Electrochemical determination of L-phenylalanine at polyaniline modified carbon electrode based on β-cyclodextrin incorporated carbon nanotube composite material and imprinted sol-gel film

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of l-phenylalanine has been proposed by utilizing β-cyclodextrin (β-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol-gel film. The electrochemical behavior of the sensor towards l-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for l-phenylalanine was based on the inclusion interaction of β-CD and molecular recognition capacity of the imprinted film for l-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁹ mol L⁻¹. With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect l-phenylalanine in blood plasma samples successfully.     

A 3,3′-dichlorobenzidine-imprinted polymer gel surface plasmon resonance sensor based on template-responsive shrinkage

Molecularly imprinted polymer gel film on the gold substrate of a chip was prepared with minute amount of cross-linker for the fabrication of a surface plasmon resonance (SPR) sensor sensitive to 3,3′-dichlorobenzidine. The molecularly imprinted gel film was anchored on a gold chip by a surface-bound photo-radical initiator. The sensing of 3,3′-dichlorobenzidine is based on responsive shrinkage of the imprinted polymer gel film that is triggered by target binding. This change can improve the responsiveness of the imprinted SPR sensor to 3,3′-dichlorobenzidine. The molecularly imprinted polymer gel film was characterized with contact angle measurements, electrochemical impedance spectroscopy, cyclic voltammogram, swelling measurements and atomic force microscopy. The changes of SPR spectroscopy wavenumber shifts revealed that the imprinted gel sensing film can ‘memorize’ the binding of 3,3′-dichlorobenzidine compared to non-imprinted one. The imprinted gel-SPR sensor showed a linear response in the range of 9.0 × 10⁻¹² to 5.0 × 10⁻¹⁰ mol L⁻¹ (R² = 0.9998) for the detection of 3,3′-dichlorobenzidine, and it also exhibited high selectivity to 3,3′-dichlorobenzidine compared to its structurally related analogues. We calculated the detection limits to be 0.471 ng L⁻¹ for tap water and 0.772 ng kg⁻¹ for soil based on a signal to noise ratio of 3. The method showed good recoveries and precision for the samples spiked with 3,3′-dichlorobenzidine. This suggest that the imprinted gel-SPR sensing method can be used as a promising alternative for the detection of 3,3′-dichlorobenzidine.     

Selective Electrochemical Determination of Salicylic Acid in Wheat Using Molecular Imprinted Polymers

Salicylic acid is a phytohormone, playing crucial roles in signal transduction, crop growth, and development, and defense to environmental challenges. In this study, a highly selective electrochemical sensor was designed and used to determine salicylic acid using molecularly imprinted polymers for recognition. The electrochemical sensor was fabricated via stepwise modification of gold nanoparticle–graphene–chitosan and molecularly imprinted polymers on a glassy carbon electrode. With electrochemical deposition, a gold nanoparticle–graphene–chitosan film was deposited on the glassy carbon electrode and enhanced the sensitivity. Molecularly imprinted polymers with adsorbed template salicylic acid were added to the surface of the modified electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrodes. Salicylic acid in wheat was quantified by the sensor using the molecularly imprinted polymer/gold nanoparticle–graphene–chitosan/glassy carbon electrode. Concentrations of salicylic acid from 5?×?10^?10 to 5?×?10^?5?mol?L^?1 were determined showing that the developed sensor was suitable for the analysis of food.     

Electrochemical Sensor for trans‐Resveratrol Determination Based on Indium Tin Oxide Electrode Modified with Molecularly Imprinted Self‐Assembled Films

A voltammetric sensor for sensitive and specific determination of trans‐resveratrol (RES) were prepared based on immobilization of an RES‐imprinted film on the surface of functionalized Indium Tin Oxide (ITO) electrode, which was modified with γ‐methacyloxypropyl trimethoxysilane (γ‐MPS). Cyclic Voltammetry (CV) was presented to extract RES from the molecularly imprinted polymer film and RES were extracted rapidly and completely. The binding performance of the imprinted electrode with the template RES were investigated using differential pulse voltammetry (DPV). The results showed that the imprinted ITO film can give selective recognition to the template RES over that of structurally analogous molecules. A linear response to RES in the concentration range of 2.0×10^?6 M to 2.0×10^?5 M was observed with a correlation coefficient of 0.992, and the detection limit of the electrochemical sensor was 8.0×10^?7 M. Whereas, binding to the reference nonimprinted electrode, made in the same way but without the addition of template RES, there was almost no response to RES.     

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.     

A novel molecularly imprinted sensor for selectively probing imipramine created on ITO electrodes modified by Au nanoparticles

A sensitive molecularly imprinted electrochemical sensor was created for selective detection of a tricyclic antidepressant imipramine by combination of Au nanoparticles (Au-NPs) with a thin molecularly imprinted film. The sensor was fabricated onto the indium tin oxide (ITO) electrode via stepwise modification of Au-NPs by self-assembly and a thin film of molecularly imprinted polymers (MIPs) via sol-gel technology. It was observed that the molecularly imprinted film displayed excellent selectivity towards the target molecule imipramine. Meanwhile, the introduced Au-NPs exhibited noticeable catalytic activities towards imipramine oxidation, which remarkably enhanced the sensitivity of the imprinted film. Due to such combination, the as-prepared sensor responded quickly to imipramine, within only 1 min of incubation. The differential voltammetric anodic peak current was linear to the logarithm of imipramine concentration in the range from 5.0 × 10⁻⁶ to 1.0 × 10⁻³ mol L⁻¹, and the detection limits obtained was 1.0 × 10⁻⁹ mol L⁻¹. This method proposed was successfully applied to the determination of imipramine in drug tablets, and proven to be reliable compared with conventional UV method. These results reveal that such a sensor fulfills the selectivity, sensitivity, speed and simplicity requirements for imipramine detection, and provides possibilities of clinical application in physiological fluids.     

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.     

Determination of Oxytetracycline with a Gold Electrode Modified by Chitosan-Multiwalled Carbon Nanotube Multilayer Films and Gold Nanoparticles

A molecularly imprinted electrochemical sensor was fabricated based on a gold electrode modified by chitosan-multiwalled carbon nanotube composite (CS-MWCNTs) multilayer films and gold nanoparticles (AuNPs) for convenient and sensitive determination of oxytetracycline (OTC). The multilayer of CS-MWCNTs composites and AuNPs were used to augment electronic transmission and sensitivity. The molecularly imprinted polymers (MIPs) were synthesized using OTC as the template molecule and o-phenylenediamine (OPD) as the functional monomer. They were modified on a gold electrode by electropolymerization. The electrochemical behavior of OTC at the imprinted sensor was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and amperometry. The molecularly imprinted sensor showed high selectivity and excellent stability toward OTC. The linear range was from 3.0 × 10^?8 to 8.0 × 10^?5 mol/L, with a limit of detection (LOD) of 2.7 × 10^?8 mol/L (S/N = 3). The developed sensor showed good recovery in spiked samples analysis.     

A sensitive and selective sensor‐coated molecularly imprinted sol–gel film incorporating β‐cyclodextrin‐multi‐walled carbon nanotubes and cobalt nanoparticles‐chitosan for oxacillin determination

A sensitive and selective imprinted electrochemical sensor for the determination of oxacillin was developed based on indium tin oxide electrode. The proposed sensor was decorated with imprinted sol–gel film and cobalt nanoparticles‐chitosan/β‐cyclodextrin‐multiwalled carbon nanotubes nanocomposites. The surface morphologies of the modified electrodes were characterized by scanning electron microscopy and transmission electron microscope. The stepwise assembly process and electrochemical behavior of the novel sensor were characterized by differential pulse voltammetry, cyclic voltammetry and Amperometric i‐t response. The imprinted sensor displayed excellent selectivity toward oxacillin. Meanwhile, the introduced cobalt nanoparticles‐chitosan and β‐cyclodextrin‐multi‐walled carbon nanotubes exhibited noticeable amplified electrochemical response signal. The differential voltammetric anodic peak current was linear to oxacillin concentration in the range from 2.0 × 10^?7 to 1.0 × 10^?4 mol·l^?1, and the detection limit was 6.9 × 10^?9 mol·l^?1. The proposed imprinted sensor was applied to the determination of oxacillin in human blood serum samples successfully. Copyright © 2011 John Wiley & Sons, Ltd.     

Development of a sensitive and selective kojic acid sensor based on molecularly imprinted polymer modified electrode in the lab-on-valve system

In this work, a kojic acid electrochemical sensor, based on a non-covalent molecularly imprinted polymer (MIP) modified electrode, had been fabricated in the lab-on-valve system. The sensitive layer was synthesized by cyclic voltammetry using o-phenylenediamine as the functional monomer and kojic acid as the template. The template molecules were then removed from the modified electrode surface by washing with NaOH solution. Differential pulse voltammetry method using ferricyanide as probe was applied as the analytical technique, after extraction of kojic acid on the electrode. Chemical and flow parameters associated with the extraction process were investigated. The response recorded with the imprinted sensor exhibited a response in a range of 0.01-0.2 μmol L⁻¹ with a detection limit of 3 nmol L⁻¹. The interference studies showed that the MIP modified electrode had excellent selectivity. Furthermore, the proposed MIP electrode exhibited good sensitivity and low sample/reagent consumption, and the sensor could be applied to the determination kojic acid in cosmetics samples.     

Preparation of Molecularly Imprinted Electrochemical Sensor for Detection of Vincristine Based on Reduced Graphene Oxide/Gold Nanoparticle Composite Film

An innovative molecularly imprinted electrochemical sensor was fabricated based on reduced graphene oxide (RGO) and gold nanocomposite (Au) for rapid detection of vincristine (VCR). The RGO‐Au composite membrane was obtained via direct one‐step electrodeposition technique of graphene oxide (GO) and chloroauric acid (HAuCl₄) on the surface of a glassy carbon electrode (GCE) by means of cyclic voltammetry (CV) in the potential range between ?1.5 and 0.6 V in phosphate buffer solution (PBS) of pH 9.18, which is capable of effectively utilizing its superior electrical conductivity, larger specific surface area due to its synergistic effect between RGO and Au. The molecularly imprinted polymers (MIPs) were synthesized on the RGO‐Au modified glassy carbon electrode surface with VCR as the template molecular, methyl acrylic acid (MAA) as the functional monomer, and ethylene glycol maleic rosinate acrylate (EGMRA) as a cross‐linker. The performance of the sensor was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) in detail. Under the optimum conditions, the fabricated sensor exhibited a linear relationship between oxidation peak current and VCR concentration over the range of 5.0×10^?8–5.0×10^?6 mol·L ^minus;1 with a correlation coefficient of 0.9952 and a detection limit (S/N=3) of 2.6×10^minus;8 mol·L^minus;1. The results indicated that the imprinted polymer films exhibited an excellent selectivity for VCR. The imprinted sensor was successfully used to determine VCR in real samples with recoveries of 90% –120% by using the standard addition method.     

Development and application of the tartrazine voltammetric sensors based on molecularly imprinted polymers

A modified glassy carbon electrode was prepared as an electrochemical voltammetric sensor based on molecularly imprinted polymer film for tartrazine (TT) detection. The sensitive film was prepared by copolymerization of tartrazine and acrylamide on the carbon nanotube-modified glassy carbon electrode. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. Under the optimum conditions, two dynamic linear ranges of 8?×?10^?8 to 1?×?10^?6?mol?L^?1 and 1?×?10^?6 to 1?×?10^?5?mol?L^?1 were obtained, with a detection limit of 2.74?×?10^?8?mol?L^?1(S/N?=?3). This sensor was used successfully for tartrazine determination in beverages.     

Development of an Electrochemical Sensor for Selective Determination of Dopamine Based on Molecularly Imprinted Poly(p-aminothiophenol) Polymeric Film

In this study, a molecularly imprinted electrochemical sensor (MIP/DA) was investigated for selective and sensitive determination of dopamine (DA) by electrochemical polymerization of p-aminothiophenol in the presence of DA on gold electrode. According to electrochemical behaviour of the sensor, gained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), MIP/DA sensor showed distinctive electron transfer characteristics in comparison to the non-imprinted (NIP/DA) sensor. Besides the MIP/DA sensor showed high selectivity for dopamine through its analyte specific cavities. The sensor had a broad working range of 5.0×10⁻⁸–2.0×10⁻⁷ M with a limit of detection (LOD) of 1.8×10⁻⁸ M and the developed sensor was successfully applied for determination of dopamine in pharmaceutical samples.     

Selective and sensitive molecularly imprinted sol–gel film-based electrochemical sensor combining mercaptoacetic acid-modified PbS nanoparticles with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Au–multi-walled carbon nanotubes–chitosan

A sensitive molecularly imprinted electrochemical sensor was developed for selective detection of streptomycin by combination of mercaptoacetic acid-modified PbS nanoparticles with Au-coated Fe₃O₄ magnetic nanoparticles dispersed multi-walled carbon nanotubes doped chitosan film. The imprinted sensor was fabricated onto the Au electrode via stepwise modification of nanocomposites and an electrodeposited thin film of molecularly imprinted polymers via sol–gel technology. The morphologies and electrochemical behaviors of the imprinted sensor were characterized by scanning electron microscope, cyclic voltammetry, and differential pulse voltammetry, respectively. The prepared sensor showed very high recognition ability and selectivity for streptomycin. Under optimal conditions, the imprinted sensor displayed good electrocatalytic activity to the redox of streptomycin. And the differential voltammetric anodic peak current was linear to the logarithm of streptomycin concentration in the range from 1.0 × 10⁻⁶ to 1.0 × 10⁻³ mol L⁻¹, and the detection limit obtained was 1.5 × 10⁻⁹ mol L⁻¹. This proposed imprinted sensor was used successfully for streptomycin determination in different injection solution samples.     

纳米氧化铜修饰的苯巴比妥分子印迹传感器的制备及其电化学性能

为了改善分子印迹传感器的灵敏度, 在四丁基高氯酸铵的支持电解质溶液中, 以甲基丙烯酸为功能单体, 马来松香丙烯酸乙二醇酯为交联剂在纳米氧化铜修饰过的玻碳电极上电聚合了一种苯巴比妥(PB)识别性能的分子印迹传感膜. 采用循环伏安(CV)法、差分脉冲伏安(DPV)法及交流阻抗(EIS)法对这种纳米氧化铜修饰过的印迹及非印迹电极的电化学性能进行了研究, 结果显示纳米氧化铜修饰过的印迹及非印迹电极的电化学性能完全不同. X射线衍射(XRD)证实纳米粒子为氧化铜. 采用扫描电镜(SEM)对纳米氧化铜修饰过的印迹传感器的形貌进行分析, 发现纳米氧化铜分散在电极表面, 改善了修饰印迹传感器的识别点. 差分脉冲伏安法(DPV)表明苯巴比妥的浓度在1.0×10^-8-1.8×10^-4 mol·L^-1 范围内呈现良好的线性关系(线性相关系数R=0.9994); 检出限2.3×10^-9 mol·L^-1 (信噪比(S/N)=3). 研究结果表明纳米氧化铜修饰过的印迹传感器具有较高灵敏度及选择性. 此印迹传感器能用于实际样品中苯巴比妥的检测, 加标回收率在95.0%-102.5%.     

A Polypyrrole‐Imprinted Electrochemical Sensor Based on Nano‐SnO2/Multiwalled Carbon Nanotubes Film Modified Carbon Electrode for the Determination of Oleanolic Acid

A sensitive molecularly imprinted electrochemical sensor with specific recognition ability for oleanolic acid was synthesized by modification of multiwalled carbon nanotubes (MWNTs) decorated with tin oxide nanoparticles (nano‐SnO₂/MWNTs) and polypyrrole‐imprinted polymer on a carbon electrode. The morphology and electrochemical performance of the imprinted sensor were investigated by using scanning electron microscope (SEM), X‐ray diffraction (XRD), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometric i–t curve. The results showed that the imprinted sensor displayed excellent selectivity toward oleanolic acid. A linear relationship between the response currents and oleanolic acid concentrations ranging from 5.0×10^?8 g/L to 2.0×10^?5 g/L was obtained for the imprinted sensor. The limit of detection (LOD) of the imprinted sensor toward oleanolic acid was calculated as 8.6×10^?9 g/L at a signal to noise ratio (S/N) of 3. This imprinted sensor was successfully applied to the determination of oleanolic acid in Acitinidia deliciosa root samples.     

Molecularly Imprinted Impedimetric Sensor for Determination of Mycotoxin Zearalenone

The mycotoxin zearalenone (ZEA) prompts reproductive toxicity due to its strong estrogenic effects. In this work, an electrochemical sensor for determination of ZEA was developed by electropolymerization of a molecularly imprinted poly (o‐phenylenediamine) (PPD) film on screen‐printed gold electrode (SPGE) surface. The sensor was examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using K₃[Fe(CN)₆]/K₄[Fe(CN)₆] as redox probe. The molecularly imprinted polymer (MIP) sensor showed a wide determination range from 2.50 to 200.00 ngmL^?1 for ZEA. The Limit of detection (LOD) was calculated to be 0.20 ngmL^?1, based on the signal to noise (S/N) ratio equal to 3.0. The sensor displayed good repeatability, with RSD values≤4.6 %, and maintained 93.2 % of its initial response after storage for 10 days in air at room temperature. The developed method was successfully applied for the determination of ZEA in corn flakes with mean recoveries ranged from 96.2 % to 103.8 % and RSDs within the interval of 2.1 % to 3.8 %.     

自组装碳纳米管-氯洁霉素分子印迹溶胶-凝胶电化学传感器研究

结合自组装技术, 采用电聚合方法在碳纳米管修饰金电极表面制备对氯洁霉素具有特异性识别位点的分子印迹溶胶-凝胶薄膜, 成功构建了一种新型印迹溶胶-凝胶电化学传感器. 通过循环伏安法(CV)、示差脉冲法(DPV)、安培计时法(I-t)和扫描电镜(SEM)表征了该印迹溶胶-凝胶膜的电化学性能和表面形貌. 结果表明, 该传感器具有良好的选择性和灵敏度, 氯洁霉素在多壁碳纳米管修饰的印迹溶胶-凝胶传感器上的响应明显提高. 该印迹溶胶-凝胶传感器对氯洁霉素的浓度响应线性范围为5.0×10^-7~8.0×10^-5 mol/L, 检出限为2.44×10^-8 mol/L. 该传感器被成功地用于人体尿液中氯洁霉素的分析测定.     

Ultrasensitive one-step rapid detection of ochratoxin A by the folding-based electrochemical aptasensor

A one-step electrochemical aptasensor using the thiol- and methylene blue- (MB-) dual-labeled aptamer modified gold electrode for determination of ochratoxin A (OTA) was presented in this research. The aptamer against OTA was covalently immobilized on the surface of the electrode by the self-assembly effect and used as recognition probes for OTA detection by the binding induced folding of the aptamer. Under the optimal conditions, the developed electrochemical aptasensor demonstrated a wide linear range from 0.1 pg mL⁻¹ to 1000 pg mL⁻¹ with the limit of detection (LOD) of 0.095 pg mL⁻¹, which was an extraordinary sensitivity compared with other common methods for OTA detection. Moreover, as a practical application, this proposed electrochemical aptasensor was used to monitor the OTA level in red wine samples without any special pretreatment and with satisfactory results obtained. Study results showed that this electrochemical aptasensor could be a potential useful platform for on-site OTA measurement in real complex samples.     

The amperometric determination of indole-3-acetic acid based on CeCl<Subscript>3</Subscript>-DHP film modified gold electrode

An amperometric sensor for the determination of indole-3-acetic acid (IAA) based on the CeCl₃-DHP film modified gold electrode was developed. CeCl₃ was dissolved into water in the presence of dihexadecyl hydrogen phosphate (DHP). The IAA sensor was prepared via evaporating solvent of the CeCl₃-DHP dispersion on the gold electrode surface. The amperometric response of IAA on the CeCl₃-DHP film modified gold electrode was investigated. The experimental results indicate that the passivation of the electrode due to the adsorption of the oxidation product of IAA decreases significantly at the CeCl₃-DHP film modified gold electrode, in contrast to that at the bare and the DHP modified gold electrode. The experimental parameters were optimized and an electrochemical method for the determination of IAA was established. The oxidation peak current is linearly with the concentration of IAA from 1 × 10⁻⁷ to 2 × 10⁻⁵ mol l⁻¹ and the detection limit is 3 × 10⁻⁸ mol l⁻¹. The relative standard deviation of eight measurements is 3.2% for 5 × 10⁻⁷ mol l⁻¹ IAA. The IAA in plant leaves were extracted and determined by the IAA sensor.