Influence of the synthesis parameters on the efficiency of fluorescent ion-imprinted polymers for lead detection

Abstract

New fluorescent ion-imprinted polymers (IIPs) specific for Pb(II) detection were synthesized by precipitation polymerization. The fluorescent activity of the IIPs was provided by a fluorescent functional monomer, ANQ-ST, based on the chelating 5-amino-8-hydroxyquinoline moiety coupled to anthracene and a styrenic group. Various synthesis parameters were tested: metal/functional monomer ratio, polymerization solvent and crosslinker (ethyleneglycol dimethacrylate, EGDMA, or divinylbenzene, DVB). The characterization of the different IIPs was carried out by solid-state 13C NMR spectroscopy, to analyse the structure of the polymers and to attest the integration of the ANQ-ST in the polymer matrix, and by scanning electron microscopy and nitrogen adsorption/desorption experiments, to study the morphology of the prepared materials. After characterization, the IIPs and their corresponding non-imprinted polymer (NIPs) were subjected to various fluorescence studies, in order to conclude on the influence of the synthesis parameters onto the polymer properties. The results demonstrated that the IIP synthesized with a metal/functional monomer ratio of 0.42 in DMSO/MeOH (1:1, v/v) and using EGDMA as a crosslinker was very sensitive to the presence of Pb(II) ions and almost not to other tested ions (Ag(I), Na(I), Ca(II), Cd(II), Co(II), Cu(II) and Zn(II)), even introduced in high excess. Calibration curves were performed in various matrices: ultra-pure water, buffered water at pH 7.0 and 8.1, seawater, tap water. They highlighted the low impact of the tested matrices onto the detection and allowed to determine a limit of detection of 2.4 μg/L and a linear range of 8.0–50 μg/L. Finally, the very good recovery obtained in natural samples emphasized the potential for the synthesized IIP to detect Pb(II) in natural waters.