Sensitive and selective determination of imidacloprid with magnetic molecularly imprinted polymer by using LC/Q-TOF/MS

In this paper, magnetic-molecularly imprinted polymer was used for the preconcentration of trace levels of imidacloprid in water and apple samples prior to liquid chromatography-quadrupole-time-of-flight mass spectrometric determination. The selectivity of the magnetic polymer was united with the sensitivity and the high resolving power of the chromatographic system. The developed method showed a linear range from 10.0 to 500.0 µg/L. The quantitative recoveries were obtained for water and apple samples in the range of 92.0%–99.0 %. The relative standard deviations of intra-day and inter-day tests were found to be in the range of 0.8%–1.2% and 1.2%–1.6 %, respectively. In addition, the same magnetic-molecularly imprinted polymer (MMIP) can be used at least ten cycles for the determination of imidacloprid. The preconcentration factor of the method was found to be 2.5, and the total preconcentration procedure can be completed in 1 h. Characterization of synthesised particles were executed with various techniques. Due to its suitable limit of detection, dynamic linear range, sensitivity and selectivity, the developed method seemed to be ideal for the determination and preconcentration of imidacloprid in water and fruit samples.     

Preparation of a multi‐hollow magnetic molecularly imprinted polymer for the selective enrichment of indolebutyric acid

A simple strategy was developed for the preparation of multi‐hollow magnetic molecularly imprinted polymers by incorporating 3‐indolebutyric acid and ferroferric oxide nanoparticles simultaneously into a poly(styrene‐co‐methacrylic acid) copolymer matrix. The as prepared absorbents were characterized using scanning electron microscopy, Fourier‐transform infrared spectroscopy and mercury porosimetry. The adsorption isotherms of indolebutyric acid revealed that there are two types of affinity binding sites in the absorbents. The apparent maximum binding capacity and dissociation constant were 17.88 mg/g and 158.7 μg/mL for high‐affinity binding sites and 9.310 mg/g and 35.04 μg/mL for low‐affinity binding sites, respectively. The results testified that multi‐hollow magnetic molecularly imprinted polymers possessed excellent recognition capacity and fast kinetic binding behavior to the objective molecules due to the high specific surface area as large as 511.3 m²/g. Recoveries of 75.5–86.8% were obtained for the indolebutyric acid spiked at three concentration levels in blank and pear samples.     

L-酪氨酸印迹分子的制备及性能研究

利用分子印迹技术采用传统加热法制备出酪氨酸他子印迹聚合物。用红外光谱分析了聚合物结构。研究了印迹他子与功能单体的物质的量对聚合物结合性的影响,吸收效率表征结果显示,与化学组成相同的空白聚合物相比,印迹聚合物具有更高的吸附效率。     

Water-compatible molecularly imprinted polymer for the selective recognition of fluoroquinolone antibiotics in biological samples

A novel water-compatible molecularly imprinted polymer (MIP), prepared with enrofloxacin (ENR) as the template, has been optimised for the selective extraction of fluoroquinolone antibiotics in aqueous media. The results of a morphological characterisation and selectivity tests of the polymer material for ENR and related derivatives are reported. High affinity for the piperazine-based fluoroquinolones marbofloxacin, ciprofloxacin, norfloxacin and ofloxacin was observed, whereas no retention was found for nonrelated antibiotics. Various parameters affecting the extraction efficiency of the polymer have been optimised to achieve selective extraction of the antibiotics from real samples and to reduce nonspecific interactions. These findings resulted in a MISPE/HPLC-FLD method allowing direct extraction of the analytes from aqueous samples with a selective wash using just 50% (v/v) organic solvent. The method showed excellent recoveries and precision when buffered urine samples fortified at five concentration levels (25–250 ng mL⁻¹ each) of marbofloxacin, ciprofloxacin, norfloxacin, enrofloxacin and sarafloxacin were tested (53–88%, RSD 1–10%, n = 3). Moreover, the biological matrix of the aqueous samples did not influence the preconcentration efficiency of the fluoroquinolones on the MIP cartridges; no significant differences were observed between the recovery rates of the antibiotics in buffer and urine samples. The detection limits of the whole process range between 1.9 and 34 ng mL^–1 when 5-mL urine samples are processed. The developed method has been successfully applied to preconcentration of norfloxacin in urine samples of a medicated patient, demonstrating the ability of the novel MIP for selective extraction of fluoroquinolones in urine samples.     

Synthesis of a molecularly imprinted polymer on mSiO2@Fe3O4 for the selective adsorption of atrazine

Atrazine contamination of water is of considerable concern because of the potential hazard to human health. In this study, a magnetic molecularly imprinted polymer for atrazine was prepared by the surface‐imprinting technique using Fe₃O₄ as the core, mesoporous silica as the carrier, atrazine as the template, and itaconic acid as the functional monomer. The magnetic molecularly imprinted polymer was characterized by Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, and vibration‐sample magnetometry. The binding properties of the magnetic molecularly imprinted polymer toward atrazine were investigated by adsorption isotherms, kinetics, and competitive adsorption. It was found that the adsorption equilibrium was achieved within 2 h, the maximum adsorption capacity of atrazine was 8.8 μmol/g, and the adsorption process could be well described by the Langmuir isotherm model and pseudo‐second‐order kinetic model. The magnetic molecularly imprinted polymer exhibited good adsorption selectivity for atrazine with respect to structural analogues, such as cyanazine, simetryne, and prometryn. The reusability of the magnetic molecularly imprinted polymer was demonstrated for at least five repeated cycles without a significant decrease in adsorption capacity. These results suggested that the magnetic molecularly imprinted polymer could be used as an efficient material for the selective adsorption and removal of atrazine from water samples.     

环氧功能化双功能磁性分子印迹聚合物的合成及其在多糖吸附中的应用

以淀粉为模板，以3-氨基苯硼酸（APBA）和2-丙烯酰胺-2-甲基丙磺酸（AMPS）为功能单体，以过硫酸铵（APS）为引发剂，在水溶液中成功合成了一种识别多糖的双功能分子印迹聚合物（Bi-MMIPs）。采用透射电镜、扫描电镜、傅里叶变换红外光谱等考察了Bi-MMIPs的合成效果。通过吸附试验深入研究了Bi-MMIPs对淀粉的吸附和识别特性。结果表明：Bi-MMIPs成功负载了两种功能单体，且对多糖（淀粉）具有很强的吸附亲和力和特异性识别能力，饱和吸附量达到13.88 mg/g；对于葡聚糖（M_r 5000 Da和70000 Da）的选择性系数分别为2.67和3.77；此外，Bi-MMIPs的印迹因子（α）达到了3.04，且易于再生。在机理上，APBA和AMPS分别提供可逆共价键和氢键，在合成双功能单体中表现出协同效应，可以有效改善模板分子结合位点的空间排列。     

Rapid measurements of curcumin from complex samples coupled with magnetic biocompatibility molecularly imprinted polymer using electrochemical detection

Curcumin widely exists in food, and rapid selective and accurate detection of curcumin have great significance in chemical industry. In this experiment, a new magnetic biocompatibility molecularly imprinted polymer was prepared with nontoxic and biocompatible Zein to adsorb curcumin selectively. The polymer has high biocompatibility, good adsorption capacity, and specific adsorption for curcumin. Combined with portable electrochemical workstations, the polymer can be used to detect curcumin rapidly and cost‐effectively. Using curcumin as a template and Zein as the crosslinking agent, the polymers were synthesized on the surface of Fe₃O₄ particles for solid phase extraction. The experimental results showed that the polymer reached large adsorption capacity (32.12 mg/g) with fast kinetics (20 min). The adsorption characteristic of the polymer followed the Langmuir isotherm and pseudo‐second‐order kinetic models. Hexacyanoferrate was used as electrochemical probe to generate signals, and the linear range was 5–200 µg/mL for measuring curcumin. The experimental analysis showed that the polymer was an ideal material for selective accumulation of curcumin from complex samples. This approach has been successfully applied to the determination of curcumin in food samples with electrochemical detection, indicating that this is a feasible and practical technique.     

Construction of a novel electrochemical sensor based on molecularly imprinted polymers for the selective determination of chlorpyrifos in real samples

We present a novel electrochemical sensor based on an electrode modified with molecularly imprinted polymers for the detection of chlorpyrifos. The modified electrode was constructed by the synthesis of molecularly imprinted polymers by a precipitation method then coated on a glassy carbon electrode. The surface morphology of the modified electrode was characterized by using field‐emission scanning electron microscopy and transmission electron microscopy. The performance of the imprinted sensor was thoroughly investigated by using cyclic voltammetry and differential pulse voltammetry. The imprinted electrochemical sensor displayed high repeatability, stability, and selectivity towards the template molecules. Under the optimal experimental conditions, the peak current response of the imprinted electrochemical sensor was linearly related to the concentration of chlorpyrifos over the range 1 × 10⁻¹⁰–1 × 10⁻⁵ mol/L with a limit of detection of 4.08 × 10⁻⁹ mol/L (signal‐to‐noise ratio = 3). Furthermore, the proposed molecularly imprinted electrochemical sensor was applied to the determination of chlorpyrifos in the complicated matrixes of real samples with satisfactory results. Therefore, the molecularly imprinted polymers based electrochemical sensor might provide a highly selective, rapid, and cost‐effective method for chlorpyrifos determination and related analysis.     

Preparation of magnetic molecularly imprinted polymers for the rapid and selective separation and enrichment of perfluorooctane sulfonate

As a persistent organic pollutant, perfluorooctane sulfonate has drawn a great worldwide attention. In this contribution, a novel material of magnetic molecularly imprinted polymers, based on perfluorooctane sulfonate, as a template, molecule was prepared. The magnetic molecularly imprinted polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The adsorption isotherm was measured, and adsorption kinetic tests were conducted. The adsorbents possess high recognition ability (2.460 mg/g) and short adsorption equilibration time (60 min). Besides, they show good specificity and good reusability with the adsorption capacities of adsorbent toward perfluorooctane sulfonate decreasing less than 3% after five adsorption–desorption cycles. The magnetic molecularly imprinted polymers were used successfully in the separation and enrichment of perfluorooctane sulfonate in real water sample and exhibited good prospects in environmental treatment and monitoring.     

Computer‐aided design and synthesis of CdTe@SiO2 core–shell molecularly imprinted polymers as a fluorescent sensor for the selective determination of sulfamethoxazole in milk and lake water

In this work, a molecular dynamics simulation method was introduced to compute the preassembled system of molecular imprinted polymers for sulfamethoxazole monomer. The results revealed that the ratio of sulfamethoxazole as template molecule to 3‐aminopropyltriethoxysilane as functional monomer to tetraethylorthosilicate as cross‐linker of 10:10:40 led to the most stable template‐functional monomer cluster. Based on the result of computational simulation, CdTe@SiO₂ core–shell imprinted polymers, a cadmium telluride quantum dots layer on the surface of aminofunctionalized SiO₂, were synthesized as the fluorescent sensor. Then, a series of measures were used to characterize the structure and morphology to get optimal sensors. The concentration range was 5.0–30.0 μmol/L between molecular imprinted polymers at CdTe at SiO₂, and sulfamethoxazole of the fluorescence intensity. To further verify the reliability and accuracy of the fluorescent sensor, the application was successfully by analyzing sulfamethoxazole in pure milk and lake water. The results showed the recoveries were above 96.89% with a relative standard deviation of 1.25–5.45%, and the fluorescence sensor with selective recognition provides an alternative solution for the determination of sulfamethoxazole.     

Synthesis and characterization of photo‐responsive magnetic molecularly imprinted microspheres for the detection of sulfonamides in aqueous solution

A dual responsive molecularly imprinted polymer sensitive to both photonic and magnetic stimuli was successfully prepared for the detection of four sulfonamides in aqueous media. The photoresponsive magnetic molecularly imprinted polymer was prepared by surface imprinting polymerization using superparamagnetic Fe₃O₄ nanoparticles functionalized with a silica layer as a support, water‐soluble 4‐[(4‐methacryloyloxy)phenylazo]benzenesulfonic acid as the functional monomer, and sulfadiazine as the template. The magnetic molecularly imprinted polymers showed specific affinity to sulfadiazine and its structural analogs in aqueous media. Upon alternate irradiation at 365 and 440 nm, the quantitative bind and release of the four sulfonamides by magnetic molecularly imprinted polymers occurred. Furthermore, the prepared magnetic molecularly imprinted polymers were used as solid‐phase extraction material selectively extracted the four sulfonamides from water samples with good recoveries. Thus, a simple, convenient, and reliable detection method for sulfonamides in the environment based on responsive magnetic molecularly imprinted polymers was successfully established.     

Preparation of bio‐based keratin‐derived magnetic molecularly imprinted polymer nanoparticles for the facile and selective separation of bisphenol A from water

In this study, new bio‐based magnetic molecularly imprinted polymer nanoparticles (∼23 nm) were synthesized from keratin extracted from chicken feathers and methacrylate‐functionalized Fe₃O₄ nanoparticles for its potential application in separation and removal of bisphenol A from water. The prepared magnetic molecularly imprinted polymer was characterized by Fourier‐transform infrared spectroscopy, field‐emission scanning electron microscopy, thermogravimetric analysis, alternative gradient field magnetometry, and energy‐dispersive X‐ray spectroscopy. The sorption of bisphenol A was investigated by changing the influencing factors such as pH, immersion time, Fe₃O₄ nanoparticles dosage, and the initial concentration of bisphenol A. Results illustrated that sorption was very fast and efficient (Q_m = 600 mg/g) having a removal efficiency of ∼98% in 40 min of immersion. The adsorption process showed better conformity with the Weber−Morris kinetics and the Freundlich isotherm model. The selectivity of bisphenol A by adsorbent was checked in the presence of hydroquinone, phenol, tetrabromobisphenol, and 4,4′‐biphenol as interferences.     

Magnetic molecularly imprinted polymer for the efficient and selective preconcentration of diazinon before its determination by high‐performance liquid chromatography

A molecularly imprinted polymer was selectively applied for solid‐phase extraction and diazinon residues enrichment before high‐performance liquid chromatography. Diazinon was thermally copolymerized with Fe₃O₄@polyethyleneglycol nanoparticles, methacrylic acid (functional monomer), 2‐hydroxyethyl methacrylate (co‐monomer), and ethylene glycol dimethacrylate (cross‐linking monomer) in the presence of acetonitrile (porogen) and 2,2‐azobisisobutyronitrile (initiator). Then, the imprinted diazinon was reproducibly eluted with methanol/acetic acid (9:1, v/v). The sorbent particles were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The comprehensive study of variables through experimental design showed that the maximum performance was achieved under these conditions: pH 7, 10 mL sample volume, 15 mg sorbent, 10 min vortex time, 5 min ultrasonic time, 200 μL methanol/acetic acid (9:1, v/v) as eluent, and 5 min desorption time. Under optimized conditions, the molecularly imprinted polymer solid‐phase extraction method demonstrated a linear range (0.02–5 g/mL), a correlation coefficient of 0.997, and 0.005 g/mL detection limit.     

Computational design and fabrication of core–shell magnetic molecularly imprinted polymer for dispersive micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the determination of rhodamine 6G

A novel core–shell magnetic nano‐adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro‐solid‐phase extraction followed by determination of rhodamine 6G using high‐performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m‐aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA₉ (3⁴) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid‐base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano‐adsorbent was successfully applied to dispersive micro‐solid‐phase extraction coupled to high‐performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0–99.1, 89.5–92.7, and 86.9–105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%.     

Facile preparation of magnetic molecularly imprinted polymers for the selective extraction and determination of dexamethasone in skincare cosmetics using HPLC

Dexamethasone‐imprinted polymers were fabricated by reversible addition–fragmentation chain transfer polymerization on the surface of magnetic nanoparticles under mild polymerization conditions, which exhibited a narrow polydispersity and high selectivity for dexamethasone extraction. The dexamethasone‐imprinted polymers were characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy, X‐ray diffraction, energy dispersive spectrometry, and vibrating sample magnetometry. The adsorption performance was evaluated by static adsorption, kinetic adsorption and selectivity tests. The results confirmed the successful construction of an imprinted polymer layer on the surface of the magnetic nanoparticles, which benefits the characteristics of high adsorption capacity, fast mass transfer, specific molecular recognition, and simple magnetic separation. Combined with high‐performance liquid chromatography, molecularly imprinted polymers as magnetic extraction sorbents were used for the rapid and selective extraction and determination of dexamethasone in skincare cosmetic samples, with the accuracies of the spiked samples ranging from 93.8 to 97.6%. The relative standard deviations were less than 2.7%. The limit of detection and limit of quantification were 0.05 and 0.20 μg/mL, respectively. The developed method was simple, fast and highly selective and could be a promising method for dexamethasone monitoring in cosmetic products.     

Preparation and characterization of a novel molecularly imprinted polymer for the separation of glycyrrhizic acid

Molecularly imprinted polymers of glycyrrhizic acid were prepared by solution polymerization using glycyrrhizic acid as the template molecule, N‐vinypyrrolidone as functional monomer, N ,N‐methylene bisacrylamide as cross‐linker and ascorbic acid and hydrogen peroxide as initiators. Focused on the adsorption capacity and separation degree of the polymer to glycyrrhizic acid, the effects of the monomers, crosslinker and initiators were investigated and optimized. Finally, the structure of the polymer was characterized by using Fourier transform infrared spectroscopy and scanning electron microscopy. To obtain objective results, non‐imprinted molecular polymers prepared under the same conditions were also characterized. The adsorption quantity of the polymer was measured by high‐performance liquid chromatography. Under the optimum conditions, the maximum adsorption capacity of glycyrrhizic acid approached 15 mg/g, and the separation degree was as high as 2.5. The adsorption kinetics could be well described by a pseudo‐first‐order model, while the thermodynamics of the adsorption process could be described by the Langmuir model.     

Synthesis of molecularly imprinted polymer adsorbents for solid‐phase extraction of strobilurin fungicides from agricultural products

Molecularly imprinted polymers for strobilurin fungicides were prepared by precipitation polymerization employing azoxystrobin as template molecular together with methacrylic acid monomer and trimethylolpropane triacrylate cross‐linker. Morphological characterization showed molecularly imprinted polymers were uniform spherical particles with about 0.2 μm in diameter, while the morphologies of nonimprinted polymers were irregular bulk. The equilibrium binding and selective experiments proved that molecularly imprinted polymers possessed a higher affinity toward four fungicides compared to nonimprinted polymers and heterogeneous binding sites were found in the molecularly imprinted polymers. Molecularly imprinted solid‐phase extraction conditions, including sample loading solvents, selective washing, and elution solvents, were carefully optimized. The developed method showed good recoveries (70.0–114.0%) with relative standard deviations in range of 1.0–9.8% (n  =  3) for samples (cucumber and peach) spiked at three different levels (10, 50, and 100 μg/ kg). The detection limit (signal/noise = 3) ranged from 0.01 to 0.08 μg/kg. The results demonstrated good potential use of this convenient and highly efficient method for determining trace strobilurin fungicides in agricultural products.     

Preparation and application of molecularly imprinted polymer solid‐phase microextraction fiber for the selective analysis of auxins in tobacco

As signal molecules, auxins play an important role in mediating plant growth. Due to serious interfering substances in plants, it is difficult to accurately detect auxins with traditional solid‐phase extraction methods. To improve the selectivity of sample pretreatment, a novel molecularly imprinted polymer ‐coated solid‐phase microextraction fiber, which could be coupled directly to high‐performance liquid chromatography, was prepared with indole acetic acid as template molecule for the selective extraction of auxins. The factors influencing the polymer formation, such as polymerization solvent, cross‐linker, and polymerization time, were investigated in detail to enhance the performance of indole acetic acid‐molecularly imprinted polymer coating. The morphological and chemical stability of this molecularly imprinted polymer‐coated fiber was characterized by scanning electron microscopy, infrared spectrometry, and thermal analysis. The extraction capacity of the molecularly imprinted polymer‐coated solid‐phase microextraction fiber was evaluated for the selective extraction of indole acetic acid and indole‐3‐pyruvic acid followed by high‐performance liquid chromatography analysis. The linear range for indole acetic acid and indole‐3‐pyruvic acid was 1–100 µg/L and their detection limit was 0.5 µg/L. The method was applied to the simultaneous determination of two auxins in two kinds of tobacco (Nicotiana tabacum L and Nicotiana rustica L) samples, with recoveries range from 82.1 to 120.6%.     

Synthesis of a molecularly imprinted polymer for the selective recognition of carmoisine (Azorubin E122) from pomegranate juice

Since natural pigments are lost during the processing of beverages such as pomegranate juice, carmoisine, as an adulterant, is often added into the pure juice to improve color characteristics. In this study, molecularly imprinted polymers, as an adsorbent of carmoisine, were synthesized using acrylamide, methacrylic acid, and 4‐vinylpyridine as functional monomers and then they were evaluated in terms of the separation and detection of carmoisine. Experiments on the batch adsorption of carmoisine 10 ppm stock solution revealed a better binding capacity for the 4‐vinylpyridine‐based polymer in comparison to methacrylic acid and acrylamide polymers. The complexation of carmoisine with the 4‐vinylpyridine‐based polymer was confirmed by Fourier transform infrared spectroscopy. The synthesized polymer exerted a high thermal degradation point and average diameter of polymer particles were obtained to be 0.2 μm by dynamic light scattering analysis. This work showed that detection of pomegranate juice adulteration with carmoisine is not necessarily difficult, time consuming or expensive with selective separation techniques such as molecularly imprinted polymers.