A review on the use of ionic liquids in preparation of molecularly imprinted polymers for applications in solid-phase extraction

Chameleon-inspired molecular imprinted polymer with bicolored states for visual and stable detection of diethylstilbestrol in water and food samples

A novel biomimetic molecular imprinted polymer chip with fluorescence (FL) and structural (STR) states, inspired by color patterns of chameleon skin, is fabricated for detecting diethylstilbestrol (DES). The chip features a regularly structured, non-closed-packed (NCP) colloidal photonic crystal (CPC) lattice made monodisperse MIP spheres containing fluorescence poly ionic liquid (FPIL) pigments. The FL color originates from FPIL pigments and is further enhanced by the Purcell effect, while the STR color results from the periodic arrangement of the NCP CPC structure. Upon the addition of DES, the molecular imprinting recognition events of the chip induce bicolored responses. These color variations are observable to the naked eye. Based on a self-correction function of colors, the chip showed direct, sensitive (as low as 0.5 ng/mL), rapid (6 min), selective and stable detection of DES. In sample analysis, the results of DES detected by the chip were by which obtained by the HPLC-MS/MS method.

Computer-Assisted Strategies as a Tool for Designing Green Monomer-Based Molecularly Imprinted Materials

Molecularly imprinted polymers (MIPs) are defined as artificial receptors due to their selectivity and specificity. Their advantageous properties compared to biological alternatives have sparked interest among scientists, as detailed in numerous review papers. Currently, there is significant attention on adhering to the principles of green chemistry and environmental protection. In this context, MIP research groups have focused on developing eco-friendly procedures. The application of "greener" monomers and reagents, along with the utilization of computational methodologies for design and property analysis, are two activities that align with the green chemistry principles for molecularly imprinted technology. This review discusses the application of computational methodologies in the preparation of MIPs based on eco-friendly non-acrylic/vinylic monomers and precursors, such as alkoxysilanes, ionic liquids, deep eutectic solvents, bio-based molecules-specifically saccharides, and biomolecules like proteins. It provides a brief introduction to MIP materials, the green aspects of MIP production, and the application of computational simulations. Following this, brief descriptions of the studied monomers, molecular simulation studies of green monomer-based MIPs, and computational strategies are presented. Finally, conclusions and an outlook on the future directions of computational analysis in the production of green imprinted materials are pointed out. To the best of my knowledge, this work is the first to combine these two aspects of MIP green chemistry principles.

Surface amphiphilic hybrid porous polymers based on cage-like organosiloxanes for pipette tip solid-phase extraction of microcystins in water

The occurrence of microcystins (MCs) during harmful algal blooms (HABs) represents a major threat to freshwater environments. In this work, a novel surface amphiphilic hybrid porous polymers based on cage-like organosiloxanes (PCSs) was prepared for the enrichment of MCs. The copolymerization of bifunctional amphiphilic monomers, 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-benzylquininium chloride (BQN), with the cross-linker methacryl substituted polyhedral oligomeric silsesquioxane (POSS) was achieved in an ionic liquid-based porogenic medium. The hierarchical porous structure, a variety of surface functional groups and weak hydrophilicity were well characterized on the prepared materials using scanning electron microscopy, nitrogen adsorption/desorption analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential analysis and water contact angle testing, respectively. The as-prepared surface amphiphilic PCSs was used as an adsorbent for pipette tip solid-phase extraction (PT-SPE) to enrich microcystins (MCs) from surface waters before their analysis by capillary electrochromatography (CEC) and liquid chromatography-mass spectrometry (LC-MS). Under the optimal conditions, the established PT-SPE-LC-MS method exhibited a wide linear range (10-10,000 ng L-1), low limits of detection (4.0-8.0 ng L-1) and satisfactory recoveries (89.5-102.8 %) for MCs. An adsorption mechanism involving electrostatic interactions, hydrogen bonding, hydrophilic interactions, and π-π stacking has been proposed. The findings suggest that the use of surface amphiphilic PCSs materials as adsorbents in the PT-SPE platform facilitates efficient enrichment of MCs for subsequent chromatographic analysis. These investigations offer a new perspective on the simple and uncomplicated pretreatment of complex environmental samples.

Recent progress on media for biological sample preparation

The analysis of biological samples is highly valuable for disease diagnosis and treatment, forensic examination, and public safety. However, the serious matrix interference effect generated by biological samples severely affects the analysis of trace analytes. Sample preparation methods are introduced to address the limitation by extracting, separating, enriching, purifying trace target analytes from biological samples. With the raising demand of biological sample analysis, a review focuses on media for biological sample preparation and analysis over the last 5 years is presented. High-performance media in biological sample preparation are first reviewed, including porous organic frameworks, imprinted polymers, hydrogels, ionic liquids, and bioactive media. Then, application of media for different biological sample preparation and analysis is briefly introduced, including liquid samples of body fluids, solid samples (hair, feces, and tissues), and gas samples of exhale breath gas. Finally, conclusions and outlooks on media promoting biological sample preparation are presented.

Chiral ionic organic single-crystal and its exfoliated two-dimensional nanosheets with enhanced enantioseparation

A chiral ionic organic single-crystal (CIOC) was prepared for the first time through ionic self-assembly using bipyridium chiral ionic liquid (CIL) and 4,4'-biphenyldisulfonic acid (BDA). The CIOC can be ultrasonically exfoliated to produce two-dimensional nanosheets (2D-NSs). The 2D-NSs presented enhanced enantioseparation compared to the CIOC and CIL when used as gas chromatography stationary phase, which may be due to the exfoliated 2D-NSs exhibiting greater exposure of functional groups. Additionally, better resolution of other organic compounds such as positional isomers, n-alkanes and n-alkanols, Grob mixture, phenols and anilines was obtained in 2D-NSs than CIOC and CIL. This work not only provides a reference for the preparation of chiral ionic organic single-crystals and two-dimensional nanosheets for chiral separation, but also stimulates the preparation of such new ionic organic single-crystals via self-assembly for other potential applications.

Preparation of imidazolium ionic liquid functionalized paper membrane for selective extraction of caffeic acid and its structural and functional analogues from Taraxaci Herba

In the search for pharmaceutically active compounds from natural products, it is crucial and challenging to develop separation or purification methods that target not only structurally similar compounds but also those with specific pharmaceutical functions. The adsorption-based method is widely employed in this field and holds potential for this application, given the diverse range of functional monomers that can be chosen based on structural or functional selectivity. In this work, an imidazolium ionic liquid (IL) modified paper membrane was synthesized via microwave reaction. Caffeic acid (CA), with potential interactions with imidazolium IL and a representative component of phenolic acids in Taraxaci Herba, was chosen as a target compound. After optimization of synthesis and extraction parameters, the resulting extraction membrane could be used to quantitatively analyze CA at ng/ml level, and to extract CA's analogues from the sample matrix. Cheminformatics confirmed the presence of structural and functional similarity among these extracted compounds. This study offers a novel approach to preparing a readily synthesized extraction membrane capable of isolating compounds with structural and functional analogies, as well as developing a membrane solid-phase extraction-based analytical method for natural products.

Covalent-Organic Frameworks for Selective and Sensitive Detection of Antibiotics from Water

As the consumption of antibiotics rises, they have generated some negative impacts on organisms and the environment because they are often unable to be effectively degraded, and seeking effective detection methods is currently a challenge. Covalent-organic frameworks (COFs) are new types of crystalline porous crystals created based on the strong covalent interactions between blocked monomers, and COFs demonstrate great potential in the detection of antibiotics from aqueous solutions because of their large surface area, adjustable porosity, recyclability, and predictable structure. This review aims to present state-of-the-art insights into COFs (properties, classification, synthesis methods, and functionalization). The key mechanisms for the detection of antibiotics and the application performance of COFs in the detection of antibiotics from water are also discussed, followed by the challenges and opportunities for COFs in future research.

Carbonized polymer dots-based molecular imprinting: An adsorbent with enhanced selectivity for highly efficient recognition and removal of ceftiofur sodium from complex samples

Highly selective removal of residual cephalosporin antibiotics from complex systems is crucial for human health and ecological environment protection. Herein, a newly molecularly imprinted polymer adsorbent (CPDs-NH2@MIP) with enhanced selectivity for ceftiofur sodium (CTFS) was developed by using the special carbonized polymer dots (CPDs-NH2) as functional monomer. The CPDs-NH2 has a nano-spherical structure and functionalized groups (CC, -NH2) via the incomplete carbonization polymerization of citric acid, acrylamide and ethylenediamine, which can accurately interact with CTFS by overcoming steric hindrance, resulting in more precisely imprinted sites and reducing non-imprinted regions in MIP. The presented CPDs-NH2@MIP exhibited excellent adsorption capacity for CTFS (68.62 mg g-1), achieving equilibrium within 10 min, and highly selectivity in mixed solution containing five coexisting substances, with an imprinted factor (5.61). Compared with commercial adsorbents and MIPs prepared with traditional chain functional monomers, the CPDs-NH2@MIP showed significant advantage in selective recognition and separation of target. Analysis of microstructure and mechanism proved that usage of the spherical functional monomer generated precise imprinting sites and dense structure in CPDs-NH2@MIP, which effectively enhanced the selectivity in complex system combined with hydrogen bonding interaction. The idea of designing and using spherical functional monomer will promote the practicality of molecularly imprinted polymer adsorbents.

Synthesis of imidazolium ionic liquid immobilized on magnetic mesoporous silica: A sorbent material in a green micro-solid phase extraction of multiclass pesticides in water

In this study, we synthesized an imidazolium ionic liquid immobilized on magnetic mesoporous silica (IL-MMS) and evaluated its performance as a sorbent material for a green micro-solid phase extraction (μ-SPE) of multiclass pesticides in water. The synthesized IL-MMS was characterized by various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses (N2 adsorption/desorption), Vibrating Sample Magnetometer (VSM), energy-dispersive spectroscopy (EDS) and Field emission scanning electron microscopy (FESEM). Our synthesized IL-MMS demonstrated excellent magnetic properties (31.5 emu/g), high surface area (1177.4 m2/g), proper pore size (⁓4.2 nm) and volume (1.80 cm3/g). Under optimized extraction conditions, the IL-MMS exhibited a high adsorption capacity for a variety of pesticides, including organophosphates, carbamates, and pyrethroids. The proposed μ-SPE method using IL-MMS showed good linearity (R2 > 0.99), low limits of detection (LODs) ranging from 0.04 to 1.63 ng/L, and suitable recovery rate was between 82.4% and 109.8% for different pesticides. In addition, the method also exhibited excellent reproducibility, with relative standard deviations (RSDs) of less than 8% for both intra and inter-day precision. In overall, the synthesized IL-MMS has proven to be a highly promising material for sorbent-based micro-solid phase extraction (μ-SPE) of multiclass pesticides in water. With its simple, efficient, and eco-friendly approach to pesticide analysis, this method shows great potential for future pesticide detection and monitoring efforts due to its sensitivity, accuracy, and adaptability to various environmental conditions.

Magnetic molecularly imprinted polymers integrated ionic liquids for targeted detecting diamide insecticides in environmental water by HPLC-UV following MSPE

Efficiently detecting diamide insecticides in environmental water is challenging due to their low concentrations and complex matrix interferences. In this study, we developed ionic liquids (ILs)-incorporated magnetic molecularly imprinted polymers (IL-MMIPs) for the detection of diamide insecticides, capitalizing on the advantages of ILs and quick magnetic separation through surface imprinting. Tetrachlorantraniliprole was used as the template, and a specific IL, 1-vinyl-3-ethylimidazolium hexafluorophosphate ([VEIm][PF6]), was employed as the functional monomer. Various synthesis conditions were investigated to optimize adsorption efficiency. The prepared IL-MMIPs were successfully employed as adsorbents in magnetic solid-phase extraction (MSPE) to selectively extract, separate, and quantify three types of diamide insecticides from water samples using HPLC-UV detection. Under optimal conditions, the analytical method achieved low limits of detection (0.69 ng mL-1, 0.64 ng mL-1, 0.59 ng mL-1 for cyantraniliprole, chlorantraniliprole and tetrachlorantraniliprole, respectively). The method also displayed a wide linear range (0.003-10 μg mL-1 for cyantraniliprole and chlorantraniliprole, and 0.004-10 μg mL-1 for tetrachlorantraniliprole, respectively) with satisfactory coefficients (R2≥0.9996), and low relative standard deviation (RSD≤2.55%). Additionally, extraction recoveries fell within the range of 79.4%-109%. The results clearly demonstrate that IL-MMIPs exhibit exceptional recognition and rebinding capabilities. The developed IL-MMIPs-MSPE-HPLC-UV method is straightforward and rapid, making it suitable for the detection and analysis of three kinds of diamide insecticides in environmental water.

Facile synthesis of hydroxylated triazine-based magnetic microporous organic network for ultrahigh adsorption of phenylurea herbicides: An experimental and density-functional theory study

Microporous organic networks (MONs) are highly porous materials that are particularly useful in analytical chemistry. However, the use of these materials is often limited by the functional groups available on their surface. Here, we described the polymerization of a sea urchin-like structure material at ambient temperature, that was functionalized with hydroxyl, carboxyl, and triazine groups and denoted as OH-COOH-MON-TEPT. A substantial proportion of OH-COOH-MON-TEPT was intricately decorated EDA-Fe3O4, creating a well-designed configuration (EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC) for superior adsorption of the target analytes phenylurea herbicides (PUHs) via magnetic solid-phase extraction (MSPE). The proposed method showed remarkably low limits of detection ranging from 0.03 to 0.22 ng·L-1. Experimental investigations and theoretical analyses unveiled the adsorption mode between EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC and PUHs. These findings establish a robust foundation for potential applications of EDA-Fe3O4 @OH-COOH-MON-TEPT-EDC in the analysis of various polar contaminants.

Advances in ionic liquids as fluorescent sensors

Ionic liquids (ILs) are a class of liquid salts with characteristics such as a low melting point, an ionic nature, non-volatility, and tunable properties. Because of their adaptability, they have a significant influence in the field of fluorescence. This paper reviews the primary literature on the use of ILs in fluorescence sensing technologies. The kind of target material is utilized to classify the fluorescence sensors made with the use of ILs. They include using ILs as probes for metals, nitro explosives, small organic compounds, anions, and gases. The efficacy of an IL-based fluorescence sensor depends on the precise design to guarantee specificity, sensitivity, and a consistent reaction to the desired analyte. The precise method can differ depending on the chemical properties of the IL, the choice of fluorophore, and the interactions with the analyte. Overall, the viability of the aforementioned materials for chemical analysis is evaluated, and prospective possibilities for further development are identified.

Development of a molecularly imprinted membrane for selective, high-sensitive, and on-site detection of antibiotics in waters and drugs: Application for sulfamethoxazole

Sulfonamides are among the widespread bacterial antibiotics. Despite this, their quick emergence constitutes a serious problem for ecosystems and human health. Therefore, there is an increased interest in developing relevant detection method for antibiotics in different matrices. In this work, a straightforward, green, and cost-effective protocol was proposed for the preparation of a selective molecularly imprinted membrane (MIM) of sulfamethoxazole (SMX), a commonly used antibiotic. Thus, cellulose acetate was used as the functional polymer, while polyethylene glycol served as a pore-former. The developed MIM was successfully characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The MIM was used as a sensing platform in conjunction with a smartphone for optical readout, enabling on-site, selective, and highly sensitive detection of SMX. In this way, a satisfactory imprinting factor of around 3.6 and a limit of detection of 2 ng mL-1 were reached after applying response surface methodologies, including Box-Behnken and central composite designs. Besides, MIM demonstrated its applicability for the accurate and selective detection of SMX in river waters, wastewater, and drugs. Additionally, the MIM was shown to be a valuable sorbent in a solid-phase extraction protocol, employing a spin column setup that offered rapid and reproducible results. Furthermore, the developed sensing platform exhibited notable regeneration properties over multiple cycles and long shelf-life in different storage conditions. The newly developed methodology is of crucial importance to overcome the limitations of classical imprinting polymers. Furthermore, the smartphone-based platform was used to surpass the typically expensive and complicated methods of detection.

Nanoconfinement of functionalized ionic liquid for enhanced adsorption and rapid sensitive detection of phenylurea herbicides in food and environmental samples

The novel ILs@CNTs was synthesized by encapsulating task-specific ionic liquids (ILs) within carbon nanotubes (CNTs) derived from ZIF-67. These hybrid materials served as multifunctional adsorbents enabling simultaneous sorptive removal, sensitive detection, molecular sieve selection, and magnetic separation. In contrast to pristine CNTs, ILs@CNTs demonstrate significantly enhanced adsorption of phenylurea herbicides (PUHs). The complex interactions between ILs@CNTs and PUHs were comprehensively analyzed using a combination of experimental results and theoretical calculations. Furthermore, a magnetic solid phase extraction-high performance liquid chromatography (MSPE-HPLC) method was developed for the determination of multiple trace PUHs in real samples. The method exhibited lower detection limits (0.02-0.03 μg L-1) and higher enrichment factors (131 < EFs < 185). Interestingly, a portable lab-in-a-syringe device was developed to facilitate rapid on-site extraction and enrichment of PUHs. Additionally, the developed methods successfully applied in river water, tea drinks, and cucumber samples, highlighting its substantial potential for rapid PUH detection.

The Failure of Molecular Imprinting in Conducting Polymers: A Case Study of Imprinting Picric Acid on Polycarbazole

The aims of this study were to investigate the potential of utilising molecularly imprinted polycarbazole layers to detect highly toxic picric acid (PA) and to provide information about their performance. Quantum chemical calculations showed that strong interactions occur between PA and carbazole (bond energy of approximately 31 kJ/mol), consistent with the theoretical requirements for effective molecular imprinting. The performance of the sensors, however, was found to be highly limited, with the observed imprinting factor values for polycarbazole (PCz) layers being 1.77 and 0.95 for layers deposited on Pt and glassy carbon (GC) electrodes, respectively. Moreover, the molecularly imprinted polymer (MIP) layers showed worse performance than unmodified Pt or GC electrodes, for which the lowest limit of detection (LOD) values were determined (LOD values of 0.09 mM and 0.26 mM, respectively, for bare Pt and MIP PCz/Pt, as well as values of 0.11 mM and 0.57 mM for bare GC and MIP PCz/GC). The MIP layers also showed limited selectivity and susceptibility to interfering agents. An initial hypothesis on the reasons for such performance was postulated based on the common properties of conjugated polymers.

Assessing the greenification potential of cyclodextrin-based molecularly imprinted polymers for pesticides detection

Cyclodextrins, with their unparalleled attributes of eco-friendliness, natural abundance, versatile utility, and facile functionalization, make a paramount contribution to the field of molecular imprinting. Leveraging the unique properties of cyclodextrins in molecularly imprinted polymers synthesis has revolutionized the performance of molecularly imprinted polymers, resulting in enhanced adsorption selectivity, capacity, and rapid extraction of pesticides, while also circumventing conventional limitations. As the concern for food quality and safety continues to grow, the need for standard analytical methods to detect pesticides in food and environmental samples has become paramount. Cyclodextrins, being non-toxic and biodegradable, present an attractive option for greener reagents in imprinting polymers that can also ensure environmental safety post-application. This review provides a comprehensive summary of the significance of cyclodextrins in molecular imprinting for pesticide detection in food and environmental samples. The recent advancements in the synthesis and application of molecularly imprinted polymers using cyclodextrins have been critically analyzed. Furthermore, the current limitations have been meticulously examined, and potential opportunities for greenification with cyclodextrin applications in this field have been discussed. By harnessing the advantages of cyclodextrins in molecular imprinting, it is possible to develop highly selective and efficient methods for detecting pesticides in food and environmental samples while also addressing the challenges of sustainability and environmental impact.

Molecularly imprinted polymers in online extraction liquid chromatography methods: Current advances and recent applications

BACKGROUND

One of the primary objectives in green analytical practices is the seamless integration of extraction and separation steps, resulting in the augmentation of both analytical throughput and method performance. Consequently, the exploration of prospective sorbent materials has drawn significant attention in the scientific community, particularly concerning the potential for online procedures. Employing the optimal sorbent material within an automated analytical approach holds the promise of elevating the precision of the analytical evaluation. Molecularly imprinted polymers (MIPs) excel in specific analyte interaction within complex matrices. However, MIPs' full potential was not widely exploring especially for online analytical methodologies.

RESULTS

Here is presented a comprehensive overview of the current applications of MIPs as sorbent materials within integrated and automated separation methodologies applied to diverse matrices including biological, food, and environmental samples. Notably, their primary advantage, as evidenced in the literature, lies in their exceptional selectivity for the target analyte discussed according to the adopted synthesis protocol. Furthermore, the literature discussed here illustrates the versatility of MIPs in terms of modification with one or more phases which are so-called hybrid materials, such as molecularly imprinted monoliths (MIM), the molecularly imprinted ionic liquid polymer (IL-MIP), and restricted access to molecularly imprinted polymer (RAMIP). The reported advantages enhance their applicability in integrated and automated separation procedures, especially to the column switching methods, across a broader spectrum of applications.

SIGNIFICANCE

This revision aims to demonstrate the MIP's potential as a sorbent phase in integrated and automated methods, this comprehensive overview of MIP polymers in integrated and automated separation methodologies can be used as a valuable guide, inspiring new research on developing novel horizons for MIP applications to have their potential emphasized in analytical science and enhanced to the great analytical methods achievement.

Exploring the potential of molecularly imprinted polymers and metal/metal oxide nanoparticles in sensors: recent advancements and prospects

Metal/metal oxide nanoparticles have gained increasing attention in recent years due to their outstanding features, including optical and catalytic properties, as well as their excellent conductivity. The implementation of metal/metal oxide nanoparticles, combined with molecularly imprinted polymers (MIPs) has paved the way for a new generation of building blocks to engineer and enhance the fascinating features of advanced sensors. This review critically evaluates the impact of combining metal/metal oxide nanoparticles with MIPs in sensors. It covers synthesis strategies, advantages of coupling these materials with MIPs, and addresses questions about the selectivity of these hybrid materials. In the end, the current challenges and future perspectives of this field are discussed, with a particular focus on the potential applications of these hybrid composites in the sensor field. This review highlights the exciting opportunities of using metal/metal oxide nanoparticles along with MIPs for the development of next-generation sensors.

A C4-modified bipyridinium multi-mode stationary phase for reversed phase, hydrophilic interaction and ion exchange chromatography

A novel C4-modified bipyridinium stationary phase (Sil-DPC4) was prepared and characterized by elemental analysis (EA) and Fourier transform infrared spectrometry (FT-IR) and further investigated for multi-mode liquid chromatography. The chromatographic performances of Sil-DPC4 were evaluated by reversed-phase chromatography using polycyclic aromatic hydrocarbons (PAHs), phenylamines and phenols, hydrophilic interaction chromatography using nucleosides and nucleobases, and ion exchange chromatography using inorganic ions and organic ions. The effects of the acetonitrile content, salt concentration and pH value of the mobile phase on the retention of Sil-DPC4 were also investigated. Sil-DPC4 showed multiple retention mechanisms including π-π, hydrophobic and electrostatic interactions for PAHs, phenylamines and phenols compared with a dipyridine modified silica stationary phase (Sil-DP) and C18 in RPLC, faster separation for nucleosides and nucleobases compared with Sil-DP, and higher hydrophilicity than HILIC in HILIC, and stronger retention and better separation ability for inorganic ions and organic ions in comparison to Sil-DP in IEC. Besides, Sil-DPC4 was used successfully to detect iodide in artificial seawater and had the potential to analyze radionuclide iodine-131 in seawater. In conclusion, multiple retention mechanisms of Sil-DPC4 could make it have potential applications in complex samples.

Ionic liquid-modified UiO-66-NH2 as sorbent of dispersive solid-phase extraction for rapid adsorption and enrichment of benzoylurea insecticides

Ionic liquid (IL)-modified UiO-66-NH2 composite was prepared and used as sorbent of dispersed solid-phase extraction (dSPE) for extracting trace benzoylurea insecticides (BUs) from complex environmental matrices. The IL in framework endowed the prepared material had electropositive characteristics, which can produce interaction with electron rich guest molecules, such as BUs. The high thermal and chemical stability of UiO-66-NH2/IL enabled it to be reused for 16 times without significant reduction in adsorption performance. Due to the multiple forces including π-π, hydrogen bonding, and fluorine-fluorine interaction, UiO-66-NH2/IL showed good adsorption performance, short adsorption time (20 s) and rapid desorption ability (60 s) for BUs. Under the optimal conditions, the method exhibited wide linear range (0.02-500 ng mL-1) with correlation coefficient (R2) not worse than 0.9928, high enrichment factor (252-300), and low detection limit (0.005-0.4 ng mL-1). The dispersed solid phase extraction coupling with high-performance liquid chromatography-diode array detector (dSPE-HPLC-DAD) was successfully used to detection of BUs in real environmental samples and satisfactory recoveries were obtained (80.5%±2.4-118%±3.2). The results indicated that UiO-66-NH2/IL composite can be a potential sorbent for the preconcentration of trace insecticides in environmental samples.

Recent development of chiral ionic liquids for enantioseparation in liquid chromatography and capillary electrophoresis: A review

Ionic liquids (ILs), which are salts in a molten state below 100 °C, have become a hot topic of research in various fields because of their negligible vapour pressure, high thermal stability, and tunable viscosity. Chiral ionic liquids (CILs) can be applied in chromatography and capillary electrophoresis fields to improve the performance of enantiomeric separation, such as chiral stationary phases (CSPs) and mobile phase additives in high-performance liquid chromatography (HPLC); CSPs in gas chromatography (GC); and background electrolyte additives (BGE), chiral ligands and chiral selectors (CSs) in capillary electrophoresis (CE). This review focuses on the applications of CILs in HPLC and CE for the separation of enantiomers in the past five years. The mechanism for separating enantiomers was explained, and the prospect of the application of CILs in chiral liquid chromatography (LC) and CE analysis was also discussed.

Selective extraction of apixaban from plasma by dispersive solid-phase microextraction using magnetic metal organic framework combined with molecularly imprinted polymer nanocomposite

This research aims to synthesize a specific and efficient sorbent to use in the extraction of apixaban from human plasma samples and its determination by high-performance liquid chromatography-tandem mass spectrometry. High specific surface area of metal-organic framework, magnetic property of iron oxide nanoparticles, selectively of molecular imprinted polymer toward the analyte, and the combination of dispersive solid-phase extraction method with a sensitive analysis system provided an efficient analytical method. In this study, first, a molecularly imprinted polymer combined with magnetic metal organic framework nanocomposite was prepared and then characterized using different techniques. Then the sorbent particles were used for selective extraction of the analyte from plasma samples. The efficiency of the method was improved by optimizing effective parameters. According to the validation results, wide linear range (1.02-200 ng mL-1 ), acceptable coefficient of determination (0.9938), low limit of detection (0.32 ng mL-1 ) and limit of quantification (1.02 ng mL-1 ), high extraction recovery (78%), and good precision (relative standard deviations ≤ 2.9% for intra- (n = 6) and interday (n = 6) precisions) were obtainable using the proposed method. These outcomes showed the high potential of the proposed method for screening apixaban in the human plasma samples.

Synthesis of magnetic molecular imprinted polymer with a new functional monomer for dispersive micro solid phase extraction of captopril from wastewater and biological samples and determination by UV-Vis spectrophotometry

A magnetic molecularly imprinted polymer (MMIP) was fabricated for captopril by surface polymerization of Fe₃O₄@SiO₂ nanoparticles using a new functional monomer of N-(allylcarbamothioyl)-2-chlorobenzamide. It was then employed as a selective nanosorbent for dispersive magnetic micro solid phase extraction (DM-μ-SPE) of captopril from biological and wastewater samples. To characterize the physicochemical properties of the MMIP, different analytical methods such as the vibrating sample magnetometer, field emission scanning electron microscopy, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy were utilized. To gain the maximum extraction recovery of captopril, the influence of various operating conditions was investigated and experimental settings optimized. After the extraction step, the concentration of captopril was measured by UV-Vis spectrophotometer at 245 nm. The assessments demonstrated that the MMIP provides higher extraction efficiency in comparison to magnetic non-imprinted polymer, suggesting the establishment of selective recognition binding sites at the MMIP surface. The method depicted desirable figures of merit of a low detection limit of 0.16 μg L^-1, a limit of quantification of 0.50 μg L^-1, a linear dynamic range of 0.50-22.0 μg L^-1, and an acceptable preconcentration factor of 333. The magnetic MIP was successfully employed for preconcentration and extraction of trace amounts of captopril in real samples, such as human blood serum, urine, and wastewater samples, with recoveries in the range 95.7 to 102.6% and relative standard deviations < 5%.

Electropolymerized molecularly imprinted polypyrrole film for dimethoate sensing: investigation on template removal after the imprinting process

The development of ultrasensitive analytical detection methods for organophosphorus pesticides such as dimethoate (DMT) plays a key role in healthy food production. DMT is an inhibitor of acetylcholinesterase (AChE), which can lead to the accumulation of acetylcholine and result in symptoms related to the autonomous and central nervous systems. Herein, we report the first spectroscopic and electrochemical study on template removal after an imprinting process from a polypyrrole-based molecularly imprinted polymer (PPy-MIP) film for the detection of DMT. Several template removal procedures were tested and evaluated using X-ray photoelectron spectroscopy. The most effective procedure was achieved in 100 mM NaOH. The proposed DMT PPy-MIP sensor exhibits a limit of detection of (8 ± 2) × 10^-12 M.

Shear-induced phase transition in the aqueous solution of an imidazolium-based ionic liquid

An ionic liquid (IL) is a salt in the liquid state that consists of a cation and an anion, one of which possesses an organic component. Because of their non-volatile property, these solvents have a high recovery rate, and, hence, they are considered as environment-friendly green solvents. It is necessary to study the detailed physicochemical properties of these liquids for designing and processing techniques and find suitable operating conditions for IL-based systems. In the present work, the flow behavior of aqueous solutions of an imidazolium-based IL, 1-methyl-3-octylimidazolium chloride, is investigated, where the dynamic viscosity measurements indicate non-Newtonian shear thickening behavior in the solutions. Polarizing optical microscopy shows that the pristine samples are isotropic and transform into anisotropic after shear. These shear thickened liquid crystalline samples change into an isotropic phase upon heating, which is quantified by the differential scanning calorimetry. The small angle x-ray scattering study revealed that the pristine isotropic cubic phase of spherical micelles distort into non-spherical micelles. This has provided the detailed structural evolution of mesoscopic aggregates of the IL in an aqueous solution and the corresponding viscoelastic property of the solution.

Aptamer affinity-based microextraction in-line coupled to capillary electrophoresis mass spectrometry using a porous layer/nanoparticle -modified open tubular column

An aptamer affinity based microextraction column is developed to be directly in-line coupled to capillary electrophoresis-mass spectrometry (CE-MS) for analyzing mycotoxins in food samples. Single-stranded DNA aptamers for selective recognition of aflatoxin B1 (AFB1) and ochratoxin A (OTA) targets are co-immobilized via covalent bonds on the surface of the inlet end of a capillary, which is pre-modified with three-dimensional porous layer and gold nanoparticles to enhance the specific surface area and loading capacity. The outlet of the capillary is designed as a porous tip to serve as the spray source for injection to the mass spectrometry. All the necessary processes for pretreatment and analysis of a sample are accomplished in one injection, including aptamer affinity-based microextraction, CE separation and MS detection of analytes. AFB1 and OTA are simultaneously determined in a wide linear range with sample consumption of only 1 μL and the limit-of-detection as low as 1 pg/mL. The microextraction column exhibits excellent repeatability and stability, which can be used over 45 runs within a month with CE separation efficiency and only MS intensity slightly decreased. Mycotoxins in three kinds of cereal based infant foods are accurately analyzed using the proposed method. The study provides a robust and universal approach that would have potential applications in a variety of analytical fields based on selective molecular recognition coupling to CE-MS analysis.

Paper-Based Molecular-Imprinting Technology and Its Application

Paper-based analytical devices (PADs) are highly effective tools due to their low cost, portability, low reagent accumulation, and ease of use. Molecularly imprinted polymers (MIP) are also extensively used as biomimetic receptors and specific adsorption materials for capturing target analytes in various complex matrices due to their excellent recognition ability and structural stability. The integration of MIP and PADs (MIP-PADs) realizes the rapid, convenient, and low-cost application of molecular-imprinting analysis technology. This review introduces the characteristics of MIP-PAD technology and discusses its application in the fields of on-site environmental analysis, food-safety monitoring, point-of-care detection, biomarker detection, and exposure assessment. The problems and future development of MIP-PAD technology in practical application are also prospected.

Application of a reversed-phase ionic liquid dispersive liquid-liquid microextraction method for the extraction and preconcentration of domoic acid from urine samples

A simple and efficient sample extraction and preconcentration method based on reversed-phase ionic liquid dispersive liquid-liquid microextraction (RP-IL-DLLME) had been developed and used to quantify the domoic acid in human urine samples. The analysis was performed by ultra-performance liquid chromatography and photodiode array detection. During the procedure, hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C₄mim] BF₄ as dispersive solvent and NaOH solution was chosen as extraction solvent. Some important parameters in the method were investigated to get high enrichment factors. Under optimal conditions, the linearity of the method was in the range of 0.1–10 ng mL⁻¹ and the correlation coefficient was above 0.9996. The relative standard deviations (RSDs) of the developed methods for intra-day (n = 5) and inter-day (n = 5) precision ranged from 1.9 to 3.9%. Meanwhile, limit of detection (LOD) was 0.03 ng mL⁻¹(S/N = 3) and that of quantification (LOQ) was 0.1 ng mL⁻¹(S/N = 10) with the enrichment factors (EF) being 230. Eventually, the proposed method was successfully applied to the determination of Dominic acid in human urine samples.

Kill two birds with one stone: Selective and fast removal and sensitive determination of oxytetracycline using surface molecularly imprinted polymer based on ionic liquid and ATRP polymerization

Oxytetracycline (OTC) residue in food and environment has potential threats to ecosystem and human health, thus its sensitive monitoring and effective elimination are very important. In this work, a new molecularly imprinted polymer (MIP) composite was prepared through atom transfer radical polymerization by using OTC as template, gold nanoparticles modified carbon nanospheres (Au-CNS) as supporter, ionic liquids (IL) as functional monomer and cross-linking agent. The obtained MIP-IL@Au-CNS composite was characterized by Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. It displayed high imprinting factor (5.50) and adsorption capacity (56.7 mg g^-1), and could achieved the adsorption equilibrium in short time (about 15 min). Results also illustrated that the adsorption process basically conformed to the quasi-second-order kinetic model and Freundlich model, and MIP-IL@Au-CNS could be recycled at least 5 times. Furthermore, a sensitive OTC electrochemical sensor was developed by combining MIP-IL@Au-CNS with IL-modified carbon nanocomposites (IL@N-rGO-MWCNT). The resulting sensor demonstrated a linear response to OTC in the wide range of 0.02-20 μM, and the detection limit was down to 5 nM. It also had the advantages of high selectivity, fast elution/regeneration and simple construction procedure. The sensor had been applied to the detection of real samples, and acceptable recovery (96.4%-106%) and RSD (3.2%-6.2%) were obtained. This work expands the application of IL-based MIP in pollutant monitoring and enriching.

Development of Molecularly Imprinted Polymers for Fenthion Detection in Food and Soil Samples

Modern agricultural production is greatly dependent on pesticide usage, which results in severe environmental pollution, health risks and degraded food quality and safety. Molecularly imprinted polymers are one of the most prominent approaches for the detection of pesticide residues in food and environmental samples. In this research, we prepared molecularly imprinted polymers for fenthion detection by using beta-cyclodextrin as a functional monomer and a room-temperature ionic liquid as a cosolvent. The characterization of the developed polymers was carried out. The polymers synthesized by using the room-temperature ionic liquid as the cosolvent had a good adsorption efficiency of 26.85 mg g⁻¹, with a short adsorption equilibrium time of 20 min, and the results fitted well with the Langmuir isotherm model and pseudo-second-order kinetic model. The polymer showed cross-selectivity for methyl-parathion, but it had a higher selectivity as compared to acetamiprid and abamectin. A recovery of 87.44–101.25% with a limit of detection of 0.04 mg L⁻¹ and a relative standard deviation of below 3% was achieved from soil, lettuce and grape samples, within the linear range of 0.02–3.0 mg L⁻¹, using high-performance liquid chromatography with an ultraviolet detector. Based on the results, we propose a new, convenient and practical analytical method for fenthion detection in real samples using improved imprinted polymers with room-temperature ionic liquid.

Investigation of Thermodynamic, Kinetic, and Isothermal Parameters for the Selective Adsorption of Bisphenol A

Herein, a novel imprinted solid-phase extraction cartridge was fabricated to investigate the kinetic, thermodynamic, and isothermal parameters for the selective adsorption of Bisphenol A (BPA). The imprinted polymeric cartridges (BMC) for the BPA adsorption were fabricated in the presence of a template and functional monomer using the in situ polymerization technique. To prove the efficiency and selectivity of BMC, the nonimprinted polymeric cartridges (BNC) and the empty polymeric cartridges (EC) were also fabricated with and without functional monomer using the same manner for the preparation of BMC. The characterization of cartridges was performed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, and swelling tests. BPA removal studies were performed by analyzing some parameters such as temperature, BPA concentration, flow rate, salt type, and concentration. The highest capacity was determined as 103.2 mg BPA/g polymer for a 0.75 mL/min flow rate of 0.75 M (NH₄)₂SO₄ containing 200 mg/L BPA solution at 50 °C. NaOH (1.0 M) was used as a desorption agent. The reusability performance was examined by performing 10 consecutive cycles. The solid-phase extraction (SPE) performance was also checked to determine the enrichment and extraction recovery factors for tap water and synthetic wastewater samples. Temkin, Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were applied to BPA adsorption data examining the adsorption mechanism, surface properties, and adsorption degree. The most suitable isotherm model for BPA adsorption was determined as the Langmuir isotherm model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were investigated to reveal the thermodynamics of adsorption. Adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated using the thermodynamic equilibrium constant (thermodynamic equilibrium constant, K°) values that change with temperature. It was determined that BPA adsorption was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) and entropy increased (ΔS° > 0) at the temperatures studied in the BPA adsorption process. The rate control step in the adsorption process was examined by applying pseudo-first-order and pseudo-second-order kinetic models to the adsorption data for the investigations of BPA adsorption kinetics, and the pseudo-second-order kinetic model was found to be more suitable for describing BPA adsorption kinetics. In examining the selectivity of cartridges, structural analogues of hydroquinone, phenol, β-estradiol, and 8-hydroxyquinoline were tested.

Polyoxometalate-based materials in extraction, and electrochemical and optical detection methods: A review

Polyoxometalates (POMs) as metal-oxide anions have exceptional properties like high negative charges, remarkable redox abilities, unique ligand properties and availability of organic grafting. Moreover, the amenability of POMs to modification with different materials makes them suitable as precursors to further obtain new composites. Due to their unique attributes, POMs and their composites have been utilized as adsorbents, electrodes and catalysts in extraction, and electrochemical and optical detection methods, respectively. A survey of the recent progress and developments of POM-based materials in these methods is therefore desirable, and should be of great interest. In this review article, POM-based materials, their properties as well as their identification methods, and analytical applications as adsorbents, electrodes and catalysts, and corresponding mechanisms of action, where relevant, are reviewed. Some current issues of the utilization of these materials and their future prospects in analytical chemistry are discussed.

Green Chemistry and Molecularly Imprinted Membranes

Technological progress has made chemistry assume a role of primary importance in our daily life. However, the worsening of the level of environmental pollution is increasingly leading to the realization of more eco-friendly chemical processes due to the advent of green chemistry. The challenge of green chemistry is to produce more and better while consuming and rejecting less. It represents a profitable approach to address environmental problems and the new demands of industrial competitiveness. The concept of green chemistry finds application in several material syntheses such as organic, inorganic, and coordination materials and nanomaterials. One of the different goals pursued in the field of materials science is the application of GC for producing sustainable green polymers and membranes. In this context, extremely relevant is the application of green chemistry in the production of imprinted materials by means of its combination with molecular imprinting technology. Referring to this issue, in the present review, the application of the concept of green chemistry in the production of polymeric materials is discussed. In addition, the principles of green molecular imprinting as well as their application in developing greenificated, imprinted polymers and membranes are presented. In particular, green actions (e.g., the use of harmless chemicals, natural polymers, ultrasound-assisted synthesis and extraction, supercritical CO2, etc.) characterizing the imprinting and the post-imprinting process for producing green molecularly imprinted membranes are highlighted.

Ionic liquid-based magnetic nanoparticles for magnetic dispersive solid-phase extraction: A review

Due to their highly tunable nature and outstanding physicochemical properties, ionic liquids (ILs) have been widely reported for use in the synthesis of multitudinous magnetic nanoparticles (MNPs). IL-based magnetic nanoparticles (IL-MNPs) have great potential in magnetic dispersive solid-phase extraction (MDSPE). At present, IL-MNPs have been successfully applied in the pretreatment of MDSPE samples from medicines, pesticides, veterinary drugs, heavy metals, dyes, additives, and proteins in agricultural products, foods and beverages, environmental water, and biological samples. In this review, the preparation of IL-MNPs and their application in MDSPE are comprehensively summarized. The structural characteristics of the introduced ILs used to prepare the IL-MNPs and the synthetic routes employed to obtain the IL-MNPs are described, including physical coating and chemical bonding methods. The IL-MNPs are then classified and described according to different modified materials, including silica-based materials, carbon-based materials, metal-organic frameworks, molecularly imprinted polymers and other interesting large/small molecules. Finally, the research prospects and development directions of IL-MNPs in the context of MDSPE are further identified.

Room-Temperature, Ionic-Liquid-Enhanced, Beta-Cyclodextrin-Based, Molecularly Imprinted Polymers for the Selective Extraction of Abamectin

To ensure environmental protection and food quality and safety, the trace level detection of pesticide residues with molecularly imprinted polymers using a more economic, reliable, and greener approach is always demanded. Herein, novel, enhanced, imprinted polymers based on beta-cyclodextrin, using room-temperature, ionic liquid as a solvent for abamectin were developed with a simple polymerization process. The successful synthesis of the polymers was verified, with morphological and structural characterization performed via scanning electron microscope analysis, nitrogen adsorption experiments, and thermogravimetric analysis. The imprinted polymers showed good adsorption ability, which was confirmed with a pseudo-second-order kinetic model and a Langmuir isotherm model, as they exhibit a theoretical adsorption of 15.08 mg g⁻¹ for abamectin. The polymers showed high selectivity for abamectin and significant reusability without significant performance loss. The MIPs were used to analyze abamectin in spiked apple, banana, orange, and grape samples, and as a result, a good recovery of 81.67−101.47%, with 1.26−4.36% relative standard deviation, and limits of detection and quantitation of 0.02 µg g⁻¹ and 0.05 µg g⁻¹, respectively, was achieved within a linear range of 0.03−1.50 µg g⁻¹. Thus, room-temperature, ionic-liquid-enhanced, beta-cyclodextrin-based, molecularly imprinted polymers for the selective detection of abamectin proved to be a convenient and practical platform.

Aggregation-induced emission monomer-based fluorescent molecularly imprinted poly(ionic liquid) synthesized by a one-pot method for sensitively detecting 4-nitrophenol

An aggregation-induced emission monomer-based fluorescent molecularly imprinted poly(ionic liquid) (AIE-FMIPIL) was synthesized for the first time with an AIE probe 4-(1,2,2-triphenylvinyl)phenyl acrylate (TPE), and an ionic liquid as dual functional monomers, and an ionic liquid as cross-linker. AIE-FMIPIL displayed a sphere-like shape and its average diameter was 410 nm. The absolute quantum yields of TPE and AIE-FMIPIL were 9.23% and 12.61%, respectively. The synergetic effect of TPE in the AIE-FMIPIL framework contributed to the higher quantum yield of AIE-FMIPIL. 4-Nitrophenol (4-NP) efficiently quenched AIE-FMIPIL with high fluorescence based on the Förster resonance energy transfer mechanism. The synthesized AIE-FMIPIL sensor was highly sensitive for 4-NP detection (linear range, 0.02-1.5 μM) in the optimal detection condition, with a low detection limit of 10 nM (S/N = 3). AIE-FMIPIL showed increased sensitivity and quenching efficiency compared with AIE-FMIP comprising a traditional monomer and cross-linker. AIE-FMIPIL exhibited selective binding to 4-NP because of the imprinted sites. AIE-FMIPIL was adopted to detect 4-NP in environmental samples.

Cobalt (II)-Mediated Molecularly Imprinted Polymer as a Monolithic Stationary Phase for Separation of Racemic Citronellal by Liquid Chromatography

A metal-mediated molecularly imprinted polymer (MMIP) monolithic column was prepared as the stationary phase for high-performance liquid chromatography (HPLC) and applied to the enantiomeric separation of rac-citronellal. MMIP column was prepared through in situ copolymerizations with the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate/[BMIM][BF₄] as the primary pore-forming agent and cobalt(II) acetate as the metal pivot. Interactions between polymer components in the synthesized monolith were assessed by FTIR to identify the functional groups. The monolith morphology was characterized with SEM, and the template removal was detected by UV Spectrophotometry at 253 nm. In this study, (R)-(+)-citronellal was used as a template, whereas 4-vinylpyridine (4-VP) was employed as the functional monomer with two monomer crosslinkers, trimethylolpropane trimethacrylate (TRIM), and ethylene glycol dimethacrylate (EDMA). The ternary mixture of porogenic solvent consisted of [BMIM][BF₄], dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) with the applied ratio of 1 : 1:1 (v/v) and 10 : 1:5 (v/v) for the preparation of MMIP using TRIM and EDMA crosslinkers, respectively. Co(II) ion was added to the porogenic solvent before being mixed with the functional monomer and the crosslinker mixtures. Separating the rac-citronellal was achieved on the synthesized MMIP, showing better selectivity than the monolithic metal-mediated nonimprinted polymer (MNIP), nonimprinted polymer (NIP), and molecularly imprinted polymer (MIP).

Improving sorption performance of a molecularly imprinted monolithic column by doping mesoporous molecular sieve SBA-15

For the first time a hybrid molecularly imprinted polymer (MIP) doped with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS)-modified mesoporous molecular sieve SBA-15 for target peptide recognition has been developed. Zinc acrylate and methacrylic acid were used as binary functional monomers, and ethylene dimethacrylate was used as cross-linking agent to prepare an imprinted monolith against Val-Tyr-Ala-Leu-Lys(glutarylation) (VYALK_glu). The morphology of the polymers was characterized by scanning electron microscopy, FT-IR spectroscopy, energy dispersive spectroscopy, and ¹H NMR. The SBA-15-MPS MIP showed high recovery of 87.1% and the IF of 12.9 for the enrichment of the template peptide. When the template peptide concentration ranged from 5 to 90 μg mL^-1, the correlation coefficients (R²) for the calibration function obtained was better 0.999. The limit of detection (LOD, 0.30 μg mL^-1) and limit of quantification (LOQ, 1.0 μg mL^-1) were achieved for signal-to-noise ratios of 3:1 and 10:1, respectively. When other kinds of synthetic peptides were used as analogs, the selectivity of the SBA-15-MPS MIP was much better than the SBA-15-MPS NIP (without template peptides) with relative selectivity coefficients of 52.8-265. In contrast, little quinolones and biogenic amines are adsorbed with the SBA-15-MPS MIP. The SBA-15-MPS MIP could enrich VYALK_glu from spiked histone digestion with the average recovery of 87.8% and the relative standard deviation (RSD) of 0.99%. As a conclusion, doping of SBA-15 is an effective approach to the improvement of performance of molecularly imprinted monolith.