Molecularly imprinted polymer-based electrochemical sensor for the sensitive detection of glyphosate herbicide

A sensitive electrochemical molecularly imprinted sensor was developed for the detection of glyphosate (Gly), by electropolymerisation of p-aminothiophenol-functionalised gold nanoparticles in the presence of Gly as template molecule. The extraction of the template leads to the formation of cavities that are able to specifically recognise and bind Gly through hydrogen bonds between Gly molecules and aniline moieties. The performance of the developed sensor for the detection of Gly was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as redox probe, the electron transfer rate increasing when concentration of Gly increases, due to a p-doping effect. The molecularly imprinted sensor exhibits a broad linear range, between 1 pg/L and 1 µg/L and a quantification limit of 0.8 pg/L. The selectivity of the proposed sensor was investigated towards the binding of Gly metabolite, aminomethylphosphonic acid, revealing excellent selectivity towards Gly. The developed sensor was successfully applied to detect Gly in tap water samples.     

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.     

Multivariate optimization of molecularly imprinted polymer solid-phase extraction applied to parathion determination in different water samples

In this work a parathion selective molecularly imprinted polymer was synthesized and applied as a high selective adsorber material for parathion extraction and determination in aqueous samples. The method was based on the sorption of parathion in the MIP according to simple batch procedure, followed by desorption by using methanol and measurement with square wave voltammetry. Plackett-Burman and Box-Behnken designs were used for optimizing the solid-phase extraction, in order to enhance the recovery percent and improve the pre-concentration factor. By using the screening design, the effect of six various factors on the extraction recovery was investigated. These factors were: pH, stirring rate (rpm), sample volume (V₁), eluent volume (V₂), organic solvent content of the sample (org%) and extraction time (t). The response surface design was carried out considering three main factors of (V₂), (V₁) and (org%) which were found to be main effects. The mathematical model for the recovery percent was obtained as a function of the mentioned main effects. Finally the main effects were adjusted according to the defined desirability function. It was found that the recovery percents more than 95% could be easily obtained by using the optimized method. By using the experimental conditions, obtained in the optimization step, the method allowed parathion selective determination in the linear dynamic range of 0.20-467.4 μg L⁻¹, with detection limit of 49.0 ng L⁻¹ and R.S.D. of 5.7% (n = 5). Parathion content of water samples were successfully analyzed when evaluating potentialities of the developed procedure.     

Molecularly imprinted spin column extraction coupled with high‐performance liquid chromatography for the selective and simple determination of trace nitrophenols in water samples

In this study, we developed a simple and selective spin column extraction technology utilizing hydrophilic molecularly imprinted polymers as the sorbents for extracting nitrophenol pollutants in water samples (the East Lake, the Yangtze River, and wastewater). The whole procedure was achieved by centrifugation of the spin column, and multiple samples were simultaneously processed with a low volume of solvent and without evaporation. Under the optimized condition, recoveries of nitrophenol compounds on the spin column packed with hydrophilic molecularly imprinted polymers ranged from 87.3 to 92.9% and an excellent purification effect was obtained. Compared with activated carbon, multi‐walled carbon nanotubes, LC‐C₁₈ sorbents, hydrophilic molecularly imprinted polymers exhibited a highly selective recognition ability for nitrophenol compounds and satisfactory sample extraction efficiency. Subsequently, the spin column extraction coupled with high‐performance liquid chromatography was established, which was found to be linear in the range of 2–1000 ng/mL for 2,4‐dinitropehnol and 2‐nitrophenol, and 6–1000 ng/mL for 4‐nitrophenol with correlation coefficients greater than 0.998. The detection limits ranged from 0.3–0.5 ng/mL. It is shown that the proposed method can be used for the determination of trace nitrophenol pollutants in complex samples, which is not only beneficial for water quality analysis but also for environmental risk assessment.     

Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids

Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of hydroxyzine in tablets and biological fluids. The molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization, using hydroxyzine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited a Nernstian response (29.4 ± 1.0 mV decade⁻¹) in a wide concentration range of 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a lower detection limit of 7.0 × 10⁻⁷ M. The electrode demonstrated a response time of ∼15 s, a high performance and a satisfactory long-term stability (more than 5 months). The method has the requisite accuracy, sensitivity and precision to assay hydroxyzine in tablets and biological fluids.     

Molecularly imprinted polymer for the extraction of parabens from environmental solid samples prior to their determination by high performance liquid chromatography-ultraviolet detection

An analytical methodology incorporating a molecularly imprinted solid-phase extraction procedure (MISPE) has been developed for the determination of parabens in environmental solid samples. Four different polymers were prepared combining the use of acetonitrile or toluene as porogen, and 4-vinylpyridine (VP) or methacrylic acid (MAA) as monomer, using benzylparaben (BzP) as a template molecule. Although all the polymers were able to recognize the template in rebinding experiments, the MIP prepared in toluene using MAA showed better performance. This polymer was also capable of recognizing other parabens (methyl, ethyl, isopropyl, propyl, isobutyl, butyl and benzylparaben) allowing to develop an appropriated MISPE procedure for this family of compounds. The extraction of the parabens from environmental solid samples was performed by ultrasonic assisted extraction in small columns (SAESC), and this procedure next to MISPE as clean-up step followed by HPLC-UV determination was successfully used for the determination of parabens in soil and sediment samples of different locations. Recoveries ranging from 80% to 90% have been achieved depending on the compound and the samples, and limits of detection (LODs) were under 1 ng g⁻¹ for all the compounds, making this method suitable for the determination of parabens in environmental solid matrices. The method was further applied to the determination of paraben contents in real samples, founding levels up to 11.5 ng g⁻¹ in sea sediments.     

Computer‐aided design and synthesis of a highly selective molecularly imprinted polymer for the extraction and determination of buprenorphine in biological fluids

Buprenorphine is widely used to aid the cessation of opioids in addicted patients. To the best of our knowledge, there is no selective extraction method for buprenorphine from biological fluids. Here, we describe the synthesis of a molecularly imprinted polymer with the aid of computational design and its application for selective extraction of buprenorphine from plasma and urine. Computational design was used to study intermolecular interactions in the pre‐polymerization mixture by the comparison of the binding energy between buprenorphine (template) and functional monomers. The largest interaction energy of template‐monomers was obtained at ratio of 1:5 buprenorphine/acrylic acid monomers. Afterwards, the molecularly imprinted polymer was synthesized through precipitation polymerization technique and was employed for selective extraction of buprenorphine. Optimization of various parameters of the molecularly imprinted polymer solid‐phase extraction of buprenorphine was carried out by a design of experiment approach using a central composite design and the analyte was determined by employing high‐performance liquid chromatography with UV detection. Equilibrium isotherms were studied, and results revealed that the sorption process was in adoption with Langmuir model. Maximum enrichment capacity and Langmuir constant were calculated as 18.2 mg/g and 0.797 L/mg, respectively. Kinetic studies indicated the sorption process followed a pseudo‐second‐order model.     

Supported liquid membrane-modified piezoelectric flow sensor with molecularly imprinted polymer for the determination of vanillin in food samples

An on-line supported liquid membrane-piezoelectric detection system, based on a molecularly imprinted polymer (SLM-QCM-MIP) manifold, has been developed and applied to the quantitative determination of vanillin in food samples. The analyte is extracted from a donor phase into the hydrophobic membrane, and then back extracted into a second aqueous phase used as the acceptor solution. The quantification of vanillin was performed using a quartz crystal microbalance modified with a molecularly imprinted polymer (MIP). The method shows a linear range between 5 and 65 μM, with a relative standard deviation of ±4.8% (at 5 μM). The method was validated by analysing food samples and comparing the results with an SLM based on spectrophotometric quantification.     

Molecularly imprinted polymer for pre-concentration of esculetin from tobacco followed by the UPLC analysis

Molecularly imprinted polymers(MIPs)for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule.Polymers of varying composition were prepared using different monomers(4-vinylpyridine,methacrylic acid,and acrylamide),ethylene glycol dimethacrylate as the cross-linker,2,2-azobis(2-methylpropinitrile)as the initiator,and different porogen solvents(ethanol,acetone/methanol,and acetonitrile).The best polymer was obtained when 4-vinylpyridine was used as the monomer and acetone/methanol(3:2)as the porogen solvent,whereas the template:-monomer:-cross-linker ratio was 1:4:20.The imprinting factor of the selected MIPs for esculetin was 3.77.The polymers were evaluated according to their selective recognition properties for esculetin and structurally-related compounds(esculin,scopoletin,coumarin,and 7-methoxycoumarin).Chemical and morphological characterizations of the polymers were investigated by FTIR and scanning electron microscope,which confirmed a high degree of polymerization.Surface area,pore volume,and pore size of the polymer were investigated by Brunauer-Emmett-Teller analysis.MIPs were also successfully used as solid-phase adsorbent materials for the extraction of esculetin from tobacco leaves.Esculetin contents in dried tobacco leaves were found to be(9.27±0.17)μg g-1.     

Molecularly imprinted polymer functionalized magnetic Fe3O4 for the highly selective extraction of triclosan

We present a facile strategy to prepare the molecularly imprinted polymers layer on the surface of Fe₃O₄ nanoparticles with core‐shell structure via sol–gel condensation for recognition and enrichment of triclosan. The Fe₃O₄ nanoparticles were first synthesized by a solvothermal method. Then, template triclosan was self‐assembled with the functional monomer 3‐aminopropyltriethoxysilane on the silica‐coated Fe₃O₄ nanoparticles in the presence of ethanol and water. Finally, the molecularly imprinted polymers were formed on the surface of silica‐coated Fe₃O₄ nanoparticles to obtain the product. The morphology, magnetic susceptibility, adsorption, and recognition property of magnetic molecularly imprinted polymers were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffractometry, vibrating sample magnetometry, and re‐binding experiments. The magnetic molecularly imprinted polymers showed binding sites with good accessibility, fast adsorption rate, and high adsorption capacity (218.34 μg/g) to triclosan. The selectivity of magnetic molecularly imprinted polymers was evaluated by the rebinding capability of triclosan and two other structural analogues (phenol and p‐chlorophenol) in a mixed solution and good selectivity with an imprinting factor of 2.46 was obtained. The application of triclosan removal in environmental samples was demonstrated.     

噻虫胺分子印迹电化学传感器的制备与应用EI北大核心CSCD

以噻虫胺为模板分子,通过恒电位沉积壳聚糖,在还原氧化石墨烯(RGO)修饰的玻碳电极表面制备了可特异性识别噻虫胺的分子印迹传感器。采用交流阻抗法(EIS)、差分脉冲伏安法(DPV)和循环伏安法(CV)对传感器的电化学性能进行表征,优化了电沉积时间、洗脱圈数、孵化时间及溶液pH等实验条件。在优化条件下,以K_(3)[Fe(CN)_(6)]作为电活性探针,DPV峰电流强度与噻虫胺浓度在1.0~1000 nmol/L范围内呈良好的线性关系,检出限0.46 nmol/L。将本方法应用于实际样品中噻虫胺的含量测定,加标回收率为97.6%~103.2%。     

A pre-concentration procedure employing a new imprinted polymer for the determination of copper in water

This work describes the development by response surface methodology (RSM) of a procedure for copper determination by inductively coupled plasma optical emission spectrometry (ICP OES) in water samples after extraction by copper imprinted polymer. Results of the two-level full factorial design (2⁴) based on an analysis of variance demonstrated that only the solution pH; amount of polymer and adsorption time were statistically significant. Optimal conditions for the extraction of copper samples were obtained by using Box-Behnken design. Solution pH; amount of polymer and adsorption time were regarded as factors in the optimisation study. The working conditions were 4.6, 0.03?g and 3.5?h, for solution pH, amount of polymer; and adsorption time, respectively. Under the optimised experimental conditions, the detection limit of the proposed method followed by ICP OES was found to be 0.8?µg?L^?1. The relative standard deviation (RSD) was found to less than 0.81%. The pre-concentration factor was 22.5. The accuracy of the optimised procedure was evaluated by analysis of certified reference material. The method was applied to the determination of copper in water samples.     

对硫磷分子印迹聚合物制备及其在水质检测中的应用

为了有效的分离富集水样中有机磷农药,以对硫磷为模板、三羟甲基丙烷三丙烯酸酯为交联剂,采用紫外聚合方法制备了对硫磷分子印迹聚合物(MIP)。利用紫外光谱、红外光谱研究了对硫磷与不同功能单体间作用力及印迹聚合物的结合位点。利用该MIP,建立MIP-固相萃取-气相色谱法测定水中痕量对硫磷,方法的检出限(3S/N)为0.48μg/L,加标回收率为86.2%～115.7%,相对标准偏差(n=6)为3.0%～6.6%。     

Molecularly imprinted conducting polymer based electrochemical sensor for detection of atrazine

An original electrochemical sensor based on molecularly imprinted conducting polymer (MICP) is developed, which enables the recognition of a small pesticide target molecule, atrazine. The conjugated MICP, poly(3,4-ethylenedioxythiophene-co-thiophene-acetic acid), has been electrochemically synthesized onto a platinum electrode following two steps: (i) polymerization of comonomers in the presence of atrazine, already associated to the acetic acid substituent through hydrogen bonding, and (ii) removal of atrazine from the resulting polymer, which leaves the acetic acid substituents open for association with atrazine. The obtained sensing MICP is highly specific towards newly added atrazine and the recognition can be quantitatively analyzed by the variation of the cyclic voltammogram of MICP. The developed sensor shows remarkable properties: selectivity towards triazinic family, large range of detection (10⁻⁹ mol L⁻¹ to 1.5 × 10⁻² mol L⁻¹ in atrazine) and low detection threshold (10⁻⁷ mol L⁻¹).     

基于分子印迹聚合物的化学发光传感器测定尿样中的甲福明

合成了甲福明的分子印迹聚合物,以此聚合物为识别物质,在线分离富集甲福明,建立了一种测定甲福明的流动式化学发光但感器。N-溴代丁二酰亚胺(NBS)和荧光素与甲福明发生化学反应,产生强的化学发光。甲福明质量浓度在2×10-8~8×10-6g/mL范围内同发光强度成良好线性关系,方法的检出限为6×10-9g/mL,相对标准偏差小于5%(n=9)。选择性实验表明将分子印迹聚合物作为识别物质应用于化学发光分析中,能大大提高化学发光分析方法的选择性。该传感器可逆性强、稳定性好,可重复使用100次以上,已用于人体尿样中甲福明的测定。     

Preparation of magnetic surface molecularly imprinted polymers for the selective extraction of triazines in environmental water samples

ABSTRACT

In this work, a magnetic molecularly imprinted polymer (Fe₃O₄@SiO₂@MIPs) was prepared via a surface-imprinted method for the determination of the triazines in environmental water samples combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer showed that the Fe₃O₄@SiO₂@MIPs was successfully synthesised and exhibited superparamagnetism. The isotherm adsorption, selectivity and adsorption kinetics experiments showed that the Fe₃O₄@SiO₂@MIPs exhibited excellent specific recognition and fast adsorption equilibrium for triazines. The adsorption process is spontaneous and endothermic. The isotherm adsorption was consistent with Scatchard model and adsorption kinetic fit pseudo-second-order kinetic model. Under the optimised adsorption conditions, the Fe₃O₄@SiO₂@MIPs was directly used to selectively enrich six triazines in environmental water samples. The enrichment volume was up to 500 mL, and the matrix effects were down to 0.7–12.4%. The built method has excellent linearities in the range of 0.25–500 ng L^?1 with R² in the range of 0.998–0.999, lower limit of detections (0.02–0.08 ng L^?1) and higher precision (2.4–7.2%). The Fe₃O₄@SiO₂@MIPs is expected to be widely applied to the direct enrichment of triazines in bulk environmental water samples.     

An optical sensor for the determination of digoxin in serum samples based on a molecularly imprinted polymer membrane

This paper reports the synthesis and testing of a molecularly imprinted polymer membrane for digoxin analysis. Digoxin-specific bulk polymer was obtained by the UV initiated co-polymerisation of methacrylic acid and ethylene glycol dimethacrylate in acetonitrile as porogen. After extracting the template analyte, the ground polymer particles were mixed with plasticizer polyvinyl chloride to form a MIP membrane. A reference polymer membrane was prepared from the same mixture of monomers but with no template. The resultant membrane morphologies were examined by scanning electron microscopy. The imprinted membrane was tested as the recognition element in a digoxin-sensitive fluorescence sensor; sensor response was measured using standard solutions of digoxin at concentrations of up to 4 × 10⁻³ mg L⁻¹. The detection limit was 3.17 × 10⁻⁵ mg L⁻¹. Within- and between-day relative standard deviations RSD (n = 5) were in the range 4.5-5.5% and 5.5-6.5% respectively for 0 and 1 × 10⁻³ mg L⁻¹ digoxin concentrations. A selectivity study showed that compounds of similar structure to digoxin did not significantly interfere with detection for interferent concentrations at 10, 30 and 100 times higher than the digoxin concentration. This simply manufactured MIP membrane showed good recognition characteristics, a high affinity for digoxin, and provided satisfactory results in analyses of this analyte in human serum.     

Application of an Hg selective imprinted polymer as a new modifying agent for the preparation of a novel highly selective and sensitive electrochemical sensor for the determination of ultratrace mercury ions

A simple and very selective electrode, based on a mercury ion imprinted polymer (IIP), and its application for the determination of Hg²⁺ ions in the real samples is introduced. Mercury ion selective cavities were created in the vinyl pyridine based cross-linked polymer. In order to fabricate the sensor carbon particles and polymer powder were mixed with melted n-eicosane. An explicit difference was observed between the responses of the electrodes modified with IIP and non imprinted polymer (NIP), indicating proper performance of the recognition sites of the IIP. Various factors, known to affect the response behavior of selective electrode, were investigated and optimized. The interference of different ionic species with the response of the electrode was also studied. The results revealed that, compared to previously developed mercury selective sensors, the proposed sensor was more selective, regarding the common potential interferer. This sensor showed a linear response range of 2.5 × 10⁻⁹–5.0 × 10⁻⁷ M and lower detection limit of 5.2 × 10⁻¹⁰ M (S/N). The sensor was successfully applied to the determination of mercury in real samples.