The preparation of Fe3O4/molecular-imprinted nanocomposite and the application on the recognition and separation of glyphosate

CoFe2O4-chitosan-graphene nanocomposite for glyphosate removal

Glyphosate is one of the most widely used herbicides globally, and there are several concerns about its environmental impact. In this work, we revealed the molecular interaction between chitosan, graphene, and CoFe2O4 nanoparticles with commercial glyphosate. The binding interaction was studied by Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The structural and magnetic properties were characterized using scanning electron microscopy (SEM) and vibrating-sample magnetometry (VSM). To quantify the removal of glyphosate from water, UV-vis spectroscopy was used. Our results demonstrate the strong interaction between glyphosate with the components of the nanocomposite by the coordination through the phosphate and carboxylic groups and a complex formation with the nanoparticles. The advantage of this work is the use of a low-cost nanocomposite as bioadsorbent and the understanding of the binding interactions for glyphosate removal.

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.

Core-Shell Molecularly Imprinted Polymer Nanocomposites for Biomedical and Environmental Applications

Core-shell polymers represent a class of composite particles comprising of minimum two dissimilar constituents, one at the center known as a core which is occupied by the other called shell. Core-shell molecularly imprinting polymers (CSMIPs) are composites prepared via printing a template molecule (analyte) in the coreshell assembly followed by their elimination to provide the everlasting cavities specific to the template molecules. Various other types of CSMIPs with a partial shell, hollow-core and empty-shell are also prepared. Numerous methods have been reported for synthesizing the CSMIPs. CSMIPs composites could develop the ability to identify template molecules, increase the relative adsorption selectivity and offer higher adsorption capacity. Keen features are measured that permits these polymers to be utilized in numerous applications. It has been developed as a modern technique with the probability for an extensive range of uses in selective adsorption, biomedical fields, food processing, environmental applications, in utilizing the plant's extracts for further applications, and sensors. This review covers the approaches of developing the CSMIPs synthetic schemes, and their application with special emphasis on uses in the biomedical field, food care subjects, plant extracts analysis and in environmental studies.

Highly Selective Polypyrrole MIP-Based Gravimetric and Electrochemical Sensors for Picomolar Detection of Glyphosate

There is a global debate and concern about the use of glyphosate (Gly) as an herbicide. New toxicological studies will determine its use in the future under new strict conditions or its replacement by alternative synthetic or natural herbicides. In this context, we designed biomimetic polymer sensing layers for the selective molecular recognition of Gly. Towards this end, complementary surface acoustic wave (SAW) and electrochemical sensors were functionalized with polypyrrole (PPy)-imprinted polymer for the selective detection of Gly. Their corresponding limits of detection were on the order of 1 pM, which are among the lowest values ever reported in literature. The relevant dissociation constants between PPy and Gly were estimated at [K_d1 = (0.7 ± 0.3) pM and K_d2 = (1.6 ± 1.4) µM] and [K_d1 = (2.4 ± 0.9) pM and K_d2 = (0.3 ± 0.1) µM] for electrochemical and gravimetric measurements, respectively. Quantum chemical calculations permitted to estimate the interaction energy between Gly and PPy film: ΔE = −145 kJ/mol. Selectivity and competitivity tests were investigated with the most common pesticides. This work conclusively shows that gravimetric and electrochemical results indicate that both MIP-based sensors are perfectly able to detect and distinguish glyphosate without any ambiguity.