Preparation of Modified Magnetic Nanocomposites Dithiooxamide/Fe3O4 for Preconcentration and Determination of Trace Amounts of Cobalt Ions in Food and Natural Water Samples

The first study on the high efficiency of nanometer-sized magnetic nanoparticles (Fe3O4) coated with sodium dodecyl sulfate (SDS) and dithiooxamide as a new sorbent solid phase extraction has been reported. Modified magnetic nanicomposites was used to preconcentrate and separate Co (II) ions in food and environmental water samples. Magnetic nanoparticles were prepared by chemical precipitation of Fe (II) and Fe (III) salts from aqueous solution by ammonia solution. These magnetic nanoparticles and nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA) and elemental analysis CHNS. A micro sample introduction system was employed for the nebulization micro-volume of diluted solution into flame atomic absorption spectrometry (FAAS). The extraction conditions were optimized by selecting the appropriate extraction parameters including the amount of nanosorbent, pH value, volume of dithiooxamide and condition of eluting solution. The detection limit of this method for Co (II) ions was 1.21 ng ml-1 and the R.S.D. was 0.9% (n=6). The advantages of this new method include rapidity, easy preparation of nanosorbents and a high preconcentration factor. The proposed method has been applied to the determination of Co (II) ions at trace levels in real samples such as, kiwi, orange, cucumber, apple, green pepper, honey, potato, tap water, river water and sea water with satisfactory results.