Synthesis of a magnetic WO3 nanocomposite for use in highly selective preconcentration of Pb(II) prior to its quantification by FAAS.

A novel sorbent consisting of WO3 and Fe3O4 is described for preconcentration of Pb(II). It was prepared without consumption of organic solvents. The nano composite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, alternating gradient force magnetometer and Brunauer-Emmett-Teller. Having high surface area and being formed oxygen sheets propose the nanocomposite as a sorbent. Adsorption and desorption conditions were optimized and Pb(II) is quantified by flame atomic absorption spectroscopy. The sorbent can highly selectively preconcentrate Pb(II) at pH values between 3 and 7. The preconcentration time is short and sorbent is re-usable. Under the optimized conditions, the method has the following figures of merit: (a) limit of detection of 0.60 ng mL-1, (b) relative standard deviation (n = 5) of 0.87%, (c) preconcentration factor of 33.33 and (d) linearity of dynamic range (10-200 ng.mL-1). Isotherm adsorption, kinetic adsorption and thermodynamic adsorption were stablished. The material was applied to the preconcentration of Pb(II) from herbal medicines. Graphical abstract Schematic presentation of a nanocomposite (Fe3O4 - WO3) that was prepared from sodium tungstate (Na2WO4), oxalic acid, HCl and magnetic Fe3O4 nanoparticles for the magnetic solid phase extraction of lead at trace levels.