Synthetic approaches to parabens molecularly imprinted polymers and their applications to the solid-phase extraction of river water samples

Molecularly imprinted polymers for environmental adsorption applications

Molecular imprinting polymers (MIPs) are synthetic materials with pores or cavities to specifically retain a molecule of interest or analyte. Their synthesis consists of the generation of three-dimensional polymers with specific shapes, arrangements, orientations, and bonds to selectively retain a particular molecule called target. After target removal from the binding sites, it leaves empty cavities to be re-occupied by the analyte or a highly related compound. MIPs have been used in areas that require high selectivity (e.g., chromatographic methods, sensors, and contaminant removal). However, the most widely used application is their use as a highly selective extraction material because of its low cost, easy preparation, reversible adsorption and desorption, and thermal, mechanical, and chemical stability. Emerging pollutants are traces of substances recently found in wastewater, river waters, and drinking water samples that represent a special concern for human and ecological health. The low concentration in which these pollutants is found in the environment, and the complexity of their chemical structures makes the current wastewater treatment not efficient for complete degradation. Moreover, these substances are not yet regulated or controlled for their discharge into the environment. According to the literature, MIPs, as a highly selective adsorbent material, are a promising approach for the quantification and monitoring of emerging pollutants in complex matrices. Therefore, the main objective of this work was to give an overview of the actual state-of-art of applications of MIPs in the recovery and concentration of emerging pollutants.

Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters

The increase of the global population and shortage of renewable water resources urges the development of possible remedies to improve the quality and reusability of waste and contaminated water supplies. Different water pollutants, such as heavy metals, dyes, pesticides, endocrine disrupting compounds (EDCs), and pharmaceuticals, are produced through continuous technical and industrial developments that are emerging with the increasing population. Molecularly imprinted polymers (MIPs) represent a class of synthetic receptors that can be produced from different types of polymerization reactions between a target template and functional monomer(s), having functional groups specifically interacting with the template; such interactions can be tailored according to the purpose of designing the polymer and based on the nature of the target compounds. The removal of the template using suitable knocking out agents renders a recognition cavity that can specifically rebind to the target template which is the main mechanism of the applicability of MIPs in electrochemical sensors and as solid phase extraction sorbents. MIPs have unique properties in terms of stability, selectivity, and resistance to acids and bases besides being of low cost and simple to prepare; thus, they are excellent materials to be used for water analysis. The current review represents the different applications of MIPs in the past five years for the detection of different classes of water and wastewater contaminants and possible approaches for future applications.

Synthesis of monodisperse magnetic restricted microspheres for recognition of thiamphenicol in milk

Taking thiamphenicol as the research object, a new type of magnetic restricted access molecularly imprinted polymer (RAM-MMIP) with specific recognition was prepared by a one-step swelling method.

Synthesis of Magnetic Molecularly Imprinted Polymer Sorbents for Isolation of Parabens from Breast Milk

Magnetic molecularly imprinted polymers (MMIPs) are an invaluable asset in the development of many methods in analytical chemistry, particularly sample preparation. Novel adsorbents based on MMIPs are characterized by high selectivity towards a specific analyte due to the presence of a specific cavity on their polymer surface, enabling the lock-key model interactions to occur. In addition, the magnetic core provides superparamagnetic properties that allow rapid separation of the sorbent from the sample solution. Such a combination of imprinted polymers with a magnetic core has an innovative influence on the development of separation techniques. Hence, the present study describes the synthesis of MMIPs with 17β-estradiol used as a template molecule in the production of imprinted polymers. The as-prepared sorbent was used for a sorption/desorption study of five parabens from breast milk samples. The obtained results were characterized by sorption efficiency exceeding 92%, which shows the high affinity of the analytes to the functional groups on the sorbent. The final determination of the selected analytes was done with high-performance liquid chromatography using a fluorometric detector. The determined linearity ranges for selected parabens were characterized by high determination coefficients (r² from 0.9992 to 0.9999), and the calculated limit of detection (LOD) and limit of quantification (LOQ) for the identified compounds were low (LOD from 1.1-2.7 ng mL^-1; LOQ from 3.6-8.1 ng mL^-1), which makes their quantitative analysis in real samples feasible.

Occurrence and Fate of Heavy Metals in Municipal Wastewater in Heilongjiang Province, China: A Monthly Reconnaissance from 2015 to 2017

As one of the major sources of pollutions in the environments, effluents from municipal wastewater recently became a hot topic. This study quantified monthly county-level releases of five heavy metals, i.e., lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg), from municipal wastewater into the environment in the Heilongjiang Province of China, based on sampling, measurement, and modeling tools. Wastewater samples were collected from 27 municipal wastewater treatment plants (MWTPs) in 15 county-level cities of Heilongjiang every month from 2015 to 2017. The concentrations of five heavy metals were analyzed in both influents (Pb: 160 ± 100 μg/L; Cd: 15 ± 9.0 μg/L; Cr: 170 ± 64 μg/L; Hg: 0.67 ± 1.5 μg/L; As: 6.2 ± 4.8 μg/L) and effluents (Pb: 45 ± 15 μg/L; Cd: 5.2 ± 5.1 μg/L; Cr: 57 ± 13 μg/L; Hg: 0.28 ± 0.12 μg/L; As: 2.6 ± 1.4 μg/L). The removal ratios of the five heavy metals ranged from 50% to 67%. Inflow fluxes of Pb, Cr, and Cd displayed increasing trends first then decreased after reaching a maximum value, whereas those of Hg and Pb remained stable. Material flow analysis reveals that constructions of MWTPs are conducive to significantly reduce the releases of heavy metals from urban areas into the aquatic environment in the study area. Additionally, municipal wastewater sludge (used as fertilizer or spread on the land) could be a significant source of heavy metals in the land.

Molecularly imprinted solid phase extraction coupled with gas chromatography-mass spectrometry for determination of N-Nitrosodiphenylamine in water samples

In this study, the molecularly imprinted polymers (MIPs) with high specific surface area and extraction efficiency of N-Nitrosodiphenylamine (NDPhA) were successfully prepared and a highly sensitive and selective method was developed for determination of NDPhA in water samples using MIPs solid-phase extraction (SPE) coupled with gas chromatography mass spectrometry (GC-MS) detection. The MIPs were successfully prepared using the method of precipitation polymerization and using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, and N, N-Diphenylformamide as the template molecule. The newly synthesized MIPs were characterized and used as SPE sorbents. Under the optimized conditions, the average recoveries of NDPhA spiked in ultrapure water were higher than 94% ± 2.9% at three different concentrations and the limit of detection and limit of quantitation were 0.8 ng L^-1 and 2.4 ng L^-1, respectively. Moreover, the high selectivity of MIPs was attained and the satisfactory recoveries of NDPhA which were spiked in to real samples were achieved in the range of 92-107% with relative standard deviations (RSDs) within 0.3-7.9%. The low levels of NDPhA were detected in the two of twelve wastewater samples with concentrations of 5.6 ng L^-1 and 3.6 ng L^-1 with RSDs of 5.6% and 2.8%, respectively. The developed MIP-SPE method was proved to be practically feasible for selective extraction and enrichment of NDPhA in real water samples.

An ionic liquid loaded magnetically confined polymeric mesoporous adsorbent for extraction of parabens from environmental and cosmetic samples

Schematic illustration of MSPE procedure for paraben analysis using a new ionic liquid loaded magnetically confined polymeric mesoporous material.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Precipitation polymerization: a versatile tool for preparing molecularly imprinted polymer beads for chromatography applications

Minireview on recent advances of application of MIPs prepared by precipitation polymerization for recognition of target analytes in complex matrices.

Applications of molecularly imprinted polymers to the analysis and removal of personal care products: A review

Personal-care products (PCPs) involve a variety of chemicals whose persistency along with their constant release into the environment raised concern to their potential impact on wildlife and humans health. Regarded as emergent contaminants, PCPs demonstrated estrogenic activity leading to the need of new methodologies to detect and remove those compounds from the environment. Molecular imprinting starts with a complex between a template molecule and a functional monomer, which is then polymerized in the presence of a cross-linker. After template removal, the polymer will contain specific cavities. Based on a good selectivity towards the template, molecularly imprinted polymers (MIPs) have been investigated as efficient materials for the analysis and extraction of the so called emergent pollutants contaminants. Rather than lowering the limit of detections, the key theoretical advantage of MIP over existing methodologies is the potential to target specific chemicals. This unique feature, sometime named specificity (as synonym to very high selectivity) allows to use cheap, simple and/or rapid quantitative techniques such as fast separation with ultra-violet (UV) detection, sensors or even spectrometric techniques. When a high degree of selectivity is achieved, samples extracted with MIPs can be directly analyzed without the need of a separation step. However, while some papers clearly demonstrated the specificity of their MIP toward the targeted PCP, such prove is often lacking, especially with real matrices, making it difficult to assess the success of the different approaches. This review paper focusses on the latest development of MIPs for the analysis of personal care products in the environment, with particular emphasis on design, preparation and practical applications of MIPs.

Novel olefinic-centered macroacyclic compounds involving tetrasubstituted 4-hydroxybenzoic acid fragments: synthesis, structural characterization and comparison of experimental and computational results

Dialkyl 4,4'-(2-(1,3-bis(4-(alkoxycarbonyl)phenoxy)propan-2-ylidene)propane-1,3-diyl)bis (oxy)dibenzoate 6a,b were synthesized through the reaction of ethene-1,1,2,2,-tetra-yl-tetra methylene tetra bromide 1 with methyl 4-hydroxy benzoate or ethyl 4-hydroxy benzoate 2a,b. In addition, compounds 6a,b were obtained by using the esterification reaction from the reaction compound 5 with methyl and ethyl alcohol in high yields. Compound 4 was synthesized from the reaction of ethene-1,1,2,2,-tetra-yl-tetra methylene tetra bromide 1 with 4-hydroxy benzonitrile 3. The structures of the novel synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR, COSY, elemental analysis, and mass spectral data. Compound 6b, C42H44O12, was also characterized with additional analysis such as UV-vis, and X-ray spectral techniques. The electronic structure of compound 6b was studied by DFT level 6-31G∗(d,p) using X-ray crystallographic data. The results obtained from this study are consistent with the X-ray data. In order to understand the electronic transitions of the compound 6b, time dependent density functional theory (TD-DFT) calculations were carried out. TD-DFT studies showed that the low-energy excitations are consistent with the experimental results.

Exploiting β-cyclodextrin in molecular imprinting for achieving recognition of benzylparaben in aqueous media

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Current analytical strategies for C-reactive protein quantification in blood

The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a marker of inflammation associated with cardiovascular diseases. CRP belongs to the pentraxin family of proteins and the routine clinical analysis of CRP in blood samples is used as an important factor in primary prevention programmes together with causative and predisposing factors. This review focuses on the most representative methodologies and strategies for CRP detection and quantification that have been recently proposed, as well as reviewing those that are currently being developed for the specific, sensitive, inexpensive and high-throughput blood analysis of this protein.

Preparation and selective recognition of a novel solid-phase microextraction fiber combined with molecularly imprinted polymers for the extraction of parabens in soy sample

A prepared molecularly imprinted polymer with ethyl p-hydroxybenzoate as template molecule was applied for the first time to a homemade solid-phase microextraction fiber. The molecularly imprinted polymer-coated solid-phase microextraction fiber was characterized by scanning electron microscopy and thermogravimetric analysis. Various parameters were investigated, including extraction temperature, extraction time, and desorption time. Under the optimum extraction conditions, the molecularly imprinted polymer-coated solid-phase microextraction fiber exhibited higher selectivity with greater extraction capacity toward parabens compared with the nonimprinted polymer-coated solid-phase microextraction fiber and commercial fibers. The molecularly imprinted polymer-coated solid-phase microextraction fiber was tested using gas chromatography to determine parabens, including methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, and propyl p-hydroxybenzoate. The linear ranges were 0.01-10 μg/mL with a correlation coefficient above 0.9943. The detection limits (under signal-to-noise ratio of 3) were below 0.30 μg/L. The fiber was successfully applied to the simultaneous analysis of three parabens in spiked soy samples with satisfactory recoveries of 95.48, 97.86, and 92.17%, respectively. The relative standard deviations (n=6) were within 2.83-3.91%. The proposed molecularly imprinted polymer-coated solid-phase microextraction method is suitable for selective extraction and determination of trace parabens in food samples.

Preparation and evaluation of molecularly imprinted microspheres for solid-phase extraction of 1,4-hydroxybenzoic acid esters in soy

Molecularly imprinted microspheres (MIMs) were prepared by precipitation polymerization for the binding and recognition of 1,4-hydroxybenzoic acid esters. Ethyl p-hydroxybenzoate (EtPHB) was used as the template molecule, methacrylic acid as the functional monomer, ethylene dimethacrylate as the linking agent. It was evaluated by solid-phase extraction column packed with MIMs combined with liquid chromatography to determine trace preservatives including benzoic acid, methyl p-hydroxybenzoate, EtPHB, propyl p-hydroxybenzoate in food products. A solid-phase extraction based on MIM procedure was used to isolate four additives from the food matrix before quantitative analysis. The Scatchard plot suggested that the template-polymer system had two-site binding behavior with the dissociation constants of 0.3577 and 3.952 mg/g, respectively. The rebinding test, based on the molecularly imprinted solid-phase extraction column technique, showed the recoveries of soy samples spiked with four additives within 88.4-110.6%, with the relative standard deviations of 1.97-3.82%. Finally, the method was successfully applied for the analysis of parabens in foodstuff without traditional pretreatment.

Current approaches to trace analysis of pharmaceuticals and personal care products in the environment

A large number of xenobiotics including pharmaceuticals and personal care products are continuously released into the environment. Effluents from sewage treatment plants are well known to be the major source for introduction of pharmaceuticals and personal care products into the aquatic system. In recent years, reliable methods have been established for residue analysis of these pollutants down to low ng/L levels. In this review, the different approaches to their trace determination are reviewed with special attention being paid to sample preparation procedures, state-of-the-art high-performance separation methods hyphenated with mass spectrometry, and immunochemical methods.