.993, the regression equation is I = (0.0455±0.0015)c + (0.4611±0.0671), I is relative signal decrease in μA and c is concentration in μmol dm-3. Relative standard deviation for six consecutive injections of 30 μmol dm-3 copper(II) was 1.47 % and for 1 μmol dm-3 copper(II) was 3.40 %. The detection limit, calculated as 3 s/m (where s is a standard deviation of nine measurement of a reagent blank and m is the slope of the calibration curve), was 0.32 μmol dm-3, which corresponds to 2.44 ng of copper(II) (loop volume was 0.12 cm3). The method enables 60 analyses per hour and it was successfully applied on determination of copper in drinking water samples. [Acknowledgements. The authors acknowledge the grant from the Ministry of Education and Science of the Republic of Serbia, Project number 172051]

Keywords

• copper determination
• gas-diffusion
• drinking water samples
• copper cyano complex