Search

Nowadays, molecularly imprinted polymers (MIPs) are well established and are considered excellent materials for performing selective extractions. However, with the progressive implementation of the principles of green chemistry, it is necessary to find greener alternatives for both the synthesis and further use of MIPs in sample preparation. Accordingly, in the present work, different deep eutectic solvents (DES, both hydrophilic and hydrophobic), as an alternative to conventional organic solvents (i.e., toluene), were evaluated as porogens for the synthesis of imprinted fibers (monoliths), using fused silica capillaries as molds, for solid-phase microextraction (SPME). From this study, the polymer prepared with propazine (dummy template), methacrylic acid (monomer), ethylene glycol dimethacrylate (cross-linker), and a formic acid:L-menthol (1:1) DES (porogen) showed the best performance for selective rebinding of triazines. After optimization of the different variables involved in SPME, the new imprinted fibers were successfully applied to the extraction of target analytes (desisopropylatrazine, desethylatrazine, simazine, and atrazine) from soil sample extracts, providing relative recoveries ranging from 75.7 to 120.1%, reaching limits of detection within the range of 6.2-15.7 ng g-1, depending upon the analyte.

Molecular imprinting technology is a well-established technique for the obtainment of tailor-made polymers, so-called molecularly imprinted polymers, with a predetermined selectivity towards a target analyte or structurally related compounds. Accordingly, molecularly imprinted polymers are considered excellent materials for sample preparation providing unprecedented selectivity to analytical methods. However, the use of molecularly imprinted polymers in sample preparation still presents some shortcomings derived from the synthesis procedure itself limiting its general applicability. In this regard, molecularly imprinted polymers use to display binding sites heterogeneity and slow diffusion mass transfer of analytes to the imprinted sites affecting their overall performance. Besides, the performance of molecularly imprinted polymers in organic solvents is excellent, but their selective binding ability in aqueous media is considerably reduced. Accordingly, the present review pretends to provide an updated overview of the recent advances and trends of molecularly imprinted polymers-based extraction, focusing on those strategies proposed for the improvement of mass transfer and selective recognition in aqueous media. Besides, with the progressive implementation of Green Chemistry principles, the different steps and strategies for the preparation of molecularly imprinted polymers are reviewed from a green perspective.

The use of molecularly imprinted polymers in sample preparation is nowadays well-established thanks to their ability to provide unprecedented selectivity during extraction and clean-up steps. However, both their synthesis and subsequent use are far from being considered green. Accordingly, in the present chapter, the greenness of the different steps and strategies for the preparation and use of molecularly imprinted polymers in sample preparation is critically reviewed, and recent alternatives to make the use of molecularly imprinted polymers more sustainable are provided.

In this work, the use of a hydrophobic natural deep eutectic solvent (NADES) as supported liquid membrane (SLM) for hollow fiber liquid-phase microextraction (HF-LPME) of triazines is proposed. The combination of formic acid:L-menthol (2:1) was selected as optimum. FT-IR spectra of selected NADES and its components associated to Fig. S1 of paper submitted to Microchemical Journal are provided as csv files as follow: FigS1 (menthol); FigS1 (formic acid); FigS1 /NADES).

In this work, the use of a hydrophobic natural deep eutectic solvent (NADES) as supported liquid membrane (SLM) for hollow fiber liquid-phase microextraction (HF-LPME) of triazines is proposed. The combination of formic acid:L-menthol (2:1) was selected as optimum. The optimized HF-LPME procedure was applied to the analysis of an artificial water containing humic acids, tap and river water, and urine samples by HPLC with UV detection at 268 nm. The chromatographic data associated to Fig.6 and 7 of paper submitted to Microchemical Journal are provided as csv files as follows: Fig6a: Milli-Q water; Fig6b; artificial water; Fig7a: Tap water; Fig7b: River water; Fig7c: Urine river. All the samples were spiked with selected sulfonamides at 5 µg/L concentration level.

This work proposes the use of a hydrophobic natural deep eutectic solvent (NADES) as a supported liquid membrane (SLM) for hollow fiber liquid phase microextraction (HF-LPME) of triazines. NADES were prepared using L-menthol as hydrogen bond acceptor combined with different hydrogen bond donors of natural origin: carboxlylic acids, alcohols and amines. Studies were carried out to determine whether the prepared NADES met the necessary requirements to be used as a SLM, such as stability in the HF and compatibility with HPLC. Then, the ability of each prepared NADES to extract 6 triazine herbicides by HF-LPME from aqueous samples was evaluated. Among them, the mixture L-menthol: formic acid (molar ratio 1:2) provided better extraction results and was selected as SLM. The influence the different parameters on extraction efficiency such as pH of both sample and acceptor solution, salting-out effect, extraction time and stirring rate on the extraction efficiency was carefully studied and optimized. The optimized HF-LPME procedure was applied to the analysis of aqueous samples such as artificial water containing humic acids, tap water, river water and urine, with excellent clean-up ability for all samples analyzed. Relative recoveries ranged from 68 to 128 %, and the LODs and LOQs obtained for the 6 triazines were 0.75–3.1 µg/L and 2.5–10.3 µg/L, respectively, depending on the analyte and the kind of sample. Additionally, according to the AGREEprep tool assessment, the proposed method appears as a greener approach compared to other microextraction methods reported in the literature for the analysis of triazines in water samples.

In the last three decades, the use of molecularly imprinted polymers (MIPs) in sample preparation has continuously increased due to the high selectivity that they provide to this critical step. Of particular interest is the combination of molecular imprinting polymers and solid-phase microextraction (SPME) that allows the development of rapid and environmental friendly analytical methods, with high sensitivity and selectivity. The protocol herein presented describes a very simple strategy for the direct preparation of monolithic MIPs using silica capillaries as molds by the copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of propazine as template. The main factors affecting the polymer synthesis (e.g., porogen, monomer, cross-linker, polymerization mixture proportions, polymerization time, and fiber thickness) are described in detail. The proposed strategy is easy to perform in any laboratory without special equipment and allows precise control of the fiber thickness, overcoming this very common drawback in MIP-based fiber preparation.

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

In the last decades analytical methods have focused on the determination of target analytes at very low concentration levels. This has been accomplished through the use of traditional analytical methods that usually require high reagent consumption, expensive equipment and long pretreatment steps. Thus, there is a demand for simple, rapid, highly selective and user-friendly detection procedures. Quantum dots (QDs) are semiconductor fluorescent nanomaterials with unique optoelectronic properties that have shown great potential for the development of fluorescence probes. Besides, the combination of QDs with molecularly imprinted polymer (MIPs), synthetic materials with selective recognition, have been proposed as useful materials in the development of optical sensors. The resulting MIP-QDs optical sensors integrate the advantages of both techniques: the high sensitivity of QDs-based fluorescence sensors and the high selectivity of MIPs. This review gives a brief overview of the strategies for the synthesis of MIPs-QDs based optical sensors, highlighting the modifications in the synthesis procedure that improve the sensor performance. Finally, a revision of recent applications in sensing and bioimaging is presented.

Magnetic nanoparticles have been surface modified by molecular imprinting and evaluated as selective sorbents for the extraction of triazines from environmental waters. The use of propazine as template allowed us to synthesize a selective material able to simultaneously recognize and selective extract not only the template but also several other herbicides of the same family. A magnetic molecularly imprinted-based dispersive solid-phase extraction procedure was developed and fully optimized. Magnetic molecularly imprinted polymer particles can be easily collected and separated from liquid solvents and samples with the help of an external magnetic field, avoiding in that way any centrifugation or filtration steps, which represents a remarkable advantage over traditional procedures. Under optimum conditions, selective extraction of several triazines (cyanazine, simazine, atrazine, propazine, and terbutylazine) from environmental water samples was performed prior to final determination by high-performance liquid chromatography with diode-array detection. Recoveries for the studied triazines were within the range of 75.2–94.1%, with relative standard deviations lower than 11.3% (n = 3). The limits of detection were within 0.16–0.51 µg/L, depending upon the triazine and the type of sample analyzed.

In this work, the use of a hydrophobic natural deep eutectic solvent (NADES) as supported liquid membrane (SLM) for hollow fiber liquid-phase microextraction (HF-LPME) of sulfonamides is proposed. The combination of formic acid:L-menthol (1:1) was selected as optimum. The optimized HF-LPME procedure was applied to the analysis of an artificial water containing humic acids, tap and river water samples by HPLC with UV detection at 268 nm. The chromatographic data associated to Fig.7 of paper published in Advances of Sample Preparation are provided as csv files as follows: Fig7Aa: Milli-Q water; Fig7Ab; artificial water; Fig7Ba: Tap water (a); Fig7Bb: Manzanares river; Fig7Bc: Jarama river. All the samples were spiked with selected sulfonamides at 10 µg/L concentration level.

In this work, a novel molecularly imprinted stir-bar was developed for the stir-bar sorptive extraction (SBSE) of thiabendazole (TBZ) and carbendazim (CBZ) from orange samples. Magnetic nanoparticles were surface modified with oleic acid and then encapsulated by a silica shell using a conventional sol-gel procedure. Subsequently, nanoparticles were functionalized with methacrylate functionalities by grafting onto the particles surface. Finally, the modified magnetic nanoparticles were entrapped in a polymer monolith synthetized by copolymerization with the imprinting polymerization mixture using a glass vial insert as a mold. Variables affecting the polymerization and rebinding conditions of target analytes were optimized. The uptake capacity for the template (TBZ) was evaluated as well as the cross-reactivity for the related compound CBZ by rebinding experiments. Finally, the proposed magnetic imprinted monolith was applied to the SBSE of TBZ and CBZ from orange sample extracts providing a remarkable clean-up ability. The calculated detection limit were 0.13 and 0.10 mg kg−1 for CBZ and TBZ respectively, low enough to satisfactory analysis of both compounds in orange samples according to current European Union regulations.

In the present work, molecularly imprinted polymer (MIP) microspheres were packed in polypropylenehollow fiber (HF) segments for the micro solid-phase extraction and clean-up of thiabendazole (TBZ) incitrus samples. Experimental parameters affecting TBZ extraction were carefully optimized. Hollow fibermembrane was able to protect MIP beads from solid matrix allowing the extraction and clean-up withoutthe inclusion of further filtration and/or centrifugation steps. Under optimum experimental conditions,recoveries for TBZ at 0.83 mg kg−1concentration level ranged from 5.1 to 6.1%, depending upon thesample analyzed (orange or lemon peel samples), with relative standard deviations (RSDs) lower than4%. The limits of detection were 0.004 mg kg−1in orange and 0.009 mg kg−1in lemon, low enough for thedetermination of TBZ according to European Union legislation.In the present work, molecularly imprinted polymer (MIP) microspheres were packed in polypropylenehollow fiber (HF) segments for the micro solid-phase extraction and clean-up of thiabendazole (TBZ) incitrus samples. Experimental parameters affecting TBZ extraction were carefully optimized. Hollow fibermembrane was able to protect MIP beads from solid matrix allowing the extraction and clean-up withoutthe inclusion of further filtration and/or centrifugation steps. Under optimum experimental conditions,recoveries for TBZ at 0.83 mg kg−1concentration level ranged from 5.1 to 6.1%, depending upon thesample analyzed (orange or lemon peel samples), with relative standard deviations (RSDs) lower than4%. The limits of detection were 0.004 mg kg−1in orange and 0.009 mg kg−1in lemon, low enough for thedetermination of TBZ according to European Union legislation.In the present work, molecularly imprinted polymer (MIP) microspheres were packed in polypropylenehollow fiber (HF) segments for the micro solid-phase extraction and clean-up of thiabendazole (TBZ) incitrus samples. Experimental parameters affecting TBZ extraction were

In this work, a propazine-imprinted polymer was synthesized on the surface of modified magnetic nanoparticles to be used in the solid-phase extraction of triazines in soil samples. The effect of different solvents on the selective extraction of target analytes was assessed to establish the optimum rebinding conditions. The obtained magnetic molecularly imprinted particles exhibited high selectivity for triazines and were easily collected and separated by an external magnetic field without additional centrifugation or filtration steps. Under optimum conditions, a magnetic molecularly imprinted solid-phase extraction method was developed allowing the extraction of several triazines (desisopropylatrazine, desethylatrazine, simazine, atrazine, and propazine) from soil samples and their subsequent final determination by high-performance liquid chromatography with diode-array detection. Recoveries for the triazines studied were within the range 5.4% to 40.6%, with relative standard deviations lower than 7.0% (n = 3). The detection limits were within 0.1 to 3 ng g−1, depending upon the triazine and the type of soil used. Copyright © 2016 John Wiley & Sons, Ltd.

The preparation of molecularly imprinted core–shell magnetic nanoparticles and their subsequent use in the solid-phase extraction of thiabendazole from citrus sample extracts is described. Molecularly imprinted core–shell magnetic nanoparticles were prepared by the precipitation copolymerization of the imprinting polymerization mix_x0002_ture on the surface of vinyl-modified silica magnetic nanoparticles and were charac_x0002_terized by Fourier transform infrared spectroscopy and scanning electron microscopy. The obtained molecularly imprinted core–shell magnetic nanoparticles exhibited a high selectivity for thiabendazole and were easily collected and separated by an exter_x0002_nal magnetic field without additional centrifugation or filtration steps. Under opti_x0002_mum conditions, a magnetic molecularly imprinted solid-phase extraction method was developed allowing the extraction of thiabendazole from citrus sample extracts and final determination by high-performance liquid chromatography with fluores_x0002_cence detection. The detection limit was 0.2 mg/kg, far lower than the maximum residue limit established within the European Union for thiabendazole in citrus samples.

In this work, novel molecularly imprinted stir-bars based upon the entrapment of modified magnetic nanoparticles within an imprinted polymer monolith is developed for stir-bar sorptive extraction (SBSE). Firstly, magnetic nanoparticles were surface modified with oleic acid followed by encapsulation inside a silica network. Then, vinyl-groups were grafted onto the particles surface for the subsequent copolymerization with the imprinting polymerization mixture using a glass vial insert as a mold. As a result, the obtained imprinted monolith presented magnetic properties allowing its use as magnetic stir-bar. Variables affecting both polymer morphology (i.e.;amount of magnetic nanoparticles, polymerization time) and binding-elution conditions of target analytes (i.e.;solvents, time) was carefully optimized. Optimum imprinted stir-bars were evaluated for the SBSE of triazines in soil sample extracts. Recoveries, at 16 ng g−1 concentration level, ranged from 2.4 to 8.7% with relative standard deviations lower than 15% (n = 3). Although low recoveries were obtained, the high selectivity provided by the new molecularly imprinted stir-bars allowed reaching detection limits below 7.5 ng g−1 by liquid chromatography coupled to UV detection. © 2016 Elsevier B.V.

In this study, molecularly imprinted polymer fibers for solid-phase microextraction have been prepared with a single bifunctional monomer, N,O-bismethacryloyl ethanolamine using the so-called "one monomer molecularly imprinted polymers" method, replacing the conventional combination of functional monomer and cross-linker to form high fidelity binding sites. For comparison, imprinted fibers were prepared following the conventional approach based on ethylene glycol dimethacrylate as cross-linker and methacrylic acid as monomer. The recognition performance of the new fibers was evaluated in the solid-phase microextraction of parabens, and from this study it was concluded that they provided superior performance over conventionally formulated fibers. Ultimately, real-world environmental testing on spiked solid samples was successful by the molecularly imprinted solid-phase microextraction of samples, and the relative recoveries obtained at enrichment levels of 10 ng/g of parabens were within 78-109% for soil and 83-109% for sediments with a relative standard deviation <15% (n = 3). © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Parabens (alkyl-p-hydroxybenzoates) are antimicrobial preservatives widely used in cosmetics, toiletries, pharmaceuticals, and food. Nowadays, they are considered emerging pollutants and their determination is becoming increasingly important since they are continuously released into the environment. In this work, a hollow fibre liquid-phase microextraction method has been developed for the extraction of parabens from environmental waters. The parameters affecting the extraction of parabens (organic solvent used as liquid membrane; pH of both sample and acceptor solution; salting-out effect; extraction time and stirring speed) were carefully optimized in order to reach high recoveries for all tested analytes. Under optimum conditions, parabens were extracted from river, reservoir and sea water samples with recoveries ranging from 16.7 to 68.6% depending upon the analyte and the sample analyzed, leading to detection limits lower than 0.2 ng mL-1 using a simple HPLC-UV instrument. © 2013 Copyright Taylor and Francis Group, LLC.

Solid-phase microextraction (SPME) is widely used in analytical laboratories for the analysis of organic compounds, thanks to its simplicity and versatility. In the present work, the synthesis and evaluation of imprinted films for SPME by electropolymerisation of pyrrole alone or in the presence of ethylene glycol dimethacrylate is proposed. Sulfadimethoxine (SDM), a sulfonamide antibiotic, was used as template molecule. Initially, a molecularly imprinted polymer film was prepared by electropolymerisation of pyrrole onto a platinum foil, using SDM as template. The SDM template was removed by overoxidation. The behaviour of SDM on imprinted and non-imprinted polymers was investigated by differential pulse voltammetry, and a clear imprinting effect was observed, which was confirmed by rebinding experiments using both conventional and electrochemically enhanced-SPME. However, in general, the extraction efficiency was rather low (<6%) and unspecific interactions are too high. Attempts to increase extraction efficiency were unsuccessful, but the incorporation of ethylene glycol dimethacrylate to the films reduced unspecific interactions to a certain extent. Copyright © 2014 John Wiley & Sons, Ltd.

The development of an electrosynthesized imprinted polypyrrole (PPY) film onto a platinum sheet as sorbent phase for a fluoroquinolone antibiotic (levofloxacin) is described. Experimental conditions for the electropolymerization of PPY in the presence of the template were optimized. The molecularly imprinted polymer (MIP) film was characterized by X-Ray Photoelectron Spectroscopy (XPS) to verify the template entrapment in the polymeric matrix. After being subject to washing procedures, MIP was analyzed by XPS and a very satisfactory template removal was estimated being equal to 83%. The effectiveness of washing protocol was assessed also by UV-vis and High Performance Liquid Chromatography (HPLC) analysis of corresponding washing solutions. Rebinding experiments were performed by exposing the imprinted PPY film to levofloxacin solutions, subsequently analyzed by HPLC. The effect of solvent and time of exposure was investigated. The imprinting effect was verified by comparing recognition abilities of both MIP and not imprinted polymer (a polymer prepared in the same conditions but in the absence of the template). © 2011 Elsevier B.V. All rights reserved.