Preparation of magnetic molecularly imprinted polymers with double functional monomers for the extraction and detection of chloramphenicol in food

Advances in magnetic analytical extraction techniques for detecting antibiotic residues in edible samples

The widespread use of antibiotics in agricultural and animal husbandry to treat bacterial illnesses has resulted in a rise in antibiotic-resistant bacteria. These bacteria can grow when antibiotic residues are present in food items, especially in edible animal products. As a result, it is crucial to monitor and regulate the amounts of antibiotics in food. Magnetic analytical extractions (MAEs) have emerged as a potential approach for extracting antibiotic residues from food using magnetic nanoparticles (MNPs). Recent improvements in MAEs have resulted in the emergence of novel MNPs with better selectivity and sensitivity for the extraction of antibiotic residues from food samples. Consequently, this review paper addresses current developments in MAE for extracting antibiotic residues from edible samples. It also provides a critical analysis of contemporary MAE practices. The current issues and potential future developments in this field are also discussed, thereby providing a framework for future study paths.

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.

Application of molecularly imprinted polymers as the sorbent for extraction of chemical contaminants from milk

Milk is one of the most consumed and balanced foods with a high nutritional value which could be contaminated with different chemicals such as antibiotics, melamine, and hormones. Because of the low concentration of these compounds and the complexity of milk samples, there is a need to use sample pre-treatment methods for purification and preconcentration of these compounds before instrumental techniques. Molecular imprinting polymers (MIPs) are synthetic materials with specific recognition sites complementary to the target molecule. MIPs have selectivity for a specific analyte or group of analytes, which could be used to extract and determine contaminants and remove the interfering compounds from complex samples. Compared to other techniques, sample preparation, high selectivity, excellent stability, and low cost are other advantages of using MIPs. The present article gives an overview of the synthesis of MIPs and their application for extracting antibiotics, hormones, and melamine in milk samples.

Application of Sorbent-Based Extraction Techniques in Food Analysis

This review presents an outline of the application of the most popular sorbent-based methods in food analysis. Solid-phase extraction (SPE) is discussed based on the analyses of lipids, mycotoxins, pesticide residues, processing contaminants and flavor compounds, whereas solid-phase microextraction (SPME) is discussed having volatile and flavor compounds but also processing contaminants in mind. Apart from these two most popular methods, other techniques, such as stir bar sorptive extraction (SBSE), molecularly imprinted polymers (MIPs), high-capacity sorbent extraction (HCSE), and needle-trap devices (NTD), are outlined. Additionally, novel forms of sorbent-based extraction methods such as thin-film solid-phase microextraction (TF-SPME) are presented. The utility and challenges related to these techniques are discussed in this review. Finally, the directions and need for future studies are addressed.

Development of Magnetic Molecularly Imprinted Polymer Coupled Nanospray Ion Source for Analysis of Cephalosporin Antibiotics in Food Samples

A magnetic molecularly imprinted polymer (MMIP) coupled nanospray ion source was developed for analysis of cephalosporin antibiotics in food samples. MIP coated Fe₃O₄ nanospheres were prepared for magnetic solid-phase extraction (MSPE) of the antibiotics in the extract of samples and then integrated into the nanospray capillary for further desorption and mass spectrometry analysis. The developed device combines the advantages of high extraction efficiency of MSPE, unique selectivity of MIPs, and fast analysis speed of ambient ionization mass spectrometry (AIMS). Five cephalosporin antibiotics in milk, egg, and beef samples were analyzed using the developed methods. High sensitivities with limits of detection (LODs) from 0.3 to 0.5 μg kg^-1 were achieved for cephalosporin antibiotics in milk, egg, and beef samples, respectively. Good linearity, determination coefficient values (R² > 0.992), and precision (RSD < 15%) with recoveries ranging from 72.6% to 115.5% were obtained using the spiked milk, egg, and beef sample matrices.

Magnetic nanofluid based on green deep eutectic solvent for enrichment and determination of chloramphenicol in milk and chicken samples by high-performance liquid chromatography-ultraviolet: Optimization of microextraction

In this work, magnetic nanofluid based on a deep eutectic solvent that constricts through a simple and easy route, and subsequently applied for the preconcentration and microextraction of chloramphenicol (CAP) as a hazardous drug from milk and chicken samples via syringe-to-syringe microextraction prior to its determination by high-performance liquid chromatography-ultraviolet (HPLC-UV). In addition, the optimum conditions of effective factors were searched by the central composite design (CCD), and subsequently, at their optimum value, the figures of merit were evaluated. Also, the suggested method illustrated a low limit of detection (0.2 ng mL^-1), a low limit of quantitation (0.67 ng mL^-1), and a good linear range with an R² of 0.996. The CAP relative recoveries in milk and chicken samples were 90.3%-95.1%, with relative standard deviations lower than 4.2%. The current enhancement technique is simple, easy, and rapid, which makes it suitable for quantification of CAP by HPLC-UV at trace levels in complicated materials with reliable and reproducible results.

Recent Advances in Molecularly Imprinted Polymers for Antibiotic Analysis

The abuse and residues of antibiotics have a great impact on the environment and organisms, and their determination has become very important. Due to their low contents, varieties and complex matrices, effective recognition, separation and enrichment are usually required prior to determination. Molecularly imprinted polymers (MIPs), a kind of highly selective polymer prepared via molecular imprinting technology (MIT), are used widely in the analytical detection of antibiotics, as adsorbents of solid-phase extraction (SPE) and as recognition elements of sensors. Herein, recent advances in MIPs for antibiotic residue analysis are reviewed. Firstly, several new preparation techniques of MIPs for detecting antibiotics are briefly introduced, including surface imprinting, nanoimprinting, living/controlled radical polymerization, and multi-template imprinting, multi-functional monomer imprinting and dummy template imprinting. Secondly, several SPE modes based on MIPs are summarized, namely packed SPE, magnetic SPE, dispersive SPE, matrix solid-phase dispersive extraction, solid-phase microextraction, stir-bar sorptive extraction and pipette-tip SPE. Thirdly, the basic principles of MIP-based sensors and three sensing modes, including electrochemical sensing, optical sensing and mass sensing, are also outlined. Fourthly, the research progress on molecularly imprinted SPEs (MISPEs) and MIP-based electrochemical/optical/mass sensors for the detection of various antibiotic residues in environmental and food samples since 2018 are comprehensively reviewed, including sulfonamides, quinolones, β-lactams and so on. Finally, the preparation and application prospects of MIPs for detecting antibiotics are outlined.

Extraction and detection of morin from Sanghuangporus lonicericola by magnetic molecularly imprinted polymers coupled with HPLC analysis

In this study, morin magnetic molecularly imprinted polymers (Morin-MMIPs) were synthesized based on magnetic nanoparticles and surface molecularly imprinted technology with superparamagnetism and extraction selectivity. The polymers allowed the separating of morin from complex matrices in the presence of an external magnetic field with no need for centrifugation or filtration. The microstructure of the polymers was characterized by scanning electron microscopy and transmission electron microscopy. Meanwhile, the functional group and magnetic properties of the polymers were characterized using Fourier transform infrared spectroscopy (FT-IR) and magnetic vibration meter (VSM). The maximum adsorption capacity of MMIPs was 3.24 mg/g, which was 2.55 times higher than that of MNIPs (1.27 mg/g). Morin was quantified by HPLC-DAD, which showed good linearity in the concentration range of 0.05-60 µg/ml with the correlation coefficient R²  = 0.9993. The limit of detection (LOD) was 0.08 µg/ml, and the spiked recoveries were 87.5-106.8%. The calculation of the adsorption isotherm and kinetic model revealed the adsorption mechanisms, and the adsorption process was consistent with the Langmuir adsorption isotherm and pseudo-secondary kinetic models. Likewise, the material has been successfully used to extract and separate morin from food samples. The method reported in this paper has the advantages of fast adsorption speed, high selectivity, and environmental friendliness. It provided a reliable method for the separation and detection of morin or other natural products.

Fabrication and characterization of magnetic molecularly imprinted polymer based on deep eutectic solvent for specific recognition and quantification of vanillin in infant complementary food

A magnetic molecularly imprinted polymer based on deep eutectic solvent was synthesized for specific identification and quantification of vanillin. Fe₃O₄@SiO₂-CC and deep eutectic solvent were applied as the carrier of magnetic material and functional monomer, respectively. According to composition and morphology characterizations and adsorption kinetics, the imprinted polymer had excellent advantages on adsorption capacity and identification specificity for vanillin compared with non-imprinted polymer, while its reusability still remained stable. According to the high-performance liquid chromatography, the detection method based on imprinted polymer produced satisfactory analytical results. The limit of quantification was 0.2 μg·mL^-1. The mean spiked recoveries for vanillin ranged from 91.2% to 100.2% with intra- and inter-day precision were both less than 7.2%. Compared to traditional extraction methods, this method presented best adsorption and extraction performances. In summary, the method could be further applied to the specific separation and quantification of vanillin in infant complementary food.

Comparison and recent progress of molecular imprinting technology and dummy template molecular imprinting technology

Molecular imprinting technology for the preparation of polymers with specific molecular recognition function had become one of the current research hotspots. It has been widely applied in chromatographic separation, antibody and receptor mimetics, solid-phase extraction, bio-sensors, and other fields in the last decades. In this study, molecular imprinting technology was summarized from the points of templates and dummy templates, and four typical target analytes were selected to compare the differences between templates and dummy templates. The current status and prospects of molecular imprinting technology were also proposed.

Molecularly Imprinted Polymers for Dispersive (Micro)Solid Phase Extraction: A Review

The review describes the development of batch solid phase extraction procedures based on dispersive (micro)solid phase extraction with molecularly imprinted polymers (MIPs) and magnetic MIPs (MMIPs). Advantages and disadvantages of the various MIPs for dispersive solid phase extraction and dispersive (micro)solid phase extraction are discussed. In addition, an effort has also been made to condense the information regarding MMIPs since there are a great variety of supports (magnetite and magnetite composites with carbon nanotubes, graphene oxide, or organic metal framework) and magnetite surface functionalization mechanisms for enhancing MIP synthesis, including reversible addition-fragmentation chain-transfer (RAFT) polymerization. Finally, drawbacks and future prospects for improving molecularly imprinted (micro)solid phase extraction (MIMSPE) are also appraised.

Imprinting Technology for Effective Sorbent Fabrication: Current State-of-Art and Future Prospects

In the last 10 years, we have witnessed an extensive development of instrumental techniques in analytical methods for determination of various molecules and ions at very low concentrations. Nevertheless, the presence of interfering components of complex samples hampered the applicability of new analytical strategies. Thus, additional sample pre-treatment steps were proposed to overcome the problem. Solid sorbents were used for clean-up samples but insufficient selectivity of commercial materials limited their utility. Here, the application of molecularly imprinted polymers (MIPs) or ion-imprinted polymers (IIPs) in the separation processes have recently attracted attention due to their many advantages, such as high selectivity, robustness, and low costs of the fabrication process. Bulk or monoliths, microspheres and core-shell materials, magnetically susceptible and stir-bar imprinted materials are applicable to different modes of solid-phase extraction to determine target analytes and ions in a very complex environment such as blood, urine, soil, or food. The capability to perform a specific separation of enantiomers is a substantial advantage in clinical analysis. The ion-imprinted sorbents gained interest in trace analysis of pollutants in environmental samples. In this review, the current synthetic approaches for the preparation of MIPs and IIPs are comprehensively discussed together with a detailed characterization of respective materials. Furthermore, the use of sorbents in environmental, food, and biomedical analyses will be emphasized to point out current limits and highlight the future prospects for further development in the field.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

A simple fluorescent strategy based on triple-helix molecular switch for sensitive detection of chloramphenicol

A simple fluorescent strategy based on the formation of triple-helix molecular switch (THMS) between a signal transduction probe (STP) and an aptamer (Apt) was constructed for the determination of chloramphenicol (CAP). A weak fluorescence intensity was observed for STP solution due to the proximity of fluorophore and quencher through intramolecular DNA hybridization, causing the fluorescence quenching. The fluorescence intensity of the system was significantly enhanced after the addition of Apt. It was attributed to the formation of THMS between the Apt and STP through the Watson-Crick and Hoogsteen base pairing, resulting in the restoration of fluorescence because of the long distance between the fluorophore and quencher of STP. The fluorescence intensity of the system decreased due to the release of STP caused by the specific binding between Apt and CAP. The quantitative analysis of CAP could be achieved based on the decreased fluorescence intensity. The parameters affecting the performance of THMS including the Apt arm length, pH of buffer solution, Mg²⁺ concentration and the formation time of THMS were investigated in detail. Under the optimal conditions (Apt arm length of 9 bases, pH of 6.5, 2.5 × 10³ μmol L^-1 Mg²⁺, THMS formation time of 30 min), the decreased fluorescence intensity and the concentration of chloramphenicol were linear in the range of 5.0 × 10^-3-2.0 × 10^-1 μmol L^-1 with the correlation coefficient of 0.9963. The limit of detection was 1.2 nmol L^-1. Subsequently, the developed method was applied to the analysis of chloramphenicol in honey sample, and the recovery was between 84.5% and 103.0% with relative standard deviation less than 4.6%.

Preparation of Restricted Access Media-Molecularly Imprinted Polymers for the Detection of Chloramphenicol in Bovine Serum

Chloramphenicol- (CAP-) restricted access media-molecularly imprinted polymers (CAP-RAM-MIPs) were prepared by precipitation polymerization using CAP as a template molecule, 2-diethylaminoethyl methacrylate (DEAEM) as a functional monomer, ethylene glycol dimethyl acrylate (EDMA) as a crosslinking agent, glycidyl methacrylate (GMA) as an outer hydrophilic functional monomer, and acetonitrile as a pore former and solvent. The CAP-RAM-MIPs were successfully characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The adsorption performance was investigated in detail using static, dynamic, and selective adsorption experiments. Adsorption equilibrium could be reached within 11 min. The CAP-RAM-MIPs had a high adsorption rate and good specific adsorption properties. Scatchard fitting curves indicated there were two binding sites for CAP-RAM-MIPs. Adsorption was Freundlich multilayer adsorption and consistent with the quasi-second kinetic model. Using CAP-RAM-MIPs for selective separation and enrichment CAP in bovine serum in combination with high-performance liquid chromatography (HPLC), CAP recovery ranged from 94.1 to 97.9% with relative standard deviations of 0.7-1.5%. This material has broad application prospects in enrichment and separation.

Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle

In this research work, a biosensor with a dual recognition system was fabricated and founded on a combination of aptasensing and the molecular imprinting union of the chloramphenicol (CAP) selective detection. CAP, is an antibiotic, was applied in veterinary and human in order to treat gram-positive and gram-negative infections. It is worth mentioning that CAP residue brings about earnest side effects on human health. According to this, in this sensing system, 3-aminomethyl pyridine functionalized graphene oxide (GO) (3-ampy-RGO) has been coated on the surface of GCE. Afterwards, the silver nanoparticle (AgNPs) was coated on the 3-ampy-RGO/GCE and, then, the CAP complex-amino-aptamer (NH₂-Apt[CAP]) was attached to the AgNP/3-ampy-RGO/GCE using a kind of bonding formation of Ag-N. In this sense, it is worth noting that the resorcinol electropolymerization around the complex of aptamer/CAP would confine the complex and, then, retain the aptamer. Following the CAP removal, the MIP cavity, as it was supposed, synergistically acted with that of the embedded aptamer in order to construct a nanohybrid receptor. Interestingly, the double exact property of the molecular imprinting polymers and aptamers led to the superb sensing properties. In the mentioned system it was illustrated that the linear range was from 1.0 pM to 1.0 nM with the detection limit of 0.3 pM; consequently, as observed, it was better than or as good as other similar assays. Moreover, the mentioned system whose activity was observed in the various interferences presence showed great selectivity in detected the CAP. Finally, the designed sensor exhibited outstanding results when applied to detect CAP in milk samples.