Adsorption Capacity Of Molecularly Imprinted Polymers Research Articles

Synthesis of molecularly printed methyl methacrylate-based polymers for the detection of di(2-ethylhexyl) phthalate and dibutyl phthalate

Molecularly imprinted polymers (MIP) were obtained by precipitation polymerization for the detection of DEHP and DBP from polymer packaging in drinking water. MIP was obtained by cross-linking DEHP and DBP with methyl methacrylate (MMA) and trimethylolpropane trimethacrylate (TRIM). FTIR, SEM-EDS, UV-Vis and SAA were used to determine properties of polymers (MIP_DEHP, MIP_DBP). The obtained materials were characterized by a mesoporous structure with small, uniform, and porous grains. The surface area and total pore volume of MIP_DEHP were more than twice smaller than MIP_DBP, with a slightly larger pore diameter. Lower C content may indicate the formation of MIP_DEHP and MIP_DBP. The FTIR method confirmed the presence of functional groups –CH, –CO, –C=C and –C=O. The adsorption capacity of MIP_DEHP and MIP_DBP was 0.68 mg/g and 1.06 mg/g, respectively, and was consistent with the Freundlich isothermal adsorption model.

Selective Adsorption of Quercetin by the Sol-Gel Surface Molecularly Imprinted Polymer.

Quercetin, as one of the most biologically active natural flavonoids, is widely found in various vegetables, fruits and Chinese herbs. In this work, molecularly imprinted polymer (MIP) was synthesized through surface molecular imprinting technology with sol-gel polymerization mechanism on SiO2 at room temperature using quercetin as the template, SiO2 as the supporter, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, and tetraethoxysilane (TEOS) as the cross-linker. The prepared MIP was characterized via scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption measurements to validate its surface morphology, structure and functionality. SEM images revealed that the morphology of MIP was rough and spherical with the particle size of 260 nm larger than that of the support SiO2. In the FTIR spectra of MIP, the band around 1499 cm-1 and 2932 cm-1 were assigned to N-H and C-H groups, respectively. The results indicated that the imprinted polymer layers were grafted on the surface of SiO2 and the MIP had been successfully prepared. Since the specific surface area and pore volume of MIP were markedly higher than those of NIP and SiO2 and were 52.10 m2 g-1 and 0.150 cm3 g-1, respectively, it was evident that the imprinting process created corresponding imprinted cavities and porosity. The MIP for adsorbing quercetin was evaluated by static adsorption experiment. The results indicated that the adsorption equilibrium could be reached within 90 min and the maximum adsorption capacity was as high as 35.70 mg/g. The mechanism for adsorption kinetics and isotherm of MIP for quercetin was proved to conform the pseudo-second-order kinetics model (R2 = 0.9930) and the Freundlich isotherm model (R2 = 0.9999), respectively, revealing that chemical adsorption and heterogeneous surface with multilayer adsorption dominated. In contrast to non-imprinted polymer (NIP), the MIP demonstrated high selectivity and specific recognition towards quercetin whose selectivity coefficients for quercetin relative to biochanin A were 1.61. Furthermore, the adsorption capacity of MIP can be maintaining above 90% after five regeneration cycles, indicating brilliant reusability and potential application for selective adsorption of quercetin.

Zipper-like thermosensitive molecularly imprinted polymers based on konjac glucomannan for metformin hydrochloride

Zipper-like thermosensitive molecularly imprinted polymers (MIPs) based on konjac glucomannan (KGM) for metformin hydrochloride were prepared using KGM, a natural polysaccharide, as the matrix, acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as the comonomers, N, N′-methylenebis(acrylamide) as the cross-linking agent, ceric ammonium nitrate as the initiator, and metformin hydrochloride as the template molecule. The resultant MIPs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), X-ray diffractometry (XRD), thermal gravimetric analyzing (TGA), and scanning electron microscopy (SEM). The interpolymer interactions between poly (AM) and poly (AMPS) were demonstrated by the results of ultraviolet spectrometry (UV), indicating that MIPs with zipper-like structure could be fabricated. The thermo-responsive MIPs with on/off-switchable characteristic were evaluated by the method of cyclic voltammetry (CV). The adsorption experiment showed that the target molecules could be controlled to be adsorbed/desorbed by changing the external temperature. The adsorption capacity at high temperature was higher than that at low temperature. Moreover, the adsorption capacity of MIPs was much higher than that of NIPs. The results of adsorption experiments showed that the MIPs could specifically recognize and adsorb metformin with excellent selectivity, repeatability, and stability. Langmuir equation and Freundlich equation were applied to fit the adsorption isotherms of MIPs and the results showed that the Langmuir equation fitted better than the Freundlich equation. The product is expected to serve as a novel adsorption and separation material.

Advanced preparation technologies and strategies for molecularly imprinted materials

Molecularly imprinted polymers (MIPs) prepared by molecular imprinting technology (MIT) are polymers with specific recognition sites matching the shape, size and functional groups of template molecules, which can selectively identify and enrich target analytes (template molecules), and have been widely used in sample pretreatment, chemical/biological sensing and other fields. However, in the processes of preparation and applications of MIPs, there are still some problems, such as difficult elution of template molecules, fewer effective recognition sites, low binding capacity, low mass transfer rate and poor recognition in aqueous media. As a multidisciplinary technology, MIT has developed rapidly by borrowing and integrating related advanced technologies/strategies of other fields. Consequently, a variety of new imprinting technologies and strategies have continuously emerged, which not only effectively solve the abovementioned problems but also push forwards the development of novel MIPs and widen their applications. In this paper, orienting the applications of MIPs in sample pretreatment, sensors and stimuli responses, some advanced preparation technologies and strategies for MIPs materials are highlighted, including ingenious imprinting technologies (surface imprinting, nanoimprinting; controlled/living polymerization, solid-phase synthesis, etc.), special imprinting strategies (multi-template/monomer imprinting, dummy imprinting, boronate affinity imprinting, etc.), and stimuli-responsive imprinting (magnetic, temperature, pH responsive, etc.). Fundamental features of the advanced imprinting technologies/strategies and their utilizations for MIPs preparations along with representative applications are described in details, involving important issues and research challenges. Firstly, a comprehensive overview of main imprinting technologies and strategies for MIPs preparation in sample pretreatment application is provided. In this regard, MIPs are used as selective adsorbents of various extraction technologies such as solid-phase extraction (SPE), dispersive SPE and magnetic SPE. Aiming at high selectivity and high adsorption capacity, the MIPs should have ideal morphology, uniform size and excellent surface properties. Besides conventional preparative methods, it is required to introduce new imprinting technologies and strategies, mainly including the ingenious imprinting technologies of surface imprinting, nanoimprinting, controlled/living free radical polymerization (CLRP), click chemistry, hollow porous polymer synthesis technology and solid-phase synthesis, and the special imprinting strategies of multi-template/monomer imprinting, dummy/segment imprinting, magnetic material and boronate affinity imprinting. Surface imprinting and nanoimprinting technologies are usually adopted by coupling with the abovementioned imprinting technologies and strategies. Secondly, advanced imprinting technologies and strategies for the construction of MIPs-based sensors are summarized. For the sensors, the MIPs as recognition elements can specifically bind target analytes and as transduction elements can generate output signals for detection. Typically, the output detection signals can be classified into three types, electrochemical, optical and piezoelectric types according to the transduction mechanism; molecular imprinting based electrochemistry, fluorescence and surface enhanced Raman scattering sensors are the research hotspots. For sensing applications, it is necessary to consider the main parameters such as response time, linear dynamic range, sensitivity, selectivity and reproducibility. Therefore, the MIPs should have excellent interface properties by employing appropriate preparative technologies and strategies. Nanoimprinting, surface imprinting and composite material imprinting strategy have become the preferences. Herein, constructions of molecular imprinting fluorescence sensors are emphatically introduced, especially ratiometric fluorescence ones. Thirdly, the imprinting technologies and strategies orienting stimuli-responsive application are briefly introduced, for preparing stimuli-responsive MIPs (SR-MIPs) with specific recognition ability toward targeted molecules under stimuli-regulation and thereby achieving intelligent control. SR-MIPs are able to sensitively respond to specific external physicochemical/biological stimuli with a considerable and reversible change in their properties, such as molecular chain structure, solubility, swelling or dissociation behavior, resulting in regular changes of imprinting properties. The most reported magnetic, temperature, photonic and pH sensitive SR-MIPs and their dual or multi stimuli responsive SR-MIPs are reviewed. The rapid development of smart ecofriendly SR-MIPs and their stimuli-responsive application will accelerate the drug delivery application and assist the widely carried out sample pretreatment and sensors applications. Lastly, future perspectives of MIT and MIPs are proposed. In order to solve the core issues of selectivity, mass transfer rate and adsorption capacity of MIPs, it is imperative to rationally combine various imprinting technologies and strategies. The ingenious fusion of MIT and various advanced technologies should be continuously strengthened to promote the preparation of MIPs materials.

Preparation and Properties of Formaldehyde Molecularly Imprinted Polymer and Its Application in Detectiong Formaldehyde in Aquatic Product

Molecularly imprinted polymer( MIP) was prepared by optimized method using formaldehyde as template molecule,α-methacrylic acid as functional monomer,ethylene glycol dimethacrylate as crosslinking agent in chloroform. The imprinted polymer has the best selective adsorption capacity when the molar ratio of template molecular,functional monomer,crosslinking agent is 1∶ 2∶ 20,the prepolymerization time is 4 h,and the polymerization time is 8 h. When the concentration of formaldehyde solution is 2 mmol / L,the adsorption capacity of MIP reaches 12. 40 × 10-2mmol / g. The analysis of squid water sample indicated formaldehyde concentration was 5. 92 mg / Kg. At the same time,formaldehyde was not detected when the test sample was diluted 100 times, while after enriched by MIP solid-phase extraction( MIPSE) the concentration of formaldehyde was 5. 76 mg / Kg. Formaldehyde MIP has high-efficiency in enriching low concentration formaldehyde for sample preparation,and there is no significant difference in the testing results.

Development of a Styrene Based Molecularly Imprinted Polymer and Its Molecular Recognition Properties of Vanadyl Tetraphenylporphyrin in Organic Media

A highly selective molecularly imprinted polymer (MIP) was synthesized and employed as an adsorbent material for the removal of vanadyl tetraphenylporphyrin (VTPP) from organic media. The maximum adsorption capacity of MIP (0.600 mg/g) toward VTPP was higher than that of the nonimprinted polymer (NIP; 0.281 mg/g). The accuracy of the method was validated by analyzing the certified reference material (CRM) NIST SRM 1634c, Trace Metals in Residual Fuel Oil, and the concentration of VTPP in the CRM was found to be 28.49 mg/kg, which was significantly comparable with the certified value of 28.19 mg/kg.

Separation and enrichment of trace ractopamine in biological samples by uniformly-sized molecularly imprinted polymers

In order to prepare a high capacity packing material for solid-phase extraction with specific recognition ability of trace ractopamine in biological samples, uniformly-sized, molecularly imprinted polymers (MIPs) were prepared by a multi-step swelling and polymerization method using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, and toluene as a porogen respectively. Scanning electron microscope and specific surface area were employed to identify the characteristics of MIPs. Ultraviolet spectroscopy, Fourier transform infrared spectroscopy, Scatchard analysis and kinetic study were performed to interpret the specific recognition ability and the binding process of MIPs. The results showed that, compared with other reports, MIPs synthetized in this study showed high adsorption capacity besides specific recognition ability. The adsorption capacity of MIPs was 0.063mmol/g at 1mmol/L ractopamine concentration with the distribution coefficient 1.70. The resulting MIPs could be used as solid-phase extraction materials for separation and enrichment of trace ractopamine in biological samples.

Synthesis of molecularly imprinted polymers from AnAc for the separation of γ-oryzanol

The selectivity of gamma-oryzanol (γ-oryzanol) was recognized by molecularly imprinted polymer (MIP). Polymeric materials were successfully synthesized via thermal polymerization method using γ-oryzanol as template, anacardic acid (AnAc) as functional monomer, toluene as porogen, benzoyl peroxide (BPO) as initiator and divinylbenzene as crosslinker. Binding performance of MIPs was evaluated by MINITAP 14 for variance of analysis, linear regression analysis and adequating model through full factorial experimental technique in terms of adsorption capacity. Analysis of variance with 95% confidence level suggested significant interaction effect (amounts of template, porogen, crosslinker) on adsorption capacity of MIPs. The strongest interaction is between the amount of porogen and the amount of crosslinker. It was also found that a linear regression model for adsorption capacity represents the experimental data with the correlation coefficients (R2) greater than 0.9. The MIP synthesis with 0.8 mmol of template, 6 ml of porogen and 10 ml of crosslinker provided the highest adsorption capacity of MIP (1.14 mg/g-adsorbent). The proposed method is relatively rapid and easy to perform for the separation of γ-oryzanol in non-aqueous systems.

Selective removal of diclofenac from contaminated water using molecularly imprinted polymer microspheres

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template. Binding characteristics of the MIP were evaluated using equilibrium binding experiments. Compared to the non-imprinted polymer (NIP), the MIP showed an outstanding affinity towards DFC in an aqueous solution with a binding site capacity ( Q max) of 324.8 mg/g and a dissociation constant ( K d) of 3.99 mg/L. The feasibility of removing DFC from natural water by the MIP was demonstrated by using river water spiked with DFC. Effects of pH and humic acid on the selectivity and adsorption capacity of MIP were evaluated in detail. MIP had better selectivity and higher adsorption efficiency for DFC as compared to that of powdered activated carbon (PAC). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance, which is a definite advantage over single-use activated carbon.