A solid phase extraction method based on magnetic iron oxide nanoparticles (MIONPs) modified by sodium dodecyl sulfate (SDS) was developed for the preconcentration and determination of trace amounts of uranium(VI) ions. Oxine (8-quinolinol) was used as chelating agent and the factors influencing the complex formation and extraction of uranium were optimized. Ethanol containing 1% (v v-1) NH3 was used as desorbing agent and the absorbance of eluent was measured at 370 nm by UV-Vis spectrophotometry. The analytical curve was linear in the range of 3.0-300 µg L-1 with a limit of detection of 0.8 µg L-1. The method was successfully applied for the determination of uranium in tap water, mineral water, river water and sea water samples with spike recoveries ranging 93-108%. This method was also applied for the determination of uranium(VI) in rock and biological samples and the obtained results were in accordance with inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GF AAS) methods
