Interference-free detection of trace copper in the presence of EDTA and other metals using two complementary chelating polymers

The presence of copper in water and wastewater is receiving close scrutiny because it is more toxic to fish and aquatic life than to humans. The use of copper, especially in the microelectronics industry, has grown significantly during the last two decades and is often present in the treated wastewater along with EDTA (ethylene diamine tetra acetate) and other strong ligands. Rapid detection of copper in such bodies of water is a scientifically challenging problem. Here, we present a novel sorption technique that senses copper by forming a distinctive turquoise-blue color at concentrations as low as 25 μg/L. Most importantly, the detection technique is free of interference from EDTA or other metals. Two chelating polymers with complementary sorption properties form the heart of the process. While one chelating polymer with only nitrogen donor atoms selectively sorb copper at a very acidic pH (∼1.5) in the presence of EDTA and competing metals (e.g. Zn, Ni, Pb), the other with imminodiacetate functionality shows distinctive blue color upon copper sorption. The sensing technique performed very well with tap water, river water and treated wastewater spiked with a trace amount of copper from the background of EDTA and other competing metals.