Synthesis and characterization of cross-linked molecularly imprinted polyacrylamide for the extraction/preconcentration of glyphosate and aminomethylphosphonic acid from water samples

The present study describes the synthesis of molecularly imprinted polyacrylamide and its applications for the selective adsorption of glyphosate (GP) and its degradation product, aminomethylphosphonic acid (AMPA). The molecularly imprinted polymers (MIPs) were prepared by polymerization in a homogeneous medium, which is known as the “in bulk” method. The reagents used for the synthesis were acrylamide (AAm) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linking reagent, and azobisisobutyronitrile (AIBN) as the radical initiator. The selectivity of the MIPs was evaluated with non-imprinted polymers (NIPs) for each polymer synthesized without the template molecule. Polymer characterization was carried out by thermogravimetry (TG) analysis, Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The experimental data on the adsorption kinetics were best explained by a pseudo-second-order kinetic model. The Langmuir-Freundlich nonlinear isotherm model for two adsorption sites had the best fit to the experimental data for glyphosate and AMPA. The maximum adsorption capacities were 3.37 and 4.74 mg g−1 for MIP-GP and MIP-AMPA, respectively. According to the relative selectivity (k′) values, higher selectivities for the analytes were observed in aqueous medium for the MIPs than for the NIPs.