Emprego de polímero híbrido poli(vinilimidazol)-sílica impresso ionicamente para pré-concentração de chumbo com posterior determinação por TS-FF-AAS

Abstract

The current work presents the synthesis of an ion imprinted hybrid polymer (IIP) and its application on the selective adsorption of Pb2+ ions, with posterior determination by TS-FF-AAS. The hybrid polymer was prepared by using [3-(methacryloxy)propyl]trimethoxysilane and 1-vinylimidazole, in which an flow injection system was employed for the Pb2+ preconcentration. Polymer characterization was carried out by infrared spectroscopy, thermal analysis and scanning electron microscopy. The preconcentration system was optimized by using chemometric tools (factorial design and Doehlert matrix). The optimized variables were: pH (6.46), buffer concentration at 9.0 mmol L-1, preconcentration flow rate at 4.0 mL min-1 and 0.5 mol L-1 eluent (HNO3). The thermodynamic parameters ΔH, ΔG and ΔS showed that Pb2+ adsorption towards IIP is an exothermic and spontaneous process due to the negative values of enthalpy and energy free from Gibbs. Interferent studies were carried out from binary solutions in the following ratios, 1:1; 1:10; 1:100 (m/m) analyte/interferent, respectively. The ions studied were: Cu2+, Cd2+, Co2+, Fe3+, Ni2+, Cr3+, Mn2+ and Zn2+. Under optimized conditions, the method presented limits of detection and quantification of 0.75 and 2.5 μg L-1, respectively, and linear analytical curve from 5.0 up to 65.0 μg L-1 (r = 0.9995). The parameters preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were found to be 128, 0.16 mL and 25.6 min-1, respectively. The selectivity coefficient of ion imprinted polymer was compared with the selectivity coefficient of NIP (non imprinted polymer) for the Pb2+/Cd2+, Pb2+/Zn2+ and Pb2+/Cu2+ binary mixtures, which the respective values of relative selectivity coefficient (k’) of 64.9, 16.0 and 9.3 were obtained. The proposed method was successfully applied for Pb2+ determination in different types of water samples, urine and certified reference material (DORM-3 Fish Protein) with satisfactory recovery values.