Cyclic voltammetric determination of calcium in water in the presence of natural organic matter (humic acid) and Cu (II) at gold electrode's surface

Abstract

Calcium and copper are essential for many physiological functions, including enzyme activation and reactive oxygen blockages. However, elevated levels of these metals (separately, synergetically or antagonistically) may result in disorders such as cancer, bone loss, and cardiovascular failure. Foods and water remain the major dietary sources of these metals. Thus, monitoring their levels in foods, water and drinks has become a matter of necessity. This paper reports for the first time the determination of calcium in water in the presence of humic acid (HA) and copper (II) ion (Cu2+) using cyclic voltammetry. The voltammogram displayed a large oxidative potential difference between the two metals (copper existed as a doublet low field while calcium showed a high field potential), enabling a reliable quantification. The detection limits (LODs) of calcium in the copper-free and copper-containing HA solutions are 6.91 × 10−4 and 2.89 × 10−3 mol/L, respectively, suggesting a potential for monitoring calcium in drinking water, soft drinks, wine and dairy products. Also, an LOD of 2.56 × 10−3 mol/L was obtained for Cu2+, implying the potential for simultaneous determination of both metals in aqueous fluids with high degree of reliability.