Preconcentration of copper by cloud point extraction with 1-(2-pyridylazo)-2-naphthol and determination by neutron activation

A method for the preconcentration of Cu(II) by cloud point extraction (CPE) followed by its determination using neutron activation analysis (NAA) was developed. The method involves the use of a nonionic surfactant, namely PONPE-7.5, and a chelating agent 1-(2-pyridylazo)-2-naphthol (PAN). The phase diagram of the surfactant was constructed and the effects of different additives on the cloud point were investigated. Factors, such as the solution pH, ionic strength, temperature, and concentrations of chelating agent and surfactant, which can influence the extraction efficiency of the metal, were optimized. The copper(II) chelate was extracted into a surfactant-rich phase of small volume with a recovery of nearly 100% and a preconcentration factor of 60. The small volume of the surfactant-rich phase obtained complies with the green chemistry concept, allowing the design of extraction procedures having lower toxicity than those using organic solvents. The method was applied to tap water samples.