Development of a molecularly imprinted polymer for selective extraction of bisphenol A in water samples

A cross‐linked methacrylate molecularly imprinted polymer (poly‐4‐vinylpyridine‐co‐trimethylolpropane‐trimethacrylate) selective for bisphenol A (BPA) was synthesized, using a fluorinated BPA derivative (4,4′‐(hexafluoroisopropylidene)‐diphenol) as a mimic template, and applied to the analysis of real‐world samples of process and potable waters. The molecularly imprinted polymer also showed a high affinity and selectivity for 17‐β‐estradiol and ethynylestradiol. A method to analyze BPA, 17‐β‐estradiol, and ethynylestradiol at ultratrace levels was thus developed from a screening procedure to monitor endocrine‐disrupting chemicals in water samples. The method consists of the BPA‐selective cleanup by molecularly imprinted SPE using cartridges packed with the polymer developed, its recovery by stir bar sorptive extraction after ad hoc derivatization to obtain the corresponding BPA‐acetate, and its analysis by GC‐time window‐SIM‐MS after online thermal desorption. The method showed good linearity in the working range (R²=0.9969), high repeatability (RSD% <10.1), recoveries always above 90%, and very low LOD (10 pg/L) and LOQ (1 ng/L) and can easily be extended to the determination of 17‐β‐estradiol and ethynylestradiol ultratraces. The method's effectiveness was evaluated by analyzing the real‐world water samples; it enabled preconcentration and detection of BPA at ultratrace levels.     

Selective extraction of bisphenol A from water by one‐monomer molecularly imprinted magnetic nanoparticles

One‐monomer molecularly imprinted magnetic nanoparticles were prepared as adsorbents for selective extraction of bisphenol A from water in this study. A single bi‐functional monomer was adopted for preparation of the molecularly imprinted polymer, avoiding the tedious trial‐and‐error optimizations as traditional strategy. Moreover, bisphenol F was used as the dummy template for bisphenol A to avoid the interference from residual template molecules. These nanoparticles showed not only large adsorption capacity and good selectivity to the bisphenol A but also outstanding magnetic response performance. Furthermore, they were successfully used as magnetic solid‐phase extraction adsorbents of bisphenol A from various water samples, including tap water, river water, and seawater. The developed method was found to be much more efficient, convenient, and economical for selective extraction of bisphenol A compared with the traditional solid‐phase extraction. Separation of these nanoparticles can be easily achieved with an external magnetic field, and the optimized adsorption time was only 15 min. The recoveries of bisphenol A in different water samples ranged from 85.38 to 93.75%, with relative standard deviation lower than 7.47%. These results showed that one‐monomer molecularly imprinted magnetic nanoparticles had the potential to be popular adsorbents for selective extraction of pollutants from water.     

Selective solid-phase extraction of a triterpene acid from a plant extract by molecularly imprinted polymer

A molecularly imprinted polymer (MIP) has been prepared by a thermal polymerisation method using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linking agent, chloroform as porogenic solvent and an oleanane triterpene compound (18-beta-glycyrrhetinic acid) as imprinted molecule (template). Equilibrium ligand binding experiments were done to assess the performance of the MIP relative to non-imprinted polymer (NIP). After optimisation of SPE protocol (CHCl3 as washing solvent and MeOH as elution solvent), successful imprinting was confirmed by comparison of the recoveries between NIP (5%) and MIP (97%) cartridges. The binding capacity of the MIP for 18-beta-glycyrrhetinic acid was determined to be 0.94 mg g(-1). Four structurally related oleanane triterpenes (18-alpha-glycyrrhetinic acid, oleanolic acid, echinocystic acid, erythrodiol) were selected to assess the MIP selectivity. Experimental data illustrated the influence of functional groups on the triterpene skeleton. The MIP was applied to the solid-phase extraction of triterpenoids from a plant extract prior HPLC analysis. However, CHCl3 was replaced by ACN during the washing step in order to suppress non-specific interactions due to polar matrix components. A selective extraction of 18-beta-glycyrrhetinic acid from hydrolyzed extract of liquorice roots was achieved with a good extraction yield (98%).     

Selective solid-phase extraction of amoxicillin and cephalexin from urine samples using a molecularly imprinted polymer

In this paper we describe, for the first time, a molecularly imprinted polymer (MIP) for the antibiotic amoxicillin (AMX), synthesised by a noncovalent molecular imprinting approach and used to extract AMX selectively from urine samples. The MIP was applied as a molecularly selective sorbent in molecularly imprinted SPE (MISPE) in an off-line mode, where it showed useful cross-selectivity for a structurally related antibiotic, cephalexin (CPX). By using a MISPE protocol, the MIP was able to selectively extract both AMX and CFX from 5 mL of water spiked with 10 mg/L with recoveries of 75 and 78% for AMX and CFX, respectively. When applied to real samples (urine) at clinically relevant concentrations, recoveries from 2 mL of human urine spiked with 20 mg/L decreased slightly to 65 and 63% for AMX and CFX, respectively. To demonstrate further the selectivity of the MIP obtained, a comparison with commercially available SPE cartridges was performed. Improvements in the retention of both AMX and CFX on the MIP were obtained relative to the commercially available cartridges, and the MISPE extracts were considerably cleaner, due to molecularly selective analyte binding by the MIP.     

Selective on-line extraction of trans-resveratrol and emodin from Polygonum cuspidatum using molecularly imprinted polymer

High-performance liquid chromatographic separation is performed to extract active components from the traditional Chinese medicine Polygonum cuspidatum using a trans-resveratrol imprinted polymer. Good separation and purification of trans-resveratrol and emodin from the Polygonum cuspidatum extract are achieved after condition optimization. The extraction recoveries are 83% and 99% for trans-resveratol and emodin, respectively. The results show that the molecularly imprinted polymer can be used as a selective extraction material for the extraction and purification of trans-resveratrol and emodin from Polygonum cuspidatum.     

Selective extraction of sulfonamides from food by use of silica-coated molecularly imprinted polymer nanospheres

We report the use of nanospheres prepared by coating silica with molecularly imprinted polymer (MIP) for sulfamethoxazole (SMO). The resulting SiO₂–SMO–MIP nanoparticles have highly improved imprinting and adsorption capacity, and can be used for separation and determination of sulfonamides in eggs and milk. In the synthesis, monodispersed SiO₂ nanoparticles (Si–NP) of diameter 80 nm were amino-modified by reaction with 3-aminopropyltriethoxylsilane. The acryloyl monolayer was then grafted onto the amine-modified Si–NP. Finally, the MIP films were coated on to the surface of Si–NP by the copolymerization of the vinyl end groups with functional monomer (acrylamide), cross-linking agent (ethylene glycol dimethacrylate), initiator (azo-bis-isobutyronitrile), and template molecule (sulfamethoxazole). The resulting SiO₂–SMO–MIP–NP were characterized by transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The adsorption properties were demonstrated by equilibrium rebinding experiments and Scatchard analysis. The results showed that the binding sites of the SiO₂–SMO–MIP were highly accessible, and the maximum adsorption capacity of the SiO₂–SMO–MIP for SMO was 20.21 mg g⁻¹. The selectivity of the SiO₂–SMO–MIP–NP obtained was elucidated by using SMO and structurally related sulfonamides. The results indicated that the SiO₂–SMO–MIP had significant selectivity for SMO. The feasibility of removing SMO and sulfadiazine (SDZ) from food samples was proved by use of spiked milk and eggs. A method for the separation and determination of trace SMO and SDZ in milk and egg samples was developed, with recoveries ranging from 69.8% to 89.1%.     

Selective extraction of derivates of p-hydroxy-benzoic acid from plant material by using a molecularly imprinted polymer

Selective SPE of derivates of p-hydroxybenzoic acid (pHBA) from plant extract of Melissa officinalis is presented using a molecularly imprinted polymer (MIP) made with protocatechuic acid (PA) as template molecule. MIP was prepared with acrylamide as functional monomer, ethylene glycol dimethacrylate as crosslinking monomer and ACN as porogen. MIP was evaluated towards six phenolic acids: PA, gallic acid, pHBA, vanillic acid (VA), gentisic acid (GeA) and syringic acid (SyrA), and then steps of molecularly imprinted SPE (MISPE) procedure were optimized. The best specific binding capacity of MIP was obtained for PA in ACN (34.7 microg/g of MIP). Other tested acids were also bound on MIP if they were dissolved in this solvent. ACN was chosen as solvent for sample application. M. officinalis was extracted into methanol/water (4:1, v/v), the extract was then evaporated to dryness and dissolved in ACN before application on MIP. Water and ACN were used as washing solvents and elution of benzoic acids was performed by means of a mixture methanol/acetic acid (9:1, v/v). pHBA, GA, PA and VA were extracted with recoveries of 56.3-82.1% using this MISPE method. GeA was not determined in plant extract.     

A molecularly imprinted polymer for solid phase extraction of allantoin

We describe a molecularly imprinted polymer (MIP) for the solid-phase extraction of the skin protectant allantoin. The MIP was deposited on the surface of monodisperse silica microspheres possessing acroyl groups on the surface (MH-SiO₂). The resulting MIP microspheres (MH-SiO₂@MIP) showed a 3.4-fold higher adsorption capacity and a 1.9-fold better selectivity for allantoin than the respective non-imprinted polymer (MH-SiO₂@NIP). The monolayer adsorption capacities of the MH-SiO₂@MIP and the MH-SiO₂@NIP were calculated with the help of the Langmuir model and found to be 6.8 and 1.9 mg•g⁻¹, respectively. Adsorption kinetics fit a pseudo-second order rate mechanism, with an initial adsorption rate of 1.44 for the MH-SiO₂@MIP, and of 0.07 mg•g⁻¹•min⁻¹ for the MH-SiO₂@NIP. The material can be regenerated, and its adsorption capacity for allantoin remains stable for at least five regeneration cycles. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

A molecularly imprinted polymer for the selective separation of allantoin was developed. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

     

A molecularly imprinted polymer for solid phase extraction of allantoin

We describe a molecularly imprinted polymer (MIP) for the solid-phase extraction of the skin protectant allantoin. The MIP was deposited on the surface of monodisperse silica microspheres possessing acroyl groups on the surface (MH-SiO₂). The resulting MIP microspheres (MH-SiO₂@MIP) showed a 3.4-fold higher adsorption capacity and a 1.9-fold better selectivity for allantoin than the respective non-imprinted polymer (MH-SiO₂@NIP). The monolayer adsorption capacities of the MH-SiO₂@MIP and the MH-SiO₂@NIP were calculated with the help of the Langmuir model and found to be 6.8 and 1.9 mg?g^?1, respectively. Adsorption kinetics fit a pseudo-second order rate mechanism, with an initial adsorption rate of 1.44 for the MH-SiO₂@MIP, and of 0.07 mg?g^?1?min^?1 for the MH-SiO₂@NIP. The material can be regenerated, and its adsorption capacity for allantoin remains stable for at least five regeneration cycles. It was successfully used as a sorbent for the selective solid-phase extraction of allantoin from Rhizoma dioscoreae.

Selective recognition of ovalbumin using a molecularly imprinted polymer

Micro-contact imprinting has been used to form thin-film molecular imprints of ovalbumin (OVA) in polymers supported on glass slides. Thermocalorimetric data was used to optimise the choice of functional monomer and cross-linker to maximise selectivity and minimise non-specific recognition.A polymer comprising polyethyleneglycol 400 dimethacrylate (95 vol.%) and methacrylic acid (5 vol.%) showed both maximum recognition for OVA when made as a molecularly imprinted polymer (MIP), and minimal recognition when made as a non-imprinted, i.e. control polymer. OVA rebinding to the molecularly imprinted polymer, from a buffered 2 µM OVA solution, was 1.55 × 10^{− 11} mol cm^{− 2}, while the control polymer showed 10-fold less re-binding, i.e. 0.154 × 10^{− 11} mol cm^{− 2}.Experiments in which human serum albumin (HSA), conalbumin, ovomucoid or lysozyme, were re-bound to the polymers, either as single proteins or in competition with OVA, showed them to have low affinity for the polymer formulation used. Of the competing proteins examined, in non-competitive binding experiments, HSA showed the greatest affinity 0.45 × 10^{− 11} mol cm^{− 2} for the OVA imprinted polymer. In two protein competition experiments, i.e. with OVA and a competing protein present at equal concentrations (2 µM), OVA binding to the OVA imprinted polymer was in all cases significantly greater than that of the competitor.     

Potentiometric sensor for determination of neutral bisphenol A using a molecularly imprinted polymer as a receptor

The aim of this paper is to develop a potentiometric sensing methodology for sensitive and selective determination of neutral phenols by using a molecularly imprinted polymer as a receptor. Bisphenol A (BPA), a significant environmental contaminant, is employed as the model target. The BPA-imprinted polymer is synthesized by the semi-covalent technique and incorporated into a plasticized poly(vinyl chloride) membrane doped with the tridodecylmethylammonium salt. The present electrode shows a linear anionic potential response over the concentration range from 0.1 to 1 μM with a detection limit of 0.02 μM, and exhibits an excellent selectivity over other phenols. The proposed approach has been successfully applied to the determination of BPA released from real plastic samples. It offers promising potential in development of potentiometric sensors for measuring neutral phenols at trace levels.     

Selective enrichment of anti-inflammatory drugs from river water samples by solid-phase extraction with a molecularly imprinted polymer

A molecularly imprinted polymer (MIP) is synthesised by a noncovalent protocol in which ibuprofen was used as a template molecule. The polymer was evaluated chromatographically and it was seen that the MIP showed cross-reactivity. Subsequently, when this polymer was used as sorbent in SPE it was possible to selectively extract a mixture of nonsteroidal anti-inflammatory drugs from aqueous samples when a cleanup step with dichloromethane was performed. The performance of the MIP was evaluated with river water and water from a wastewater treatment plant, and compared with the performance of a commercial Isolute ENV+ sorbent.     

A microvolume molecularly imprinted polymer modified fiber-optic evanescent wave sensor for bisphenol A determination

A fiber-optic evanescent wave sensor for bisphenol A (BPA) determination based on a molecularly imprinted polymer (MIP)-modified fiber column was developed. MIP film immobilized with BPA was synthesized on the fiber column, and the sensor was then constructed by inserting the optical fiber prepared into a transparent capillary. A microchannel (about 2.0 μL) formed between the fiber and the capillary acted as a flow cell. BPA can be selectively adsorbed online by the MIP film and excited to produce fluorescence by the evanescent wave produced on the fiber core surface. The conditions for BPA enrichment, elution, and fluorescence detection are discussed in detail. The analytical measurements were made at 276 nm/306 nm (λ _ex/λ _em), and linearity of 3?×?10^?9–5?×?10^?6 g mL^?1 BPA, a limit of detection of 1.7?×?10^?9 g mL^?1 BPA (3σ), and a relative standard deviation of 2.4 % (n?=?5) were obtained. The sensor selectivity and MIP binding measurement were also evaluated. The results indicated that the selectivity and sensitivity of the proposed fiber-optic sensor could be greatly improved by using MIP as a recognition and enrichment element. Further, by modification of the sensing and detection elements on the optical fiber, the proposed sensor showed the advantages of easy fabrication and low cost. The novel sensor configuration provided a platform for monitoring other species by simply changing the light source and sensing elements. The sensor presented has been successfully applied to determine BPA released from plastic products treated at different temperatures.

Development of andrographolide molecularly imprinted polymer for solid-phase extraction

A method employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) to pretreat samples was developed. The polymers were prepared by precipitation polymerization with andrographolide as template molecule. The structure of MIP was characterized and its static adsorption capacity was measured by the Scatchard equation. In comparison with C(18)-SPE and non-imprinted polymer (NIP) SPE column, MIP-SPE column displays high selectivity and good affinity for andrographolide and dehydroandrographolide for extract of herb Andrographis paniculata (Burm.f.) Nees (APN). MIP-SPE column capacity was 11.9±0.6 μmol/g and 12.1±0.5 μmol/g for andrographolide and dehydroandrographolide, respectively and was 2-3 times higher than that of other two columns. The precision and accuracy of the method developed were satisfactory with recoveries between 96.4% and 103.8% (RSD 3.1-4.3%, n=5) and 96.0% and 104.2% (RSD 2.9-3.7%, n=5) for andrographolide and dehydroandrographolide, respectively. Various real samples were employed to confirm the feasibility of method. This developed method demonstrates the potential of molecularly imprinted solid phase extraction for rapid, selective, and effective sample pretreatment.     

A new molecularly imprinted polymer for the on-column solid-phase extraction of diethylstilbestrol from aqueous samples

The estrogenic compound diethylstilbestrol (DES) is widely studied because of its potential endocrine disruption effects. The prohibition of the use of diethylstilbestrol as a growth promoter has not been enough to ensure the total disappearance of this compound from environmental matrices. Due to the low levels of DES present in the environment, preconcentration and clean up methods are necessary for its analysis. This paper describes the synthesis and use of a molecularly imprinted polymer (MIP) as sorbent for on-column solid-phase extraction of DES from aqueous samples. The selectivity of the DES-MIP was evaluated towards several selected estrogens such as hexestrol (HEX), estrone (E1), estriol (E3), estradiol (E2) and ethynylestradiol (EE2). HPLC-DAD was used to quantify all analytes at 230-nm wavelength. The method has been successfully applied to the analysis of DES in spiked river and tap water samples, with recoveries of 72% and 83% respectively.     

A new molecularly imprinted polymer for selective extraction of cotinine from urine samples by solid-phase extraction

Cotinine, the main metabolite of nicotine in human body, is widely used as a biomarker for assessment of direct or passive exposure to tobacco smoke. A method for molecularly imprinted solid-phase extraction (MISPE) of cotinine from human urine has been investigated. The molecularly imprinted polymer (MIP) with good selectivity and affinity for cotinine was synthesized using cotinine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with aqueous standards, by comparing recovery data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from the aqueous solutions resulted in more than 80% recovery. A range of linearity for cotinine between 0.05 and 5 μg mL⁻¹ was obtained by loading 1 mL blank urine samples spiked with cotinine at different concentrations in acetate buffer of pH 9.0, and by using double basic washing and acidic elution. The intra-day coefficient of variation (CV) was below 7% and inter-day CV was below 10%. This investigation has provided a reliable MISPE–HPLC method for determination of cotinine in human urine from both active smokers and passive smokers. Figure     

表面分子印迹磁性固相萃取-液相色谱-荧光光谱法测定河水中双酚A

通过原子转移自由基聚合(Atom Transfer Radical Polymerization-ATRP)法制备核壳结构单分散性磁性亚微米粒子( Fe304@ MIPs),并建立了磁性固相萃取-高效液相色谱荧光光谱(MSPE- HPLC - FLD)测定河水中环境类雌激素 双酚A (BPA)的方法.利用透射...     

Synthesis of a molecularly imprinted polymer for the selective solid-phase extraction of chloramphenicol from honey

Solid-phase extraction (SPE) with a molecularly imprinted polymer (MIP) as sorbent has been investigated for the clean-up of the broad-spectrum bacteriostatic antibiotic chloramphenicol (CAP) in honey samples. The MIP was prepared by using methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as cross-linker, chloroform as porogen and CAP as template molecule. The binding behaviour of the template CAP on the MIP was evaluated by high-performance liquid chromatography, and then the MIP was applied as a sorbent in SPE to selectively extract CAP from honey. It was shown that recoveries of nearly 100% of a CAP standard solution and up to 94% from spiked honey samples could be obtained after SPE.