Hypercrosslinked strong anion-exchange resin for extraction of acidic pharmaceuticals from environmental water.

Two novel high-specific surface area polymeric sorbents (HXLPP-SAXa and HXLPP-SAXb) were synthesised and evaluated as solid-phase extraction sorbents. The novel sorbents under study are based on hypercrosslinked polymer microspheres and designed specifically to offer ion-exchange properties; the specific polymers of interest in the current work have been chemically modified in such a way as to impart a tuneable level of strong anion-exchange character onto the sorbents. The novel sorbents were applied as strong anion-exchange sorbents in solid-phase extraction studies, with the goal being to selectively extract a group of acidic compounds from complex environmental samples in an efficient manner. Out of two HXLPP-SAX resins evaluated in this study, it was found that the sorbent with the lower ion-exchange capacity (HXLPP-SAXa) gave rise to the best overall performance characteristics and, indeed, was found to compare favourably to the solid-phase extraction performance of commercial strong anion-exchange sorbents. When the HXLPP-SAXa sorbent was applied to the solid-phase extraction of environmental water samples, the result showed quantitative and selective extraction of low levels of acidic pharmaceuticals from 500 mL of river water and 100 mL of effluent wastewater.

Affinity chromatography in dynamic combinatorial libraries: one-pot amplification and isolation of a strongly binding receptor.

We report the one-pot amplification and isolation of a nanomolar receptor in a multibuilding block aqueous dynamic combinatorial library using a polymer-bound template. By appropriate choice of a poly(N,N-dimethylacrylamide)-based support, nonselective ion-exchange type behaviour between the oppositely charged cationic guest and polyanionic hosts was overcome, such that the selective molecular recognition arising in aqueous solution reactions is manifest also in the analogous templated solid phase DCL syntheses. The ability of a polymer bound template to identify and isolate a synthetic receptor via dynamic combinatorial chemistry was not compromised by the large size of the library, consisting of well over 140 theoretical members, demonstrating the practical advantages of a polymer-supported DCL methodology.

Modification of chiral dimethyl tartrate through transesterification: immobilization on POSS and enantioselectivity reversal in sharpless asymmetric epoxidation.

Modification of dimethyl tartrate has been investigated through transesterification with aminoalcohols to provide reactive functionalities for the covalent bonding of chiral tartrate to polyhedral oligomeric silsesquioxanes. The transesterification of dimethyl tartrate has been widely studied using different catalytic systems and reaction conditions. Through the proper selection of both the catalytic system and the reaction conditions, it is possible to achieve monosubstituted or bis-substituted tartrate derivatives as sole products. All the intermediate chiral tartrate-derived ligands were successfully used in the homogeneous enantioselective epoxidation of allylic alcohols providing moderate enantiomeric excess over the products. Attached amine groups have been used to support the modified tartrate ligands on to a haloaryl-functionalized silsesquioxane moiety. This final chiral tartrate ligand displays reverse enantioselectivity in the asymmetric epoxidation of allylic alcohols with regard to the starting dimethyl tartrate ligand, both molecules having the same chiral sign. However, the POSS-containing ligand can be easily recovered in almost quantitative yield and reused in asymmetric epoxidation reactions. In addition, recovered silsesquioxane-pendant ligand, though displaying decreasing catalytic activity in recycling epoxidation tests, showed very stable enantioselective behavior.

Dynamic combinatorial discovery of a [2]-catenane and its guest-induced conversion into a molecular square host.

A simple water-soluble naphthalenedithiol building block is converted quantitatively into a series of octameric [2]-catenanes, composed of two interlocked molecular squares. When this mixture is re-equilibrated in the presence of an adamantyl ammonium guest, the catenanes disassemble into their macrocyclic components that bind the guest with nanomolar affinity in water.

Polymer-supported cationic templates for molecular recognition of anionic hosts in water.

Translocating solution-phase molecular recognition of oppositely charged hosts and guests to the solid phase represents a major challenge; we report a successful immobilisation strategy which allows selective host-guest interactions in water unencumbered by unwanted ion exchange-type interactions.

Hypercrosslinked polymer microspheres with weak anion-exchange character. Preparation of the microspheres and their applications in pH-tuneable, selective extractions of analytes from complex environmental samples.

In the present study, we describe the preparation of two high-specific-surface area hypercrosslinked polymer resins (HXLPPs) in the form of monodisperse microspheres with average diameters around 6 microm, modified subsequently with two amine moieties: 1,2-ethylenediamine (EDA) and piperazine. The two resins were evaluated subsequently as weak anion-exchange (WAX) sorbents in solid-phase extraction (SPE), with the aim being to extract a group of acidic compounds from complex environmental samples and thereby free them from basic compounds, including interferences. The new hypercrosslinked sorbents with WAX capacity (HXLPP-WAX) were benchmarked against commercial, macroporous sorbents, namely Oasis-WAX and Strata-X-AW, and to the corresponding neutral sorbents, namely the HXLPP precursor, Oasis-HLB and Strata-X, with promising results. The off-line SPE method developed using the WAX sorbents was applied to Ebre river water samples and led to high recoveries of all the analytes when 500 ml of sample was applied to the cartridges, whereas lower recoveries were obtained with the neutral sorbents. The HXLPP-WAX resin modified with the EDA moiety displayed the most attractive overall performance characteristics; it was tested further with 1,000 ml of Ebre river water samples, spiked at lower levels of the analyte mixture, and with effluent waste water from a treatment plant. In both cases, the resin provided good recoveries and net chromatogram, due to the ion-exchange moieties which enable the selective extraction of target compounds.

Monodisperse, hypercrosslinked polymer microspheres as tailor-made sorbents for highly efficient solid-phase extractions of polar pollutants from water samples.

In this detailed analytical study, we have evaluated in-house synthesised polymeric solid-phase extraction (SPE) sorbents in the form of monodisperse, hypercrosslinked polymer microspheres with diameters in the low micrometre range (approximately 4 microm). More specifically, their performance in the on-line SPE of a group of polar pollutants has been investigated thoroughly. The novel hypercrosslinked materials were compared with satisfactory results to commercial SPE sorbents with similar chemical and morphological properties, albeit that the commercial materials had higher particle sizes and broader particle size distributions. The on-line SPE method developed using these novel particles as packing material was applied successfully to ultrapure, mineral, tap and Ebre river water samples, with near total recoveries of all the analytes studied when 500 ml samples were percolated through the sorbents. Method validation with river water samples demonstrated good linearity, low detection limits as well as satisfactory precision in terms of repeatability and reproducibility, with values of relative standard deviation (%RSD) lower than 6.7 and 8.7%, respectively.

Selective solid-phase extraction of amoxicillin and cephalexin from urine samples using a molecularly imprinted polymer.

In this paper we describe, for the first time, a molecularly imprinted polymer (MIP) for the antibiotic amoxicillin (AMX), synthesised by a noncovalent molecular imprinting approach and used to extract AMX selectively from urine samples. The MIP was applied as a molecularly selective sorbent in molecularly imprinted SPE (MISPE) in an off-line mode, where it showed useful cross-selectivity for a structurally related antibiotic, cephalexin (CPX). By using a MISPE protocol, the MIP was able to selectively extract both AMX and CFX from 5 mL of water spiked with 10 mg/L with recoveries of 75 and 78% for AMX and CFX, respectively. When applied to real samples (urine) at clinically relevant concentrations, recoveries from 2 mL of human urine spiked with 20 mg/L decreased slightly to 65 and 63% for AMX and CFX, respectively. To demonstrate further the selectivity of the MIP obtained, a comparison with commercially available SPE cartridges was performed. Improvements in the retention of both AMX and CFX on the MIP were obtained relative to the commercially available cartridges, and the MISPE extracts were considerably cleaner, due to molecularly selective analyte binding by the MIP.

Chromatographic comparison of bupivacaine imprinted polymers prepared in crushed monolith, microsphere, silica-based composite and capillary monolith formats.

A comprehensive comparison of five chromatographic stationary phases based on molecularly imprinted polymers is presented. Efficiency, imprinting factors, water compatibility and batch-to-batch reproducibility are discussed for crushed monolith, microspheres, two silica-based composites and capillary monoliths, all imprinted with the local anaesthetic bupivacaine. Synthesis protocol and chromatographic test conditions have been kept fixed within certain limits, in order to provide further insight into the strengths and weaknesses of the different formats. Excluding microparticles, all formats give satisfactory performance, especially in aqueous mobile phases. An assessment of batch-to-batch reproducibility in different mobile phases adds further value to this comparison study.

Evaluation of a new hypercrosslinked polymer as a sorbent for solid-phase extraction of polar compounds.

A new hypercrosslinked polymer (HXLGp) with hydrophilic character due to the presence of hydroxyl moieties has been tested as a sorbent for the solid-phase extraction (SPE) of several polar compounds from water samples. This new sorbent enables the on-line extraction of 300 ml of sample with recoveries higher than 80% for polar compounds such as oxamyl, methomyl or desisopropylatrazine (DIA). The HXLGp has also been compared to other commercially available sorbents such as Oasis HLB (hydrophilic macroporous), to hydrophobic hypercrosslinked resins and to a previously synthesized sorbent based on N-vinylimidazole-divinylbenzene. The results are consistently better with the new synthesized sorbent. The method was successfully applied to the on-line SPE-HPLC of tap and river water samples. The validation with river water samples provided good linearity range and detection limits between 0.03 for methomyl and 4-nitrophenol (4NP) to 0.2 microg l(-1) for phenol (Ph).

Synthesis of branched poly(methyl methacrylate)s via controlled/living polymerisations exploiting ethylene glycol dimethacrylate as branching agent.

With appropriate choice of reaction composition and conditions, copolymerisation of methyl methacrylate and ethylene glycol dimethacrylate using Cu-based ATRP or GTP methodologies yields soluble branched polymers in facile one-pot reactions.

On-line solid-phase extraction with molecularly imprinted polymers to selectively extract substituted 4-chlorophenols and 4-nitrophenol from water.

Three polymers have been synthesised using 4-chlorophenol (4-CP) as the template, following different protocols (non-covalent and semi-covalent) and using different functional co-monomers, 4-vinylpyridine (4-VP) and methacrylic acid (MAA). The polymers were evaluated to check their selectivity as molecularly imprinted polymers (MIPs) in solid-phase extraction (SPE) coupled on-line to liquid chromatography. The solid-phase extraction procedure using MIPs (MISPE), including the clean-up step to remove any interferences, was optimised. The 4-VP non-covalent polymer was the only one which showed a clear imprint effect. This MIP also showed cross-reactivity for the 4-chloro-substituted phenols and for 4-nitrophenol (4-NP) from a mixture containing the 11 priority EPA (Environmental Protection Agency) phenolic compounds and 4-chlorophenol. The MIP was applied to selectively extract the 4-chloro-substituted compounds and 4-NP from river water samples.

Molecularly imprinted solid-phase extraction of naphthalene sulfonates from water.

A new polymeric sorbent synthesised by exploiting molecular imprinting technology has been used to selectively extract naphthalene sulfonates (NSs) directly from aqueous samples. In the non-covalent molecular imprinting approach used to prepare this polymer, 1-naphthalene sulfonic acid (1-NS) and 4-vinylpyridine (4-VP) were used as a template molecule and functional monomer, respectively, and both dissolved in a mixture of methanol/water (4:1) as porogen together with the cross-linker ethylene glycol dimethacrylate. The new non-covalent molecularly imprinted polymer (MIP) prepared in aqueous environment was used as a sorbent in solid-phase extraction (SPE) to selectively extract a group of naphthalene mono- and disulfonates. When one litre of a standard aqueous solution, which contained a mixture of eight NSs, was percolated through the SPE cartridge, all the NSs were retained on the MIP because of the cross-reactivity of the polymer. Recoveries were higher than 80% for all the compounds even after a clean-up step with methanol (MeOH). The MIP was also used to analyse water from the Ebro river.

Non-covalent and semi-covalent molecularly imprinted polymers for selective on-line solid-phase extraction of 4-nitrophenol from water samples.

Two molecularly imprinted polymers (MIPs) have been synthesised for the selective extraction of 4-nitrophenol (4-NP) from water samples. One polymer was synthesised via a non-covalent approach and the other via a semi-covalent approach. The selectivity of the polymers for 4-NP was evaluated when these polymers were applied in on-line solid-phase extraction (MISPE) coupled to reversed-phase HPLC. The MISPE conditions for both MIPs were optimised and a clean-up step was included to eliminate non-specific interactions. Differences between the two MIPs were observed with the non-covalent MIP being the more selective of the two, whereas the recoveries were slightly higher for the semi-covalent MIP. The performance of the imprinted polymers in the MISPE of real water samples was also evaluated.

A new molecularly imprinted polymer for the selective extraction of naproxen from urine samples by solid-phase extraction.

A non-covalent molecularly imprinted polymer (MIP) was synthesised using naproxen (a non-steroidal, anti-inflammatory drug (NSAID)) as a template molecule. The MIP was chromatographically evaluated to confirm the imprinting effect, and was then applied as a selective sorbent in solid-phase extraction (SPE) to selectively extract naproxen. After this study, the MIP was used to extract naproxen from urine samples; it was demonstrated that by applying a selective washing step with acetonitrile (ACN) the compounds in the sample that were structurally related to naproxen could be eliminated.

Weak anion-exchange hypercrosslinked sorbent in on-line solid-phase extraction-liquid chromatography coupling to achieve automated determination with an effective clean-up.

A mixed-mode polymeric sorbent was on-line coupled to liquid chromatography (LC) for the first time and applied to the selective solid-phase extract a group of pharmaceuticals in complex environmental water samples. The mixed-mode polymeric sorbent is a high-specific surface area hypercrosslinked polymer resin (HXLPP) in the form of monodisperse microspheres further modified with 1,2-ethylenediamine (EDA) moieties. These properties allow its application as a weak anion-exchange (WAX) sorbent in the on-line solid-phase extraction (SPE) coupling. The on-line SPE-LC method developed using the HXLPP-WAX sorbent was successfully applied to percolate a large volume of ultrapure (500 ml), river (250 ml) and effluent sewage (100 ml) water samples. In all the cases, the HXLPP-WAX resin provided near total recoveries of the most acidic compounds studied and clean chromatograms. This is because the ion-exchange interactions enable a washing step to be added to the SPE protocol that removes the compounds with weak acidic, neutral and basic properties from the sample matrix.