Optimization and application of homogeneous liquid-liquid extraction in preconcentration of copper (II) in a ternary solvent system

In this study a homogeneous liquid-liquid extraction based on the Ph-dependent phase-separation process was investigated using a ternary solvent system (water-acetic acid-chloroform) for the preconcentration of Cu²⁺ ions. 8-Hydroxy quinoline was used as the chelating agent prior to its extraction. Flame atomic absorption spectrophotometry using acetylene-air flame was used for the quantitation of analyte after preconcentration. The effect of various experimental parameters in extraction step was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was done at five levels of operating parameters. Nearly the same optimized results were obtained using both methods: sample size, 5 mL; volume of NaOH 10 M, 2 mL; chloroform volume, 300 μL; 8-hydroxy quinoline concentration more than 0.01 M and salt amount did not affect the extraction significantly. Under the optimum conditions the calibration graph was linear over the range 10-2000 μg L^-1. The relative standard deviation was 7.6% for six repeated determinations (C = 500 μg L^-1). Furthermore, the limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method were obtained as 1.74 and 6 μg L^-1, respectively.