Synthesis of a novel molecularly imprinted polymer based on functionalized multi-walled carbon nanotubes for selective extraction of sulfadiazine prior to spectrophotometric determination

A novel and efficient sulfadiazine imprinted polymer was synthesized via co-precipitation method and successfully grafted on magnetic multi-walled carbon nanotubes. The synthesized magnetic imprinted polymer was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction analysis, thermal analysis and applied as a sorbent for selective magnetic solid-phase extraction of sulfadiazine. The retained sulfadiazine was eluted by 150.0 µL methanol/acetic acid (6:4) solution and quantified by fiber optic linear array spectrophotometry via formation of a detectable azo dye. All parameters affecting the extraction of sulfadiazine were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 2.0–50.0 µg L^?1 with a detection limit of 0.56 µg L^?1 and enrichment factor of 300.0. The relative standard deviation at 30.0 µg L^?1 of sulfadiazine (N = 6) was 2.8 and 4.6% for intra-day and inter-day, respectively. The method was successfully applied to determine sulfadiazine in human urine, honey, milk and environmental water samples.     

Synthesis and Characterization of Molecularly Imprinted Nanoparticle Polymers for Selective Separation of Anthracene

Two anthracene molecularly imprinted nanoparticle polymers namely; An–MINP1 and An–MINP2, were synthesized using the precipitation polymerization method. An–MINPs were used for selective separation of anthracene from aqueous solutions. The data revealed that the maximum binding capacity of An–MINPs for anthracene were 320.8 and 374.3 mg g^?1 for An–MINP1 and An–MIPN2, respectively, compared with 2.8 and 4 µg g^?1 obtained by using their corresponding non-imprinted polymers NIP1 and NIP2, respectively. Under optimized conditions, An–MINPs give high selectivity and sensitivity of anthracene separation. The anthracene uptake percentage from aqueous solutions ranged from 90.3 to 99.9%.     

Extraction of Anthraquinones from Rhubarb by a Molecularly Imprinted–Matrix Solid-Phase Dispersion Method with HPLC Detection

A simple method based on matrix solid-phase dispersion for selective extraction of anthraquinones from rhubarb samples was developed using a molecularly imprinted polymer as sorbent. The molecularly imprinted polymer was prepared using emodin as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking agent. The polymer was characterized by scanning electron microscopy and Fourier-transform infrared spectrometry. Isothermal adsorption and dynamic adsorption experiments were performed. The best extraction conditions for anthraquinones were obtained at a ratio of molecularly imprinted polymer to sample of 1:1, a dispersion time of 5 minutes, with 5% aqueous methanol as the washing solvent, and an elution solvent of methanol-acetic acid (99:1, v/v). Once the matrix solid-phase dispersion process was optimized, the extract was reacted with 8% hydrochloric acid for hydrolysis. The anthraquinones extracted from rhubarb were determined by liquid chromatography. The detection limits of chrysophanol, emodin, physcion, and aloe-emodin were 0.23, 0.24, 0.28, and 0.27 µg mL^?1, respectively. The proposed method was compared with the method in Chinese pharmacopoeia, and the results show that the extraction yield of anthraquinones obtained by molecularly imprinted polymer–matrix solid-phase dispersion method was higher. Moreover, the proposed method is faster and simpler and can achieve extraction and purification in the same system.     

Synthesis,characterization and application of dummy-template molecularly imprinted microspheres for 2,4-d butyl ester

Dummy-template molecularly imprinted microspheres were synthesized via precipitation polymerization employing 2,4-D isooctyl ester as the template molecule instead of 2,4-D butyl ester, while methacrylic acid and divinylbenzene were used as functional monomer and cross-linker in acetonitrile or a mixture of acetonitrile and toluene. The microspheres were characterized by scanning electron microscopy, laser particle size analyzer and fourier transform infrared spectrometry. Binding capacity experiment showed that the molecularly imprinted polymers prepared in a mixture of acetonitrile and toluene had a high binding capacity. The performance of microspheres was further assessed by equilibrium binding and kinetic adsorption experiments. The results showed that the apparent maximum adsorption reached up to 1.35 mg·g^?1 within 10 min. Based on the dummy-template microspheres, a molecularly imprinted solid phase extraction-gas chromatography method was developed for the selective analysis of 2,4-D butyl ester in soil samples. The mean recoveries of 2,4-D butyl ester from blank soil samples ranged from 85.9 to 99.3% with relative standard deviations of 4.5–14.3% (n = 5). The limit of detection and the limit of quantification of 2,4-D butyl ester were 0.8 μg·kg^?1 and 2.3 μg·kg^?1, respectively.     

Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NS_s) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L^?1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L^?1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L^?1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L^?1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L^?1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L^?1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.     

A molecular imprint-coated stirrer bar for selective extraction of caffeine, theobromine and theophylline

We have prepared a novel caffeine imprinted polymer on a stir bar that can be used for selective extraction of caffeine, theobromine and theophylline from beverages. The polymerization time and quantities of reagents (template, cross-linker, porogenic solvent) were optimized. The morphology of the molecularly imprinted polymer-coating was studied by scanning electron microscopy and Fourier transform IR spectroscopy. A rapid and sensitive method was worked out for the extraction of caffeine, theobromine and theophylline from beverages by using the molecularly imprinted stir bar followed by HPLC analysis. The effects of extraction solvent, stirring speed, desorption solvent, adsorption and desorption time were optimized. The method displays a linear response in the 5–150 μg L^?1 caffein concentration range, with a correlation coefficient of >0.9904. The recoveries for three analytes in tea, carbonated and functional beverages were 91–108 %, 90–110 % and 93–109 %, with relative standard deviations ranging from 3.6–5.7 %, 3.5–7.9 % and 3.2–7.9 %, respectively.

Selective Determination of Fourteen Nitroimidazoles in Honey by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A selective method for the determination of fourteen nitroimidazoles and their hydroxy-metabolites in honey was developed based on improved molecularly imprinted solid-phase extraction followed by liquid chromatography–tandem mass spectrometry. The separation of analytes was performed on a C₁₈ column using a mobile phase of 0.1% formic acid in acetonitrile and 0.1% formic acid in water with gradient elution. The method was suitable for metronidazole, hydroxymetronidazole, dimetridazole, ronidazole, hydroxydimetridazole, ipronidazole, hydroxyipronidazole, carnidazole, menidazole, nimorazole, ornidazole, secnidazole, ternidazole, and tinidazole. The procedure was evaluated according to EU Commission Decision 2002/657/EC requirements by determining linearity, specificity, recovery, repeatability, within-laboratory reproducibility, decision limit, detection capability, matrix effects, and stability. The method determined nitroimidazoles and their hydroxy-metabolites below the recommended concentration level of 3 µg kg^?1. The decision limits and detection capabilities ranged from 0.110 µg kg^?1 to 0.387 µg kg^?1 and from 0.179 µg kg^?1 to 0.508 µg kg^?1, respectively. The results from stability tests indicated that all analyzed nitroimidazoles were stable in honey stored at 4°C for at least 28 weeks and that elevated temperature and exposure to light exposure accelerated their degradation. The method was successfully applied to the analysis of a wide variety of honey samples.     

Simple and selective extraction of quercetin with microextraction in packed syringe method using modified glass powder by a molecularly imprinted polymer followed by spectrophotometric determination

A new sample preparation method based on microextraction in packed syringe was developed for preconcentration of quercetin prior to its spectrophotometric determination. Molecularly imprinted polymers as packing material was used for higher extraction efficiency. First, glass powder as support material because of low cost and available substrate was modified, and then molecularly imprinted polymers were synthesized by the sol–gel method using 3-aminopropyltriethoxysilane as a functional monomer and tetraethyl orthosilicate as cross-linker agent. The combination of a molecularly imprinted polymers and microextraction in packed syringe increased the selectivity and sensitivity. The surface morphology and functionality of the prepared molecularly imprinted polymers was characterized using Fourier-transform infrared spectroscopy, Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and thermogravimetric analysis. Different influencing parameters on extraction efficiency such as effect of the number of sample sorption/desorption cycles, type and volume of desorption solvent, pH of the sample solution, and molecularly imprinted polymers amounts were optimized. Under the optimum condition, the proposed method displayed a linear range from 0.01 to 5 µg mL⁻¹ and limit of detection 3.68 ng mL⁻¹. Relative standard deviation for three replicate determination of 1 µg mL⁻¹ quercetin was 2.1 %. The proposed method was applied successfully for the selective extraction of quercetin from tea and coffee samples.     

Preparation of a semicovalent, molecularly surface imprinted polymer for the rapid determination of trace acid orange II in food and environmental samples

In this work, molecularly imprinted polymer (MIP) particles were synthesized using a semicovalent method based on a specific thermally reversible bond, and these particles were used for the rapid detection of the azo dye acid orange II. The imprinted polymers—which were prepared via the covalent reaction of 3-(triethoxysilyl)propyl isocyanate with the template molecules—were attached to the surface of silica-coated magnetic nanoparticles, and a simple thermal reaction was then performed to remove the templates, leaving spaces with specific noncovalent bonds for target re-recognition. The conditions for the synthesis of the MIP were optimized during the polymerization experiments to improve the adsorption capacity and selectivity. The resulting polymers were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy to confirm their structure. The MIPs were subjected to an online solid-phase extraction and a magnetic molecularly imprinted solid-phase extraction procedure. For both methods, all samples were prepared with spiking levels of 5.0, 10.0, and 15.0 μg kg^-1 using high-performance liquid chromatography with UV/vis detection; after the preconcentration of 50-mL sample solutions, the enhancement factors reached 710 and 629. The limits of detection (signal-to-noise ratio of 3) were 9.83 and 17.41 ng L^-1, with relative standard deviations (n?=?9) of 6.72 % and 8.25 %, respectively, for a 4.0 μg L^?1 standard template solution. These two methods were developed to quantify trace acid orange II contents in food and environmental samples; the recoveries ranged from 72 to 105 % and from 70 to 94 %, respectively.     

Determination of Tetracyclines by Solid-Phase Extraction with a Molecularly Imprinted Polymer and High-Performance Liquid Chromatography

Tetracyclines are widely used antibiotics classified as emerging pollutants and may lead to an increase in bacterial resistance in the environment. In order to determine these compounds at low concentrations, a water-compatible molecularly imprinted polymer was developed for solid-phase extraction followed by high-performance liquid chromatography analysis. The monomers 2-hydroxyethyl methacrylate and glycerol dimethacrylate were added 1 h after the start of the synthesis to provide hydroxyl groups on the polymer surface. This hydrophilic layer established hydrogen bonds with water, minimizing interferences of this solvent in the analyte-polymer complex, increasing analyte adsorption. The polymer was then used for solid-phase extraction to preconcentrate the tetracyclines. The method provided low limits of quantification (5 µg L^?1), good linearity, precision, and accuracy for tetracyclines, with preconcentration factors of 14, 19, 29, and 41 for oxytetracycline, tetracycline, chlortetracycline, and doxycycline, respectively.     

Determination of Chloramphenicol Residues in Foods by ELISA and LC-MS/MS Coupled with Molecularly Imprinted Solid Phase Extraction

The combination of molecularly imprinted solid-phase extraction (MISPE) with ELISA and LC-MS/MS was developed for the detection of chloramphenicol (CAP) in honey samples. Significant recoveries of 99.1 ± 7.1 and 98.8 ± 8.2% were obtained for intra- and inter-assay determination by ELISA determination, respectively. The limit of detection of CAP was 0.034 μg kg^?1 and the limit of quantification was 0.046 μg kg^?1. Determination and validation of CAP by using LC-MS/MS were performed following the same extraction and purification process as for the ELISA. The results demonstrated that the CAP samples purified by using MISPE were simultaneously applicable to analysis by ELISA and LC-MS/MS.     

Preconcentration of Nicotinamide Using Molecularly Imprinted Microspheres for Solid-phase Extraction with Determination by High-performance Liquid Chromatography

The determination of target molecules in complicated matrices such as biological samples is largely dependent on sample pretreatment. Molecularly imprinted solid-phase extraction (SPE), using molecularly imprinted polymers as the adsorbent, has been demonstrated to be effective for the selective enrichment of target molecules in biological samples. In this study, molecularly imprinted polymeric microspheres were fabricated by two-step swelling polymerization using polystyrene particles as seeds, nicotinamide as the template, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker. The molecularly imprinted polymeric microspheres were packed into empty SPE cartridges, and the spiked urine and serum samples were loaded separately. After an initial washing and elution step, the effluents were analyzed by high-performance liquid chromatography (HPLC) using 1:9 methanol/0.05% phosphoric acid. The obtained molecularly imprinted polymeric microspheres were uniform, and the spherical particles were well distributed. The established method was validated, and the results showed that the method was linear from 0.499 to 19.96?µg?mL^?1. The limits of detection and quantification for nicotinamide were 0.3 and 0.9?µg?mL^?1, respectively. The relative standard deviations were 1.55 and 2.86% in urine and serum, respectively. The spiked recoveries of nicotinamide were 86.0–98.8% and 87.0–96.8% in urine and serum, respectively. The molecularly imprinted SPE and HPLC methods in this study are useful for the pretreatment and determination of the target compounds in these matrices.     

Preparation and Adsorption Characteristics of Cordycepin Molecularly Imprinted Polymers

The separation of a molecularly imprinted polymer for cordycepin was investigated. The synthesis employed cordycepin as the molecular template, alpha-methylacrylic acid as the functional monomer, glycol dimethyl acrylate as the cross-linking agent, azobisisobutyronitrile as the initiator, and tetrahydrofuran as the solvent and pore-foaming agent. The interaction between cordycepin and the functional monomer was investigated by ultraviolet-visible and infrared spectroscopy. The properties of the molecularly imprinted polymer were analyzed by scanning electron microscopy, equilibrium adsorption experiments, and the Scatchard equation. Static adsorption, solid phase extraction, and high-performance liquid chromatography experiments were employed to evaluate the adsorption properties and selective recognition characteristics. The results showed that the molecularly imprinted polymer had specific adsorption with cordycepin, and the maximum absorption capacity was 1920 µg/g. Scatchard analysis suggested that high affinity and low affinity binding sites were present. For the high affinity case, the dissociation constant and apparent maximum numbers of the binding sites were 0.0089 mmol/L and 4.78 µmol/g, respectively. The dissociation constant and apparent numbers of binding sites were 0.035 mmol/L and 6.047 µmol/g for the low affinity sites. Compared with the corresponding nonimprinted polymer, the cordycepin molecularly imprinted polymer exhibited higher adsorption and selectivity for cordycepin than structural analogs.     

An Ionic Liquid Loaded β-Cyclodextrin-Cross-Linked Polymer as the Solid Phase Extraction Material Coupled with High-Performance Liquid Chromatography for the Determination of Rhodamine B in Food

A novel method for separation and determination of rhodamine B in food samples is described. The work is based on the utilization of an ionic liquid loaded β-cyclodextrin cross-linked polymer coupled with high-performance liquid chromatography for the determination of rhodamine B. The inclusion interaction of the ionic liquid-β-cyclodextrin cross-linked polymer with rhodamine B was studied by FTIR. Under optimum conditions, the preconcentration factor achieved for this method was approximately 20. The linear range, detection limit, and relative standard deviation were 0.80 to 130.0 µg L^?1, 0.09 µg L^?1, and 0.66% (n = 3, concentration = 10.0 µg L^?1), respectively. The technique was successfully applied for determination of rhodamine B in food samples.     

Differential pulse voltammetric determination of trace rotenone using molecularly imprinted polymer microspheres

A new voltammetric method for the determination of rotenone is described. It is based on the reduction of an electroactive derivative of rotenone on the surface of an electrode. Rotenone in water was pre-concentrated using a new type of molecularly imprinted polymer microspheres and can react with hydrazine chloride to produce the electroactive derivative. The experimental conditions were discussed. Under optimum conditions, it was found that the peak potential (Ep) of the derivative of rotenone is ?1.02 V (vs. Ag/AgCl). Using the proposed procedure rotenone can be determined in the range 0.2–400 μg L^?1. The detection limit for rotenone is 0.1 μg L^?1 and the relative standard deviation for 100 μg L^?1 rotenone is 1.99 %. The method was applied to the determination of rotenone in water samples with satisfactory results.     

On-Line Preconcentration and Analysis of Metribuzin Residues in Corn Fields by Use of a Molecularly Imprinted Polymer

A molecularly imprinted polymer as a selective solid-phase extraction adsorbent for efficient preconcentration and analysis of metribuzin residues in corn fields has been synthesised and evaluated. Results showed that molecular imprinting of the polymer was highly effective and the polymer had high affinity and selectivity for metribuzin in water-containing systems. A monolithic column containing molecularly imprinted polymer was prepared and used for on-line preconcentration, separation, and detection of metribuzin residues in soil sampled during investigation of the degradation of the herbicide metribuzin in corn fields. The detection limit of the method was 8.3 × 10^?4 mg kg^?1, recovery was between 94.9% and 103%, and RSD in analysis of soil samples was less than 3.2%.     

Magnetic molecularly imprinted polymer nanoparticles for the solid-phase extraction of paracetamol from plasma samples,followed its determination by HPLC

We are presenting magnetic molecularly imprinted polymer nanoparticles (m-MIPs) for solid-phase extraction and sample clean-up of paracetamol. The m-MIPs were prepared from magnetite (Fe₃O₄) as the magnetic component, paracetamol as the template, methacrylic acid as a functional monomer, and 2-(methacrylamido) ethyl methacrylate as a cross-linker. The m-MIPs were then characterized by transmission electron microscopy, FT-IR spectroscopy, X-ray diffraction and vibrating sample magnetometry. The m-MIPs were applied to the extraction of paracetamol from human blood plasma samples. Following its elution from the column loaded with the m-MIPs with an acetonitrile-buffer (9:1) mixture, it was submitted to HPLC analysis. Paracetamol can be quantified by this method in the 1 μg L^?1 to 300 μg L^?1 concentration range. The limit of detection and limit of quantification in plasma samples are 0.17 and 0.4 μg L^?1. The preconcentration factor of the m-MIPs is 40. The HPLC method shows good precision (4.5 % at 50 μg L^?1 levels) and recoveries (between 83 and 91 %) from spiked plasma samples. Figure

We are presenting magnetic molecularly imprinted polymer nanoparticles (m-MIPs) for solid-phase extraction and sample clean-up of paracetamol. The m-MIPs were applied to the extraction of paracetamol from human blood plasma samples     

Quantification of Tricyclic and Nontricyclic Antidepressants in Spiked Plasma and Urine Samples Using Microextraction in Packed Syringe and Analysis by LC and GC-MS

In this paper, a highly selective Sudan IV molecularly imprinted polymer was synthesized by surface molecular imprinting technique in combination with a sol?Cgel process using ??-aminopropyl triethoxysilane as functional monomer, tetraethoxysilane as cross-linker and activated silica gel as support material. The imprinted polymer was characterized by FT-IR spectra, scanning electron micrograph and adsorption experiments and it was exhibited good recognition and selective ability, offered a faster rate for the adsorption of Sudan IV. Using the imprinted material as sorbent, a solid-phase extraction coupled with high-performance liquid chromatography method for determination of trace Sudan IV was presented. The detection limit (S/N = 3) was 25.2 ng L^?1, and the RSD for five replicate was 2.86%. With a loading flow rate of 2.5 mL min^?1 for loading 30 mL, an enrichment factor of 104 was achieved. This method was applied for extraction and determination of chilli powder and duck egg samples with good recoveries ranging from 85.3 to 98.1%.     

Monodisperse restricted access material with molecularly imprinted surface for selective solid‐phase extraction of 17β‐estradiol from milk

In this study, novel monodisperse restricted access media‐molecularly imprinted polymers were successfully prepared by surface initiated reversible addition‐fragmentation chain transfer polymerization using monodisperse crosslinked poly (glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) microspheres as the carrier and acryloyl chloride‐modified β‐cyclodextrin as the hydrophilic functional monomer. The surface morphology, protein exclusion, and adsorption properties of the molecularly imprinted polymers were investigated. The results show that the material has excellent monodispersity and hydrophilicity, and simultaneously exhibit high adsorption capacity, fast binding kinetics, high selectivity, and significant thermal stability. The molecularly imprinted polymers as dispersive solid‐phase extraction adsorbent combined with reversed‐phase high‐performance liquid chromatography was used to selectively enrich, separate, and analyze trace 17β‐estradiol in milk samples. The recovery of 17β‐estradiol is 88–95% with relative standard deviation of <4%, and the limits of detection and quantification of this method are 2.08 and 9.29 µg/L, respectively. The novel restricted access media‐molecularly imprinted polymer adsorbents provide an effective method for the selective extraction and detection of 17β‐estradiol directly from complex samples.     

Synthesis of molecularly imprinted polypyrrole as an adsorbent for solid‐phase extraction of warfarin from human plasma and urine

The aim of this work was to develop a method for the clean‐up and preconcentration of warfarin from biological sample employing a new molecularly imprinted polymer (MIP) as a selective adsorbent for solid‐phase extraction (SPE). This MIP was synthesized using warfarin as a template, pyrrole as a functional monomer and vinyl triethoxysilane as a cross‐linker. The molar ratio of 1:4:20 (template–functional monomer–cross‐linker) showed the best results. Nonimprinted polymers (NIPs) were prepared and treated with the same method, but in the absence of warfarin. The prepared polymer was characterized by Fourier transmission infrared spectrometry and scanning electron microscopy. An adsorption process (SPE) for the removal of warfarin using the fabricated MIPs and NIPs was evaluated under various conditions. Effective parameters on warfarin extraction, for example, type and volume of elution solvent, pH of sample solution, breakthrough volume and maximum loading capacity, were studied. The limits of detection were in the range of 0.0035–0.0050 µg mL^?1. Linearity of the method was determined in the range of 0.0165–10.0000 µg mL^?1 for plasma and 0.0115–10.0000 µg mL^?1 for urine with coefficients of determination (R²) ranging from 0.9975 to 0.9985. The recoveries for plasma and urine samples were >95%. Copyright © 2015 John Wiley & Sons, Ltd.