A novel extraction and preconcentration of ultra-trace levels of uranium ions in natural water samples using functionalized magnetic-nanoparticles prior to their determination by inductively coupled plasma-optical emission spectrometry

New modified magnetic nanoparticles functionalized with salicylaldehyde groups were designed and synthesized to produce a Schiff base-sorbent for extraction/preconcentration of sub-ppb levels of uranium ions in water samples prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). In the separation process, an aqueous solution of U(VI) ions was mixed with 100 mg of functionalized Fe3O4 magnetic nanoparticles with salicylaldehyde groups (Sal-APS-FMNPs) and then an external magnetic field was applied for isolation of Sal-APS-FMNPs containing uranium ions. Experimental conditions for an effective adsorption including pH, sample volume, eluent concentration, and presence of co-existing ions have been studied and established. Under the optimal extraction and preconcentration conditions, a limit of detection (LOD) of 0.24 ng mL(-1) and a relative standard deviation (RSD) of 1.5% (n = 8) were achieved by ICP-OES. The analytical curve was linear in the range 1-5000 ng mL(-1). Under the optimum conditions, the sorption capacity of Sal-APS-FMNPs has been found to be 49 mg of U(VI) ions per gram at pH 7 with a preconcentration factor of 1000 (1 mL of elution for a 1000 mL sample volume). The proposed method is characterized with high enrichment factor, easy preparation and regeneration of sorbent, short time of sample pretreatment, fast and really clean separation, high extraction yields, wide linear curve, and low detection limits. Finally, the proposed method was successfully used for extraction, preconcentration, and determination of U(VI) ions in some real samples.