Preparation and application of simetryn-imprinted nanoparticles in triazine herbicide residue analysis

Ambient Temperature Metal-Free Thiomethylation of Chloroheteroarenes and Chloropurines

Herein, we report an in-situ mild and metal-free protocol for thiomethylation of heteroarenes in high yields. The thiomethylation of various chloropurines, nucleosides, and chloroheteroarenes has been accomplished offering easy access to agrochemicals and synthetic molecules useful for drug discovery.

In situ synthesis and dynamic simulation of molecularly imprinted polymeric nanoparticles on a micro-reactor system

Current practices in synthesizing molecularly imprinted polymers face challenges-lengthy process, low-productivity, the need for expensive and sophisticated equipment, and they cannot be controlled in situ synthesis. Herein, we present a micro-reactor for in situ and continuously synthesizing trillions of molecularly imprinted polymeric nanoparticles that contain molecular fingerprints of bovine serum albumin in a short period of time (5-30 min). Initially, we performed COMSOL simulation to analyze mixing efficiency with altering flow rates, and experimentally validated the platform for synthesizing nanoparticles with sizes ranging from 52-106 nm. Molecular interactions between monomers and protein were also examined by molecular docking and dynamics simulations. Afterwards, we benchmarked the micro-reactor parameters through dispersity and concentration of molecularly imprinted polymers using principal component analysis. Sensing assets of molecularly imprinted polymers were examined on a metamaterial sensor, resulting in 81% of precision with high selectivity (4.5 times), and three cycles of consecutive use. Overall, our micro-reactor stood out for its high productivity (48-288 times improvement in assay-time and 2 times improvement in reagent volume), enabling to produce 1.4-1.5 times more MIPs at one-single step, and continuous production compared to conventional strategy.

Simultaneous analysis of multiple pesticide residues in tobacco by magnetic carbon composite-based QuEChERS method and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid-phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh-performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2-200 µg/L. The limit of detection ranged from 0.14 to 2.67 µg/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 µg/kg were in the ranges of 80.8%-113.3% and 0.6%-16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process.

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.

Theoretical design and preparation research of molecularly imprinted polymers for steviol glycosides

In this paper, a novel molecularly imprinted polymer (MIP) for specific adsorption of steviol glycosides was designed, and the imprinting mechanism of self-assembly system between template and monomers was clearly explored. Firstly, steviol (STE) was chosen as dummy template, and the density functional theory (DFT) at B3LYP/6-31 + G (d, p) level was used to select monomers, imprinting molar ratios, solvents, and cross-linking agents. The selectivity to five steviol glycosides was also calculated. Importantly, reduced density gradient (RDG) theory combined with atom in molecules (AIM) and infrared spectrum (IR) was applied to investigate the bonding situation and the nature of noncovalent interaction in self-assembly system. The theoretical designed results showed that the template which interacts with acrylic acid (AA) has the minimum binding energy, and the complex with the molar ratio of 1 : 4 has the most stable structure. Toluene (TL) and ethylene glycol dimethacrylate (EGDMA) were chosen as the optimal solvent and cross-linking agent, respectively. Five hydrogen bonds formed in the self-assembly system are the key forces at the adsorption sites of MIPs through the RDG and AIM analyses. The MIPs were synthesized by theoretical predictions, and the results showed that the maximum adsorption capacity towards dulcoside A is 26.17 mg/g. This work provided a theoretical direction and experimental validation for deeper researches of the MIPs for steviol glycosides. In addition, the method of RDG theory coupled with AIM and IR also could be used to analyze other imprinting formation mechanisms systematically.

Fabrication and application of a MIL-68(In)-NH2 incorporated high internal phase emulsion polymeric monolith as a solid phase extraction adsorbent in triazine herbicide residue analysis

In this work, a metal–organic framework MIL-68(In)–NH₂ incorporated high internal phase emulsion polymeric monolith (MIL-68(In)–NH₂/polyHIPE) was prepared and applied as a solid phase extraction adsorbent for the extraction and detection of trace triazine herbicides in environmental water samples by coupling with HPLC-UV detection. The fabricated material showed good adsorption for simazine, prometryn, and prometon in water samples because of π–π interactions and hydrogen bonding interactions. Under optimal conditions, the maximum adsorption capacity of simazine, prometon and prometryn was 800 μg g⁻¹, 800 μg g⁻¹ and 6.01 mg g⁻¹, respectively. The linearities were 10–800 ng mL⁻¹ for simazine, prometon and prometryn. The limits of detection were 31–97 ng L⁻¹, and the recoveries were 85.6–118.2% at four spiked levels with relative standard deviations lower than 5.0%. The method has a high sensitivity for the determination of three triazine herbicides in environmental water samples.

MIL-68(In)–NH₂ incorporated high internal phase emulsion polymeric monoliths were fabricated and applied to extract and determine triazine herbicide residues in environmental water samples.

An Update on Molecularly Imprinted Polymer Design through a Computational Approach to Produce Molecular Recognition Material with Enhanced Analytical Performance

Molecularly imprinted polymer (MIP) computational design is expected to become a routine technique prior to synthesis to produce polymers with high affinity and selectivity towards target molecules. Furthermore, using these simulations reduces the cost of optimizing polymerization composition. There are several computational methods used in MIP fabrication and each requires a comprehensive study in order to select a process with results that are most similar to properties exhibited by polymers synthesized through laboratory experiments. Until now, no review has linked computational strategies with experimental results, which are needed to determine the method that is most appropriate for use in designing MIP with high molecular recognition. This review will present an update of the computational approaches started from 2016 until now on quantum mechanics, molecular mechanics and molecular dynamics that have been widely used. It will also discuss the linear correlation between computational results and the polymer performance tests through laboratory experiments to examine to what extent these methods can be relied upon to obtain polymers with high molecular recognition. Based on the literature search, density functional theory (DFT) with various hybrid functions and basis sets is most often used as a theoretical method to provide a shorter MIP manufacturing process as well as good analytical performance as recognition material.

Microwave absorption medium-assisted extraction coupled with reversed-phase dispersive liquid-liquid microextraction of triazine herbicides in corn and soybean samples

A new extraction method, microwave absorption medium-assisted extraction coupled with reversed-phase dispersive liquid-liquid microextraction, was developed for the determination of triazine herbicides in corn and soybean samples. Triazine herbicides were extracted with hexane and then directly enriched into the ionic liquid phase. The purification of sample and concentration of target analytes were performed simultaneously. The method combines the advantages of nonpolar solvent dynamic microwave extraction and reversed-phase dispersive liquid-liquid microextraction, which could greatly simplify the operation and reduce the whole pretreatment time. The Box-Behnken design was used to the optimization of experimental factors involved in the dynamic microwave-assisted extraction. In the present study, good linearity in the range of 5.00-500.00 µg/kg was obtained. The limits of detection and quantification varying from 1.3 to 4.2 and 4.1 to 13.9 µg/kg were achieved, respectively. The intra- and interday precisions were between 2.7 and 6.9%. The present method was applied to the analysis of corn and soybean samples, and the recoveries of analytes ranged from 80.7 to 106.9% with the relative standard deviations of 2.1-7.8%. The present method shows the potentials of practical applications in the treatment of the complex fatty solid samples.

Molecularly Imprinted Polymer Micro- and Nano-Particles. A review

In recent years, molecularly imprinted polymers (MIPs) have become an excellent solution to the selective and sensitive determination of target molecules in complex matrices where other similar and relative structural compounds could coexist. Although MIPs show the inherent properties of the polymers, including stability, robustness, and easy/cheap synthesis, some of their characteristics can be enhanced, or new functionalities can be obtained when nanoparticles are incorporated in their polymeric structure. The great variety of nanoparticles available significantly increase the possibility of finding the adequate design of nanostructured MIP for each analytical problem. Moreover, different structures (i.e., monolithic solids or MIPs micro/nanoparticles) can be produced depending on the used synthesis approach. This review aims to summarize and describe the most recent and innovative strategies since 2015, based on the combination of MIPs with nanoparticles. The role of the nanoparticles in the polymerization, as well as in the imprinting and adsorption efficiency, is also discussed through the review.