Cloud-point extraction, preconcentration and spectrophotometric determination of trace quantities of copper in food, water and biological samples

• New sensitive cloud point extraction method for determination of Cu(II) in various samples.
• Beer’s law is obeyed in the concentration range 4.0–115 ng mL−1.
• The detection limit of 1.20 ng mL−1 with preconcentration factor of 125.

A new, simple and sensitive cloud point extraction procedure was presented for the preconcentration and determination of copper(II) ion in food, water and biological samples. The analyte was complexed with a new synthesized reagent, 2-amino-4-(m-tolylazo)pyridine-3-ol (ATAP) as a new complexing agent and Triton X-114 as the surfactant. After centrifugation, dilution of the surfactant-rich phase with 0.4 mL of ethanol acidified with 1.0 M HNO3 was performed after phase separation, and the copper contents were measured by spectrophotometry at λmax 608 nm. The influence of analytical parameters including concentration of complexing agent, Triton X-114, pH, equilibration temperature and time, centrifuge rate and time were optimized. The analytical characteristics of the method (e.g. linear range, molar absorptivity, Sandell sensitivity, optimum Ringbom concentration ranges limits of detection and quantification, preconcentration factor, and improvement factors) were obtained. Linearity was obeyed in the range of 4.0–115 ng mL−1 of Cu(II) ion. The detection and quantification limits of the method were 1.20 and 3.94 ng mL−1 of Cu(II) ion, respectively. The interference effect of some anions and cations was also tested. The method was applied for determination of copper in food, water and biological samples.

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