Xylenol orange adsorbed on silica surface as a solid phase reagent for lead determination using diffuse reflectance spectroscopy

The solid-phase reagents on the base of xylenol orange and its complex with Fe(III) immobilized on silica surface were obtained. The interaction of Pb(II) with developed reagents was studied. The conditions of quantitative recovery of Pb(II) from diluted solutions, such as acidity of aqueous phase, the amount of the sorbent, the volume of solutions and the time of equilibrium reaching, were examined. The tolerance limits of metal ions in the sorption of Pb(II) at pH 4.5–5.5 are reported. The capabilities of immobilized xylenol orange for Pb(II) pre-concentration prior to its diffusion reflectance spectroscopic detection was evaluated. The detection limit was 2 μg l−1. The developed method was applied to Pb(II) determination in natural water and foodstuffs.