Simultaneous preconcentration of copper and mercury in water samples by cloud point extraction and their determination by inductively coupled plasma atomic emission spectrometry

A cloud-point extraction process coupled to ICP-OES by using 3-nitro benzaldehyde thiosemicarbazone (3-NBT) as complexing agent was developed for the simultaneous preconcentration and determination of copper and mercury in water samples. The variables affecting the complexation and extraction steps were optimized. Under the optimum conditions (i.e. 1.5 × 10−5 mol L−1 ligand, 0.3% (v/v) Triton X-114, 55 °C equilibrium temperature, incubation time of 30 min) the calibration graphs were linear in the range of 5–120 and 10–100 ng mL−1 with enhancement factor of 82.7 and 51.3 for Cu2+ and Hg2+, respectively. The preconcentration factors were 28.6 in both cases and detection limits were obtained 0.48 for Cu and 1.1 ng mL−1 for Hg. The precisions (R.S.D.%) for five replicate determinations at 50 ng mL−1 of copper and mercury were better than 1.8% and 3.2%, respectively. The accuracy of the proposed method is validated by analyzing a certified reference material of water (RTC-QCI-049) with satisfactory results. Finally, the proposed method was utilized successfully for the determination of copper and mercury in surface water (river), tap water and bottled mineral water samples.

In this work, firstly spectrophotometric studies on 3-nitro benzaldehyde thiosemicarbazone (3-NBT) were carried out and indicated that it forms complexes with Cu(II) and Hg(II) (following figures). Then based on these complex formations, a cloud point extraction method coupled with ICP-OES was developed for the simultaneous preconcentration and determination of copper and mercury.Figure optionsDownload as PowerPoint slideHighlights
► Preliminary experiments indicated that 3-NBT forms complexes with Cu(II) and Hg(II).
► A CPE method was developed for preconcentration and determination of Cu and Hg.
► The developed method provides a good reproducibility with lower LODs.
► The proposed method was applied to the water samples containing Cu and Hg.