Magnetic molecularly imprinted polymer extraction of chloramphenicol from honey

A sensitive enzyme-free electrochemical sensor based on ZnWO4@co-MNPC@MIP for specific recognition and determination of chloramphenicol in milk sample

We have carefully built a new chloramphenicol (CAP) electrochemical sensor, which takes the zinc tungstate @ cobalt magnetic nanoporous carbon @ molecularly imprinted polymer (ZnWO4@Co-MNPC@MIP) as the core. First, we successfully prepared Co-MNPC nanomaterials using an efficient one-step hydrothermal method and a direct carbonization method. Next, we recombined ZnWO4 with Co-MNPC and synthesized the completely new ZnWO4@Co-MNPC complex by using the hydrothermal method. To further improve its performance, we combined ZnWO4@Co-MNPC with a molecular imprinted polymer and coated a molecular imprinted (MIP) shell on the surface of ZnWO4@Co-MNPC by precipitation polymerization. This shell not only gives the sensor a new performance but also gives it a stronger peak current, resulting in a more accurate detection of CAP. Under optimal conditions, the ZnWO4@Co-MNPC@MIP (MMIP) electrode has a stronger CAP detection peak current than the one-component electrode, with a fairly wide linear range: 0.007-200 μM and 200-1400 μM. Even more surprisingly, the detection limit is as low as 0.0027 μM, which allows the sensor to maintain excellent selectivity and stability in the face of various interferences, making it an excellent electrochemically modified electrode. Compared to magnetic non-molecular imprint sensors (MNIPs), MMIP sensors have higher detection efficiency. After practical application, we found that the ZnWO4@Co-MNPC@MIP modified electrode was satisfactory in milk samples.

Electrochemistry of chloramphenicol on laser-induced graphene electrodes and its voltammetric determination in honey

Laser scribing is a promising technology for the rapid and large-scale production of low-cost electrochemical sensors from diverse substrates. Polyimide has been the most popular so far because of its low cost, flexibility and capability of generating high-quality porous graphene films, known as laser-induced graphene (LIG). Herein we report the electrochemistry of chloramphenicol (CAP) on LIG electrodes and its determination in honey samples. LIG electrodes were fabricated by the photothermal conversion of sp3 carbon within the polymeric matrix into sp2 carbon using a CO2 laser cutter. The LIG electrode associated with differential pulse voltammetry (DPV) showed good linearity (R2 > 0.99) in the range from 10 to 160 μmol L-1 with a limit of detection of 1.0 μmol L-1 and good precision (RSD < 5%) for the electrochemical reduction of CAP species. Detection was possible free from the interference of other antibiotics, such as amoxicillin, tetracycline, sulfanilamide, and sulfamethoxazole. Spiked honey samples were analyzed by the standard-addition method and recovery values between 86 and 109% were obtained, which confirmed the absence of sample matrix effects. Therefore, the proposed sensor is an alternative, feasible, low-cost, and powerful analytical tool for the determination of CAP in honey.

Synthesis and characterization of magnetic molecularly imprinted polymers for the rapid and selective determination of clofazimine in blood plasma samples

Clofazimine (CLF) is a riminophenazine derivative and a new therapeutic option with high efficacy for patients with rifampicin-resistant tuberculosis (TB). The blood levels of CLF are low and suboptimal, so therapeutic drug monitoring is required. Prior to this study, there were no molecular imprinting-based solid phase extraction (SPE) sorbents that could be used to determine the blood CLF levels. Hence, we prepared a magnetic molecularly imprinted polymer (MMIPs) to capture CLF. We employed computational selection of a functional monomer and crosslinker and confirmed these selections based on the association constant (K a) and a Job plot. We synthesised MMIPs with two surface modifiers and characterized the polymers. Our computational analysis based on the bond energy revealed that methyl methacrylate (MMA) was the most suitable functional monomer at a CLF-to-MMA molar ratio of 1:4. Based on the bond energy, the most suitable crosslinker was trimethylolpropane trimethacrylate (TRIM) at a CLF-to-TRIM molar ratio of 1:1. We determined the K a of MMA and TRIM in different solvents. Isopropanol produced the highest K a. The Job plot showed that a template-to-MMA-to-TRIM molar ratio of 1:4:20 was optimal to synthesize imprinted polymer in isopropanol. We prepared MMIPs using two different modifiers, namely aminopropyltrimethoxysilane (APTES) and oleic acid (OA), using the ratio determined from the Job plot. Physical characteristic tests carried out using FT-IR, SEM-EDS, PSA, BET and VSM, showed that the synthesis was success with a spherical and uniform agglomeration of particles, also a flat surface with many holes with a particle size of MMIP-APTES and MMIP-OA respectively 0.14 μm and 0.28 μm, showed a surface area for MMIP-APTES is 2874.51 m2/g and MMIP-OA 2913.07 m2/g, exhibiting superparamagnetic properties with a saturation magnetization value of MMIP-APTES 21.1 emu/g-1 and MMIP-OA 49.9 emu/g-1. Adsorption capacity result showed that MMIP-OA fits well with the Langmuir model, while MMIP-APTES fits better with the Freundlich. Application of MMIP-SPE (Magnetic Molecular Imprinted Polymer-Solid Phase Extraction) APTES resulted 92.3 ± 6.1 % and MMIP-SPE-OA 51.5 ± 8.1 % for recovering CLF in blood. The result of selectivity test also showed that MMIP-SPE-APTES is better than MMIP-SPE-OA and selectively recover CLF from human blood plasma existed together with other TB-Drugs. The study result shows that MMIPs with APTES modification can be used for CLF determination in human blood plasma.

An Imine-Based Porous 3D Covalent Organic Polymer as a New Sorbent for the Solid-Phase Extraction of Amphenicols from Water Sample

In this paper, an imine-based porous 3D covalent organic polymer (COP) was synthesized via solvothermal condensation. The structure of the 3D COP was fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and powder X-ray diffractometry, thermogravimetric analysis, and Brunauer-Emmer-Teller (BET) nitrogen adsorption. This porous 3D COP was used as a new sorbent for the solid-phase extraction (SPE) of amphenicol drugs, including chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in aqueous solution. Factors were investigated for their effects on the SPE efficiency, including the types and volume of eluent, washing speed, pH, and salinity of water. Under the optimized conditions, this method gave a wide linear range (0.1-200 ng/mL) with a high correlation coefficient value (R² > 0.99), low limits of detection (LODs, 0.01-0.03 ng/mL), and low limits of quantification (LOQs, 0.04-0.10 ng/mL). The recoveries ranged from 83.98% to 110.7% with RSDs ≤ 7.02%. The good enrichment performance for this porous 3D COP might contribute to the hydrophobic and π-π interactions, the size-matching effect, hydrogen bonding, and the good chemical stability of 3D COP. This 3D COP-SPE method provides a promising approach to selectively extract trace amounts of CAP, TAP, and FF in environmental water samples in ng quantities.

Pulsed-sonochemiluminescence combined with molecularly imprinted polymerized high internal phase emulsion adsorbent for determination of bentazone

A small low-power humidifier with a simple programmable on/off switch was used as a pulsed ultrasound generator. Using this tool, a novel sonochemiluminescence (SCL) method was developed to determine bentazone. To the best of our knowledge, no chemiluminescence method has been proposed to determine this pesticide. Only five studies have been proposed for SCL quantitative applications so far. Therefore, revealing new aspects of SCL promises to develop analytical methods for the quantitative determination of different substances. A molecularly imprinted polymerized high internal phase emulsion (MIP-polyHIPE) was synthesized, bentazone separated from aqueous solutions, and pre-concentrated by the MIP-polyHIPE foam. The adsorption of bentazone on the MIP-polyHIPE adsorbent was theoretically studied by density functional theory through molecular dynamics simulation. Both experimental and simulation results indicated removal and pre-concentration of bentazone by the MIP-polyHIPE adsorbent. Using the proposed SCL method and without pre-concentration process, a linear dynamic range (LDR) of 2.5 × 10^-7-5.0 × 10^-5 mol L^-1 and a limit of detection (LOD) of 8.4 × 10^-8 mol L^-1 were obtained for bentazone with a relative standard deviation of 2.64%. The LDR and LOD were improved to 2.6 × 10^-9-2.0 × 10^-7 mol L^-1 and 8.8 × 10^-10 mol L^-1, respectively, using MIP-polyHIPE adsorbents. The method's application was evaluated by removing and pre-concentration of bentazone from water samples, including well, river, and tap water. The results showed that the pre-concentration factor and recovery percentages were 113-131 times and 93-106%, respectively, using the MIP-polyHIPE absorbent.

Factors Affecting the Analytical Performance of Magnetic Molecularly Imprinted Polymers

During the last few years, separation techniques using molecular imprinting polymers (MIPs) have been developed, making certain improvements using magnetic properties. Compared to MIP, Magnetic molecularly imprinted polymers (MMIPs) have high selectivity in sample pre-treatment and allow for fast and easy isolation of the target analyte. Its magnetic properties and good extraction performance depend on the MMIP synthesis step, which consists of 4 steps, namely magnetite manufacture, magnetic coating using modified components, polymerization and template desorption. This review discusses the factors that will affect the performance of MMIP as a selective sorbent at each stage. MMIP, using Fe₃O₄ as a magnetite core, showed strong superparamagnetism; it was prepared using the co-precipitation method using FeCl₃·6H₂O and FeCl₂·H₂O to obtain high magnetic properties, using NH₄OH solution added for higher crystallinity. In magnetite synthesis, the use of a higher temperature and reaction time will result in a larger nanoparticle size and high magnetization saturation, while a higher pH value will result in a smaller particle size. In the modification step, the use of high amounts of oleic acid results in smaller nanoparticles; furthermore, determining the correct molar ratio between FeCl₃ and the shielding agent will also result in smaller particles. The next factor is that the proper ratio of functional monomer, cross-linker and solvent will improve printing efficiency. Thus, it will produce MMIP with high selectivity in sample pre-treatment.

Facile and single-step entrapment of chloramphenicol in ZIF-8 and evaluation of its performance in killing infectious bacteria with high loading content and controlled release of the drug

CLN@ZIF-8 was prepared by trapping chloramphenicol during ZIF-8 synthesis with high DLC and DLE. It showed H2O2-sensitive controlled release with higher drug release under the simulated infectious conditions and short-time antibacterial activity.

A Fluorimetric Method Based On Magnetic Molecularly Imprinted Polymer For Selective Detection Of Chlorferon

In the present work, reusable magnetic molecularly imprinted polymers have been used for the first time as an adsorbent for the determination of chlorferon. Magnetic molecularly imprinted polymers have been used for the selective separation of chlorferon from the solution and sensitive fluorimetric determination has been performed using the native fluorescence of chlorferon. The developed method is rapid and determination of chlorferon was completed in an hour. Limit of detection (LOD) of the method was found to be 0.0027 µM and the linearity of the calibration graph was observed within the range of 0.01-0.36 µM (2.5 - 75 µg L^-1). Adsorption isotherms point out the multilayer adsorption and the heterogeneous distribution of binding sites for imprinted polymer and homogeneous binding site for non-imprinted polymer. The adsorption capacities of imprinted polymer and non-imprinted polymer were calculated as 2.03 μmol g^-1 and 0.96 μmol g^-1, respectively and the imprinting factor was found to be 2.11. The interference effects of some organic compounds and characterization studies were also evaluated. The method has been applied to honey and tap water samples and the recoveries were found to be in the range of 91.3 and 101.1 %.

Molecularly Imprinted Silica-Coated CdTe Quantum Dots for Fluorometric Determination of Trace Chloramphenicol

A dual recognition system with a fluorescence quenching of quantum dots (QDs) and specific recognition of molecularly imprinted polymer (MIP) for the detection of chloramphenicol (CAP) was constructed. MIP@SiO₂@QDs was prepared by reverse microemulsion method with 3-aminopropyltriethoxysilane (APTS), tetraethyl orthosilicate (TEOS) and QDs being used as the functional monomer, cross-linker and signal sources, respectively. MIP can specifically recognize CAP, and the fluorescence of QDs can be quenched by CAP due to the photo-induced electron transfer reaction between CAP and QDs. Thus, a method for the trace detection of CAP based on MIP@SiO₂@QDs fluorescence quenching was established. The fluorescence quenching efficiency of MIP@SiO₂@QDs displayed a desirable linear response to the concentration of CAP in the range of 1.00~4.00 × 10² μmol × L⁻¹, and the limit of detection was 0.35 μmol × L⁻¹ (3σ, n = 9). Importantly, MIP@SiO₂@QDs presented good detection selectivity owing to specific recognition for CAP, and was successfully applied to quantify CAP in lake water with the recovery ranging 102.0~104.0%, suggesting this method has the promising potential for the on-site detection of CAP in environmental waters.

Dummy molecularly imprinted membranes based on an eco-friendly synthesis approach for recognition and extraction of enrofloxacin and ciprofloxacin in egg samples

In this work, novel dummy molecularly imprinted membranes (MIMs) were fabricated using the nylon-66 (NY-66) membranes as the subtracts based on an eco-friendly "sandwich" technology with less consumption of organic reagents at mild conditions for recognition and extraction of enrofloxacin (ENR) and ciprofloxacin (CIP) in egg samples. The prepared MIMs were characterized by SEM, ATR-FTIR and TGA, showing the successful construction of uniform and porous polymers on the surface of membranes. A series of adsorption affinity tests were investigated, indicating the prepared materials had specific recognition capacity and excellent stability as novel sorbents. Furthermore, Box-Benhnken design (BBD) and single factor investigations were applied to optimize pretreatment procedures, coupling with Ultra High Performance Liquid Chromatograph (UHPLC) detection. The method showed a good correlation (r²>0.9999) within the linear range of 5.0~5000.0 µg kg^-1, and limit of detection (LOD) of ENR and CIP were 0.3 and 0.7 µg kg^-1, respectively. The mean recovery ranged from 84.5% to 97.0% within relative standard deviations (RSDs) of 10.2%. Finally, ENR and CIP were not detected in 3 batches of egg samples. The current study developed the dummy MIMs as sorbents combined with UHPLC analysis for extraction and detection of target analytes in food matrices.

Magnetic-molecularly imprinted polymers in electrochemical sensors and biosensors

Magnetic particles, as well as molecularly imprinted polymers, have revolutionized separation and bioanalytical methodologies in the 1980s due to their wide range of applications. Today, biologically modified magnetic particles are used in many scientific and technological applications and are integrated in more than 50,000 diagnostic instruments for the detection of a huge range of analytes. However, the main drawback of this material is their stability and high cost. In this work, we review recent advances in the synthesis and characterization of hybrid molecularly imprinted polymers with magnetic properties, as a cheaper and robust alternative for the well-known biologically modified magnetic particles. The main advantages of these materials are, besides the magnetic properties, the possibility to be stored at room temperature without any loss in the activity. Among all the applications, this work reviews the direct detection of electroactive analytes based on the preconcentration by using magnetic-MIP integrated on magneto-actuated electrodes, including food safety, environmental monitoring, and clinical and pharmaceutical analysis. The main features of these electrochemical sensors, including their analytical performance, are summarized. This simple and rapid method will open the way to incorporate this material in different magneto-actuated devices with no need for extensive sample pretreatment and sophisticated instruments.

Rapid extraction of domoic acid by a magnetic molecularly imprinted silica before HPLC measurement

A magnetic molecularly imprinted silica solid was obtained by sol-gel polymerization for the separation of domoic acid. The solid showed rapid adsorption kinetics with an adsorption equilibrium time of 5 min. The solid showed affinity to domoic acid under the interference of tryptophan and could be repeatedly used for 5 times at least. The solid was used as a solid-phase-extraction sorbent for the extraction of domoic acid from clam samples before measurement with liquid chromatography. The detection limit of 0.20 mg kg-1 was lower than the allowable limits in several countries or areas. The recoveries in the spiked samples were 88% approximately.

Dual Triple Helix-Aptamer Probes for Mix-and-Read Detecting Antibiotics in Fish and Milk

Antibiotic abuse in agricultural products leads to serious food safety issues. To this end, we proposed a mix-and-read and enzyme-free amplified assay for antibiotics based on a dual triple helix-aptamer probe, potentially applicable for on-site monitoring of antibiotic residues. A dual triple helix-aptamer probe can leverage the response toward target molecules without enzyme-based amplification, rendering it sensitive and robust for profiling target molecules. The proposed assay allowed mix-and-read detection of chloramphenicol with a detection limit of 0.18 nM. Besides, it accommodated for specifically resolving chloramphenicol among other antibiotics. Chloramphenicol residual in aquatic products in fish and milk can be precisely determined. Thus, the aptamer probe deems to enrich the toolbox for managing antibiotic use.

Modern Methods for Assessing the Quality of Bee Honey and Botanical Origin Identification

This paper is a summary of the latest literature on methods for assessing quality of natural bee honey. The publication briefly characterizes methods recommended by the International Honey Commission, published in 2009, as well as newer methods published in the last 10 years. Modern methods of assessing honey quality focus mainly on analyzing markers of individual varieties and classifying them into varieties, using, among others, near infrared spectroscopy techniques (NIR), potentiometric tongue, electronic nose, nuclear magnetic resonance (NMR), zymography, polymerase chain reaction (PCR), DNA metabarcoding, and chemometric techniques including partial least squares (PLS), principal component analysis (PCA) and artificial neural networks (ANN). At the same time, effective techniques for analyzing adulteration, sugar, and water content, hydroxymethylfurfural (HMF), polyphenol content, and diastase activity are being sought. Modern techniques enable the results of honey quality testing to be obtained in a shorter time, using the principles of green chemistry, allowing, at the same time, for high precision and accuracy of determinations. These methods are constantly modified, so that the honey that is on sale is a product of high quality. Prospects for devising methods of honey quality assessment include the development of a fast and accurate alternative to the melissopalynological method as well as quick tests to detect adulteration.

Sample treatment based on molecularly imprinted polymers for the analysis of veterinary drugs in food samples: a review

The use of veterinary drugs in medical treatments and in the livestock industry is a recurrent practice. When applied in subtherapeutic doses over prolonged times, they can also act as growth promoters. However, residues of these substances in foods present a risk to human health. Their analysis is thus important and can help guarantee consumer safety. The critical point in each analytical technique is the sample treatment and the analytical matrix complexity. The present manuscript summarizes the development, type of synthesis, characterization, and application of molecularly imprinted polymers in the separation, identification, and quantification techniques for the determination of veterinary drug residues in food samples in extraction, clean-up, isolation, and pre-concentration systems. Synthesized sorbents with specific recognition properties improve the interactions between the analytes and the polymeric sorbents, providing better analysis conditions and advantages in comparison with commercial sorbents in terms of high selectivity, analytical sensitivity, easy performance, and low cost analysis.

Restricted access magnetic imprinted microspheres for directly selective extraction of tetracycline veterinary drugs from complex samples

A novel restricted access media-magnetic molecularly imprinted polymers (RAM-MMIPs) was prepared as magnetic-solid phase extraction (M-SPE) material for tetracyclines (TCs). The RAM-MMIPs can not only specifically adsorb target molecules in samples, but also effectively eliminate the interference of protein macromolecules. The protein exclusion rate is 99.4%. Besides, RAM-MMIPs have a uniform imprinted and hydrophilic layer (600 nm), rapid binding kinetic (35 min), high selectivity and larger adsorption capacity. The M-SPE was coupled with HPLC/UV to extract TCs from untreated milk and egg samples, and several major factors affecting M-SPE efficiency were optimized. Under optimized conditions, the developed method achieved good linearity (R²>0.9989), lower limits of detection (LOD) and higher recoveries of TCs. For milk samples, the LOD is 1.03-1.31 μg L^-1 and the recovery is 86.7% to 98.6% with relative standard deviation (RSD) of 1.4-5.7%. For the egg samples, the LOD, recovery and RSD are 2.21-2.67 μg L^-1, 84.2-96.5% and 1.7-5.9%, respectively. Consequently, this work provides an improved strategy for the selective extraction and detection of target molecules directly from complex samples with proteins.

Fabrication of carbon dots@restricted access molecularly imprinted polymers for selective detection of metronidazole in serum

A custom-tailored design was proposed for the fabrication of carbon dots coupled with restricted access materials and molecularly imprinted polymers (CDs@RAM-MIPs) to detect metronidazole (MNZ). Biomass carbon dots (CDs) were derived from longan peels assisted with high pressure microwave, and had the merits of eco-friendly, excellent photostability and low toxicity. In this work, glycidyl methacrylate was used as a co-polymeric monomer to increase hydroxyl groups on the surface of synthetic materials, which eliminated the interference of biological macromolecules. The specific binding cavities of CDs@RAM-MIPs were formed after removing the template molecule (MNZ). The obtained CDs@RAM-MIPs can selectively capture MNZ through the specific interaction between recognition sites and MNZ, and obey photoinduced electron transfer fluorescence quenching mechanism. The highly sensitive and selective fluorescent sensor based CDs@RAM-MIPs had a wide linear range (50-1200 ng mL^-1) and a low detection limit (17.4 ng mL^-1) for MNZ. It has been utilized to detect MNZ in serum with recoveries of 93.5%-102.7%, and the relative standards (RSDs) were 1.9%-3.6%, respectively. This work provides a thoughtful strategy for preparation and application of CDs@RAM-MIPs, which presages its great potential for detecting trace compounds in real samples.

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

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

Development of rapid, sensitive and selective fluorimetric method for determination of 1-naphthalene acetic acid in cucumber by using magnetite-molecularly imprinted polymer

In this study, a novel method based on the determination of 1-naphthalene acetic acid with the usage of magnetite-molecularly imprinted polymer prior to fluorimetric detection has been developed. Magnetite-molecularly imprinted polymer has been used for the first time as selective adsorbent for the determination of 1-naphthalene acetic acid. The adsorption capacity of the synthesized polymer was found to be 2.18 ± 0.36 mg g^-1 (n = 3). Limit of detection (LOD) and limit of quantification (LOQ) of the method were found to be 0.75 and 2.50 μg L^-1, respectively. Linearity of the calibration graph for the proposed method was observed within the range of 20-700 μg L^-1. The proposed method seems to be rapid where the detection procedure for 1-naphthalene acetic acid can be completed within a total time of 1 h. The same imprinted polymer can be used for the determination of 1-naphthalene acetic acid with quantitative sorption and recovery values repeatedly for at least ten times. The effects of some potential organic interferences were investigated. Proposed method has been successfully applied to determine 1-naphthalene acetic acid in cucumber, where the recoveries of the spiked samples were found to be in the range of 93.7-104.5%. Characterization of the synthesized polymer was also evaluated. By combining the high capacity, cheapness, reusability and selectivity of the magnetic adsorbent with the dynamic calibration range, rapidity, simplicity, and sensitivity of fluorimetry, the proposed method seems to be an ideal method for the determination of trace levels of 1-naphthalene acetic acid.

Synthesis of molecularly imprinted fluorescent probe based on biomass-derived carbon quantum dots for detection of mesotrione

A novel fluorescent probe based on molecularly imprinted polymers (MIPs) coupled with carbon quantum dots (CQDs) was fabricated and successfully used for selective recognition of mesotrione. In this probe, the biomass-derived CQDs were prepared through a hydrothermal method using mango peels as carbon source, and the whole synthesis procedure was green without chemical reagents. The CQDs were encapsulated into MIPs by using sol-gel technology. After removal of the template molecule mesotrione, specific binding sites are formed and there is electrostatic attraction between the probe and the template molecule. The synthetic CQDs@MIPs were able to selectively capture the target mesotrione with fluorescence quenching via the specific interaction between mesotrione and the recognition cavities. The probe was used for determination of mesotrione in corn to verify the practicality of the proposed method. The detection limit of mesotrione was 4.7 nmol L^-1, and the linear range was 15 nmol L^-1 to 3000 nmol L^-1. Meanwhile, the recoveries of this method for mesotrione were 91.4-96.2%, and the relative standard deviations (RSDs) were 3.2-6.1%. This work provides a novel research method to synthesize CQDs@MIPs with high selectivity (imprinting factor = 5.6), and which can be used for convenient, rapid recognition and sensitive detection of trace compounds from complex matrices.

Highly sensitive and selective method for the rapid determination and preconcentration of haloperidol by using a magnetite-molecularly imprinted polymer

A sensitive and selective method based on the determination of haloperidol with the usage of magnetite-molecularly imprinted polymer and high-resolution liquid chromatography has been developed. This novel method is rapid as the detection procedure for haloperidol can be completed within a total time of 1 h. The same imprinted polymer can be used for the determination of haloperidol at least 20 times. The proposed method has been succesfully applied to synthetic urine and serum samples and the recoveries of the spiked samples were in the range of 94.7-100.7%. The limit of detection and limit of quantification of the method were 2.25 and 7.50 μg/L, respectively. Linearity of the calibration graph was observed within the range of 10-250 μg/L. By combining the high capacity, high selectivity, and reusability of the magnetic adsorbent with the dynamic calibration range, high sensitivity and high resolution of liquid chromatography with quadrupole time-of-flight mass spectrometry, the proposed method is an ideal method for the determination and preconcentration of trace levels of haloperidol. A magnetite-molecularly imprinted polymer has been used for the first time as a selective adsorbent for the determination of haloperidol.

Detection of chloramphenicol in meat with a chemiluminescence resonance energy transfer platform based on molecularly imprinted graphene

In this study, a novel composite was synthesized by polymerizing the dummy-template molecularly imprinted microspheres on the surface of magnetic graphene. This composite was used as recognition reagent and energy acceptor to develop a platform for determination of chloramphenicol according to the principle of chemiluminescence resonance energy transfer. The light signal was induced with luminolH₂O₂4-(imidazole-1-yl)phenol system, and the chemiluminescence intensity was positively correlated with the analyte concentration. The limit of detection for chloramphenicol in meat sample was 2.0 pg/g, and the recoveries from the standard fortified blank meat sample were in the range of 69.5%-97.3%. Furthermore, one single assay could be finished within 10 min, and the magnetic composite could be reused for at least thirty times. Therefore, this platform could be used as a rapid, simple, sensitive, accurate and recyclable tool for screening the residue of chloramphenicol in meat.

Detection of chloramphenicol in chicken, pork and fish with a molecularly imprinted polymer-based microtiter chemiluminescence method

In this study, 4-nitrotoluene (NT) was used as dummy template to synthesize a molecularly imprinted polymer that was highly specific for chloramphenicol. The polymer was coated in the wells of 96-well microplates as recognition reagent to develop a chemiluminescence method. The analyte solution and an enzyme-labelled hapten were added into the wells to perform competition, and the light signal was induced with a highly efficient luminol-H₂O₂-4-(imidazol-1-yl)phenol system. Then, the optimized method was used to determine chloramphenicol in meat (chicken, pork and fish), and the limit of detection (LOD) was 5.0 pg g^-1. Furthermore, the polymer-coated plate could be reused four times, and one test could be finished within 20 min. The recoveries from the standard fortified blank meat samples were in the range of 71.5-94.4%. Therefore, this method could be used as a useful tool for routine screening the residue of chloramphenicol in meat samples.

Theoretical and experimental research on self-assembly system of molecularly imprinted polymers formed via chloramphenicol and methacrylic acid

Chloramphenicol was chosen as the imprinting molecule and the methacrylic acid was chosen as the functional monomer to prepare molecularly imprinted polymers. Ethylene glycol dimethacrylate, pentaerythritol triacrylate, and trimethylolpropane trimethylacrylate were used as the cross-linking agents, respectively. The interaction processes between chloramphenicol and methacrylic acid were simulated by using the ωB97XD/6-31G (d,p) method. The self-assembled configuration, bonding sites, binding number, binding energy, and interaction principle of stable complex formed by chloramphenicol and methacrylic acid with different molar ratios have been studied. The selectivity of the most stable complex formed from chloramphenicol and methacrylic acid was discussed with the thiamphenicol and florfenicol as the analogues of chloramphenicol. The results showed that chloramphenicol and methacrylic acid were interacted through the hydrogen bonds. When the molar ratio was 1:10 and pentaerythritol triacrylate as the cross-linking agent, the ordered complex formed by chloramphenicol and methacrylic acid has the largest amount of hydrogen bonds and the lowest binding energy. Scatchard analysis showed that the maximum apparent adsorption capacity was 173.3 mg/g (0.536 mol/g), and the selection factor of florfenicol was the largest. This study provides a reliable theoretical and experimental basis for the design, preparation, and characterization of chloramphenicol molecularly imprinted polymers.

Selective detection of chloramphenicol based on molecularly imprinted solid-phase extraction in seawater from Jiaozhou Bay, China

This study highlights an efficient sample pre-treatment method for preconcentration and detection of chloramphenicol in marine water using molecularly imprinted solid-phase extraction (MISPE). Chloramphenicol molecularly imprinted microspheres were prepared and evaluated on the base of morphology, capacity and selectivity. The imprinted microspheres exhibited specific recognition and high retention capability to chloramphenicol and were applied as special solid-phase extraction adsorbents. An off-line MISPE protocol has been optimized and a creative analytical method coupled to HPLC-DAD was successfully developed for the cleanup and determination of chloramphenicol in seawater samples. Method performance was satisfactory with recoveries ranging from 81 to 90% and relative standard deviation (RSD) was <4.93% (n = 3). Accuracy of the method was assessed at three spiking concentration levels and the limit of detection was 5 ng L^-1. Finally, five seawater samples from Jiaozhou Bay of China were determined and the results showed that there was no chloramphenicol detected.