Solid phase extraction and preconcentration of trace mercury(II) from aqueous solution using magnetic nanoparticles doped with 1,5-diphenylcarbazide

A new method for solid-phase extraction and preconcentration of trace mercury(II) from aqueous solution was developed using 1,5-diphenylcarbazide doped magnetic Fe₃O₄ nanoparticles as extractant. The surface treatment did not result in the phase change of Fe₃O₄. Various factors which influenced the recovery of the analyte were investigated using model solutions and batch equilibrium technique. The maximum adsorption occurred at pH > 6, and equilibrium was achieved within 5 min. Without filtration or centrifugation, these mercury loaded nanoparticles could be separated easily from the aqueous solution by simply applying an external magnetic field. At optimal conditions, the maximum adsorption capacity was 220 μmol g⁻¹. The mercury ions can be eluted from the composite magnetic particles using 0.5 mol L⁻¹ HNO₃ as a desorption reagent. The detection limit of the method (3σ) was 0.16 μg L⁻¹ for cold vapor atomic absorption spectrometry, and the relative standard deviation was 2.2%. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The method was applied to the preconcentration and determination of trace inorganic mercury(II) in natural water and plant samples with satisfactory results.