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

A method for the preconcentration of copper(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) for the quantitative extraction. A phase diagram of the surfactant was constructed and the effects of different additives on the cloud point were investigated. Studies of the distribution equilibria of PAN and its copper chelate between the aqueous and surfactant rich phases were done. Factors that can influence the extraction efficiency of the metal were evaluated. The optimum values of the solution pH, ionic strength, temperature, and concentrations of chelating agent and surfactant were obtained. The copper(II) chelate was extracted into a surfactant rich phase of small volume. The extraction recovery is nearly 100%. A preconcentration factor of 60 was obtained, which leads to low detection limits. Elemental comparator standards were irradiated and a control chart was constructed for internal quality assessment of the analytical procedure. The results showed that the method was operating under a good statistical control. External quality assurance was evaluated by analyzing certified reference materials. The sensitivity and the detection limit for copper were calculated using the standard experimental conditions. The method has been applied to tap water samples