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

► Fe3O4@ZrO2 nanoparticles were simply prepared by sol-gel method. ► Speciation of Cr(VI) and Cr(III) in different matrix have been easily and cheaply realized by using Fe3O4@ZrO2 nanoparticles magnetic solid phase extraction and FAAS. ► A magnetic separation mode with speediness and convenience was carried out under an extra magnetic field in SPE techniques. ► The analytical performance established by this work is superior to other methods.