Solid phase spectrophotometric determination of copper in water by using immobilized zincon in a Sephadex A25 resin

A new simple, sensitive and selective solid phase spectrophotometric method has been developed for determination of copper in water. A sensitive analytical zone was prepared by immobilization of zincon in a Sephadex A25 resin, in which copper reacts selectively, at pH 7, to form a colored complex on the surface of the resin. Absorbances can be read directly on the solid phase at 621.5 mn. The batch mode was adopted in this work, because the resin is not reusable due the reaction product that is retained irreversible on it. Physico-chemical variables of the method were optimized in order to find the best analytical conditions for the determination. Under the selected conditions copper can be accurately determined oil the range 0.4-300 ng/mL, with a detection limit of 0.12 ng/mL and a repeatability, expressed as the relative standard deviation, lower than 3.8%. The recovery in the analysis of a certified reference material was 100.4%. By changing the pH of the sample, other metals also react (Fe, Cd, Ni, Zn, Hg. Pb), indicating that this system also can be used for screening to determine the possible presence of other trace metals in waters