Fe3O4@ZrO2 nanoparticles magnetic solid phase extraction coupled with flame atomic absorption spectrometry for chromium(III) speciation in environmental and biological samples

A new method for Cr(III) speciation in seven kinds of environmental and biological samples by Fe3O4@ZrO2 nanoparticles magnetic solid phase extraction (MSPE) and flame atomic absorption spectrometry (FAAS) has been developed. Fe3O4@ZrO2 nanoparticles were simply prepared by sol–gel method, and the adsorptive behaviors of Cr(III) and Cr(VI) on Fe3O4@ZrO2 nanoparticles were assessed. At pH 8.0–9.0, Fe3O4@ZrO2 nanoparticles were selective towards Cr(III) but hardly Cr(VI). The retained Cr(III) was subsequently eluted with 3.0 mL of 0.5 mol L−1 HNO3 followed by magnetic decantation. Total chromium was determined after reduction of Cr(VI) to Cr(III) by ascorbic acid. Various parameters affecting Fe3O4@ZrO2 nanoparticles MSPE were optimized systematically. Under the optimum conditions, the adsorption capacity of Fe3O4@ZrO2 nanoparticles for Cr(III) is 24.5 mg g−1. With an enrichment factor (EF) of 25, detection limit of Cr(III) was 0.69 ng mL−1, and the proposed method has been successfully applied for Cr(III) speciation in seven kinds of environmental and biological samples with satisfactory results.