Central Composite Design Applied to Optimization of Dispersive Liquid-Liquid Microextraction of Cu(II) and Zn(II) in Water Followed by High Performance Liquid Chromatography Determination

In this study a new method for the simultaneous determination of Cu(II) and Zn(II) ions in water samples was developed by dispersive liquid-liquid microextraction preconcentration followed by HPLC with UV detection. An experimental design, central composite design, coupled with response-surface methodology was used for the optimization of the involved experimental parameters. In the proposed approach, 8-hydroxy quinoline (HOX) was used as a chelating agent and chloroform and methanol were chosen as the best extraction and dispersive solvents, respectively. Some factors influencing the extraction efficiency of copper and zinc ions and their subsequent determinations, including extraction and dispersive solvents kinds and volumes, pH of sample solution, concentration of the chelating agent, salting out effect and reaction time were studied and optimized. Under the optimum conditions, the calibration graphs were linear in the range of 10-4000 mu g/L with the detection limits of 3 mu g/L and the quantification limits of 10 mu g/L for both analytes. The RSD for six replicate measurements of 500 mu g/L of Cu2+ and Zn2+ were 2.9% and 5.7%, respectively.