Magnetic dual-template molecularly imprinted polymer based on syringe-to-syringe magnetic solid-phase microextraction for selective enrichment of p-Coumaric acid and ferulic acid from pomegranate, grape, and orange samples

Quick separation and enrichment of chlorogenic acid and its analogues by a high-efficient molecularly imprinted nanoparticles and evaluation of antioxidant and hypoglycemic activities

Multiple interaction strategy to target was tried to use in the design of surface imprinting polymer. To validate this, active chlorogenic acid, a representative phenolic acid compound existing in many natural products, was selected as the template molecule and a magnetic molecularly imprinted nanoparticles (CGA-MMIPs) was synthesized. The characterizations indicated CGA-MMIPs was 20-50 nm, stable below 229.56 °C and had a saturation magnetic intensity of 17.90 emu/g. The prepared CGA-MMIPs exhibited high adsorption capacity (441.81 mg/g) and fast adsorption equilibrium for chlorogenic acid. It also was easy separation, high selectivity and good reusability, which was successfully used in quick separation of chlorogenic acid from Orthosiphon aristatus and Taraxacum mongolicum and Salvia miltiorrhiza. Moreover, the isolated substances possessed great antioxidant and hypoglycemic activities. These verified the strategy was useful and had huge prospects in the quick separation of chlorogenic acid or other phenolic acid compounds from natural products.

Ferulic Acid—A Brief Review of Its Extraction, Bioavailability and Biological Activity

Ferulic acid is a widespread phenolic compound that occurs in seeds and leaves, both in its free form and conjugated to polysaccharides, carbohydrates, glycoproteins and lignins in the plant cell walls. It exhibits various biological activities, like antioxidant, anticarcinogenic, anti-inflammatory, hepatoprotective, antimicrobial, and antiviral activity, and it modulates enzyme activity. Given these wide potential health benefits, ferulic acid has attracted considerable research interest and may be considered a biomolecule with strong prospects as a functional food ingredient. Great attempts have been made to enhance its extraction process and recovery from natural matrices and agro-industrial wastes for its various applications relating to human health and nutrition. This review presents the recently available information on the extraction methods for quantifying ferulic acid in different samples, along with its bioavailability and stability in processing foods and biological activities.

Fabrication of a ratiometric fluorescence nanoprobe for detecting tryptophan enantiomers

A novel ratiometric fluorescence nanoprobe was developed to detect tryptophan enantiomers with high selectivity and sensitivity. Fluorescein (FL) was doped into SiO2 nanoparticles with little dye leakage, acting as an internal reference signal. The chiral center of L-histidine (L-His) was introduced by partially replacing the carboxyl on the surface of SiO2. The response signal of Eu3+ was coordinated with carboxyl to obtain the FL@SiO2-Eu/His nanoprobe. The nanoprobe shows enantioselective luminescence responses for tryptophan enantiomers. The red emission of Eu3+ can be effectively quenched by the tryptophan enantiomers, but the quenching efficiency is different due to the different interactions with the chiral recognition sites. The fluorescence intensity ratio (I613/I515) shows excellent linearity with tryptophan enantiomers in the range of 0-100 μM (R2 > 0.99). The limit of detection (LOD) is 1.0 μM and 1.3 μM for L-tryptophan (L-Trp) and D-tryptophan (D-Trp), respectively. The FL@SiO2-Eu/His nanoprobe shows good selectivity and specific recognition in serum actual samples. In addition, the nanoprobe can realize visual detection under UV light due to the obvious color change. This work provides an innovative idea for the development of new probes in the detection field.

Thiamethoxam dynamics in pepper plants: Deciphering deposition and dissipation pattern across diverse planting modes and regions

To reduce the application dosage of thiamethoxam (TMX), we investigated the deposition and dissipation patterns in a pepper-planted ecosystem under different planting modes across four regions in China, namely Hainan (HN), Zhejiang (ZJ), Anhui (AH) and Hebei (HB). This study focused on the deposition and dissipation of TMX at concentrations of 63.00, 47.25, 31.50, 23.63 and 15.75 g a.i.hm-2. As the application dose increased, the deposition amount of TMX initially increased in the plants and cultivated soil, showing obvious geographic differences in four cultivation areas. Surprisingly, the initial amount of TMX deposited the pepper-cultivated greenhouse of ZJ and AH was 1.1-2.1-fold and 1.0-3.6-fold higher than that in the open field system at the same application dose, respectively. In pepper leaves, stems, fruits and soil, the dissipation exhibited rapid growth and then slowed. However, the residual concentration showed an increasing trend, followed by a subsequent decrease in the pepper roots. In different planting regions, the dissipation rate of TMX followed the order HN > ZJ > AH > HB in pepper plants and cultivated soil. In comparison to the open field, the total TMX retention rate in greenhouse was higher, indicating overall greater persistence in the greenhouse conditions. These findings reveal the deposition and dissipation characteristics of TMX within the pepper-field ecosystem, offering a significant contribution to the risk assessment of pesticides.

Determination of concentrations of Sr and Ba in coal and coal combustion by-products: A comparison between results by ICP-MS and XRF techniques

Concentrations of trace elements in coal and coal combustion products are commonly analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) due to large number of elements detected and the relatively the low detection limits of this technique. Like other geological samples, complete dissolution of coal and coal combustion products is also essential for accurate ICP-MS results. In this study, Sr and Ba in coal and coal combustion products (fly and bottom ashes) from two coal-combustion power plants from North China analyzed by XRF and ICP-MS were comparatively studied. The concentrations of Sr and Ba analyzed by ICP-MS, when a mixture of acids (2 ml HF + 5 ml HNO3 for each 50 mg coal sample and 5 ml HF + 2 ml HNO3 for each 50 mg ash sample) was used for microwave-assisted digestion, do not fit well with the their relative XRF results. This is most probably due to the formation of the fluorides during microwave digestion, and this assumption is supported by the presence of various fluoride compounds, NaMgAl(F, OH)6·H2O, NH4MgAlF6, AlF3, and K2SiF6, in the residues of all the coal and ash samples in our sequential extraction experiment. Cations of Sr and Ba were probably trapped into the divalent cation sites of the fluorides. Concentrations of Sr and Ba analyzed by ICP-MS using increased HF and HF/HNO3 ratio (7 ml HF and 2 ml HNO3 for each 50 mg coal/ash sample) are in better agreement with the XRF results. Our results indicate that excess amount of HF probably has led to the suppression of these elements due to fluoride precipitation. The results indicate that the modified digestion method is capable of achieving complete digestion of coal samples and results in a reliable analysis of Sr and Ba concentrations in coal samples and most fly ashes by ICP-MS. However, the formation of insoluble fluorides is probably not completely suppressed for some bottom ash samples, which can result in underestimation of Sr and Ba concentrations. Nevertheless, XRF analysis can serve as a reliable cross-check method to assist in the evaluation of the accuracy of ICP-MS results.

Purification and characterization of pure curcumin, desmethoxycurcumin, and bisdemethoxycurcumin from North-East India Lakadong turmeric (Curcuma longa)

Lakadong turmeric has been outlined for its high content of curcuminoids across the globe. Three significant molecular markers are widely present in turmeric viz, curcumin, desmethoxycurcumin, and bisdemethoxycurcumin, and they are present very high amount in Lakadong turmeric. Curcuminoids have been reported for structural and spectrum similarity of 3 to 4 nm (432, 434, and 436 nm, respectively). Current purification methods are based on recrystallisation where it is difficult to get highly pure material and preparative methods associated with tedious separation with high cost. Lakadong turmeric has not been explored commercially since long time. No reports are available in the literature with highly pure reference materials with in-depth characterization data and purity assessment. Curcumin, desmethoxycurcumin, and bisdemethoxycurcumin were characterized using different analytical techniques viz, UV-Visible Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Proton Nuclear Magnetic Resonance (1HNMR), Carbon-13 Nuclear Magnetic Resonance (13CNMR), High-Resolution Mass Spectrometry (HR-MS) and Inductive Coupled Plasma Mass Spectrometry (ICP-MS). Purified 3 markers has shown High-Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD) purity more than 99.5%. DSC the melting peaks of curcumin, desmethoxycurcumin and bisdemethoxycurcumin were observed at 168 °C, 165 °C, and 210 °C, respectively. These plant-based markers have high commercial potential as reference material for routine Quality Assurance and Quality Control (QAQC) in herbal industries.

Template-assisted synthesis of molecularly imprinted polymers for the removal of methyl red from aqueous media

This study entails the synthesis of molecularly imprinted polymers (MIPs) with good selectivity coefficients for azo dye as a potential sorbent material to extract azo dye from polluted aqueous media. A series of MIPs for methyl red (MR) as a template, were synthesized by changing the molar ratio of functional monomers, via precipitation polymerization format of non-covalent approach. Water-soluble functional monomer; acrylic acid (AA) was used to weave the frame work of polymers while ethylene glycol dimethacrylate (EGDMA) was utilized as crosslinking monomer. The impact of different experimental parameters, such as mole ratio of monomer (functional) to crosslinking monomer on the molecular recognition was investigated. The highly efficient and selective MR-MIP was used for the removal of spiked MR dye from different water samples. The selected imprinted polymer, MR1-MIP was able to selectively remove the MR molecules from aqueous media. A significant amount of dye was removed by MR1-MIP from the river water samples with a high degree of removal efficiency i.e. 92.25%. The imprinting factor of 3.75 for MR1-MIP indicated that the high selectivity in terms of adsorption for MR. A minimum loss of only ~ 3.35% in the removal efficiency within ten sequential cycles of adsorption-desorption study evidenced that MR-MIPs could be used as the most cost effective and best sorbent for the removal of MR from polluted water. Furthermore, the structural properties of MR-MIPs were characterized by FTIR and EDX, whereas TGA, SEM and BET were used to describe the thermal, morphological and surface structures of the particles, respectively.

Magnetic nanofluid based on hydrophobic deep eutectic solvent for efficient and rapid enrichment and subsequent determination of cinnamic acid in juice samples: Vortex-assisted liquid-phase microextraction

A quick, environmentally friendly and easy approach for the determination of cinnamic acid in juice samples based on the creation and usage of a novel magnetic nanofluid (mixture of hydrophobic deep eutectic solvent and magnetic nanoparticles) has been reported. Response surface methodology was applied to justify the contribution of the efficient factors including pH, nanofluid volume, ionic strength and vortex time. Cinnamic acid concentrations were monitored and quantified based on their HPLC peak representing linear correlations under the best operational circumstances showing linearity between 3 and 550 ng mL^-1. The LOD, LOQ, and enrichment factor for cinnamic acid were 0.8 ng mL^-1, 2.7 ng mL^-1 and 57.2, respectively. The proposed method was used for enrichment and subsequent determination of cinnamic acid from juice samples which suggests a potential alternative approach for cinnamic acid analysis in complicated food samples.

Transition metal composites for selective analysis of vitamin B2 in rice by ultrahigh-performance liquid chromatography-tandem mass spectrometry

A novel amino-functionalized zinc ferrite nanoparticles/MXene (ZnFe₂O₄-NH₂/MXene composite which consist of ZnFe₂O₄-NH₂ and single/few layers MXene was designed and synthesized as an efficient extractant for analysis of vitamin B₂ in rice first combined with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). As a result, the single/few layer MXene was tightly attached to the spherical ZnFe₂O₄-NH₂ nanoparticles by electrostatic self-assembly interaction, which present large specific surface area and fast mass transfer rate. The relevant experimental parameters, including the pH of the solution, extraction time, adsorbent amount, desorption solvent, desorption solvent volume and desorption time were investigated and optimized. Under optimum conditions, the ZnFe₂O₄-NH₂/MXene composite exhibited excellent selectivity and adsorption capacity for vitamin B₂ through hydrogen bonding interactions and the metal-π complexation interaction. The adsorption kinetics, isotherms, and thermodynamic studies were systemically investigated to evaluate the adsorption mechanism and characteristics, which ascribed to chemical adsorption, monolayer adsorption and a spontaneous endothermic process. Furthermore, the performance of the proved method was validated with the good linear correlation coefficient (r = 0.999), low limit of detection (0.86 ng·mL^-1) and the limit of quantification (2.98 ng·mL^-1), satisfactory recoveries (81.7-102.5%) and reasonable accuracy (RSD<7.8%). The theoretical and technological underpinning for investigating the kinship amongst vitamin alterations and the degree of rice storage was set using this suggested approach to assess vitamin B₂ in rice from various years.

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.

Preparation of a New Solid-Phase Microextraction Fiber Based on Molecularly Imprinted Polymers for Monitoring of Phenobarbital in Urine Samples

A simple solid-phase microextraction technique using molecularly imprinted polymers (MIP-SPME) was prepared to monitor phenobarbital in urine samples. In this technique, the fiber was prepared via insertion of the modified stainless-steel wire in the reaction solution including 3-aminopropyltriethoxysilane and tetraethyl orthosilicate in the presence of an acidic catalyst (acetic acid). The fabricated MIP-SPME fiber was utilized to selectively extract phenobarbital from urine samples and prepare it for detection through high-performance liquid chromatography with ultraviolet detection. The synthesized MIPs were characterized by several techniques such as Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and thermal gravimetric analysis. The effects of various influencing factors on the extraction yield of phenobarbital were considered and optimized. The conditions that yielded the maximum extraction efficiency were as follows: pH of 5, 25 min extraction time, 500 rpm stirring rate, 15 min desorption time and using methanol as elution solvent. Within the range of concentrations of 0.02 to 100 μg mL-1, the method had linear characteristics, with a suitable coefficient of determination (0.9983). We determined limits of detection and limits of quantification to be 9.88 and 32.9 ng mL-1, respectively. The repeatability and reproducibility of the prepared fibers were 4.6 and 6.5%, respectively.

Extraction and Identification of Antioxidant Ingredients from Cyclocarya paliurus (Batal.) Iljinsk Using UHPLC-Q-Orbitrap-MS/MS-Based Molecular Networking

Cyclocarya paliurus (Batal.) Iljinskaja (LCP) leaves have been widely employed in food and traditional medicine for treating hyperlipidaemia and its complications, possibly owing to their antioxidant properties. The aim of the present study is to identify the chemical ingredients of antioxidant extracts from LCP by using UHPLC-Q-Orbitrap-MS/MS-based molecular networking, a very recent and useful tool for annotation of chemical constituents in mixtures. The extraction conditions of antioxidant extracts from LCP were optimised by single-factor analysis and response surface methodology (RSM). The optimised conditions were a methanol concentration of 32%, a liquid-to-solid ratio of 0.4 ml/mg, an extraction temperature of 25°C, and an extraction time of 32 min. Under these conditions, the antioxidant yield was 516.20 ± 28.52 μmol TE/ml. The main active ingredients in the antioxidants were identified by UHPLC-Q-Exactive Orbitrap-MS-based molecular networking. In total, 42 compounds were identified, including 20 flavonoids, 16 quinic acid derivatives, 4 caffeoyl derivatives, and 2 coumaroyl derivatives. The findings of the present work suggest that LCP could be a suitable source of natural antioxidant compounds, which might be applicable in the development of potential pharmaceutical drugs targeting diseases related to oxidative stress.

One-step synthesis of well-defined molecularly imprinted nanospheres for the class-selective recognition and separation of β-blockers in human serum

β-blockers are a class of medications that are used to treat abnormal heart rhythms and hypertension. Molecularly imprinted polymers (MIPs) capable of selective recognizing and extracting β-blockers from complex biological samples hold great promise in bioanalytical and biomedical applications, but developing such artificial receptor materials is still challenging. Herein, we introduce a simple one-step method for the synthesis of well-defined molecularly imprinted nanospheres in high yield (83.6-94.4%) via reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization for the selective recognition and extraction of the β-blockers from human serum. The prepared MIPs are characterized in terms of morphology, pore properties, binding kinetics, capacity, selectivity, and recognition mechanisms. The uniform nanoscale-imprinted layer favored the rapid mass transfer of β-blockers. The binding studies showed the high adsorption capacity (126.8 μmol/g) and selectivity of the developed nanomaterial. The investigation on the recognition mechanism reveals that multiple driving forces participate in the binding between MIP and β-blockers, where hydrogen bonding plays as the dominating role for the specific recognition. The MIP was successfully applied for the direct enrichment of five β-blockers from human serum with HPLC recoveries ranging from 82.9 to 100.3% and RSD of 0.5-6.9% (n = 3).

Air-assisted liquid-liquid microextraction of total 3-monochloropropane-1,2-diol from refined edible oils based on a natural deep eutectic solvent and its determination by gas chromatography-mass spectrometry

In this paper, a fast, sensitive, and selective sample preparation procedure was presented for the determination of 3-monochloropropane-1,2-diol (3-MCPD) in refined edible oils using gas chromatography-mass spectrometry. In this method, firstly, the sample lipids and analyte fatty esters are saponified by sodium hydroxide under sonication. After that the analyte was derivatized using phenylboronic acid (as the derivatization agent) and the obtained derivative was extracted during an air-assisted liquid-liquid microextraction procedure (AALLME). Six different deep eutectic solvents (DESs) were prepared as the extraction solvents and the most effective extraction for 3-MCPD was obtained in the presence of a natural DES (NDES) consisting of choline chloride (ChCl)-acetic acid (AcOH). Important variables such as sodium hydroxide concentration and volume, sonication time, temperature, extraction solvent type and volume, and phenylboronic acid concentration and volume have been optimized. Using the optimum conditions, broad linear range (0.88-1000 ng g^-1), suitable coefficient of determination (0.995), and low limits of detection (0.26 ng g^-1) and quantification (0.88 ng g^-1) were obtained. Relative standard deviations for intra- (n=8) and inter-day (n=6) precisions at a concentration of 5 ng g^-1 were 2.6 and 3.2%, respectively. The developed method has been successfully applied to 3-MCPD determination in refined edible oil samples including sunflower, corn, and canola oils.

Highly effective pre-concentration of thymol and carvacrol using nano-sized magnetic molecularly imprinted polymer based on experimental design optimization and their trace determination in summer savoury, Origanum majorana and Origanum vulgare extracts

To ascertain thymol and carvacrol in pharmaceutical syrups, a valid and effective magnetic molecular imprinted polymer dispersive solid phase microextraction (MMIP-DSPME) process was developed in this study, which was in combination with a high performance liquid chromatography-ultra violet (HPLC-UV) technique for the assessment of thymol and carvacrol separation and pre-concentration. Contact time, eluent kind and volume, pH, the mass of the MMIP were all taken into consideration as key factors. Design expert and multi-objective response surface methodology (RSM) were used to optimize these variables. The mass of the MMIP, sample pH, eluent kind, time of sorption, the volume of eluent, and time of elution were 10 mg, 6, acetonitrile, 28 min, 200 µL, and 5.5 min, respectively, for the maximum extraction recovery of the analytes. The limit of detection (LOD) was 0.042 ng mL^-1 at the optimal conditions, while the value for the limit of quantification (LOQ) was 0.140 ng mL^-1. At the optimized conditions for thymol and carvacrol, the suggested MMIP sorbent had sorption capacities of 64.1 and 72.6 mg g^-1, respectively. Furthermore, for triplicate measurements, the linear dynamic range (LDR) was 0.40-5000 ng mL^-1, and the method's accuracy (RSD %) was 6.26%. The saturation magnetization for the MMIP was 19.0 emu g^-1 obtained by VSM, allowing the sorbent to be separated quickly. The sorption experiments confirmed the large sorption capacity of the MMIP for thymol and carvacrol, as well as its homogeneous binding sites. The extraction recovery for thymol and carvacrol was 96.9-103.8% and 96.6-105.4%, respectively, at all spiked amounts (20, 100, 200, and 500 ng mL^-1). The findings of seven desorption-regeneration cycles using MMIP demonstrated the high stability of the sorbent. The MMIP revealed a particular behavior of sorption for thymol and carvacrol, implying a selective, simple, effective, and flexible analytical method.

Magnet integrated fabric phase sorptive extraction of selected endocrine disrupting chemicals from human urine followed by high-performance liquid chromatography - photodiode array analysis

In current paper, a new advanced modification of fabric phase sorptive extraction is introduced for the first time. This advantageous configuration that integrates the stirring and extraction mechanism into a single sample preparation device was originated by equally considering the beneficial role of the increase of extraction kinetics and more specifically of diffusion on the extraction efficiency of the equilibrium based microextraction techniques and the need for integrating and unite processes for better promotion and implementation of the principles of Green Analytical Chemistry. The resulted magnet integrated fabric phase sorptive extraction (MI-FPSE) device was the spearhead to develop a new analytical methodology for the determination of selected very common endocrine disrupting chemicals as model analytes in human urine by high-performance liquid chromatography-photodiode array analysis. More specifically, the sol-gel Carbowax 20 M coated on hydrophilic cellulose fabric substrate, MI-FPSE device was efficiently employed for the establishment of a new extraction protocol before the chromatographic determination. The sample preparation workflow was methodically optimized in terms of the elution solvent mixture, the volume of the sample, the extraction and the elution time, the stirring speed during the extraction, the ionic strength, and the pH of the sample matrix. The chromatographic separation was performed on a Spherisorb C18 column and a gradient elution program within 14 minutes. Mobile phase consisted of 0.05 ammonium acetate aqueous solution and acetonitrile. The method was validated towards linearity, sensitivity, selectivity, precision, accuracy, and stability. LOD and LOQ ranged between 1.05-1.80 and 3.5-6.0 ng/mL, while %RSD values were found lower than 9.0% in all cases. The method was efficiently applied to the bioanalysis of real samples. All the chosen EDCs were measured at high detection levels. The new MI-FPSE device has demonstrated its performance superiority as a magnet integrated stand-alone extraction device and could be considered as a significant improvement in the field of analytical/bioanalytical sample preparation.

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

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

Current Progress in Natural Deep Eutectic Solvents for the Extraction of Active Components from Plants

In the last decade, natural deep eutectic solvents (NADESs) have gained more and more attention due to their green, convenient preparation, low toxicity and biodegradability. It is widely used in various fields, especially in the extraction of active components from plants, formed by the combination of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) at a certain condition. In this article, six preparation methods of NADESs were summarized and the interactions that occur in the eutectic behavior of NADES including hydrogen bonding, electrostatic interaction and van der Waals force were also reviewed. What is more, its significant extraction capacity on flavonoids, phenols, alkaloids and plant pigments endows its extensive applications in the extraction of active components from medicinal plants. Extraction factors including solvents properties (viscosity, carbon chain length, number of hydroxyl groups), extraction condition (water content, extraction temperature, extraction time, solid-liquid ratio), extraction method and recycling method were discussed. In addition, NADESs can also be combined with other technologies, like molecular imprinting, monolithic column, to achieve efficient and specific extraction of active ingredients. Further systematic studies on the biodegradability and biotoxicity are put forward to be urgent.

Sensitive detection of 2,4,6-trinitrotoluene utilizing fluorescent sensor from carbon dots and reusable magnetic core-shell nanomaterial

Carbon dots have been a promising nano-carbon material with many advantages, and attracted many more attentions. This study designed a new chemosensor integrating the strong fluorescent property of carbon dots and the magnetism of amino-functionalized magnetic core-shell nanomaterial, Fe@SiO₂-NH₂ for determination of 2,4,6-trinitrotoluene (TNT). In this system, fluorescent carbon dots interacted with amino groups on the surface of amino-functionalized magnetic core-shell nanomaterial leading to fluorescence quenching of carbon dots, appearance of TNT competitively replaced of carbon dots on the surface of the magnetic material through forming a Meisenheimer complex. This sensor exhibits excellent selectivity and sensitivity for TNT, and which provided a good dynamic linear range for TNT from 10 to 2000 ng mL^-1. The experiments demonstrate a low detection limit of 2.15 ng mL^-1. The intra-day precisions for 25, 100 and 500 ng mL^-1 were 4.6, 2.3 and 0.5% (RSD, n = 6), inter-day precisions for 25, 100 and 500 ng mL^-1 were 4.2, 2.5 and 0.9% (RSD, n = 6), respectively. The developed sensor was validated with river water, dust, and soil samples, and the achieved spiked recoveries were immensely satisfied from 98.1% to 102.0%. The Fe@SiO₂-NH₂ possessed excellent reusability. This sensor exhibits that it is simple, sensitive and selective, and will be a vital analytical tool for TNT in many fields.

Highly selective magnetic dual template molecularly imprinted polymer for simultaneous enrichment of sulfadiazine and sulfathiazole from milk samples based on syringe-to-syringe magnetic solid-phase microextraction

Antibiotics, such as sulfadiazine and sulfathiazole, are widely used in veterinary applications which can result in remains in edible animal products. Therefore, there is an immense need for a reliable, selective, sensitive, and simple analytical technique for monitoring the concentration of sulfadiazine (SDZ) and sulfathiazole (STZ) in edible animal products. In this regard, we developed a magnetic dual template molecularly imprinted polymer (MMIP) to determine the SDZ and STZ in milk samples. For the sensitive and selective extraction and determination of target analytes, MMIPs have been combined with the syringe-to-syringe magnetic solid-phase microextraction (SS-MSPME) method. In addition, we used central composite design (CCD) for the extraction of SDZ and STZ. With optimum conditions, an efficient, rapid, and convenient technique for the preconcentration and determination of SDZ and STZ in milk samples by SS-MSPME coupling with HPLC-UV was developed. Using our combined approach, the limits of detection are 0.9 and 1.3 ng mL^-1 for SDZ and STZ, respectively, along with good linearity and determination coefficients higher than 0.98. Our method demonstrates a practical approach for the deduction of antibiotics in milk samples with high recoveries and selectivity.

Recent Advances and Future Trends in the Detection of Contaminants by Molecularly Imprinted Polymers in Food Samples

Drug residues, organic dyes, heavy metals, and other chemical pollutants not only cause environmental pollution, but also have a serious impact on food safety. Timely and systematic summary of the latest scientific advances is of great importance for the development of new detection technologies. In particular, molecularly imprinted polymers (MIPs) can mimic antibodies, enzymes and other biological molecules to recognize, enrich, and separate contaminants, with specific recognition, selective adsorption, high affinity, and strong resistance characteristics. Therefore, MIPs have been widely used in chemical analysis, sensing, and material adsorption. In this review, we first describe the basic principles and production processes of molecularly imprinted polymers. Secondly, an overview of recent applications of molecularly imprinted polymers in sample pre-treatment, sensors, chromatographic separation, and mimetic enzymes is highlighted. Finally, a brief assessment of current technical issues and future trends in molecularly imprinted polymers is also presented.