Molecularly Imprinted Solid-phase Extraction Research Articles

Molecularly imprinted polymer as efficient sorbent of solid-phase extraction for determination of gonyautoxin 1,4 in seawater followed by high-performance liquid chromatography-fluorescence detection.

A kind of new molecularly imprinted polymer (MIP) was synthesized by bulk polymerization using guanosine as dummy template molecule, α-methacrylic acid as functional monomer and ethylene glycol dimethyl acrylic ester as crosslinker. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) showed that the MIP had homogenous and uniform-sized cavities. It was confirmed that the MIP had higher binding affinity and selectivity towards gonyautoxins 1,4 (GTX 1,4) than the non-imprinted polymer (NIP) according to the static equilibrium adsorption. An off-line molecularly imprinted solid-phase extraction (MISPE) method followed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD) was established for the analysis of GTX 1,4. 0.1mol/L acetic acid and 95:5 (v:v) methanol/water were optimized as the washing and elution solutions, respectively. The recoveries of spiked cultured seawater samples were satisfactory, as high as 88%. Using this method, the concentrations of GTX 1,4 from cultured seawater samples of Alexandrium minutum and Alexandrium tamarense were detected to be 1.10μg/L and 0.99μg/L, respectively. Graphical Abstract The synthesis of molecularly imprinted polymer and molecularly imprinted solid-phase extraction analysis for gonyautoxin 1,4.

Experimental and computational studies on molecularly imprinted solid-phase extraction for gonyautoxins 2,3 from dinoflagellate Alexandrium minutum.

An innovative and effective extraction procedure based on molecularly imprinted solid-phase extraction (MISPE) was developed for the isolation of gonyautoxins 2,3 (GTX2,3) from Alexandrium minutum sample. Molecularly imprinted polymer microspheres were prepared by suspension polymerizationand and were employed as sorbents for the solid-phase extraction of GTX2,3. An off-line MISPE protocol was optimized. Subsequently, the extract samples from A. minutum were analyzed. The results showed that the interference matrices in the extract were obviously cleaned up by MISPE procedures. This outcome enabled the direct extraction of GTX2,3 in A. minutum samples with extraction efficiency as high as 83%, rather significantly, without any need for a cleanup step prior to the extraction. Furthermore, computational approach also provided direct evidences of the high selective isolation of GTX2,3 from the microalgal extracts.

Molecularly imprinted polymers as the extracted sorbents of clenbuterol ahead of liquid chromatographic determination.

A pre-treatment methodology for clenbuterol hydrochloride (CLEN) isolation and enrichment in a complex matrix environment was developed through exploiting molecularly imprinted polymers (MIPs). CLEN-imprinted polymers were synthesized by the combined use of ally-β-cyclodextrin (ally-β-CD) and methacrylic acid (MAA), allyl-β-CD and acrylonitrile (AN), and allyl-β-CD and methyl methacrylate (MMA) as the binary functional monomers. MAA-linked allyl-β-CD MIPs (M-MAA) were characterized by Fourier transform-infrared (FT-IR) spectroscopy and a scanning electron microscope (SEM). Based upon the results, M-MAA polymers generally proved to be an excellent selective extraction compared to its references: AN-linked allyl-β-CD MIPs (M-AN) and MMA-linked allyl-β-CD MIPs (M-MMA). M-MAA polymers were eventually chosen to run through a molecularly imprinted solid-phase extraction (MISPE) micro-column to enrich CLEN residues spiked in pig livers. A high recovery was achieved, ranging from 91.03% to 96.76% with relative standard deviation (RSD) ≤4.45%.

Preparation of hydrophilic molecularly imprinted polymers via bulk polymerization combined with hydrolysis of ester groups for selective recognition of iridoid glycosides.

Hydrophilic molecularly imprinted polymers (H-MIP) with molecular recognition ability for iridoid glycosides (IGs) have been obtained via bulk polymerization combined with hydrolysis of ester groups. H-MIP were characterized by Fourier transform infrared spectroscopy (FT-IR). The hydrophilcity was measured by the contact angle measurement and the water dispersion stability. The obtained H-MIP demonstrated high selectivity and specific binding ability to five IGs in aqueous media. The group extraction efficiency of molecular imprinted solid-phase extraction (MISPE) for five IGs was investigated, including loading sample, breakthrough volume, washing solvent, and elution solvent. Compared with non-imprinted solid-phase extraction (NISPE), the higher average recovery (95.5%) of five IGs with lower relative standard deviations values (below 6.1%) using MISPE combined with high-performance liquid chromatography (HPLC) were achieved at three spiked levels in three blank samples. Under the optimum MISPE conditions, the wide linear range with the correlation coefficient of R (2) ≥ 0.9950 for five IGs with low limits of detection (LOD) and quantification (LOQ) (0.01-0.08 and 0.03-0.27μgmL(-1), respectively) were obtained. Chromatograms obtained using MISPE columns demonstrated that the matrix interference has been minimized and great interferences around IGs were also eliminated efficiently. These results indicated that the developed MISPE-HPLC method was selective, accurate, and applicable for the determination of IGs in water media. Graphical Abstract Preparation of hydrophilic molecularly imprinted polymers via bulk polymerization combined with hydrolysis of ester groups.

Preparation, characterization and usage of molecularly imprinted polymer for the isolation of quercetin from hydrolyzed nettle extract.

Quercetin (3,3',4',5,7-pentahydroxyflavone, QC) is a health-beneficial flavonoid, widely occurring in leaves, fruits, and flowers of various plants. In this work aiming isolation, purification and pre-concentration of QC, QC imprinted polymers (QC-MIPs) in different molar ratios {template:monomer:cross-linker (1:4:20, 1:5:30, 1:8:40, 1:10:50)} were prepared thermally through bulk polymerization by using QC as the template molecule, 4-vinylpyridine (4-VP), methacrylic acid (MAA), acrylamide (AA) as the functional monomers, ethylene glycol dimethacrylate (EDMA) as the cross-linker and 2,2'-azobisisobutyronitrile (AIBN) as initiator in the porogens of acetone and tetrahydrofuran. Their recognition and selectivity properties were investigated in solutions containing QC and other similar-structure phenolics by equilibrium binding experiments using different proportions of acetonitrile (ACN)-dimethylsulfoxide (DMSO) mixtures and methanol (MeOH) as solvents. The MIP with 1:4:20 molar ratio of QC:4-VP:EDMA was established as the most suitable for recognition of QC. Sorption parameters of the MIP and the NIP (non-imprinted polymer) were calculated by using Freundlich and Langmuir isotherms with QC solutions in ACN:DMSO (98:2, v/v). The mentioned MIP was found to be highly selective for quercetin over other phenolic compounds (rutin, catechin, etc.). Thus, molecularly imprinted solid-phase extraction (MISPE) procedures were applied for selective pre-concentration and purification of QC from synthetic mixtures of phenolic compounds and nettle extract, known as a source of official and folk medicine. The results demonstrated the possibility of direct extraction of certain pharmacophoric constituents such as QC and QC derivatives from nettle by MIP separation.

Matrix molecularly imprinted mesoporous sol–gel sorbent for efficient solid-phase extraction of chloramphenicol from milk

Highly selective and efficient chloramphenicol imprinted sol–gel silica based inorganic polymeric sorbent (sol–gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol–gel catalyst. Non-imprinted sol–gel polymer (sol–gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences.The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol.Competition and cross reactivity tests have proved that sol–gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol–gel MIP was 23 mg/g. The sol–gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work-flow. Intra and inter-assay RSD values were less than 13% and accuracy expressed as relative recovery ranged from 85 to 106%.

Preparation of Tetracycline Surface Molecularly Imprinted Material for the Selective Recognition of Tetracycline in Milk

Silica particles were modified with 3-methacryloxypropyl trimethoxysilane (MPS) as a carrier material. The tetracycline (TC) molecular imprinting polymer based on the surface of modified silica (MPS/SiO2) was prepared by adopting the novel surface molecular imprinting technique with tetracycline as template molecule and ethylene glycol diglycidyl ether (EGDE) as crosslinker. The rebinding capacity of molecularly imprinted polymer (MIP) was evaluated according to the adsorption kinetics and the adsorption isotherm. The two distinct linear portions in Scatchard analysis indicate that two classes of binding sites existed in the imprinted polymer. The MIP obtained was used as a selective sorbent for molecularly imprinted solid-phase extraction (MISPE) prior to HPLC analysis. The results showed that good linearity was observed in the range of 150∼950 μg/L for TC, with a correlation coefficient of 0.9972. Adding level of 300∼700 μg/L, the average of spiked recoveries of TC is about 81.1 %, with a relative standard deviation (RSD) range from 3.0 to 4.4 %, and the limit of detection (LOD) reached 25 μg/L. The proposed method is easy to operate, reliable, and applicable to analyze the TC residues in milk samples.

Development of Solid-Phase Extraction Using Molecularly Imprinted Polymer for the Analysis of Organophosphorus Pesticides-(Chlorpyrifos) in Aqueous Solution

A new and selective sorbent for molecularly imprinted solid-phase extraction (MISPE) was prepared to extract chlorpyrifos (CPF) residue from solutions. The extracted analyte was analyzed by high performance liquid chromotography (HPLC) coupled with photodiode array detection. To synthesize the molecularly imprinted polymers, four different pyrogens (acetonitrile, toluene, dichloromethane and chloroform) were initially studied. CPF was used as the template molecule, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinker. Thermo-polymerization method was used to produce bulk polymers. In order to determine the medium that enhances the best molecular recognition, the adsorption study of CPF to the MIPs was investigated. Both organic solvents and water were utilized as media. The acetonitrile solvent was finally selected as pyrogen for the synthesis of the polymers and water was chosen as the medium for loading the analytes into the polymers. The selectivity of the MISPE method for CPF and other pesticides in aqueous solution was also assessed.

Development of on-line molecularly imprinted solid phase extraction-liquid chromatography-mass spectrometry for triazine analysis in corn samples

A highly selective method for the analysis of triazine herbicides in corn samples based on molecularly imprinted solid phase extraction (MISPE) has been developed.

Selective solid-phase extraction using molecularly imprinted polymer as a sorbent for the analysis of fenarimol in food samples

In the present communication, a non-covalent fenarimol-imprinted polymer was synthesized by precipitation polymerization technique using methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator in different porogenic solvent. Binding study of molecularly imprinted and non-imprinted polymer (MIP and NIP) showed that MIP possesses a higher affinity towards this analyte compared to NIP. The binding affinity of MIP was calculated by static and kinetic adsorption study. Further, a MIP based cartridge was designed to use in extraction process, necessary for specific determination and quantification of the fungicide in food matrices. Under the optimum conditions, developed method was found to be linear (R2=0.9999–0.9994). Limit of detection (LOD) and limit of quantitation (LOQ) in samples were 0.03–0.06 and 0.12–0.21μgmL−1, respectively. The rate of recovery of fenarimol was 91.16–99.52% on MIPs. The validated method of molecularly imprinted solid-phase extraction (MISPE) cartridge was successfully applied to the food matrices and compared with commercial sorbent (RP18 and Oasis HLB). However we feel, this method has promising applications in the routine analysis of food samples in industry.

Water-compatible imprinted pills for sensitive determination of cannabinoids in urine and oral fluid

A novel molecularly imprinted solid phase extraction (MISPE) methodology followed by liquid chromatography tandem mass spectrometry (LC–MS/MS) has been developed using cylindrical shaped molecularly imprinted pills for detection of Δ9-tetrahydrocannabinol (THC), 11-nor-Δ9-tetrahydrocannabinol carboxylic acid (THC-COOH), cannabinol (CBN) and cannabidiol (CBD) in urine and oral fluid (OF). The composition of the molecular imprinted polymer (MIP) was optimized based on the screening results of a non-imprinted polymer library (NIP-library). Thus, acrylamide as functional monomer and ethylene glycol dimethacrylate as cross-linker were selected for the preparation of the MIP, using catechin as a mimic template. MISPE pills were incubated with 0.5mL urine or OF sample for adsorption of analytes. For desorption, the pills were transferred to a vial with 2mL of methanol:acetic acid (4:1) and sonicated for 15min. The elution solvent was evaporated and reconstituted in methanol:formic acid (0.1%) 50:50 to inject in LC–MS/MS. The developed method was linear over the range from 1 to 500ngmL−1 in urine and from 0.75 to 500ngmL−1 in OF for all four analytes. Intra- and inter-day imprecision were <15%. Extraction recovery was 50–111%, process efficiency 15.4–54.5% and matrix effect ranged from −78.0 to −6.1%. Finally, the optimized and validated method was applied to 4 urine and 5 OF specimens. This is the first method for the determination of THC, THC-COOH, CBN and CBD in urine and OF using MISPE technology.

Determination of Citrinin Using Molecularly Imprinted Solid Phase Extraction Purification, HPLC Separation, and Fluorescence Detection

A liquid chromatography based method to detect citrinin in corn was developed using molecularly imprinted solid phase extraction (MISPE) sample clean-up. Molecularly imprinted polymers were synthesized using 1,4-dihydroxy-2-naphthoic acid as the template and an amine functional monomer. Density functional calculations suggest the mimic template interacts with the functional monomer in a similar manner as citrinin. Freundlich isotherm analysis indicated the template provided a significant imprinting effect for citrinin binding. A high performance liquid chromatography with fluorescence detection (HPLC-FD) method to detect citrinin in maize was developed utilizing the imprinted polymers for sample clean-up (excitation at 330 nm; emission at 500 nm). Recoveries of citrinin in spiked corn samples (0.03–3 µg g−1) were between 82.3–91.5%. This study demonstrates that molecularly imprinted polymers are applicable in the solid phase extraction clean-up of corn samples for citrinin determination by HPLC-FD.

A (-)-norephedrine-based molecularly imprinted polymer for the solid-phase extraction of psychoactive phenylpropylamino alkaloids from Khat (Catha edulis Vahl. Endl.) chewing leaves.

A molecularly imprinted polymer (MIP) was prepared using (-)-norephedrine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and chloroform as the porogen. The MIP was used as a selective sorbent in the molecularly imprinted solid-phase extraction (MIP-SPE) of the psychoactive phenylpropylamino alkaloids, norephedrine and its analogs, cathinone and cathine, from Khat (Catha edulis Vahl. Endl.) leaf extracts prior to HPLC-DAD analysis. The MIP was able to selectively extract the alkaloids from the aqueous extracts of Khat. Loading, washing and elution of the alkaloids bound to the MIP were evaluated under different conditions. The clean baseline of the Khat extract obtained after MIP-SPE confirmed that a selective and efficient sample clean-up was achieved. Good recoveries (90.0-107%) and precision (RSDs 2.3-3.2%) were obtained in the validation of the MIP-SPE-HPLC procedure. The content of the three alkaloids in Khat samples determined after treatment with MIP-SPE and a commercial Isolute C18 (EC) SPE cartridge were in good agreement. These findings indicate that MIP-SPE is a reliable method that can be used for sample pre-treatment for the determination of Khat alkaloids in plant extracts or similar matrices and could be applicable in pharmaceutical, forensic and biomedical laboratories. Copyright © 2015 John Wiley & Sons, Ltd.

Determination of diethylstilbestrol in seawater by molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography

An effective and highly selective molecularly imprinted material was prepared by suspension polymerization for the isolation and pre-concentration of synthetic estrogen diethylstilbestrol (DES) in seawater. The obtained MIPMs were proved to have more uniform size and porous structure, with maximum adsorption capacity of 8.43mgg−1 almost two times more than NIPMs (4.43mgg−1). The MIPMs showed no significant deterioration of the adsorption capacity after five rounds of regeneration. An off-line molecularly imprinted solid phase extraction (MISPE) method followed by HPLC–DAD was proposed for the detection of DES in seawater, and recoveries were satisfactorily higher than 77%. Four seawater samples in aquaculture area were analyzed and 0.61ngmL−1 DES was detected in one sample. The result demonstrated that this method can be used for the rapid separation and clean up of trace residual of DES in seawater.

Tailoring molecularly imprinted polymer beads for alternariol recognition and analysis by a screening with mycotoxin surrogates

Molecularly imprinted porous polymer microspheres have been prepared for selective binding of alternariol (AOH), a phenolic mycotoxin produced by Alternaria fungi. In order to lead the synthesis of recognition materials, four original AOH surrogates have been designed, prepared and characterized. They bear different number of phenol groups in various positions and different degree of O-methylation on the dibenzo[b,d]pyran-6-one skeleton. A comprehensive library of mixtures of basic, acidic or neutral monomers, with divinylbenzene or ethyleneglycol dimethacrylate as cross-linkers, were polymerized at a small scale in the presence of the four molecular mimics of the toxin molecule. This polymer screening has allowed selection of the optimal composition of the microbeads (N-(2-aminoethyl)methacrylamide, EAMA, and ethylene glycol dimethacrylate). The latter are able to bind AOH in water–acetonitrile (80:20, v/v) with an affinity constant of 109±10mM−1 and a total number of binding sites of 35±2μmolg−1, being alternariol monomethylether the only competitor species. Moreover, 1H NMR titrations have unveiled a 1:2 surrogate-to-EAMA stoichiometry, the exact interaction sites and a binding constant of 1.5×104M−2. A molecularly imprinted solid phase extraction (MISPE) method has been optimized for selective isolation of the mycotoxin from aqueous samples upon a discriminating wash with 3mL of acetonitrile/water (20:80, v/v) followed by determination by HPLC with fluorescence detection. The method has been applied, in combination to ultrasound-assisted extraction, to the analysis of AOH in tomato samples fortified with the mycotoxin at five concentration levels (33–110μgkg−1), with recoveries in the range of 81–103% (RSD n=6). To the best of our knowledge, this is the first imprinted material capable of molecularly recognizing this widespread food contaminant.

Superhydrophilic molecularly imprinted polymers based on a water-soluble functional monomer for the recognition of gastrodin in water media

In this study, the first successfully developed superhydrophilic molecularly imprinted polymers (MIPs) for gastrodin recognition have been described. MIPs were prepared via the bulk polymerization process in an aqueous solution using alkenyl glycosides glucose (AGG) as the water-soluble functional monomer. The non-imprinted polymers (NIPs) were also synthesized using the same method without the use of the template. The dynamic water contact angles and photographs of the dispersion properties confirmed that the molecularly imprinted polymers displayed excellent superhydrophilicity. The results demonstrated that the MIPs exhibited high selectivity and an excellent imprinting effect. A molecularly imprinted solid phase extraction (MISPE) method was established. Optimization of various parameters affecting MISPE was investigated. Under the optimized conditions, a wide linear range (0.001–100.0μgmL−1) and low limits of detection (LOD) and quantification (LOQ) (0.03 and 0.09ngmL−1, respectively) were achieved. When compared with the NIPs, higher recoveries (90.5% to 97.6%) of gastrodin with lower relative standard deviations values (below 6.4%) using high performance liquid chromatography were obtained at three spiked levels in three blank samples. These results demonstrated one efficient, highly selective and environmentally-friendly MISPE technique with excellent reproducibility for the purification and pre-concentration of gastrodin from an aqueous extract of Gastrodia elata roots.

Review on Analysis Methodology of Phenoxy Acid Herbicide Residues

Phenoxy acid herbicides are a class of commercial herbicides widely used all over the world. Some of them will disrupt the endocrine of human beings and animals. As a result, European Union, USA, Japan, China, and other nations have defined the maximum residue limits for phenoxy acid herbicides. Obviously, sensitive and reliable detection methods are very necessary for monitoring these herbicide residues. In order to better understand the research progress in this aspect, this review summarizes the analysis methods of these herbicide residues in food and water from the year 1989 to 2014. On one hand, the separation analysis methods of multi-residues have been the mainstream of research, including gas chromatography, gas chromatography–mass spectrometry, high-performance liquid chromatography, liquid chromatography-mass spectrometry, and capillary electrophoresis. Single-residue detection mainly occurred in the early days, involving various types of immunoassay methods which account for 5.6 % literatures we can refer. On the other hand, sample pretreatment technique has always been an important part of the analysis methods for isolation and enrichment of analytes in multi-residue determination. These techniques include a variety of liquid-phase micro-extraction, solid-phase extraction methods, and the following developed solid-phase micro-extraction and molecular imprinted solid-phase extraction based on the above traditional methods. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, suitable for sample preparation of food and other complex matrices, is also reviewed. In general, multi-residue detection and environmentally friendly methods are the trends of development.

Molecularly imprinted polymer beads for clean-up and preconcentration of β-lactamase-resistant penicillins in milk.

This work describes the development and application of class-selective molecularly imprinted polymers (MIPs) for the analysis of beta-lactamase-resistant penicillins, namely cloxacillin (CLOXA), oxacillin (OXA), and dicloxacillin (DICLOXA), in milk samples. Our method is based on molecularly imprinted solid-phase extraction (MISPE) coupled to high-performance liquid chromatography (HPLC) with diode-array detection (DAD). 2-Biphenylylpenicillin (2BPEN), a surrogate with a close resemblance to beta-lactamase-resistant penicillins in terms of size, shape, hydrophobicity, and functionality, was synthesized and used as the template for the polymer synthesis. A MIP library was prepared and screened to select the optimum functional monomer, N-(2-aminoethyl)methacrylamide, and cross-linker, trimethylolpropane trimethacrylate, that provided the best recognition for the target antibiotics. For the MISPE application, the MIPs were prepared in the form of microspheres, using porous silica beads (40-75μm) as sacrificial scaffolds. The developed MISPE method enables efficient extraction from aqueous samples and analysis of the antimicrobials, when followed by a selective washing with 2mL acetonitrile-water (20:80 v/v) and elution with 1mL 0.05molL(-1) tetrabutylammonium in methanol. The analytical method was validated according to EU guideline 2002/657/EC. The limits of quantification (S/N = 10) were in the 5.3-6.3μgkg(-1) range, well below the maximum residue limits (MRLs) currently established. Inter-day mean recoveries were in the range 99-102% with RSDs below 9%, improving on the performance of previously reported MISPE methods for the analysis of CLOXA, OXA, or DICLOXA in milk samples.

Ion-exchange molecularly imprinted polymer for the extraction of negatively charged acesulfame from wastewater samples

Acesulfame is a known indicator that is used to identify the introduction of domestic wastewater into water systems. It is negatively charged and highly water-soluble at environmental pH values. In this study, a molecularly imprinted polymer (MIP) was synthesized for negatively charged acesulfame and successfully applied for the selective solid phase extraction (SPE) of acesulfame from influent and effluent wastewater samples. (Vinylbenzyl)trimethylammonium chloride (VBTA) was used as a novel phase transfer reagent, which enhanced the solubility of negatively charged acesulfame in the organic solvent (porogen) and served as a functional monomer in MIP synthesis. Different molecularly imprinted polymers were synthesized to optimize the extraction capability of acesulfame. The different materials were evaluated using equilibrium rebinding experiments, selectivity experiments and scanning electron microscopy (SEM). The most efficient MIP was used in a molecularly imprinted-solid phase extraction (MISPE) protocol to extract acesulfame from wastewater samples. Using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) analysis, detection and quantification limits were achieved at 0.12μgL−1 and 0.35μgL−1, respectively. Certain cross selectivity for the chemical compounds containing negatively charged sulfonamide functional group was observed during selectivity experiments.

Synthesis of a molecularly imprinted sorbent for selective solid-phase extraction of β-N-methylamino-l-alanine

The aim of the work was to synthesize a molecularly imprinted material for the selective solid-phase extraction (SPE) of β-N-methylamino-l-alanine (l-2-amino-3-methylpropionic acid; BMAA) from cyanobacterial extracts. BMAA and its structural analogs that can be used as template are small, polar and hydrophilic molecules. These molecules are poorly soluble in organic solvents that are commonly used for the synthesis of acrylic-based polymers. Therefore, a sol gel approach was chosen to carry out the synthesis and the resulting sorbents were evaluated with different extraction procedures in order to determine their ability to selectively retain BMAA. The presence of imprinted cavities in the sorbent was demonstrated by comparing elution profiles obtained by using molecularly imprinted silica (MIS) and non-imprinted silica (NIS) as a control. The molecularly imprinted solid-phase extraction (MISPE) procedure was first developed in a pure medium (acetonitrile) and further optimized for the treatment of cyanobacterial samples. It was characterized by high elution recoveries (89% and 77% respectively in pure and in real media).The repeatability of the extraction procedure in pure medium, in real medium and the reproducibility of MIS synthesis all expressed as RSD values of extraction recovery of BMAA were equal to 3%, 12% and 5%, respectively. A MIS capacity of 0.34µmol/g was measured. The matrix effects, which affected the quantification of BMAA when employing a mixed mode sorbent, were completely removed by adding a clean-up step of the mixed-mode sorbent extract on the MIS.