Selective extraction and preconcentration of ultra-trace level of mercury ions in water and fish samples using Fe3O4-magnetite-nanoparticles functionalized by triazene compound prior to its determination by inductively coupled plasma-optical emission spectrometry

Abstract

In this paper, new modified magnetite nanoparticles functionalized with triazene groups were designed and synthesized for extraction/preconcentration of sub-ppb level of mercury ions in water and fish samples prior to its determination with inductively coupled plasma optical emission spectrometry (ICP-OES). In the separation process, aqueous solution of Hg²⁺ ions was mixed with 150 mg of Fe₃O₄ magnetite nanoparticles modified with 1-(p-acetyl phenyl)-3-(o-ethoxy phenyl) triazene (AET) and then external magnetic field was applied for isolation of magnetite nanoparticles containing mercury ions. Experimental conditions for effective adsorption including pH, sample volume, eluent concentration and existing co-existing ions have been studied and established. Under the optimal extraction and preconcentration conditions, the limit of detection (LOD) of 0.04 ng mL⁻¹ and the relative standard deviation (R.S.D) of 2.09% for five replicate extractions and measurements of 10 μg of Hg²⁺ ion in 1000 mL water solution were achieved by ICP-OES. The sorption capacity of functionalized Fe₃O₄ magnetite nanoparticles under optimum conditions has been found to be 10.26 mg of mercury ion per gram at pH 7 with the preconcentration factor of 500 (2 mL of elution for a 1000 mL sample volume). Standard solutions containing Hg²⁺ in the concentration range of 0.2–200 ng mL⁻¹ were examined by the proposed procedure and it was observed that calibration curve was linear in this range (R² = 0.999). The special advantages of the proposed method are high enrichment factor, fast separation and low detection limits compared with other methods.