Magnetic Molecularly Imprinted Polymer for the Selective Enrichment of Glyphosate, Glufosinate, and Aminomethylphosphonic Acid Prior to High-Performance Liquid Chromatography

A novel mixed iron hydroxide molecularly imprinted polymer (MIH-MIP) was synthesized via polymerization using mixed-valence iron hydroxide as a magnetic supporter, glyphosate as a template, acrylamide as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. The resulting material was characterized and applied as a sorbent for the selective enrichment of glyphosate, aminomethylphosphonic acid, and glufosinate by magnetic solid-phase extraction (MSPE) prior to high-performance liquid chromatography. MIH-MIP possessed a high adsorption capacity in the range of 2.31-5.40 mg g-1 with good imprinting factors ranging from 1.52 to 7.59. The Langmuir model proved that the recognition sites were distributed as a monolayer on the surface of MIH-MIP. Scatchard analysis showed two types of binding sites on MIH-MIP. The kinetic characteristics of MIH-MIP suggested that the binding process of all analytes fit well with the pseudosecond-order model. The developed methodology provides good linearity in the range of 72.0-2000.0 μg L-1. Low detection limits of 21.0-22.5 μg L-1 and enrichment factors of up to 18 were achieved. The precision in terms of relative standard deviations of the intra- and interday experiments was better than 7 and 9%, respectively. The applicability of the developed MSPE facilitates the accurate and efficient determination of water, soil, and vegetable samples with satisfactory recoveries in the range of 86-118%. The results confirmed the suitability of the MIH-MIP sorbent for selective extraction and quantification of glyphosate, aminomethylphosphonic acid, and glufosinate.