Selective solid‐phase extraction of artificial chemicals from milk samples using multiple‐template surface molecularly imprinted polymers

A novel multiple‐template surface molecularly imprinted polymer (MTMIP) was synthesized using ofloxacin and 17β‐estradiol as templates and modified monodispersed poly(glycidylmethacrylate‐co‐ethylene dimethacrylate) (P_GMA/EDMA) beads as the support material. Static adsorption, solid‐phase extraction and high‐performance liquid chromatography were performed to investigate the adsorption properties and selective recognition characteristics of the polymer templates and their structural analogs. The maximum binding capacities of ofloxacin and 17β‐estradiol on the MTMIP were 9.0 and 6.6 mg/g, respectively. Compared with the corresponding nonimprinted polymer, the MTMIP exhibited a much higher adsorption performance and selectivity toward three quinolones and three estrogens, which are common drug residues in food. The MTMIP served as a simple and effective pretreatment method and could be successfully applied to the simultaneous analysis of multiple target components in complex samples. Furthermore, the MTMIP may find useful applications as a solid‐phase absorbent in the simultaneous determination of trace quinolones and estrogens in milk samples, as the recoveries were in the range 77.6–98.0%. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Polydopamine‐coated magnetic molecularly imprinted polymer for the selective solid‐phase extraction of cinnamic acid,ferulic acid and caffeic acid from radix scrophulariae sample

We describe novel cinnamic acid polydopamine‐coated magnetic imprinted polymers for the simultaneous selective extraction of cinnamic acid, ferulic acid and caffeic acid from radix scrophulariae sample. The novel magnetic imprinted polymers were synthesized by surface imprinting polymerization using magnetic multi‐walled carbon nanotubes as the support material, cinnamic acid as the template and dopamine as the functional monomer. The magnetic imprinted polymers were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The results revealed that the magnetic imprinted polymers had outstanding magnetic properties, high adsorption capacity, selectivity and fast kinetic binding toward cinnamic acid, ferulic acid and caffeic acid. Coupled with high‐performance liquid chromatography, the extraction conditions of the magnetic imprinted polymers as a magnetic solid‐phase extraction sorbent were investigated in detail. The proposed imprinted magnetic solid phase extraction procedure has been used for the purification and enrichment of cinnamic acid, ferulic acid and caffeic acid successfully from radix scrophulariae extraction sample with recoveries of 92.4–115.0% for cinnamic acid, 89.4–103.0% for ferulic acid and 86.6–96.0% for caffeic acid.     

Recent advances and applications of molecularly imprinted polymers in solid‐phase extraction for real sample analysis

Sample pretreatment is essential for the analysis of complicated real samples due to their complex matrices and low analyte concentrations. Among all sample pretreatment methods, solid‐phase extraction is arguably the most frequently used one. However, the majority of available solid‐phase extraction adsorbents suffer from limited selectivity. Molecularly imprinted polymers are a type of tailor‐made artificial antibodies and receptors with specific recognition sites for target molecules. Using molecularly imprinted polymers instead of conventional adsorbents can greatly improve the selectivity of solid‐phase extraction, and therefore molecularly imprinted polymer‐based solid‐phase extraction has been widely applied to separation, clean up and/or preconcentration of target analytes in various kinds of real samples. In this article, after a brief introduction, the recent developments and applications of molecularly imprinted polymer‐based solid‐phase extraction for determination of different analytes in complicated real samples during the 2015‐2020 are reviewed systematically, including the solid‐phase extraction modes, molecularly imprinted adsorbent types and their preparations, and the practical applications of solid‐phase extraction to various real samples (environmental, food, biological, and pharmaceutical samples). Finally, the challenges and opportunities of using molecularly imprinted polymer‐based solid‐phase extraction for real sample analysis are discussed.     

Extraction and identification of matrine‐type alkaloids from Sophora moorcroftiana using double‐templated molecularly imprinted polymers with HPLC–MS/MS

Double‐templated molecularly imprinted polymers with specific recognition of three matrine‐type alkaloids were prepared using matrine and oxymatrine as the template molecules. An approach based on double‐templated molecularly imprinted solid‐phase extraction coupled with high‐performance liquid chromatography and tandem mass spectrometry was then developed to extract and purify matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana in the Tibetan plateau herbs. The polymers were characterized by Fourier‐transform infrared spectroscopy and scanning electron microscopy. Their adsorption characteristics were evaluated using adsorption kinetics, isotherms, selectivity, and recycling experiments. This polymer exhibited excellent molecular recognition ability and good selectivity. The obtained polymers as adsorbent was further used for the determination of three matrine‐type alkaloids coupled to high‐performance liquid chromatography with tandem mass spectrometry, the recoveries of three matrines spiked at three concentration levels in samples were 73.25–98.42% (n = 5) with a relative standard deviation less than 6.82%. The limits of detection for the method were 9.23–15.42 μg/kg (S/N = 3). This proposed method was assessed to be an effective method for simultaneous extraction, isolation, and identification of matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana.     

Rapid preparation of molecularly imprinted polymers by custom‐made microwave heating for analysis of atrazine in water

The rapid preparation of an atrazine‐imprinted polymer in a cost‐effective custom‐made microwave reactor was demonstrated. The polymerization reaction was accelerated by microwave heating, and the preparation time was greatly shortened (to 1 h). The resulting polymer was successfully applied as solid‐phase extraction adsorbent for the selective extraction and preconcentration of atrazine in environmental water samples. The binding capacity of the polymer was 1.11 mg/g polymer. The polymer provided selectivity with higher recovery of atrazine than of other interfering related contaminants. The proposed method had good limits of detection and quantitation at 0.20 and 0.60 ng/mL, respectively. The recoveries were from 83 to 89% at two spiking levels, with relative standard deviations less than 5%. This method was successfully applied to determine the atrazine levels in environmental water samples.     

Molecularly imprinted polymers for the solid‐phase extraction of four fluoroquilones from milk and lake water samples

A method based on molecular crowding and ionic liquids as reaction solvents has been used for the synthesis of molecularly imprinted polymers. Levofloxacin was selected as the template, polymethyl methacrylate was the molecular crowding agent, and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (ionic liquid) was selected as the reaction solvent and porogen. The optimized proportion for the mixed porogen was dimethyl sulfoxide/ionic liquid/polymethyl methacrylate 1:1.6:5 in chloroform (150 mg mL^?1). The morphology and chemical composition of levofloxacin imprinted polymers were assessed by scanning electron microscopy and Fourier transform infrared spectroscopy. The absorption experiments demonstrated that the levofloxacin imprinted polymers possess high selective recognition property to levofloxacin and analogs, including enrofloxacin, ciprofloxacin and gatifloxacin, which all belong to fluoroquinolones. An extraction method using levofloxacin imprinted polymers as sorbent followed by high‐performance liquid chromatography analysis was optimized for the determination of four fluoroquinolones in milk and lake water samples. Under the optimized conditions, good linearity was observed in a range of 5–1000 ng g^?1 with the limit of detection between 0.3 and 0.5 ng g^?1 for the four fluoroquinolones. The recoveries at three spiked levels ranged 82.4–98.3% with the relative standard deviation ≤4.9.     

Selective solid‐phase extraction using a molecularly imprinted polymer for the analysis of patulin in apple‐based foods

The aim of this work was to evaluate the use of a molecularly imprinted polymer as a selective solid‐phase extraction sorbent for the clean‐up and pre‐concentration of patulin from apple‐based food products. Ultra high pressure liquid chromatography coupled to ultraviolet absorbance detection was used for the analysis of patulin. The molecularly imprinted polymer was applied, for the first time, to the determination of patulin in apple juice, puree and jam samples spiked within the maximum levels specified by the European Commission No. 1881/2006. High recoveries (>77%) were obtained. The method was validated and found to be linear in the range 2–100 μg/kg with correlation coefficients greater than 0.965 and repeatability relative standard deviation below 11% in all cases. Compared with dispersive solid‐phase extraction (QuEChERS method) and octadecyl sorbent, the molecularly imprinted polymer showed higher recoveries and selectivity for patulin. The application of Affinisep molecularly imprinted polymer as a selective sorbent material for detection of patulin fulfilled the method performance criteria required by the Commission Regulation No. 401/2006, demonstrating the suitability of the technique for the control of patulin at low ppb levels in different apple‐based foods such as juice, puree and jam samples.     

Development of a validated strategy for the determination of tryptamine in human cerebrospinal fluid in the presence of competitors using molecularly imprinted polymers

This study presents a validated strategy for the determination of tryptamine in the presence of its competitors, which involves the molecularly imprinted solid‐phase extraction combined with high‐performance liquid chromatography coupled with fluorimetric detection. Tryptamine‐imprinted microscale sorbent was produced from 4‐vinylbenzoic acid and ethylene glycol dimethacrylate in methanol by precipitation polymerization, and its imprinting factor was equal to 15.4 in static experiments or 18.6 in dynamic binding experiments. The method for tryptamine determination in the presence of serotonin and l ‐tryptophan was validated using a complex matrix of bovine serum albumin yielding the recoveries of tryptamine that ranged between 98.7 and 107.0%. Very low limits of detection and limits of quantification for tryptamine (19.9 and 60.3 nmol/L, respectively) allow the quantification of tryptamine in human cerebrospinal fluid in the presence of tryptophan and serotonin.     

Preparation of dummy‐imprinted polymers by Pickering emulsion polymerization for the selective determination of seven bisphenols from sediment samples

The dummy molecularly imprinted polymers were prepared by Pickering emulsion polymerization. 4,4′‐(1‐Phenylethylidene) bisphenol was selected as the dummy template to avoid the leakage of the target bisphenols. The microsphere particles were characterized by scanning electron microscopy and nitrogen adsorption–desorption measurements, demonstrating that the regular‐shaped and medium‐sized particles (40–70 μm) were obtained with a specific surface area of 355.759 m²/g and a total pore volume of 0.561 cm³/g. The molecular imprinting properties of the particles were evaluated by static adsorption and chromatographic evaluation experiments. The association constant and maximum adsorption amount of bisphenol A were 0.115 mmol/L and 3.327 μmol/g using Scatchard analysis. The microsphere particles were then used as a solid‐phase extraction sorbent for selective extraction of seven bisphenols. The method of dummy molecularly imprinted solid‐phase extraction coupled with high‐performance liquid chromatography and diode array detection was successfully established for the extraction and determination of seven bisphenols from environmental sediment samples with method detection limits of 0.6–1.1 ng/g. Good recoveries (75.5–105.2%) for sediment samples at two spiking levels (500 and 250 ng/g) and reproducibility (RSDs < 7.7%, n = 3) were obtained.     

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.     

Magnetic molecularly imprinted polymers for recognition and enrichment of polysaccharides from seaweed

New magnetic molecularly imprinted polymers with two templates were fabricated for the recognition of polysaccharides (fucoidan and alginic acid) from seaweed by magnetic solid‐phase extraction, and the materials were modified by seven types of deep eutectic solvents. It was found that the deep eutectic solvents magnetic molecularly imprinted polymers showed stronger recognition and higher recoveries for fucoidan and alginic acid than magnetic molecularly imprinted polymers, and the deep eutectic solvents‐4‐magnetic molecularly imprinted polymers had the best effects. The practical recovery of the two polysaccharides (fucoidan and alginic acid) purified with deep eutectic solvents‐4‐magnetic molecular imprinted polymers in seaweed under the optimal conditions were 89.87, and 92.0%, respectively, and the actual amounts extracted were 20.6 and 18.7 μg/g, respectively. To sum up, the developed method proved to be a novel and promising method for the recognition of complex polysaccharide samples from seaweed.     

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.     

A new ionic liquid surface‐imprinted polymer for selective solid‐phase‐extraction and determination of sulfonamides in environmental samples

Toward improving the selective adsorption performance of molecularly imprinted polymers in strong polar solvents, in this work, a new ionic liquid functional monomer, 1‐butyl‐3‐vinylimidazolium bromide, was used to synthesize sulfamethoxazole imprinted polymer in methanol. The resulting molecularly imprinted polymer was characterized by Fourier transform infrared spectra and scanning electron microscopy, and the rebinding mechanism of the molecularly imprinted polymer for sulfonamides was studied. A static equilibrium experiment revealed that the as‐obtained molecularly imprinted polymer had higher molecular recognition for sulfonamides (e.g., sulfamethoxazole, sulfamonomethoxine, and sulfadiazine) in methanol; however, its adsorption of interferent (e.g., diphenylamine, metronidazole, 2,4‐dichlorophenol, and m‐dihydroxybenzene) was quite low. ¹H NMR spectroscopy indicated that the excellent recognition performance of the imprinted polymer was based primarily on hydrogen bond, electrostatic and π‐π interactions. Furthermore, the molecularly imprinted polymer can be employed as a solid phase extraction sorbent to effectively extract sulfamethoxazole from a mixed solution. Combined with high‐performance liquid chromatography analysis, a valid molecularly imprinted polymer‐solid phase extraction protocol was established for extraction and detection of trace sulfamethoxazole in spiked soil and sediment samples, and with a recovery that ranged from 93–107%, and a relative standard deviation of lower than 9.7%.     

分子印迹聚合物固相萃取研究进展

对最新报道的分子印迹聚合物作为固相萃取剂及其在色谱样品前处理方面的应用进行综述和展望,主要包括固相萃取、基质固相分散萃取、固相微萃取、搅拌棒吸附萃取和磁性材料萃取,同时总结了分子印迹聚合物制备技术面临的挑战和问题,提出了可能的解决方案。     

Design of selective molecularly imprinted sorbent for the optimized solid‐phase extraction of S‐pramipexole from the model multicomponent sample of human urine

The objective of this article was to design the selective molecularly imprinted sorbent dedicated to the solid‐phase extraction of S‐pramipexole from the complex matrix such as human urine. For that purpose, S‐2,6‐diamino‐4,5,6,7‐tetrahydrobenzothiazole was used as the template acting as the structural analog of S‐pramipexole and five various monomers were employed in the presence of ethylene glycol dimethacrylate to produce molecularly imprinted polymers. The binding capabilities of resulted polymers revealed that the highest imprinting effect was noted for polymer prepared from the itaconic acid. The comprehensive analysis of morphology and the characterization of binding sites showed not only negligible differences in the extension of surfaces of imprinted and nonimprinted polymers but also higher heterogeneity of binding sites in the imprinted material. Comprehensive optimization of the molecularly imprinted solid‐phase extraction allowed to select the most appropriate solvents for loading, washing, and elution steps. Subsequent optimization of mass of sorbent and volumes of solvents allowed to achieve satisfactory total recoveries of S‐pramipexole from the model multicomponent real sample of human urine that equals to 91.8 ± 3.2% for imprinted sorbent with comparison to only 37.1 ± 1.1% for Oasis MCX.     

吲哚美辛纳米胶体金分子印迹聚合物的制备及其在固相萃取中的应用

以吲哚美辛(IDM)为模板分子,丙烯酰胺(AA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,本体聚合法制备过程中加入纳米胶体金,合成了吲哚美辛胶体金分子印迹聚合物(MIPs/Au),利用MIPs/Au表面胶体金对蛋白吸附作用,将抗吲哚美辛的多克隆抗体固定在MIPs/Au上,得到表面固定有抗体的新型聚合物(MIPs/Au-Ab)并对其进行了表征。制备了填充材料为MIPs/Au-Ab的固相萃取柱并对其上样、淋洗和洗脱条件进行了优化,并将所制备的新型萃取柱用于水样中IDM的分离富集。抗吲哚美辛抗体交联在聚合物表面,不仅增加了萃取柱的特异性吸附容量,而且有效地降低了MIP的非特异性吸附。     

Magnetic molecularly imprinted polymers based on silica modified by deep eutectic solvents for the rapid simultaneous magnetic‐based solid‐phase extraction of Salvia miltiorrhiza bunge,Glycine max (Linn.) Merr and green tea

Novel magnetic molecularly imprinted polymers (MMIPs) with multiple‐template based on silica were modified by four types of deep eutectic solvents (DESs) for the rapid simultaneous magnetic solid‐phase extraction (MSPE) of tanshinone Ⅰ, tanshinone ⅡA, and cryptotanshinone from Salvia miltiorrhiza bunge; glycitein, genistein, and daidzein from Glycine max (Linn.) Merr; and epicatechin, epigallocatechin gallate, and epicatechin gallate from green tea, respectively. The synthesized materials were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Single factor experiments were to explore the relationship between the extraction efficiency and four factors (the sample solution pH, amount of DESs for modification, amount of adsorbent, and extraction time). It was showed that the DES4‐MMIPs have better extraction ability than the MMIPs without DESs and the other three DESs‐modified MMIPs. The best extraction recoveries with DES4‐MMIP were tanshinone Ⅰ (85.57%), tanshinone ⅡA (80.58%), cryptotanshinone (92.12%), glycitein (81.65%), genistein (87.72%), daidzein (92.24%), epicatechin (86.43%), epigallocatechin gallate (80.92%), and epicatechin gallate (93.64%), respectively. The novel multiple‐template MMIPs materials modified by DES for the rapid simultaneous MSPE of active compounds were proved to reduce the experimental steps than single‐template technique, and increase the extraction efficiency.     

Preparation and characterization of molecularly imprinted polymers based on β‐cyclodextrin‐stabilized Pickering emulsion polymerization for selective recognition of erythromycin from river water and milk

Molecularly imprinted polymers were prepared via β‐cyclodextrin‐stabilized oil‐in‐water Pickering emulsion polymerization for selective recognition and adsorption of erythromycin. The synthesized molecularly imprinted polymers were spherical in shape, with diameters ranging from 20 to 40 µm. The molecularly imprinted polymers showed high adsorption capacity (87.08 mg/g) and adsorption isotherm data fitted well with Langmuir model. Adsorption kinetics study demonstrated that the molecularly imprinted polymers acted in a fast adsorption kinetic pattern and the adsorption features of molecularly imprinted polymers followed a pseudo‐first‐order model. Adsorption selectivity analysis revealed that molecularly imprinted polymers had a much better specificity for erythromycin than that for spiramycin or amoxicillin, and the relative selectivity coefficient values on the bases of spiramycin and amoxicillin were 3.97 and 3.86, respectively. The Molecularly imprinted polymers also showed a satisfactory reusability after four times of regeneration. In addition, molecularly imprinted polymers exhibited good adsorption capacities for erythromycin under complicated environment, that is, river water and milk. These results proved that the as‐prepared molecularly imprinted polymers is a potent absorbent for selective recognition of erythromycin, and therefore it may be a promising candidate for practical applications, such as wastewater treatment and detection of erythromycin residues in food.     

Preparation of restricted access media molecularly imprinted polymers for efficient separation and enrichment ofloxacin in bovine serum samples

We prepared ofloxacin restricted access media molecularly imprinted polymers using surface‐initiated atom transfer radical polymerization on the surface of brominated silica gel using ofloxacin as a template molecule, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a crosslinking agent. We then characterized and studied the surface morphology and adsorption properties of the polymer. Experimental results show that saturation is reached within 25 min, and that the saturated adsorption capacity was 80.67 mg/g and the imprinting factor was 1.94. Our findings also showed that the polymer surface had good hydrophilicity and an excellent protein exclusion rate, which was 98.49%. The restricted access media molecularly imprinted polymers were then successfully applied to the enrichment and separation of ofloxacin in bovine serum. When combined with high‐performance liquid chromatography, and the average recovery of ofloxacin was 95.6%, and the relative standard deviation was in the range of 2.47–3.38%. In a word, the restricted access media molecularly imprinted polymers is a method that involves a simple preparation procedure that results in excellent performance, which is a great improvement in the speed of detection of antibiotics. These qualities are what bestow upon this method its great potential for broad application.