Dispersive Liquid–Liquid Microextraction of Copper Ions as Neocuproine Complex in Environmental Aqueous Samples

In the present study, a simple and efficient extraction method based on dispersive liquid-liquid microextraction prior to UV-Vis spectrophotometry was developed for the preconcentration and determination of copper ions in environmental samples. Briefly, cupric ions (Cu II) were reduced to cuprous (Cu I) with addition of hydroxyl amine hydrochloride and formed hydrophobic chelates with neocuproine. Then, a proper mixture of acetonitrile (as dispersive solvent) and choloroform (as extraction solvent) was rapidly injected into the solution and a cloudy solution was formed. After centrifuging, choloroform was sedimented at the bottom of a conical tube and diluted with 100 μL of methanol for further UVVis spectrophotometry measurement. An orthogonal array design (OAD) was employed to study the effects of different parameters on the extraction efficiency. Under the optimum experimental conditions, a preconcentration factor up to 63.6 was achieved for extraction from 5.0 mL of sample solution. The limit of detection (LOD) based on S/N = 3 was 0.33 μg L–1 and the calibration curve was linear in the range of 1–200 μg L–1 with reasonable linearity (r2 > 0.997). Finally, the accuracy of the proposed method was successfully evaluated by determination of trace amounts of copper ions in different water samples and satisfactory results were obtained.