Core–shell molecularly imprinted polymer-based solid-phase microextraction fiber for ultra trace analysis of endosulfan I and II in real aqueous matrix through gas chromatography–micro electron capture detector

Anion Exchange Affinity-Based Controllable Surface Imprinting Synthesis of Ultrathin Imprinted Films for Protein Recognition

Anion exchange affinity-based controllable surface imprinting is an effective approach to overcome low imprinting efficiency and high non-specific binding capacity. The template proteins were first immobilized on the anchored tetraalkylammonium groups of the nanoparticles via anion exchange affinity-based interactions, enabling monolayer sorption using a low template concentration. The combined use of surface-initiated photoiniferter-mediated polymerization to precisely control the imprinted film thickness, allowing the formation of homogeneous binding cavities, and the construction of effective binding sites resulted in a low non-specific binding capacity and high imprinting efficiency. The obtained imprinted films benefited from the anion exchange mechanism, exhibiting a higher imprinting factor and faster binding rate than the reference material. Binding tests revealed that the binding strength and selective recognition properties could be tuned to a certain extent by adjusting the NaCl concentration. Additionally, in contrast to the harsh template elution conditions of the covalent immobilization approach, over 80% of the template molecules were readily removed from the imprinted films using supersonic elution with an aqueous mixture of NaCl and HAc. Introducing template immobilization by anion exchange interactions to the synthesis of imprinted materials may provide a new approach for effective biomacromolecular imprinting.

R. Rocha C, Teixeira JA, Pereira JAM. Green Extraction Techniques as Advanced Sample Preparation Approaches in Biological, Food, and Environmental Matrices: A Review

Green extraction techniques (GreETs) emerged in the last decade as greener and sustainable alternatives to classical sample preparation procedures aiming to improve the selectivity and sensitivity of analytical methods, simultaneously reducing the deleterious side effects of classical extraction techniques (CETs) for both the operator and the environment. The implementation of improved processes that overcome the main constraints of classical methods in terms of efficiency and ability to minimize or eliminate the use and generation of harmful substances will promote more efficient use of energy and resources in close association with the principles supporting the concept of green chemistry. The current review aims to update the state of the art of some cutting-edge GreETs developed and implemented in recent years focusing on the improvement of the main analytical features, practical aspects, and relevant applications in the biological, food, and environmental fields. Approaches to improve and accelerate the extraction efficiency and to lower solvent consumption, including sorbent-based techniques, such as solid-phase microextraction (SPME) and fabric-phase sorbent extraction (FPSE), and solvent-based techniques (μQuEChERS; micro quick, easy, cheap, effective, rugged, and safe), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), in addition to supercritical fluid extraction (SFE) and pressurized solvent extraction (PSE), are highlighted.

Development and Application of Molecularly Imprinted Polymers for the Selective Extraction of Chlordecone from Bovine Serum

The widespread use of chlordecone (CLD), an organochlorine pesticide, until the 1990s to protect banana crops in the French West Indies led to significant pollution of water and soil and, subsequently, of bovine intended for human consumption. Carcasses are submitted to official controls based on perirenal fat CLD determination. In order to allow for pre-slaughter controls, a selective analytical method based on a molecularly imprinted polymer (MIP) associated to the LC/MS-MS method was developed to determine the level of CLD in bovine serum that can be collected before slaughter. Different synthesis conditions were therefore assayed by varying the nature of the monomer and of the porogen, and the most promising MIP in terms of selective retention for CLD (extraction recovery close to 100%) was completely characterized by solid-phase extraction (repeatability of the extraction procedure, of the synthesis, and of the cartridge filling) in pure medium. The capacity of the MIP was determined at 0.13 µmol g−1 of MIP. After application of a spiked bovine serum sample on the MIP, the selective retention was maintained (87 and 21%, respectively, on the MIP and on the corresponding non-imprinted polymer). Moreover, extraction on the MIP led to a cleaner extract compared to those issued from a conventional C18 sorbent.

Core-shell structured Fe2O3/CeO2@MnO2 microspheres with abundant surface oxygen for sensitive solid-phase microextraction of polycyclic aromatic hydrocarbons from water

Core-shell structured Fe₂O₃/CeO₂@MnO₂ microspheres were fabricated and used as solid-phase microextraction coating for determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. XPS spectra demonstrated the generation of abundant surface oxygen on Fe₂O₃/CeO₂@MnO₂ microspheres, which provided binding sites for enhancement of analyte extraction. Under optimized conditions, the proposed method presented good linearity in the concentration range 0.04-100 ng mL^-1, with low limits of detection varying from 0.38 to 3.57 ng L^-1 for eight PAHs. Relative standard deviations for a single fiber and five batches of fibers were in the ranges of 4.1-8.2% and 7.1-11.4%, respectively. The proposed method was successfully used for determination of PAHs in real river water samples with recoveries ranging from 87.1 to 115.9%. The proposed method using as-prepared Fe₂O₃/CeO₂@MnO₂ microspheres as SPME coating exhibit significant potential for real sample analysis due to its excellent reproducibility, high sensitivity, and good linearity.

The Use of Computational Methods for the Development of Molecularly Imprinted Polymers

Recent years have witnessed a dramatic increase in the use of theoretical and computational approaches in the study and development of molecular imprinting systems. These tools are being used to either improve understanding of the mechanisms underlying the function of molecular imprinting systems or for the design of new systems. Here, we present an overview of the literature describing the application of theoretical and computational techniques to the different stages of the molecular imprinting process (pre-polymerization mixture, polymerization process and ligand-molecularly imprinted polymer rebinding), along with an analysis of trends within and the current status of this aspect of the molecular imprinting field.

Synthesis of molecularly imprinted polymers based on boronate affinity for diol-containing macrolide antibiotics with hydrophobicity-balanced and pH-responsive cavities

In this research, in order to separate and purify diol-containing macrolide antibiotics, like tylosin, from complex biological samples, molecularly imprinted polymer (MIP) based on boronate affinity for tylosin was synthesized by using precipitation polymerization method with 4-vinylphenylboronic acid (VPBA) and dimethyl aminoethyl methacrylate (DMAEMA) as pH-responsive functional monomers, and N,N'-methylene bisacrylamide (MBAA)/ ethylene glycol dimethacrylate (EGDMA) as the co-crosslinkers that balance the hydrophobicity of the MIP. The synthesized tylosin-MIP had the advantages of high adsorption capacity (120 mg/g), fast pH-responsiveness responsible for the accessibility of imprinted cavities, and high selectivity coefficient towards tylosin versus its analogues (2.8 versus spiramycin, 7.3 versus desmycosin) in an aqueous environment. The mechanism of boronate affinity between tylosin and VPBA in the form of charged hydrogen bonding was analyzed via density functional theory (DFT). MIPs were used to successfully separate diol-containing macrolides through molecularly imprinted solid phase extraction (MISPE). The results show that MIPs prepared in this method have a good application prospect in the separation and purification of the diol-containing macrolide antibiotics.

Chitosan-Based Surface Molecularly Imprinted Polymer Microspheres for Sustained Release of Sinomenine Hydrochloride in Aqueous Media

The surface molecular imprinting technique has been proposed as a prospective strategy for template molecule recognition and separation by devising the recognition sites on the surface of imprinted materials. The purpose of this study was to establish a novel drug delivery system which was developed by surface molecular imprinting method using β-cyclodextrin (β-CD)-grafted chitosan (CS) (CS-g-β-CD) microspheres as matrix and sinomenine hydrochloride (SM) as the template molecule. By adjusting the amount of functional monomer and cross-linking agent, we got the more excellent adsorption of CS-g-β-CD molecularly imprinted polymers (MIPs-CS-g-β-CD). When the amount of functional monomer was 6 mmol and cross-linking agent was 20 mmol, the maximum binding capacity of MIPs and non-imprinted polymers (NIPs) was 55.9 mg/g and 37.2 mg/g, respectively. The results indicated that the recognition of SM with MIPs was superior to NIPs. The adsorption isotherms of MIPs-CS-g-β-CD indicated that the adsorption behavior fitted better to the Langmuir model, which showed that the adsorption process of polymer was monomolecular layer. In in vitro drug release studies, the accumulative release amount of MIPs-CS-g-β-CD was up to 78% within 24 h. MIPs exhibited an excellent controlled SM release profile without burst release and the mechanism of SM release was shown to conform to non-Fick diffusion. Therefore, MIPs-CS-g-β-CD were successfully applied to extraction of SM and used as the materials for drug delivery system.

Selective and sensitive fluorimetric determination of carbendazim in apple and orange after preconcentration with magnetite-molecularly imprinted polymer

In this study, magnetite-molecularly imprinted polymer has been used for the first time as selective adsorbent before the fluorimetric determination of carbendazim. Adsorption capacity of the magnetite-molecularly imprinted polymer was found to be 2.31±0.63mgg^-1 (n=3). Limit of detection (LOD) and limit of quantification (LOQ) of the method were found to be 2.3 and 7.8μgL^-1, respectively. Calibration graph was linear in the range of 10-1000μgL^-1. Rapidity is an important advantage of the method where re-binding and recovery processes of carbendazim can be completed within an hour. The same imprinted polymer can be used for the determination of carbendazim without any capacity loss repeatedly for at least ten times. Proposed method has been successfully applied to determine carbendazim residues in apple and orange, where the recoveries of the spiked samples were found to be in the range of 95.7-103%. Characterization of the adsorbent and the effects of some potential interferences were also evaluated. With the reasonably high capacity and reusability of the adsorbent, dynamic calibration range, rapidity, simplicity, cost-effectiveness and with suitable LOD and LOQ, the proposed method is an ideal method for the determination of carbendazim.

Determination of five endosulfan pesticides in the fish pond water by dispersive liquid-liquid microextraction combined with GC-MS

A simple and rapid dispersive liquid–liquid microextraction (DLLME) technique coupled with gas chromatography–ion trap mass spectrometry (GC–MS) was developed for the extraction and analysis of five endosulfan pesticides from the fish pond water. In this work, different parameters affecting the extraction process such as the type and volume of extraction solvent, type and volume of disperser solvent, and extraction time were studied and optimized. Under optimized conditions, the enrichment factor ranged from 189 to 269 and the relative recovery ranged from 88.5% to 94.9%. The linear range was 2.0–80.0 µg/L; the limits of detection and quantitation were in the range 0.04–1.06 µg/L and 0.12–3.53 µg/L, respectively. The relative standard deviations were in the range 0.94%–2.08% (n = 5). The obtained results show that DLLME combined with GC–MS is a fast and simple method for the determination of endosulfan pesticides in fish pond water.

Plastic antibody based surface plasmon resonance nanosensors for selective atrazine detection

This study reports a surface plasmon resonance (SPR) based affinity sensor system with the use of molecular imprinted nanoparticles (plastic antibodies) to enhance the pesticide detection. Molecular imprinting based affinity sensor is prepared by the attachment of atrazine (chosen as model pesticide) imprinted nanoparticles onto the gold surface of SPR chip. Recognition element of the affinity sensor is polymerizable form of aspartic acid. The imprinted nanoparticles were characterized via FTIR and zeta-sizer measurements. SPR sensors are characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR) and contact angle measurements. The imprinted nanoparticles showed more sensitivity to atrazine than the non-imprinted ones. Different concentrations of atrazine solutions are applied to SPR system to determine the adsorption kinetics. Langmuir adsorption model is found as the most suitable model for this affinity nanosensor system. In order to show the selectivity of the atrazine-imprinted nanoparticles, competitive adsorption of atrazine, simazine and amitrole is investigated. The results showed that the imprinted nanosensor has high selectivity and sensitivity for atrazine.

Molecularly imprinted polymers for the analysis and removal of polychlorinated aromatic compounds in the environment: a review

Molecularly imprinted polymers selective to polychlorinated aromatic compounds for application in environmental studies.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Turn-on detection of pesticides via reversible fluorescence enhancement of conjugated polymer nanoparticles and thin films

Pesticide detection via fluorescence enhancements of nanoparticles enables the sensitive and selective detection of DDT and its metabolites/co-occurring analogues.

Preparation of malathion MIP-SPE and its application in environmental analysis

Malathion is an organophosphorous insecticide for controlling insects on fruits and vegetables, miscellaneous household insects, and animal parasites. It is important to develop highly efficient and selective pre-treatment method for analyzing malathion residues in environment and samples from agricultural products based on the molecularly imprinted polymers (MIPs). In this study, we developed a tailor-made MIP method with highly specific recognization to the template. The MIPs were prepared using malathion as a template, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, azodiisobutyronitrile (AIBN) as an initiator, and the acetonitrile-chloroform (1:1, v/v) as a porogen. The molecular recognization mechanism of malathion and MAA was evaluated by molecular simulation, ultraviolet spectrometry (UV), and (1)H-nuclear magnetic resonance ((1)H-NMR). MAA interacted specifically with malathion by hydrogen bond with a ratio of 2:1. The MIPs exhibit a high affinity, recognition specificity, and efficient adsorption performance for malathion. The Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), surface area and porosimeter analyzer, thermogravimetric/differential thermal analyzer (TG/DTA) were used to characterize the properties of MIP. The malathion residues in soil, tap water, and cabbage were cleaned up by MIP-SPE, detected quantitatively using GC-FPD, and confirmed by GC-MS/MS. The limits of tap water, soil, and cabbage were confined to 0.001 mg L(-1), 0.004 and 0.004 mg kg(-1), respectively. The spiked recoveries of malathion were 96.06-111.49% (with RSD being 5.7-9.2%), 98.13-103.83% (RSD, 3.5-8.7%), and 84.94-93.69% (RSD, 4.7-5.8%) for tap water, soil, and cabbage samples, respectively. Thus, the method developed here can be used effectively in assessing malathion residues in multiple environmental samples. The aim of the study was to provide an efficient, selective, and accurate method for analyzing malathion at trace levels in multiple media.

Uniform core–shell molecularly imprinted polymers: a correlation study between shell thickness and binding capacity

A model of core–shell MIPs was constructed to evaluate the correlation between shell thickness and binding capacity.