Preconcentration of some metal ions with magnetic solid phase extraction and determination by USN-ICP-OES

The presented studies describe synthesis of Fe3O4 nanoparticles coated with different ligands as adsorbents for magnetic solid phase extraction. Nanoparticles synthesized for heavy metal determination were characterized by FESEM, EDX, XRD, FT-IR and TGA and determined by USN-ICP-OES. Optimum conditions for speciation and enrichment were found by adjusting pH value, adsorbent amount and contact time. Also, adsorption isotherms, adsorption kinetics, foreign ion studies and analytical values were carried out. Magnetic nanoparticles (MNP) carrying the target metals are easily separated from the aqueous solution by applying an external magnetic field; therefore, filtration or centrifugation was not required. Both methods are compatible with Langmuir and Freundlich isotherm models. Samples that carried target metals have been analyzed in order to found accuracy of the method and relative recoveries were found between 95 and 105%. In was used as internal standard in all experiments. In the first study, Fe3O4 nanoparticles were coated with SiO2, (3-chloropropyl)triethoxysilane and 3-amino-1,2,4-triazole-5-thiol and used in antimony speciation. At pH = 9, 20 mg of magnetic nanoparticles and 60 minutes contact time were found for optimized conditions and Sb3+ was retained from the aqueous solution while Sb5+ remained in solution. The enrichment factor (EF), limit of detection (LOD) and relative standard deviaton (RSD) was calculated as 116, 4,5 μg.L-1 and 1,03%, respectively. In the second study, Fe3O4 nanoparticles were coated with Tween 80 and used in As3+ and Mo6+ preconcentration. At pH = 2, 10 mg of magnetic nanoparticles and 30 minutes contact time were found for optimized conditions. Under these conditions, heavy metals of As3+ and Mo6+ were preconcentrated in aqueous solutions. The enrichment factor (EF), limit of detection (LOD) and relative standard deviaton (RSD) was calculated as 35, 1,58 μg.L-1 and 0,81% for As and 32, 3,43 μg.L-1 and 1,36% for Mo, respectively.