[Show abstract][Hide abstract] ABSTRACT: A new approach of magnetic solid phase extraction (MSPE) coupled with graphite furnace atomic absorption spectrometry (GFAAS) has been developed for the speciation of Cr(III) and Cr(VI) using zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles (Zincon–Si–MNPs) as the MSPE absorbent. Cr(III) was quantitatively reserved on the absorbent at pH 9.1 while total Cr was reserved at pH 6.5. The absorbed Cr species were eluted by using 2 mol/L HCl and detected by GFAAS. The concentration of Cr(VI) could be calculated by subtracting Cr(III) from total Cr. All the parameters affecting the separation and extraction efficiency of Cr species such as pH, extraction time, concentration and volume of eluent, sample volume and influence of co-existing ions were systematically examined and the optimized conditions were established accordingly. The detection limit (LOD) of the method was 0.016 and 0.011 ng mL−1 for Cr(III) and Cr(VI), respectively, with the enrichment factor of 100 and 150. The precisions of this method (Relative standard deviation, RSD, n=7) for Cr(III) and Cr(VI) at 0.1 ng mL−1 were 6.0% and 6.2%, respectively. In order to validate the proposed method, a certified reference material of environmental water was analyzed, and the result of Cr speciation was in good agreement with the certified value. This MSPE–GFAAS method has been successfully applied for the speciation of Cr(III) and Cr(VI) in lake and tap waters with the recoveries of 88–109% for the spiked samples. Moreover, the MSPE separation mechanism of Cr(III) and Cr(VI) based on their adsorption–desorption on Zincon–Si–MNPs has been explained through various spectroscopic characterization.
[Show abstract][Hide abstract] ABSTRACT: A new protocol using zincon-immobilized silica-coated magnetic Fe(3)O(4) nanoparticles (Zincon-Si-MNPs) as solid-phase extraction (SPE) medium has been developed for the separation and preconcentration of trace lead in water. Various parameters such as pH, extraction time, concentration and volume of eluent, sample volume, and influence of co-existing ions have been investigated in order to establish the optimum conditions for the determination of lead in combination with graphite furnace atomic absorption spectrometry (GFAAS). The detection limit (LOD) of the proposed method for lead based on an enrichment factor of 200 was 10 ng L(-1). The relative standard deviations (RSDs, n=5) were 8.3%, 7.8% and 9.2%, respectively, at 5, 0.5 and 0.05 ng mL(-1) levels. This method has been successfully applied to the analysis of trace lead in natural and drinking water samples and the recoveries for the spiked samples were in the range of 84-104%.