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.     

Microspheres Sensor Based on Molecularly Imprinted Polymer Synthesized by Precipitation Polymerization

IntroductionSincethepiezoelectricbulkacousticwave (BAW)sen sorswereappliedinliquidphaseinthe 1980s ,manypapershavebeenreported .1,2 However,theapplicationofBAWsen sorsbasedonmasseffectislimitedbecauseoflackofthespecialselectivitytotheanalyte.Variousmethodshavebeenproposedtosolvethisproblem ,especiallytheapplicationofthebiomaterials .3Unfortunately ,theresultwasnotsogoodasexpected,duetotheinstinctdisadvantageofthebiomateri als ,e.g .,poorstability ,shortlifespan ,althoughpossess inghighselec…     

原位聚合那格列奈分子印迹手性固定相的分子识别特性研究

以手性药物那格列奈为模板分子,采用原位聚合法制备了具有特定识别性能和手性拆分能力的分子印迹聚合物,并用作高效液相色谱固定相实现了那格列奈与其对映体的手性拆分．通过静态结合方法考察了该聚合物的选择结合能力,并讨论了手性分离过程中的热力学性质．结果表明,原位聚合法制备的棒状聚合物固定相对模板分子及其对映体有很好的手性拆分性能．     

Determination of 2,6-Dichlorophenol by Surface-Enhanced Raman Scattering with Molecular Imprinting

A novel method has been reported for 2,6-dichlorophenol using surface-enhanced Raman scattering (SERS). SiO₂/gold composites were selected as the SERS substrates to provide the response of gold nanoparticles. Molecular imprinting was subsequently used for the development of a specific detector to 2,6-dichlorophenol with precipitation polymerization. The molecularly imprinted polymer provided sensitive and selective SERS detection for the determination of 2,6-dichlorophenol. The intensity and concentration obeyed a linear relationship from 1?×?10^?5 to 1?×?10^?9?mol?L^?1 2,6-dichlorophenol. The sensitivity of SERS with the molecularly imprinted polymers provides a promising approach for practical analysis.     

Flow‐Through Assay of Quinine Using Solid Contact Potentiometric Sensors Based on Molecularly Imprinted Polymers

Miniaturized potentiometric membrane sensors for quinine incorporated with molecular imprinted polymer (MIP) were synthesized and implemented. Planar PVC based polymeric membrane sensors containing quinine‐methacrylic and/or acrylic acid‐ethylene glycol methacrylate were dispensed into anisotropically etched wells on polyimide wafers. The determination of quinine was carried out in acidic solution at pH 6, where positively charged species predominated prevalently. The suggested miniaturized planner sensors exhibited marked selectivity, sensitivity, long‐term stability and reproducibility. At their optimum conditions, the sensors displayed wide concentration ranges of 4.0×10^?6–1.0×10^?2mol L^?1 and 1.0×10^?5–1.0×10^?2 mol L^?1 with slopes of about 61.3–55.7 mV decade^?1; respectively. Sensors exhibit detection limits of 1.2×10^?6 and 8.2×10^?6 mol L^?1 upon the use of methacrylic and acrylic acid monomers in the imprinted polymer, respectively. Validation of the assay method according to the quality assurance standards (range, within‐day repeatability, between‐day variability, standard deviation, accuracy, and good performance characteristics) which could assure good reliable novel sensors for quinine estimation was justified. Application of the proposed flow‐through assay method for routine determination of quinine in soft drinks was assayed and the results compared favorably with data obtained by the standard fluorimetric method.     

Preparation and performance valuation of high selective molecularly imprinted polymers for malachite green

Molecular imprinting is a technology that facilitates the production of artificial receptors toward compounds of interest. In this study, we prepared a series of molecularly imprinted polymers (MIPs) by precipitation polymerization for the purpose of binding specifically to malachite green (MG). The presence of monomer–template solution complexes in non-covalent MIPs systems had been verified by UV-spectrometric detection and molecular dynamics simulations. The synthesized parameters were, respectively, optimized and the optimal conditions for the efficient adsorption property were as follows: template: MG, 1 mmol; functional monomer: methacrylic acid (MAA), 8 mmol; cross-linker: ethylene glycol dimethacryllate, 16 mmol; and porogen: acetonitrile, 30 mL. Fourier transform infrared spectroscopy and nitrogen adsorption experiments were used to characterize the MIPs. Scatchard analysis was used for estimation of the dissociation constants and maximum amounts of binding sites. The polymer based on MAA had two classes of heterogeneous binding sites characterized by two values of K _D and B _max: K _D = 14.10 μmol L^?1 and B _max = 1.37 μmol g^?1 for the higher affinity binding sites, and K _D = 384.62 μmol L^?1 and B _max = 24.77 μmol g^?1 for the lower affinity binding sites. The specificity of MIPs on SPE column was evaluated by rebinding the other structurally similar compounds. The results indicated that the imprinted polymers exhibited an excellent stereo-selectivity toward MG.     

Pulse perturbation technique for determination of piroxicam in pharmaceuticals using an oscillatory reaction system

A simple and reliable novel kinetic method for the determination of piroxicam (PX) was proposed and validated. For quantitative determination of PX, the Bray-Liebhafsky (BL) oscillatory reaction was used in a stable non-equilibrium stationary state close to the bifurcation point. Under the optimized reaction conditions (T = 55.0°C, [H₂SO₄]₀ = 7.60×10^?2 mol L^?1, [KIO₃]₀ = 5.90×10^?2 mol L^?1, [H₂O₂]₀ = 1.50×10^?1 mol L^?1 and j ₀ = 2.95×10^?2 min^?1), the linear relationship between maximal potential shift ΔE _m , and PX concentration was obtained in the concentration range 11.2–480.5 μg mL^?1 with a detection limit of 9.9 μg mL^?1. The method had a rather good sample throughput of 25 samples h^?1 with a precision RSD = 4.7% as well as recoveries RCV ≤ 104.4%. Applicability of the proposed method to the direct determination of piroxicam in different pharmaceutical formulations (tablets, ampoules and gel) was demonstrated.      

Electrochemical sensor for determination of aflatoxin B1 based on multiwalled carbon nanotubes-supported Au/Pt bimetallic nanoparticles

A sensitive and selective imprinted electrochemical sensor for the determination of aflatoxin B₁ (AFB₁) was constructed on a glassy carbon electrode by stepwise modification of functional multiwalled carbon nanotubes (MCNTs), Au/Pt bimetallic nanoparticles (Au/PtNPs), and a thin imprinted film. The fabrication of a homogeneous porous poly o-phenylenediamine (POPD)-grafted Au/Pt bimetallic multiwalled carbon nanotubes nanocomposite film was conducted by controllable electrodepositing technology. The sensitivity of the sensor was improved greatly because of the nanocomposite functional layer; the proposed sensor exhibited excellent selectivity toward AFB₁ owing to the porous molecular imprinted polymer (MIP) film. The surface morphologies of the modified electrodes were characterized using a scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. A linear relationship between the sensor response signal and the logarithm of AFB₁ concentrations ranging from 1?×?10^?10 to 1?×?10^?5 mol L^?1 was obtained with a detection limit of 0.03 nmol L^?1. It was applied to detect AFB₁ in hogwash oil successfully.     

Preparation of an amperometric sensor for norfloxacin based on molecularly imprinted grafting photopolymerization

A sensitive amperometric sensor for norfloxacin (NF) was introduced. The receptor layer was prepared by molecularly imprinted photopolymerization of acrylamide and trimethylolpropane trimethacrylate on the surface of a gold electrode. The binding mechanism of the molecularly imprinted polymer was explored by ultraviolet (UV) and infrared (IR) spectroscopy. The chemosensor was characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance (EI), and scanning electron microscopy (SEM). The electrode prepared by photopolymerization has a better recognition ability to template molecules than that of electropolymerization and NIP. Some parameters affecting sensor response were optimized. Norfloxacin was detected by measurements of an amperometric i–t curve. The linear relationships between current and logarithmic concentration are obtained from 1.0?×?10^?9 to 1.0?×?10^?3?mol?L^?1. The detection limit of the sensor was 1.0?×?10^?10?mol?L^?1. The proposed method is sensitive, simple, and cheap, and is applied to detect NF in human urine successfully.

Validated Voltammetric Method for the Simultaneous Determination of Anti‐diabetic Drugs,Linagliptin and Empagliflozin in Bulk,Pharmaceutical Dosage Forms and Biological Fluids

A cobalt oxide nanoparticles (Co₃O₄NPs) and multi walled carbon nanotubes (MWCNTs) modified carbon paste electrodes were used to study the electrochemical behavior of linagliptin and empagliflozin in Britton Robinson buffer solution of pH 8.0 using cyclic and square wave voltammetry. The above mentioned modified electrodes showed highly sensitive sensing and gave an excellent anodic response for both drugs. The peak current varied linearly over the concentration ranges: 3.98×10^?5–1.53×10^?3 mol L^?1 (18.82–723.00 μg/mL) and 7.94×10^?6–1.07×10^?4 mol L^?1 (3.65–48.25 μg/mL) with determination coefficients of 0.9999 and 0.9998 for linagliptin and empagliflozin, respectively. The recoveries and relative standard deviations were found in the following ranges: 98.80 %–102.00 % and 0.23 %–1.90 % for linagliptin and 98.30 %–101.80 % and 0.11 %–1.86 % for empagliflozin. The detection and quantification limits were 1.13×10^?5 and 3.76×10^?5 mol L^?1 (5.34and17.77 μg/mL) for linagliptin, 1.71×10^?6and 5.68×10^?6 mol L^?1 (0.77 and 2.56 μg/mL) for empagliflozin. The proposed sensors have been successfully applied for the determination of the drugs in bulk, pharmaceutical formulations and biological fluids.     

Determination of Tetracyclines in Water Samples Using Liquid Chromatography with Fluorimetric Detection

A liquid chromatographic method with fluorimetric detection is proposed for the determination of trace levels of oxytetracycline, tetracycline, chlortetracycline and doxycycline in water samples. The analytes are preconcentrated by solid phase extraction using reversed phase polymeric cartridges and acetonitrile as eluent. Preconcentration factors up to 125 can be obtained. The chromatographic separation is performed on a polymeric column with a gradient elution program using mobile phases based on mixtures of acetonitrile and 0.01 mol L^?1 oxalic acid aqueous solution at a flow rate of 1.2 mL min^?1. Tetracyclines are post-column derivatized with a reagent solution consisting of 0.1 mol L^?1 Mg(II) at pH 9 at a flow rate of 0.6 mL min^?1. The highly fluorescent Mg(II) chelates are detected at λ _ex = 374 nm and λ _em = 499 nm. The detection limits of the whole process are in the low μg L^?1 level. The proposed method has been applied to the analysis of spiked natural water samples, and recovery rates higher than 80% have been obtained.     

Molecularly imprinted polymers as artificial steroid receptors

The polymers selective to six different steroids (testosterone, Δ⁴-androstene-3,17-dione, 1,4-androstadiene-3,17-dione, β-estradiol, progesterone, testosterone propionate) have been synthesized using molecular imprinting based on noncovalent interactions. Analysis of the influence of structural features of the steroids under study has shown that molecules with a relatively rigid structure and the OH group at C-17 position are the most efficient templates for methacrylic acid-containing imprinted polymers. The chromatographic study of the polymers synthesized has demonstrated a strong dependence of the selectivity and intensity of interaction with analytes on the composition of solvents used both as porogen and chromatographic mobile phase. To obtain polymers with highly selective recognition sites and to create the optimal conditions for molecular recognition, all possible interactions (between template and functional monomer, template and solvent, solvent and functional monomer) should be taken into account. <?TF="palat-i"> The batch rebinding study of testosterone by the imprinted polymer in acetonitrile has revealed some heterogeneity of recognition sites, and permitted determination of K_ass = 1.05 × 10⁴ M ⁻¹, ΔG° = −5.4 kcal/mol and N = 1.2 μmol/g for high-affinity sites and K_ass = 0.33 × 10⁴ M ⁻¹, ΔG° = −4.8 kcal/mol and N = 2.2 μmol/g for low-affinity sites. <?TF="palat-i"> The results obtained show how it is possible to regulate in different modes the molecular recognition by imprinted polymers as well as to fabricate polymers possessing the necessary properties depending on their practical application.© 1998 John Wiley & Sons, Ltd.     

Man‐Tailored Biomimetic Sensor of Molecularly Imprinted Materials for the Potentiometric Measurement of Rivastigmine in Tablets and Biological Fluids and Employing the Taguchi Optimization Methodology to Optimize the MIP‐Based Membranes

This work proposes a novel biomimetic sensor for the potentiometric transduction of rivastigmine based on molecularly imprinted polymer (MIP). Using the Taguchi method, this study analyzed the optimum conditions for preparing the MIP‐based membranes. The rank order of each controllable factor was also determined. MIP‐based membranes exhibited a Nernstian response (30.7±1.1 mV decade^?1) in a concentration range from 1.0×10^?5 to 1.0×10^?2 mol L^?1 with a LOD of 6.3×10^?6 mol L^?1. The sensor was successfully applied to the determination of rivastigmine concentrations in human serum, plasma, urine, rat brain and tablets.     

Validated LC Determination of the Piroxicam-β-Cyclodextrin Inclusion Complex in Tablets and in Human Plasma

A simple, rapid, specific, sensitive HPLC method has been developed for the determination of piroxicam in the tablet dosage form and in human plasma. The method totally eliminates solvent extraction and time-consuming separation procedures. Plasma proteins were precipitated by addition of 3:1 (v/v) acetonitrile-methanol, ZnSO₄, and MgSO₄ and the supernatant was injected directly on to a 250 mm × 4.6 mm, 5 μm particle Spherisorb analytical column. Acetonitrile-methanol-0.04 mol L^?1 KH₂PO_4, 40:10:50 (v/v); pH 3.8, was used as mobile phase. The drug was detected by UV detection at 330 nm. The response was linear over the range of 0.01–10 μg mL^?1 and 0.025–5 μg mL^?1 in mobile phase and human plasma samples, respectively. The proposed method was used without interference from the endogenous substances, for determination of piroxicam in plasma samples obtained from healthy volunteers. The results revealed that the method would be useful in monitoring plasma levels of the drug during pharmacokinetic studies. Assay of piroxicam in its dosage forms for quality-control purposes could also be performed successfully by use of this method.     

Study on the Binding Characteristic of Methamidophos‐Specific Molecularly Imprinted Polymer and the Interactions between Template and Monomers

A new molecularly imprinted polymer (MIP) was prepared using methamidophos (MAP) as the template molecule based on non‐covalent interaction. The complexes formed between template and monomers before polymerization were characterized by ¹H NMR titration test, FT‐IR and UV spectrometry study. These studies indicated that a 1:2 molecular complex formed dominantly between MAP and functional monomers. A model mainly involving cooperative hydrogen interaction was proposed by exact placement of functional groups. Association constant was estimated to be 2.894 × 10⁶ L²/mol². When the initial concentration of MAP was 1.0 mmol L^?1, the affinity capacity of MIP was 4.23 times that of NIP. The binding performance of MIP was modeled with the Freundlich isotherm (FI) and the total number of binding sites was calculated to be 33.97 μmol/g. The MIP showed great homogeneity with a heterogeneity index of m = 0.7356. The specificity of MIP was investigated by single‐analyte binding and molecularly imprinted solid‐phase extraction (MISPE) assays using MAP and other structurally related organophorous pesticides (OPPs). The results indicated that the MIP had a marked preference for MAP.     

Simultaneous determination of caffeine,paracetamol, and ibuprofen in pharmaceutical formulations by high‐performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection

Paracetamol, caffeine and ibuprofen are found in over‐the‐counter pharmaceutical formulations. In this work, we propose two new methods for simultaneous determination of paracetamol, caffeine and ibuprofen in pharmaceutical formulations. One method is based on high‐performance liquid chromatography with diode‐array detection and the other on capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation by high‐performance liquid chromatography with diode‐array detection was achieved on a C₁₈ column (250×4.6 mm², 5 μm) with a gradient mobile phase comprising 20–100% acetonitrile in 40 mmol L^?1 phosphate buffer pH 7.0. The separation by capillary electrophoresis with capacitively coupled contactless conductivity detection was achieved on a fused‐silica capillary (40 cm length, 50 μm i.d.) using 10 mmol L^?1 3,4‐dimethoxycinnamate and 10 mmol L^?1 β‐alanine with pH adjustment to 10.4 with lithium hydroxide as background electrolyte. The determination of all three pharmaceuticals was carried out in 9.6 min by liquid chromatography and in 2.2 min by capillary electrophoresis. Detection limits for caffeine, paracetamol and ibuprofen were 4.4, 0.7, and 3.4 μmol L^?1 by liquid chromatography and 39, 32, and 49 μmol L^?1 by capillary electrophoresis, respectively. Recovery values for spiked samples were between 92–107% for both proposed methods.     

Preparation and Performance Research on Glutathione Molecularly Imprinted Polymers

Methacrylic acid and ethylene glycol dimethacrylate were respectively used as functional monomer and cross-linker to synthesize molecularly imprinted polymers (MIPs), for adsorption of glutathione (GSH), named GSH-MIPs. Evaluation of various polymers by static experiment indicated the optimum ratio of template to functional monomer was 1:4; the optimal concentration and pH of loading buffer were 5.00?C6.50 mmol L^?1 and 5.0, respectively. By Scatchard analysis, the GSH binding site was found in GSH-MIPs, with K _d and Q _max of 1.96 mmol L^?1 and 47.19 ??mol g^?1, respectively. The method validated the extraction of GSH from yeast cells samples with the enrichment rate of 76%.     

Synthesis of Molecularly Imprinted Polymer for Sensitive Penicillin Determination in Milk

Abstract

Penicillin G (PG) in milk is unsafe for human and is a big problem for the foods industry. Hence, the better analytical and eliminative techniques are demanded. We investigated a PG molecular imprinted polymer (MIP), which can sensitively detect and extract the PG from milk and other samples. The MIP synthesis involved a β-lactam antibiotics PG, methacrylic acid (MAA) and dimethyl formamide (DMF). Its properties were analyzed with Scatchard plot, which showed that there were two affinity sites of the PG polymer. The first equilibrium dissociation constant of the high-affinity binding sites Kd₁ was 1.14 × 10^?4 mol/L and the binding capacity Q_max1 was 46.01 µmol/g; the second equilibrium dissociation constant of the low-affinity binding sites Kd₂ was 1.35 × 10^?3 mol/L and the binding capacity Q_max2 was 72.55 µmol/g. Furthermore, two PG determination methods using the polymer were developed. The first was carried out quantitatively with a spectrophotometer and the detection limit was 1 ppm. The other one was the combination of the MIP particles with milk fermentation for PG analysis and the sensitivity was 10 ppb.     

Differential Pulse Voltammetric Determination of Selenocystine and Selenomethionine Using SAM nanoSe0/Vc/SeCys‐Film Modified Au Electrode

The SAM nanoSe⁰/Vc/SeCys‐film modified Au electrode has been prepared to determine selenocystine and selenomethionine. The AFM and SEM showed the special three‐dimensional (3D) network structure of the sol‐gel films. The affinity between nanoparticles and biomolecules created special chemical characters analyzed by the XRD and fluorescence. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified films partly had resistance in the charge transduction of Fe(CN) , but the less electron‐transfer resistance. Differential pulse voltammetric (DPV) determination of selenoamino acids using SAM nanoSe⁰/Vc/SeCys‐film modified Au electrode was presented. In PBS (pH 7.0)+0.1 mol L^?1 NaClO₄ solution, selenoamino acids yielded a sensitive reduction peak at about +400±50 mV. The peak current had a linear relationship with the concentration of selenoamino acids in the range of 5.0×10^?8–1.0×10^?5 mol L^?1, and a 3σ detection limit of selenoamino acids was 1.2×10^?8 mol L^?1. The relative standard deviation of DPV signals of 0.50×10^?6 mol L^?1 selenoamino acids was 3.8% (n=8) using the same electrode and was 4.4% (n=5) when using three modified electrodes prepared at different times. The content of selenoamino acids in the organo‐selenium powder were determined by DPV. The results showed 71.5 μg g^?1 of SeCys and 65.1 μg g^?1 of SeMet in the organo‐selenium powder.     

An Electrochemical Sensor Based on Reduced Graphene Oxide,Gold Nanoparticles and Molecular Imprinted Over‐oxidized Polypyrrole for Amoxicillin Determination

An electrochemical sensor for amoxicillin (AMX) detection based on reduced graphene oxide (RGO), molecular imprinted overoxidized polypyrrole (MIOPPy) modified with gold nanoparticles (AuNPs) is described in this work. The electrochemical behavior of the imprinted and non‐imprinted polymer (NIP) was carried out by cyclic voltammetry (CV) and impedance spectroscopy (IS). The structure and morphology of the prepared MIP sensor were characterized by scanning electron microscopy (SEM), UV‐Visible, Fourier transform infrared spectroscopy (FTIR) and its experimental parameters such as monomer and template concentration, pH buffer solution, incubation time of AMX and AuNPs, scan rate as well as electropolymerization scan cycles were optimized to improve the performance of the sensor. The peak current obtained at the MIP electrode was proportional to the AMX concentration in the range from 10^?8 to 10^?3 mol L^?1 with a detection limit and sensitivity of 1.22 10^?6 mol L^?1 (Signal to noise ratio=3) and 2.52×10^?6 μAmol^?1 L, respectively. It was also found that this sensor exhibited reproducibility and excellent selectivity against molecules with similar chemical structures. Besides, the analytical application of the AMX sensor confirms the feasibility of AMX detection in milk and human serum.