Solid-phase extraction of vanadium(V) from tea infusions and wines on immobilized nanometer titanium dioxide followed by ICP-OES analysis

Nanosized titanium dioxide immobilized on silica gel was synthesized and used as fixed-bed phase for V(V) pre-concentration, followed by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. Three different sorbents were prepared by sol–gel method starting from a mixture of titanium isopropoxide, 2-propanol and water, and characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and BET analysis. V(V), the most stable and toxic oxidation state of the element, present in water and beverages samples, was selectively sorbed, pre-concentrated, quantitatively eluted by 0.1M HCl and analyzed by ICP-OES. The effectiveness of the procedure was first assessed on tap water enriched with 1μgL−1 of V(V) obtaining recoveries up to 92% (n=4). The pre-concentration step was then optimized for complex matrices such as tea infusions and red and white wines. The reliability of the procedure was assessed on the same beverages samples spiked with 20–250μgL−1. Quantitative recoveries (82–95%, n=4) were assured avoiding any sample pre-treatment, generally essential in such complex matrices, obtaining good precision (RSD<12%, n=3). The method was then applied to the determination of V(V) in commercial tea infusions and wines.