Application of Chemometrics Methods for the Simultaneous Determination of Zinc and Copper after Preconcentration and Separation by Liquid– Liquid Microextraction Based on Solidification of Floating Organic Drop Coupled to Flow Injection Spectrophotometry

A new dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLMESFO)/ flow injection-spectrophotometry (FI) method for simultaneous separation and preconcentration of trace amounts of copper and zinc was developed. 1-(2-pyridylazo)-2-naphthol (PAN), 1-undecanol and acetonitrile were used as chelating agent, extraction solvent and disperser solvent, respectively. The factors influencing the complex formation and extraction by DLLME-SFO such as volumes of extraction and disperser solvents, pH, concentration of salt and concentration of the chelating agent were optimized. The optimal conditions were: volumes of extraction and dispersive solvents, 80 and 200 μL, respectively; concentration of the complexing agent, 4 x10x3mol L-1 and pH,7.5. Partial least squares (PLS) were applied for multivariate calibration and noise reduction by eliminating less important latent variables. The data obtained from the experiments were processed by chemometrics method of PLS. The linear dynamic range for Cu2+ and Zn2+ was 3–30 μg L-1 and 1–23 μg L-1, respectively. Detection limits were 1.5 μg L-1 and 0.25 μg L-1 for Cu and Zn, respectively. The relative standard deviations (R.S.D., n = 10) were found to be less than 4.5% for both of metal ions. The method was successfully applied to the simultaneous determination of Cu and Zn in the real water samples and satisfactory relative recoveries (92–107.5%) were achieved. The enhancement factors for Cu2+ and Zn2+ were found to be 85 and 86.3, respectively.