Silica-Alumina-Niobia (SiO2/Al2O3/Nb2O5) Matrix Obtained by the Sol-gel Processing Method: New Material for Online Extraction of Zinc Ions

In the present work, a new material, SiO2/Al2O3/Nb2O5 (designated as SiAlNb), was evaluated as an adsorbent in a flow injection spectrophotometric method for online preconcentration and determination of trace amounts of Zn2+ ions. The preconcentration method is based on Zn2+ adsorption onto the surface of SiAlNb in alkaline medium (pH 9.0). The elution step is carried out using HNO3 solution, followed by reaction of the Zn2+ ions with 1-(2-piridylazo)-2-naphtol (pan) in ammoniacal buffer solution (pH 9.3) containing Tween-80. The [Zn(pan)(2)] complex formed is determined at 560 nm. The method presented a linear range between 7.6 and 180.0 mu g L-1 (r = 0.9992) and limits of detection and quantification of 2.3 and 7.6 mu g L-1, respectively. According to the Langmuir linear model, the maximum adsorption capacity was found to be 7.0 mg of Zn2+ g(-1) of SiAlNb. The proposed method was successfully applied to the Zn2+ determination in water samples (lake, mineral, tap) and certified reference material (TORT-2 Lobster Hepatopancreas).