Cloud point extraction preconcentration and spectrophotometric determination of copper in food and water samples using amino acid as the complexing agent

A new method for the determination of trace copper was developed by cloud point extraction preconcentration and spectrophotometry. In the proposed approach, amino acid (isoleucine) was used as the chelating agent, and Triton X-100 was selected as the surfactant. Some factors including pH of sample solution, concentration of the chelating agent and surfactant, and equilibration temperature and time, which affected the extraction efficiency of Cu and its subsequent determination, were studied and optimized. Under the optimum conditions, the calibration graph was linear in the range of 10-1000 mu g L(-1), preconcentration of 25 mL sample gave an enhancement factor of 22 and a detection limit of 5 mu g L(-1). The method was successfully applied to the determination of Cu in food and water samples. (C) 2009 Elsevier Inc. All rights reserved.