A facile, sensitive, and rapid spectrophotometric method for copper(II) ion detection in aqueous media using polyethyleneimine

In this work, we developed a facile, sensitive, and rapid spectrophotometric method for copper(II) ion detection in aqueous media using polyethyleneimine. Polyethyleneimine is a cationic polymer that has no absorption in the wavelength range of 250–800   nm. When trace amounts of copper(II) ion was added to the colorless polyethyleneimine solution, copper(II) ion could react with the amino groups of the polyethyleneimine to form a dark blue cuprammonium complex whose absorption spectrum exhibited two absorption peaks at 275 and 630   nm, respectively. The effects of parameters such as polyethyleneimine concentration, pH, temperature, reaction time, and the most suitable medium for the reaction were investigated. A linear relationship ( R 2   =   0.9997) between absorbance and the concentration of copper(II) ion was found at the maximum absorption peak of 275   nm in the concentration range of 2–400   μM. The detection limit for copper(II) ion was 566   nM. The response of polyethyleneimine toward different metal ions was investigated, and polyethyleneimine displayed a high selectivity for the copper(II) ion among the metal ions examined. This biocompatible and sensitive sensor may find applications in copper(II) ion detection in environmental and biological processes.