Synthesis and characterization of molecularly imprinted polymers for selective solid-phase extraction of pseudoephedrine

Molecular imprinted solid-phase extraction (MISPE) is a well known technique for the selective extraction and pre-concentration of analytes, are present at low levels in chemically complex materials. Herein, water-soluble, molecularly imprinted polymers (MIP) were prepared for solid-phase extraction of pseudoephedrine hydrochloride (PSE), which was monitored at 256 nm by the UV spectroscopy. MISPE conditions were optimized to allow the selective and determination of PSE in aqueous samples and composite materials, such as biological fluids and human urine. MIP was prepared by precipitation polymerization method, using methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a cross-linking agent in either acetonitrile or chloroform. The results suggest that the obtained MISPE exhibits high affinity for PSE, and the imprinted polymer demonstrates much higher efficiency than a non-imprinted polymer (NIP). The imprinting-induced extraction was confirmed by the determination of recovery values for NIP (4%) and MIP (80%) polymers, respectively. The binding capacity of the MIP for PSE was found of 47.6 mg g⁻¹.     

Molecularly imprinted polymers for the selective solid-phase extraction of chloramphenicol

A variety of bulk polymers for the selective separation of chloramphenicol were synthesised from 2-vinylpyridine, diethylaminoethyl methacrylate or methacrylic acid monomers. Chromatographic evaluation indicated that chloramphenicol was retained under nonpolar elution conditions (k = 58.65) through selective hydrogen bonding and ionic interactions. The retention of chloramphenicol under aqueous elution conditions (k > 100) results from nonselective hydrophobic interactions. Under nonpolar elution conditions, the functional monomer employed imparted a significant influence on the recognition properties of the corresponding polymer. After solid-phase extraction using a molecularly imprinted polymer as sorbent and either an organic or aqueous washing solvent, nearly 100% recovery from the chloramphenicol standard solution was achieved, and nearly 90% recovery could be attained from spiked honey samples. The molecularly imprinted polymer was well suited to suppress matrix effects, and provided optimal preconcentration of the target molecule (chloramphenicol) prior to chromatographic analysis.     

Magnetic molecularly imprinted polymers for selective extraction and determination of naphthols

Microchimica Acta - The authors describe a magnetic molecular imprinted polymer (MMIP) for the extraction and detection of naphthols synthesized by surface imprinting technology using 1-naphthol as...     

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

Cotinine, the main metabolite of nicotine in human body, is widely used as a biomarker for assessment of direct or passive exposure to tobacco smoke. A method for molecularly imprinted solid-phase extraction (MISPE) of cotinine from human urine has been investigated. The molecularly imprinted polymer (MIP) with good selectivity and affinity for cotinine was synthesized using cotinine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with aqueous standards, by comparing recovery data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from the aqueous solutions resulted in more than 80% recovery. A range of linearity for cotinine between 0.05 and 5 μg mL⁻¹ was obtained by loading 1 mL blank urine samples spiked with cotinine at different concentrations in acetate buffer of pH 9.0, and by using double basic washing and acidic elution. The intra-day coefficient of variation (CV) was below 7% and inter-day CV was below 10%. This investigation has provided a reliable MISPE–HPLC method for determination of cotinine in human urine from both active smokers and passive smokers. Figure     

Citrinin selective molecularly imprinted polymers for SPE

Molecularly imprinted polymers (MIPs) for citrinin (Cit) with 1‐hydroxy‐2‐naphthoic acid (HNA) as mimic template were prepared and the molecularly imprinted SPE method was developed for the detection of Cit in rice with HPLC. The adsorption properties of HNA and Cit on the MIPs and nonimprinted polymers were investigated. It proved that MIPs showed higher selectivity adsorption to HNA and Cit than nonimprinted polymers were. The recoveries of Cit in rice were in the range of 86.7–97.7%. The spiked rice samples and five rice samples in Beijing market were detected using molecularly imprinted SPE method and satisfied results were obtained as discussed in this article.     

Development and application of molecularly imprinted polymers as solid-phase sorbents for erythromycin extraction

Six molecularly imprinted polymers (MIPs) of erythromycin (ERY) were prepared by noncovalent bulk polymerization using methacrylic acid (MAA) as the functional monomer. On the basis of binding analysis, the MIPs with 1:2 optimum ratio of template to MAA were selected for subsequent scanning electron microscopy and Brunauer–Emmett–Teller analyses, which indicated that the MIPs had more convergent porous structures than the nonimprinted polymers. The equilibrium binding experiments showed that the binding sites of MIPs were heterogeneous, with two dissociation constants of 0.005 and 0.63 mg mL⁻¹, respectively. Furthermore, the performance of the MIPs as solid-phase extraction (SPE) sorbents was evaluated, and the selectivity analysis showed that the MIPs could recognize ERY with moderate cross-reactivity for other macrolides. The overall investigation of molecularly imprinted SPE for cleanup and enrichment of the ERY in pig muscle and tap water confirmed the feasibility of utilizing the MIPs obtained as specific SPE sorbents for ERY extraction in real samples. Figure Schematic diagram of the preparation and application of the erythromycin imprinted molecularly imprinted polymers Suquan Song and Aibo Wu contributed equally to this work.     

Synthesis of molecularly imprinted polymers via ring-opening metathesis polymerization for solid-phase extraction of bisphenol A

The use of molecularly imprinted polymers (MIPs) prepared by ring-opening metathesis polymerization (ROMP) for bisphenol A (BPA) was reported in this article. The resulting MIPs have high imprinting and adsorption capacities, and can be used for separation and determination of BPA in environmental water samples. The successful application of ROMP in the molecular imprinting field is described here. For the first time, two cross-linkers (dicyclopentadiene and 2,5-norbornadiene) and two Grubbs catalysts (first and second generation) were investigated to compare their effects on the binding performance of MIPs. The ROMP technique is able to create the imprinted polymers within 1 h under mild conditions. Furthermore, it can provide MIPs with obvious imprinting effects towards the template, very fast template rebinding kinetics, high binding capacity and appreciable selectivity over structurally related compounds. The adsorption process for MIPs in this study can be completed within 45 min, which is much faster than that of bulk MIPs synthesized by traditional free-radical polymerization. The resulting imprinting polymer was evaluated for its use as a sorbent support in an off-line solid-phase extraction approach to recover BPA from diluted aqueous samples. The optimized extraction protocol resulted in a reliable MISPE method suitable for selective extraction and preconcentration of BPA from tap water, human urine and liquid milk samples. This article demonstrates the practical feasibility of the MIPs prepared via ROMP as solid-phase extraction materials.     

Water-compatible molecularly imprinted polymers for selective extraction of ciprofloxacin from human urine

Water-compatible molecularly imprinted polymers (MIPs) were prepared in water-methanol systems for selective extraction and separation of ciprofloxacin from human urine samples. Molecular recognition properties, binding capability, and chromatographic applications of the MIPs were evaluated and the results revealed the obtained MIPs have high affinity for ciprofloxacin in aqueous environment and the selectivity can be easily controlled by adjusting the pH of mobile phase. After centrifugation, the urine samples were directly injected into the MIPs column and ciprofloxacin could be selectively retained on the column while other biological matrixes were quickly washed out. Good linearity was obtained from 0.1 to 100 mg L(-1) (r=0.999) with the relative standard deviations less than 3.6%. The limit of detection of the method was 0.03 microg/mL and the recoveries were more than 94.5% at three different concentrations. Moreover, by increasing the injection volume, the detection limits of the method could be improved more than 100-folds.     

Solid-phase extraction using molecularly imprinted polymers for selective extraction of a mycotoxin in cereals

The aim of this work was to develop a method for the clean-up of a mycotoxin, i.e. Ochratoxin A (OTA), from cereal extracts employing a new molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) and to compare with an immunoaffinity column. A first series of experiments was carried out in pure solvents to estimate the potential of the imprinted sorbent in terms of selectivity studying the retention of OTA on the MIP and on a non-imprinted polymer using conventional crushed monolith. The selectivity of the MIP was also checked by its application to wheat extracts. Then, after this feasibility study, two different formats of MIP: crushed monolith and micro-beads were evaluated and compared. Therefore an optimization procedure was applied to the selective extraction from wheat using the MIP beads. The whole procedure was validated by applying it to wheat extract spiked by OTA at different concentration levels and then to a certified contaminated wheat sample. Recoveries close to 100% were obtained. The high selectivity brought by the MIP was compared to the selectivity by an immunoaffinity cartridge for the clean-up of the same wheat sample. The study of capacity of both showed a significant higher capacity of the MIP.     

Preparation of highly selective solid-phase extractants for Cibacron reactive dyes using molecularly imprinted polymers

Selective polymeric extractants were prepared for preconcentration of Cibacron reactive red dye, a dye that is often applied with Cibacron reactive blue and Cibacron reactive yellow for dyeing of fabrics. The best extractant was fabricated (in chloroform) using methacrylic acid (as monomer), ethylene glycol dimethacrylate (as crosslinker), AIBN (as initiator for polymerization), and red dye as template molecule, with a molar stoichiometric ratio of 8.0:40.0:2.5:0.63, respectively. The structure of the molecularly imprinted polymer (MIP) was robust, and resisted dissolution up to 260 °C. Compared with the un-imprinted polymer, the imprinted product has a large specific surface area which improved its adsorption capacity. The effect of imprinting was obvious from the adsorption capacity measured at pH 4 for red dye (the imprinted molecule), which was increased from 24.0 to 79.3 mg g⁻¹ after imprinting. Equilibrium adsorption studies revealed that the dye-imprinted-polymer enables efficient extraction of red dye even in the presence of blue and yellow dyes which have similar chemical natures to the red dye. The selectivity coefficients S _{red dye/dye}, were 13.9 and 17.1 relative to the yellow and blue dyes, respectively. The MIP was found to be effective for red dye preconcentration, with a preconcentration factor of 100, from tap water and treated textile wastewater. The factors affecting extraction of red dye by the MIP were studied and optimized. Under the optimized extraction conditions, red dye was selectively quantified in the presence of other competing dyes at a concentration of 20 μg L⁻¹ from different water systems with satisfactory recoveries (91–95%) and RSD values (∼5.0%).     

Rationally designed molecularly imprinted polymers for selective extraction of methocarbamol from human plasma

Molecularly imprinted polymers (MIPs) with high selectivity toward methocarbamol have been computationally designed and synthesized based on the general non-covalent molecular imprinting approach. A virtual library consisting of 18 functional monomers was built and possible interactions between the template and functional monomers were investigated using a semiempirical approach. The monomers with the highest binding scores were then considered for additional calculations using a more accurate quantum mechanical (QM) calculation exploiting the density functional theory (DFT) at B3LYP/6-31G(d,p) level. The cosmo polarizable continuum model (CPCM) was also used to simulate the polymerization solvent. On the basis of computational results, acrylic acid (AA) and tetrahydrofuran (THF) were found to be the best choices of functional monomer and polymerization solvent, respectively. MIPs were then synthesized by the precipitation polymerization method and used as selective adsorbents to develop a molecularly imprinted solid-phase extraction (MISPE) procedure before quantitative analysis. After MISPE the drug could be determined either by differential pulse voltammetry (DPV), on a glassy carbon electrode modified with multiwalled-carbon nanotubes (GC/MWNT), or high performance chromatography (HPLC) with UV detection. A comparative study between MISPE-DPV and MISPE-HPLC-UV was performed. The MISPE-DPV was more sensitive but both techniques showed similar accuracy and precision.     

Development of a selective molecularly imprinted polymer-based solid-phase extraction for indomethacin from water samples

A selective molecularly imprinted solid-phase extraction (MISPE) for indomethacin (IDM) from water samples was developed. Using IDM as template molecule, acrylamide (AM) or methacrylic acid (MAA) as functional monomer, ethylene dimethacrylate (EDMA) as crosslinker, and bulk or suspension polymerization as the synthetic method, three molecularly imprinted polymers (MIPs) were synthesized and characterized with a rebinding experiment. It was found that the MIP of AM-EDMA produced by bulk polymerization showed the highest binding capacity for IDM, and so it was chosen for subsequent experiments, such as those testing the selectivity and recognition binding sites. Scatchard analysis revealed that at least two kinds of binding sites formed in the MIP, with the dissociation constants of 7.8 μmol L⁻¹ and 127.2 μmol L⁻¹, respectively. Besides IDM, three structurally related compounds — acemetacin, oxaprozin and ibuprofen — were employed for selectivity tests. It was observed that the MIP exhibited the highest selective rebinding to IDM. Accordingly, the MIP was used as a solid-phase extraction sorbent for the extraction and enrichment of IDM in water samples. The extraction conditions of the MISPE column for IDM were optimized to be: chloroform or water as loading solvent, chloroform with 20% acetonitrile as washing solution, and methanol as eluting solvent. Water samples with or without spiking were extracted by the MISPE column and analyzed by HPLC. No detectable IDM was observed in tap water and the content of IDM in a river water sample was found to be 1.8 ng mL⁻¹. The extraction efficiencies of the MISPE column for IDM in spiked tap and river water were acceptable (87.2% and 83.5%, respectively), demonstrating the feasibility of the prepared MIP for IDM extraction. Figure Molecularly imprinted polymer-based solid-phase extraction for indomethacin     

Development of andrographolide molecularly imprinted polymer for solid-phase extraction

A method employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) to pretreat samples was developed. The polymers were prepared by precipitation polymerization with andrographolide as template molecule. The structure of MIP was characterized and its static adsorption capacity was measured by the Scatchard equation. In comparison with C(18)-SPE and non-imprinted polymer (NIP) SPE column, MIP-SPE column displays high selectivity and good affinity for andrographolide and dehydroandrographolide for extract of herb Andrographis paniculata (Burm.f.) Nees (APN). MIP-SPE column capacity was 11.9±0.6 μmol/g and 12.1±0.5 μmol/g for andrographolide and dehydroandrographolide, respectively and was 2-3 times higher than that of other two columns. The precision and accuracy of the method developed were satisfactory with recoveries between 96.4% and 103.8% (RSD 3.1-4.3%, n=5) and 96.0% and 104.2% (RSD 2.9-3.7%, n=5) for andrographolide and dehydroandrographolide, respectively. Various real samples were employed to confirm the feasibility of method. This developed method demonstrates the potential of molecularly imprinted solid phase extraction for rapid, selective, and effective sample pretreatment.     

Molecularly imprinted polymers for selective solid-phase extraction of phospholipids from human milk samples

Microchimica Acta - The authors describe a method for the extraction and determination of phospholipids (PLs) from human milk fat by using a molecularly imprinted polymer (MIP) as the sorbent...     

Use of molecularly imprinted solid-phase extraction for the selective clean-up of clenbuterol from calf urine

A feasibility study was performed in order to study the possibilities in using molecularly imprinted polymers (MIPs) as sorbent material in solid-phase extraction (MISPE) for clean-up of clenbuterol from urine. A binding study of clenbuterol in several solvents was performed on a clenbuterol imprinted polymer as well as on a blank polymer. These binding experiments were used to find suitable loading, washing and elution solvents for the MISPE procedure. Extraction of clenbuterol from calf urine was performed by directly loading a 10-ml urine sample onto the MIP column. Thereafter the column was washed with 10 ml of acetonitrile containing 1% acetic acid, and finally clenbuterol was eluted with 6 ml of methanol containing 10% acetic acid. A recovery of 65% was obtained. This recovery could be increased up to 75% if a sample volume of 1 ml was used or up to 100% if urine was freeze-dried and the residue was dissolved in acetonitrile and spiked with clenbuterol prior to analysis. Chromatograms of the wash and eluate solutions show an efficient clean-up, which supports the potential of MISPE for clean-up of trace amounts of clenbuterol from calf urine.     

Synthesis of a molecularly imprinted polymer for the selective solid-phase extraction of chloramphenicol from honey

Solid-phase extraction (SPE) with a molecularly imprinted polymer (MIP) as sorbent has been investigated for the clean-up of the broad-spectrum bacteriostatic antibiotic chloramphenicol (CAP) in honey samples. The MIP was prepared by using methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as cross-linker, chloroform as porogen and CAP as template molecule. The binding behaviour of the template CAP on the MIP was evaluated by high-performance liquid chromatography, and then the MIP was applied as a sorbent in SPE to selectively extract CAP from honey. It was shown that recoveries of nearly 100% of a CAP standard solution and up to 94% from spiked honey samples could be obtained after SPE.     

Novel molecularly imprinted polymer prepared by nanoattapulgite as matrix for selective solid-phase extraction of diethylstilbestrol

Using nanoattapulgite as matrix, both diethylstilbestrol surface molecularly imprinted polymer and non-imprinted polymer were synthesized in this work. Compared with each other, the diethylstilbestrol surface molecularly imprinted polymer is superior to non-imprinted polymer in adsorption capacity, selectivity and mass transfer property. The maximum static adsorption capacities of diethylstilbestrol surface molecularly imprinted polymer, non-imprinted polymer and nanoattapulgite for diethylstilbestrol was 105.14, 78.54 and 28.50 mg g⁻¹, respectively. As the packing material of solid-phase extraction, the diethylstilbestrol surface molecularly imprinted polymer has been applied to concentrating diethylstilbestrol in pond water and fish samples. A corresponding analytical method to determine diethylstilbestrol has been developed. The limit of detection for diethylstilbestrol in pond water sample and fish samples were 3 μg L⁻¹ and 15 μg kg⁻¹.     

分子印迹聚合物固相萃取研究进展

对最新报道的分子印迹聚合物作为固相萃取剂及其在色谱样品前处理方面的应用进行综述和展望,主要包括固相萃取、基质固相分散萃取、固相微萃取、搅拌棒吸附萃取和磁性材料萃取,同时总结了分子印迹聚合物制备技术面临的挑战和问题,提出了可能的解决方案。     

Selective solid-phase extraction of tebuconazole in biological and environmental samples using molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using tebuconazole (TBZ) as a template. Frontal chromatography and selectivity experiments were used to determine the binding capabilities and binding specificities of different MIPs. The polymer that had the highest binding selectivity and capability was used as the solid-phase extraction (SPE) sorbent for the direct extraction of TBZ from different biological and environmental samples (cabbage, pannage, shrimp, orange juice and tap water). The extraction protocol was optimized and the optimum conditions were: conditioning with 5 mL methanol:acetic acid (9:1), 5 mL methanol and 5 mL water respectively, loading with 5 mL aqueous samples, washing with 1.2 mL acetonitrile (ACN):phosphate buffer (5:5, pH3), and eluting with 3 mL methanol. The MIPs were able to selectively recognize, effectively trap and preconcentrate TBZ over a concentration range of 0.5–15 μmol/L. The intraday and interday RSDs were less than 9.7% and 8.6%, respectively. The limit of quantification was 0.1 μmol/L. Under optimum conditions, the MISPE recoveries of spiked cabbage, pannage, shrimp, orange juice and tap water were 62.3%, 75.8%, 71.6%, 89% and 93.9%, respectively. MISPE gave better HPLC separation efficiencies and higher recoveries than C18 SPE and strong cation exchange (SCX) SPE. Figure HPLC analysis of spiked pannage after MISPE (A) and after C18 SPE (B). HQ (1), E3 (2), p-NP (3), FTF (4), TBZ (5), PNZ (6), HXZ (7) Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.