Determination of melamine in aquaculture feed samples based on molecularly imprinted solid‐phase extraction

This research highlights the application of highly efficient molecularly imprinted solid‐phase extraction for the preconcentration and analysis of melamine in aquaculture feed samples. Melamine‐imprinted polymers were synthesized employing methacrylic acid and ethylene glycol dimethacrylate as functional monomer and cross‐linker, respectively. The characteristics of obtained polymers were evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy and binding experiments. The imprinted polymers showed an excellent adsorption ability for melamine and were applied as special solid‐phase extraction sorbents for the selective cleanup of melamine. An off‐line molecularly imprinted solid‐phase extraction procedure was developed for the separation and enrichment of melamine from aquaculture feed samples prior to high‐performance liquid chromatography analysis. Optimum molecularly imprinted solid‐phase extraction conditions led to recoveries of the target in spiked feed samples in the range 84.6–96.6% and the relative standard deviation less than 3.38% (n = 3). The aquaculture feed sample was determined, and there was no melamine found. The results showed that the molecularly imprinted solid‐phase extraction protocols permitted the sensitive, uncomplicated and inexpensive separation and pre‐treatment of melamine in aquaculture feed samples.     

Extraction and identification of matrine‐type alkaloids from Sophora moorcroftiana using double‐templated molecularly imprinted polymers with HPLC–MS/MS

Double‐templated molecularly imprinted polymers with specific recognition of three matrine‐type alkaloids were prepared using matrine and oxymatrine as the template molecules. An approach based on double‐templated molecularly imprinted solid‐phase extraction coupled with high‐performance liquid chromatography and tandem mass spectrometry was then developed to extract and purify matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana in the Tibetan plateau herbs. The polymers were characterized by Fourier‐transform infrared spectroscopy and scanning electron microscopy. Their adsorption characteristics were evaluated using adsorption kinetics, isotherms, selectivity, and recycling experiments. This polymer exhibited excellent molecular recognition ability and good selectivity. The obtained polymers as adsorbent was further used for the determination of three matrine‐type alkaloids coupled to high‐performance liquid chromatography with tandem mass spectrometry, the recoveries of three matrines spiked at three concentration levels in samples were 73.25–98.42% (n = 5) with a relative standard deviation less than 6.82%. The limits of detection for the method were 9.23–15.42 μg/kg (S/N = 3). This proposed method was assessed to be an effective method for simultaneous extraction, isolation, and identification of matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana.     

Facile preparation of polydopamine‐coated imprinted polymers on the surface of SiO2 for estrone capture in milk samples

Estrone molecularly imprinted polymers were synthesized through the self‐polymerization of dopamine on the surface of silica gels, which had the characteristics of mild polymerization conditions, simple reaction procedure and good specific recognition ability for estrone. The estrone molecularly imprinted polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and nitrogen adsorption–desorption tests. The characterization confirmed that the imprinted polymers were successfully grafted on the surface of silica gels. Through investigating the adsorption performance, the prepared estrone molecularly imprinted polymers exhibited high adsorption capacity, fast mass transfer, as well as excellent selectivity toward estrone. The estrone molecularly imprinted polymers as the solid‐phase extraction adsorbent coupled with high‐performance liquid chromatography was developed to determine estrone from the milk samples. The developed estrone molecularly imprinted polymer solid‐phase extraction with high‐performance liquid chromatography method exhibited satisfactory specificity, precision, accuracy and good linearity relationship in the range of 0.2–20 μg/mL. The developed method is simple, fast, effective and high specificity method and it provides a new method to detect the residues of estrone in animal foods.     

A new ionic liquid surface‐imprinted polymer for selective solid‐phase‐extraction and determination of sulfonamides in environmental samples

Toward improving the selective adsorption performance of molecularly imprinted polymers in strong polar solvents, in this work, a new ionic liquid functional monomer, 1‐butyl‐3‐vinylimidazolium bromide, was used to synthesize sulfamethoxazole imprinted polymer in methanol. The resulting molecularly imprinted polymer was characterized by Fourier transform infrared spectra and scanning electron microscopy, and the rebinding mechanism of the molecularly imprinted polymer for sulfonamides was studied. A static equilibrium experiment revealed that the as‐obtained molecularly imprinted polymer had higher molecular recognition for sulfonamides (e.g., sulfamethoxazole, sulfamonomethoxine, and sulfadiazine) in methanol; however, its adsorption of interferent (e.g., diphenylamine, metronidazole, 2,4‐dichlorophenol, and m‐dihydroxybenzene) was quite low. ¹H NMR spectroscopy indicated that the excellent recognition performance of the imprinted polymer was based primarily on hydrogen bond, electrostatic and π‐π interactions. Furthermore, the molecularly imprinted polymer can be employed as a solid phase extraction sorbent to effectively extract sulfamethoxazole from a mixed solution. Combined with high‐performance liquid chromatography analysis, a valid molecularly imprinted polymer‐solid phase extraction protocol was established for extraction and detection of trace sulfamethoxazole in spiked soil and sediment samples, and with a recovery that ranged from 93–107%, and a relative standard deviation of lower than 9.7%.     

Magnetic molecularly imprinted composite for the selective solid‐phase extraction of p‐aminosalicylic acid followed by high‐performance liquid chromatography with ultraviolet detection

A new method for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples has been developed using magnetic molecularly imprinted polymer nanoparticles before determination by high‐performance liquid chromatography. The Fe₃O₄ nanoparticles were first prepared through the chemical coprecipitation of Fe²⁺ and Fe³⁺ and then coated with a vinyl shell. Subsequently, a layer of molecularly imprinted polymers was grafted onto the vinyl‐modified magnetic nanoparticles by precipitation polymerization. FTIR spectroscopy, scanning electron microscopy, vibrating sample magnetometry, and thermogravimetric analysis were applied to characterize the sorbent properties. Moreover, the predominant parameters affecting the magnetic solid phase extraction such as sample pH, sorption and elution times, the amount of sorbent, and composition and volume of eluent were investigated thoroughly. The maximum sorption capacity of the imprinted polymer toward p‐aminosalicylic acid was 70.9 mg/g, which is 4.5 times higher than that of the magnetic nonimprinted polymer. The magnetic molecularly imprinted polymer nanoparticles were applied for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples and satisfactory results were achieved. The results illustrate that magnetic molecularly imprinted polymer nanoparticles have a great potential in the extraction of p‐aminosalicylic acid from environmental and biological matrices.     

Preparative isolation of flavonoid glycosides from Sphaerophysa salsula using hydrophilic interaction solid‐phase extraction coupled with two‐dimensional preparative liquid chromatography

An offline preparative two‐dimensional reversed‐phase liquid chromatography/hydrophilic interaction liquid chromatography coupled with hydrophilic interaction solid‐phase extraction method was developed for the preparative isolation of flavonoid glycosides from a crude sample of Sphaerophysa salsula . First, the non‐flavonoids were removed using an XAmide solid‐phase extraction cartridge. Based on the separation results of three different chromatographic stationary phases, the first‐dimensional preparation was performed on an XAqua C18 prep column, and 15 fractions were obtained from the 5.2 g target sample. Then, three representative fractions were selected for additional purification on an XAmide preparative column to further isolate the flavonoid glycosides. In all, eight flavonoid glycosides were isolated in purities over 97%. The results demonstrated that the two‐dimensional liquid chromatography method used in this study was effective for the preparative separation of flavonoid glycosides from Sphaerophysa salsula . Additionally, this method showed great potential for the separation of flavonoid glycosides from other plant materials.     

Monodisperse restricted access material with molecularly imprinted surface for selective solid‐phase extraction of 17β‐estradiol from milk

In this study, novel monodisperse restricted access media‐molecularly imprinted polymers were successfully prepared by surface initiated reversible addition‐fragmentation chain transfer polymerization using monodisperse crosslinked poly (glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) microspheres as the carrier and acryloyl chloride‐modified β‐cyclodextrin as the hydrophilic functional monomer. The surface morphology, protein exclusion, and adsorption properties of the molecularly imprinted polymers were investigated. The results show that the material has excellent monodispersity and hydrophilicity, and simultaneously exhibit high adsorption capacity, fast binding kinetics, high selectivity, and significant thermal stability. The molecularly imprinted polymers as dispersive solid‐phase extraction adsorbent combined with reversed‐phase high‐performance liquid chromatography was used to selectively enrich, separate, and analyze trace 17β‐estradiol in milk samples. The recovery of 17β‐estradiol is 88–95% with relative standard deviation of <4%, and the limits of detection and quantification of this method are 2.08 and 9.29 µg/L, respectively. The novel restricted access media‐molecularly imprinted polymer adsorbents provide an effective method for the selective extraction and detection of 17β‐estradiol directly from complex samples.     

Preparation and evaluation of a molecularly imprinted sol–gel material as the solid‐phase extraction adsorbents for the specific recognition of cloxacilloic acid in cloxacillin

Highly selective molecularly imprinted polymers on the surface of silica gels were prepared by a sol–gel process and used as solid‐phase extraction adsorbents for the specific recognition, enrichment and detection of cloxacilloic acid in cloxacillin. The obtained polymers were characterized by scanning electron microscopy, FTIR spectroscopy, nitrogen adsorption and desorption, elemental analysis and thermogravimetric analysis. The imprinted polymers not only possessed high adsorption capacity (6.5 μg/mg), but also exhibited fast adsorption kinetics (they adsorb 80% of the maximum amount within 20 min) and excellent selectivity (the imprinted factor was 3.6). A method using the imprinted polymers as solid‐phase extraction adsorbents coupled with high‐performance liquid chromatography was established with good specificity, linearity (r = 0.9962), precision (ranging from 0.5 to 6.7%), accuracy (ranging from 93.9 to 97.7%) and extraction recoveries (ranging from 78.8 to 89.8%). The limits of detection and quantification were 0.07 and 0.25 mg/g, respectively. This work could provide a promising method in the enrichment, extraction and detection of allergenic impurities in the manufacture, storage and application of cloxacillin.     

Preparation of l‐phenylalanine‐imprinted solid‐phase extraction sorbent by Pickering emulsion polymerization and the selective enrichment of l‐phenylalanine from human urine

A novel l‐ phenylalanine molecularly imprinted solid‐phase extraction sorbent was synthesized by the combination of Pickering emulsion polymerization and ion‐pair dummy template imprinting. Compared to other polymerization methods, the molecularly imprinted polymers thus prepared exhibit a high specific surface, large pore diameter, and appropriate particle size. The key parameters for solid‐phase extraction were optimized, and the result indicated that the molecularly imprinted polymer thus prepared exhibits a good recovery of 98.9% for l‐ phenylalanine. Under the optimized conditions of the procedure, an analytical method for l‐ phenylalanine was well established. By comparing the performance of the molecularly imprinted polymer and a commercial reverse‐phase silica gel, the obtained molecularly imprinted polymer as an solid‐phase extraction sorbent is more suitable, exhibiting high precision (relative standard deviation 3.2%, n = 4) and a low limit of detection (60.0 ± 1.9 nmol·L^?1) for the isolation of l‐ phenylalanine. Based on these results, the combination of the Pickering emulsion polymerization and ion‐pair dummy template imprinting is effective for preparing selective solid‐phase extraction sorbents for the separation of amino acids and organic acids from complex biological samples.     

Determination of sulfadiazine in eggs using molecularly imprinted solid‐phase extraction coupled with high‐performance liquid chromatography

The development of a simple and effective method for the isolation and purification of sulfadiazine residues in food of animal origin is of great significance since it is a great danger to human health. An off‐line molecularly imprinted solid‐phase extraction with high‐performance liquid chromatography method was proposed for the selective pretreatment and determination of sulfadiazine in eggs, rapidly and effectively. The molecularly imprinted polymer was proved to have a homogeneous spherical structure and porous surface morphology with excellent adsorption capacity of 5258 μg/g for sulfadiazine. The newly established method showed a good linearity in the range of 0–200 μg/L, low limits of detection (0.06 μg/L), acceptable reproducibility (RSD, 2.60–5.03%, n = 3), and satisfactory relative recoveries (78.22–86.10%). It was demonstrated that the proposed molecularly imprinted solid‐phase extraction with high‐performance liquid chromatography method could be applied to determine sulfadiazine in eggs, which simplified the pretreatment procedure and improved the accuracy of the analysis process by reducing the loss of sulfadiazine in the fat‐removing procedure compared with traditional methods. Molecularly imprinted solid‐phase extraction with excellent selectivity and adsorption capacity is a simple, rapid, selective, and effective pretreatment method for the determination of sulfadiazine in egg samples.     

Novel molecularly imprinted magnetic nanoparticles for the selective extraction of protoberberine alkaloids in herbs and rat plasma

In this work, a novel magnetic nanomaterial functionalized with a molecularly imprinted polymer was prepared for the extraction of protoberberine alkaloids. Molecularly imprinted polymers were made on the surface of Fe₃O₄ nanoparticles by using berberine as template, acetonitrile/water as porogen, acrylamide as functional monomer and ethylene glycol dimethacrylate as cross‐linker. The optimized molar ratio of template/functional monomer was 1:7. The polymeric magnetic nanoparticles were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The stability and adsorption capacity of the molecularly imprinted polymers were investigated. The molecularly imprinted polymers were used as a selective sorbent for the magnetic molecularly imprinted solid‐phase extraction and determination of jatrorrhizine, palmatine, and berberine. Extraction parameters were studied including loading pH, sample volume, stirring speed, and extraction time. Finally, a magnetic molecularly imprinted solid‐phase extraction coupled to high‐performance liquid chromatography method was developed. Under the optimized conditions, the method showed good linear range of 0.1–150 ng/mL for berberine and 0.1–100 ng/mL for jatrorrhizine and palmatine. The limit of detection was 0.01 ng/mL for berberine and 0.02 ng/mL for jatrorrhizine and palmatine. The proposed method has been applied to determine protoberberine alkaloids in Cortex phellodendri and rat plasma samples. The recoveries ranged from 87.33–102.43%, with relative standard deviation less than 4.54% in Cortex phellodendri and from 102.22–111.15% with relative standard deviation less than 4.59% in plasma.     

Preparation and application of molecularly imprinted polymer solid‐phase microextraction fiber for the selective analysis of auxins in tobacco

As signal molecules, auxins play an important role in mediating plant growth. Due to serious interfering substances in plants, it is difficult to accurately detect auxins with traditional solid‐phase extraction methods. To improve the selectivity of sample pretreatment, a novel molecularly imprinted polymer ‐coated solid‐phase microextraction fiber, which could be coupled directly to high‐performance liquid chromatography, was prepared with indole acetic acid as template molecule for the selective extraction of auxins. The factors influencing the polymer formation, such as polymerization solvent, cross‐linker, and polymerization time, were investigated in detail to enhance the performance of indole acetic acid‐molecularly imprinted polymer coating. The morphological and chemical stability of this molecularly imprinted polymer‐coated fiber was characterized by scanning electron microscopy, infrared spectrometry, and thermal analysis. The extraction capacity of the molecularly imprinted polymer‐coated solid‐phase microextraction fiber was evaluated for the selective extraction of indole acetic acid and indole‐3‐pyruvic acid followed by high‐performance liquid chromatography analysis. The linear range for indole acetic acid and indole‐3‐pyruvic acid was 1–100 µg/L and their detection limit was 0.5 µg/L. The method was applied to the simultaneous determination of two auxins in two kinds of tobacco (Nicotiana tabacum L and Nicotiana rustica L) samples, with recoveries range from 82.1 to 120.6%.     

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid‐based ultrasonic‐assisted extraction and ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

A powerful ionic liquid‐based ultrasonic‐assisted extraction (ILUAE) method combined with ultra‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC/ESI‐QTOFMSⁿ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid–liquid ratio. A comparison with conventional heat‐reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6‐O‐E‐feruloyl catalpol, 2.20%) within a short extraction time of 30 min. Negative ion mode ESI‐QTOFMS² analysis of the fragmentation reactions of the [M–H]^– ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5 min. Moreover, 6'‐O‐vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R²), and reproducibility (RSD, n = 5) of three iridoid glycosides: 89.60%–109.02%, 0.9991–0.9998, and 0.93%–1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI‐QTOFMSⁿ for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of molecularly imprinted polymers based on magnetic nanoparticles for the selective extraction of protocatechuic acid from plant extracts

In this study, highly selective core–shell molecularly imprinted polymers on the surface of magnetic nanoparticles were prepared using protocatechuic acid as the template molecule. The resulting magnetic molecularly imprinted polymers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and vibrating sample magnetometry. The binding performances of the prepared materials were evaluated by static and selective adsorption. The binding isotherms were obtained for protocatechuic acid and fitted by the Langmuir isotherm model and Freundlich isotherm model. Furthermore, the resulting materials were used as the solid‐phase extraction materials coupled to high‐performance liquid chromatography for the selective extraction and detection of protocatechuic acid from the extracts of Homalomena occulta and Cynomorium songaricum with the recoveries in the range 86.3–102.2%.     

Computational design and fabrication of core–shell magnetic molecularly imprinted polymer for dispersive micro‐solid‐phase extraction coupled with high‐performance liquid chromatography for the determination of rhodamine 6G

A novel core–shell magnetic nano‐adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro‐solid‐phase extraction followed by determination of rhodamine 6G using high‐performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m‐aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA₉ (3⁴) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid‐base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano‐adsorbent was successfully applied to dispersive micro‐solid‐phase extraction coupled to high‐performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0–99.1, 89.5–92.7, and 86.9–105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%.     

Simultaneous determination of levofloxacin and ciprofloxacin in human urine by ionic‐liquid‐based,dual‐template molecularly imprinted coated graphene oxide monolithic solid‐phase extraction

A novel method was developed to simultaneously determine the ciprofloxacin and levofloxacin levels in human urine using an ionic‐liquid‐based, dual‐molecularly imprinted polymer‐coated graphene oxide solid‐phase extraction monolithic column coupled with high‐performance liquid chromatography. The molecularly imprinted monolithic column was prepared using ciprofloxacin and levofloxacin as templates, 1‐vinyl‐3‐ethylimidazolium bromide as the functional monomer, and graphene oxide as the core material. The resulting imprinted monoliths were characterized by scanning electron microscopy and fourier transform‐infrared spectroscopy. The efficiency and capacity of the ionic‐liquid‐based imprinted monolithic column were investigated by varying the synthesis conditions (ciprofloxacin/levofloxacin ratio and template/functional monomer/cross‐linker ratio). The solid‐phase extraction process was optimized by changing the washing and eluting conditions. The results suggested that the proposed ionic‐liquid‐based molecularly imprinted solid‐phase extraction monolithic‐high‐performance liquid chromatography method could separate ciprofloxacin and levofloxacin efficiently and simultaneously from human urine. The mean recoveries of ciprofloxacin and levofloxacin ranged from 89.2 to 93.8 and 86.7 to 94.6%, respectively. The intra‐ and interday relative standard deviation ranged from 0.9 to 3.2 and 0.8 to 2.9%, respectively. Under the optimized conditions, the recoveries of ciprofloxacin and levofloxacin were more than 93.8%.     

Thermosensitive molecularly imprinted poly(1‐vinyl‐2‐pyrrolidone/methyl methacrylate/N‐vinylcaprolactam) for selective extraction of imatinib mesylate in human biological fluid

The efficiency of a molecularly imprinted polymer as a selective packing material for the solid‐phase extraction of imatinib mesylate sorption was investigated. The molecularly imprinted polymer was prepared using N,N′‐methylenebisacrylamide as a cross‐linker agent, N‐vinylcaprolactam as a thermo‐sensitive monomer, 1‐vinyl‐2‐pyrrolidone and methyl methacrylate as functional monomers, azobisisobutyronitrile as an initiator and imatinib mesylate as a template. The drug‐imprinted polymer was identified by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and scanning electron microscopy. It was found that this polymer can be used for determination of trace levels of imatinib mesylate with a recovery percentage that could reach over 90%. Furthermore, the synthesized molecularly imprinted polymer indicated higher selectivity towards imatinib mesylate than other compounds. From isotherm study, the equilibrium adsorption data of imatinib mesylate by imprinted polymer were analyzed by Langmuir, Freundlich, and Temkin isotherm models. The developed method was used for determination of imatinib mesylate in human fluid samples by high performance liquid chromatography with excellent results.     

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin for selective extraction of di(2‐ethylhexyl) phthalate in environmental waters

Graphene oxide based molecularly imprinted polymers modified with β‐cyclodextrin were prepared as solid‐phase extraction column sorbents for specific recognition and sensitive detection of di(2‐ethylhexyl) phthalate in water samples. The morphology and composition of synthesized sorbents were characterized by scanning electron microscopy, thermo‐gravimetric analysis, Raman spectroscopy, and Fourier‐transform infrared spectroscopy. The conditions affecting the performance of extraction procedures such as desorption solvent types and volume, sample pH and volume were investigated. The loading capacity (8.2 μg/mg) of the prepared sorbents increased eight times after modification with β‐cyclodextrin. The developed extraction procedures coupled to high‐performance liquid chromatography exhibited good linearity (0.2–500 μg/L), low limit of detection (0.052 μg/L), and good precision (relative standard deviation?5.7%) under optimized conditions. The developed solid‐phase extraction technique with prepared sorbents has been successfully applied in extracting trace di(2‐ethylhexyl) phthalate from real natural waters with high efficiency, good selectivity, and desirable recoveries.     

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

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

Development of a molecularly imprinted solid‐phase extraction sorbent for the selective extraction of telmisartan from human urine

A novel molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed for the selective extraction of telmisartan from human urine. Molecularly imprinted polymers were prepared by a noncovalent imprinting approach through UV‐radical polymerization using telmisartan as a template molecule, 2‐dimethylamino ethyl methacrylate as a functional monomer, ethylene glycol dimethacrylate as a cross‐linker, N,N‐azobisisobutyronitrile as an initiator, chloroform as a porogen. Molecularly imprinted polymers and nonimprinted control polymer sorbents were dry‐packed into solid‐phase extraction cartridges, and eluates from cartridges were analyzed using a spectrofluorimeter. Limit of detection and limit of quantitation values were 11.0 and 36.0 ng/mL, respectively. A very high imprinting factor (16.1) was achieved and recovery values for the telmisartan spiked in human urine were in the range of 76.1–79.1%. In addition, relatively low within‐day (0.14–1.6%) and between‐day (0.11–1.31%) precision values were obtained. Valsartan was used to evaluate the selectivity of sorbent as well. As a result, a sensitive, selective, and simple molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed and successfully applied to the direct determination telmisartan in human urine.