加速溶剂萃取快速洗脱印迹聚合物中的模板分子

通过优化实验条件,选择洗脱温度80℃、加热时间5min、萃取压力10.4MPa、洗脱溶剂为300mL的甲醇/乙酸(90∶10,V/V),静态萃取时间8min、吹扫时间100s,对1.000g尼古丁印迹聚合物中的模板分子进行连续6次的萃取洗脱,洗脱效率达94.2%,模板渗漏量仅为9.8μg/L,萃取时间<70min。将2000mg洗脱后的印迹聚合物颗粒装填于3mL的聚丙烯固相萃取小柱中,用10mL甲醇/乙酸(90∶1,V/V)淋洗小柱,用高效液相色谱检测淋洗液中的尼古丁,获得模板的渗漏量为9.8μg/L。     

Determination of khellin and visnagin in Ammi visnaga fruits by capillary electrophoresis

A sensitive method for the simultaneous determination of phenolic xenoestrogens such as bisphenol A, 2,4-dichlorophenol, 4-tert,-butylphenol, 4-n2-pentylphenol, 4-n-hexylphenol, 4-n-heptylphenol, 4-octylphenol, 4-nonylphenol was developed using reversed-phase LC and coulometric-array detection. Stepwise gradient elution with phosphoric acid in water-acetonitrile was used. The calibration curves were linear in the range of 5.0 (or 10.0)-1000 ng ml(-1) with correlation coefficients of 0.9978-0.9999, the limits of detection were 0.01-0.02 ng ml(-1). Sample clean-up was performed by solid-phase extraction (SPE) using 3M Empore extraction disks. Three commercial sorbents, C18, SDB-XD (styrene-divinylbenzene polymer) and SDB-RPS (sulfonated styrene-divinylbenzene polymer) were compared. The highest recoveries were obtained with SDB-RPS. They were above 70% with a relative standard deviation of less than 15%. The proposed method was applied to the determination of phenolic xenoestrogens in various water samples.     

Isolation and preparative purification of microcystin variants

Preparative reversed-phase liquid chromatography was successfully used to purify two microcystins (microcystin LR and microcystin LA) from a cyanobacterial process waste. The separation protocol involved extraction of lyophilized cells by methanol, isolation and concentration by solid-phase extraction, and purification by reversed-phase HPLC. Milligram-level loading of microcystins was obtained on a solid-phase extraction cartridge packed with 0.5 g of C18 stationary phase. The separations were first carried out on an analytical column and then scaled-up to a preparative column. The microcystins were quantified by HPLC and enzyme-linked immunosorbent assay. A method to remove microcystins rapidly and economically from the cyanobacterial process waste is also described.     

Isolation and quantitation of amygdalin in Apricot-kernel and Prunus Tomentosa Thunb. by HPLC with solid-phase extraction

Apricot-kernel and Prunus Tomentosa Thunb. are traditional Chinese herb medicines that contain amygdalin as their major effective ingredient. In this report, three methods for the extraction of amygdalin from the medicinal materials are compared: ultrasonic extraction by methanol, Soxhlet extraction by methanol, and reflux extraction by water. The results show that reflux extraction water containing 0.1% citric acid is the best option. The optimal reflux is 2.5 h and water bath temperature is 60 degrees C. The solid-phase extraction method using C18 and multiwalled carbon nanotube as adsorbents is established the pretreatment of reflux extract, and the result shows that the two adsorbents have greater adsorptive capacity for amygdalin and good separation effect. In order to quantitate amygdalin in Apricot-kernel and Prunus Tomentosa Thunb., a reversed-phase high-performance liquid chromatography method using methanol-water (15:85, for 30 min and pure methanol after 30 min) as mobile phase is developed and a good result is obtained.     

Simultaneous analysis of hydrochlorothiazide, triamterene and reserpine in rat plasma by high performance liquid chromatography and tandem solid-phase extraction

A tandem solid-phase extraction method (SPE) of connecting two different cartridges (C(18) and MCX) in series was developed as the extraction procedure in this article, which provided better extraction yields (>86%) for all analytes and more appropriate sample purification from endogenous interference materials compared with a single cartridge. Analyte separation was achieved on a C(18) reversed-phase column at the wavelength of 265 nm by high-performance liquid chromatography (HPLC). The method was validated in terms of extraction yield, precision and accuracy. These assays gave mean accuracy values higher than 89% with RSD values that were always less than 3.8%. The method has been successfully applied to plasma samples from rats after oral administration of target compounds.     

The application of pseudo template molecularly imprinted polymer to the solid-phase extraction of cyromazine and its metabolic melamine from egg and milk

The combination of molecularly imprinted polymer with high performance liquid chromatography has been developed to determine cyromazine and its metabolic melamine in some samples. However, the potential risk of template leakage used in molecularly imprinted polymer is a major disadvantage. To solve this problem, 2-(4,6-diamino-1,3,5-triazin-2-ylamino) ethanethiol disulfide, a molecule that shares the similar imprinting sites with cyromazine and melamine, was selected as pseudo template to prepare molecularly imprinted polymer. Methacrylic acid, ethylene glycol dimethyl acrylate and toluene were selected as functional monomer, crosslinker and porogen, respectively. The molecular recognition property and binding capability of cyromazine and melamine were evaluated by adsorption test and Scatchard analysis. The results showed that the molecularly imprinted polymer based on pseudo template had more excellent affinity and selectivity for cyromazine and melamine. The resulting molecularly imprinted polymer was used as a solid-phase extraction material to enrich cyromazine and melamine in egg and milk samples for high performance liquid chromatography analysis. The solid-phase extraction process was carefully optimized. It was found that when different concentration of cyromazine and melamine standards were spiked into samples, satisfactory recovery rate of cyromazine and melamine were obtained as 85.6-98.8% with relative standard deviation <5.5%.     

Application of multivariate analysis to the screening of molecularly imprinted polymers (MIPs) for ametryn

Among the solid-phase extraction (SPE) techniques, a novel system for a triazine herbicide named ametryn, has been developed based on a molecular imprinted polymer (MIP) phase. Through this method, the synthesis of the complementary to ametryn MIP was accomplished and the factors influencing its efficiency have been optimized. Through the optimization process, the type and the amounts of functional monomer and solvents, template amount, cross-linker, initiator as well as the polymerization temperature were considered to be evaluated. Based on the obtained results, the optimum conditions for the efficient polymerized sorbent, considering the recovery efficiency were solvent: acetonitrile, 6.41 mL; monomer: methacrylic acid, 5.41 mmol; template: 1.204 mmol; cross-linker: 27.070 mmol; initiator: 2.03 mmol; temperature: 40.86 degrees C. The optimum molar ratio among the template, monomer and cross-linker for ametryn was 1:4.49:22.48. The reversed-phase HPLC-UV was used for the ametryn determination, using an isocratic solvent delivery system (acetonitrile: H(2)O, 60:40), flow-rate of 0.8 mL min(-1) and a UV wavelength of 220 nm. In line with the obtained results, using central composite design (CCD) can increase the precision and accuracy of synthesis and optimization of MIP to ametryn and possibly other similar analogues.     

Selective separation of active inhibitors of epidermal growth factor receptor from Caragana jubata by molecularly imprinted solid-phase extraction

A feasibility research was performed to study the possibilities of using a molecularly imprinted polymer as sorbent material in solid-phase extraction for the separation of active inhibitors of epidermal growth factor receptor (EGRF) from Caragana Jubata, a Chinese traditional Tibetan medicine. A molecularly imprinted polymer using quercetin, an active anti-EGFR inhibitor (IC50 = 15 microM), as the template and acrylamide as the functional monomer was prepared. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction. The EtOAc extract of Caragana Jubata was loaded on the polymer, and two novel active anti-EGFR inhibitors were found to be selectively retained after washing the polymer with appropriate solvent to disrupt the non-specific interactions occurring between the sample and the polymer matrix, which were identified as (E)-piceatannol (IC50 =4.9 microM) and butein (IC50 = 10 microM). The present work affords us a new potential method for selective separation of bioactive components from herb by using molecularly imprinted polymer as a solid-phase extraction adsorbent.     

Extraction of Anthraquinones from Rhubarb by a Molecularly Imprinted–Matrix Solid-Phase Dispersion Method with HPLC Detection

A simple method based on matrix solid-phase dispersion for selective extraction of anthraquinones from rhubarb samples was developed using a molecularly imprinted polymer as sorbent. The molecularly imprinted polymer was prepared using emodin as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linking agent. The polymer was characterized by scanning electron microscopy and Fourier-transform infrared spectrometry. Isothermal adsorption and dynamic adsorption experiments were performed. The best extraction conditions for anthraquinones were obtained at a ratio of molecularly imprinted polymer to sample of 1:1, a dispersion time of 5 minutes, with 5% aqueous methanol as the washing solvent, and an elution solvent of methanol-acetic acid (99:1, v/v). Once the matrix solid-phase dispersion process was optimized, the extract was reacted with 8% hydrochloric acid for hydrolysis. The anthraquinones extracted from rhubarb were determined by liquid chromatography. The detection limits of chrysophanol, emodin, physcion, and aloe-emodin were 0.23, 0.24, 0.28, and 0.27 µg mL^?1, respectively. The proposed method was compared with the method in Chinese pharmacopoeia, and the results show that the extraction yield of anthraquinones obtained by molecularly imprinted polymer–matrix solid-phase dispersion method was higher. Moreover, the proposed method is faster and simpler and can achieve extraction and purification in the same system.     

Selective trace enrichment of acidic pharmaceuticals in real water and sediment samples based on solid-phase extraction using multi-templates molecularly imprinted polymers

A novel multi-templates molecularly imprinted polymer (MIP), using acidic pharmaceuticals mixture (ibuprofen (IBP), naproxen (NPX), ketoprofen (KEP), diclofenac (DFC), and clofibric acid (CA)) as the template, was prepared as solid-phase extraction (SPE) material for the quantitative enrichment of acidic pharmaceuticals in environmental samples and off-line coupled with liquid chromatography–mass spectrometry (LC/MS/MS). Washing solvent was optimized in terms of kind and volume for removing the matrix constituents nonspecifically adsorbed on the MIP. When 1 L of water sample spiked at 1 μg/L was loaded onto the cartridge, the binding capacity of the MIP cartridge were 48.7 μg/g for KEP, 60.7 μg/g for NPX, 52 μg/g for CA, 61.3 μg/g for DFC and 60.7 μg/g for IBP, respectively, which are higher than those of the commercial single template MIP in organic medium (e.g. toluene) reported in the literature. Recoveries of the five acidic pharmaceuticals extracted from 1 L of real water samples such as lake water and wastewater spiked at 1 μg/L were more than 95%. The recoveries of acidic pharmaceuticals extracted from 10-g sediment sample spiked at the 10 ng/g level were in the range of 77.4–90.6%. To demonstrate the potential of the MIP obtained, a comparison with commercial C18 SPE cartridge was performed. Molecularly imprinted solid-phase extraction (MISPE) cartridge showed higher recoveries than commercial C18 SPE cartridge for acidic pharmaceuticals. These results showed the suitability of the MISPE method for the selective extraction of a group of structurally related compounds such as acidic pharmaceuticals.     

Selective solid-phase extraction of a triterpene acid from a plant extract by molecularly imprinted polymer

A molecularly imprinted polymer (MIP) has been prepared by a thermal polymerisation method using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linking agent, chloroform as porogenic solvent and an oleanane triterpene compound (18-beta-glycyrrhetinic acid) as imprinted molecule (template). Equilibrium ligand binding experiments were done to assess the performance of the MIP relative to non-imprinted polymer (NIP). After optimisation of SPE protocol (CHCl3 as washing solvent and MeOH as elution solvent), successful imprinting was confirmed by comparison of the recoveries between NIP (5%) and MIP (97%) cartridges. The binding capacity of the MIP for 18-beta-glycyrrhetinic acid was determined to be 0.94 mg g(-1). Four structurally related oleanane triterpenes (18-alpha-glycyrrhetinic acid, oleanolic acid, echinocystic acid, erythrodiol) were selected to assess the MIP selectivity. Experimental data illustrated the influence of functional groups on the triterpene skeleton. The MIP was applied to the solid-phase extraction of triterpenoids from a plant extract prior HPLC analysis. However, CHCl3 was replaced by ACN during the washing step in order to suppress non-specific interactions due to polar matrix components. A selective extraction of 18-beta-glycyrrhetinic acid from hydrolyzed extract of liquorice roots was achieved with a good extraction yield (98%).     

Determination of the coumarin derivative cloricromene acid in rabbit plasma and platelets.

Two methods for the determination of cloricromene acid in biological samples are described. Cloricromene acid is a catabolite of cloricromene, a coumarin derivative which is active in the cardiovascular system. After oral administration of cloricromene to a rabbit, plasma and platelets were taken at different times and cloricromene acid was then isolated by solid-phase extraction with Sep-Pak C18 cartridges using acetonitrile-tetrahydrofuran-20% aqueous acetic acid (15:11:74, v/v/v) as eluent. The analyses were performed by reversed-phase high-performance liquid chromatography (RP-HPLC) combined with fluorescence detection with excitation at 310 nm and emission at 390 nm. The limit of quantification by RP-HPLC was about 50 pg. The catabolite in the plasma was identified by continuous-flow fast atom bombardment mass spectrometry (CF-FAB-MS), also used as a complementary means of RP-HPLC determination. The results obtained by RP-HPLC and CF-FAB-MS showed good agreement.     

Determination of water-soluble vitamin B and vitamin C in combined feed,premixes, and biologically active supplements by reversed-phase HPLC

A procedure was developed for determining water-soluble vitamins B and vitamin C in premixes, biologically active supplements, and combined feed by reversed-phase HPLC using sodium heptanesulfonate as an ion-pair reagent. A procedure was proposed for purifying a combined food extract by solid-phase extraction on a column packed with a Sep-Pak C18 adsorbent. The stability of ascorbic acid and riboflavin in aqueous solutions with different pH values was studied.     

Room temperature ionic liquid-mediated molecularly imprinted polymer monolith for the selective recognition of quinolones in pork samples

A novel molecularly imprinted polymer monolith was prepared by the room temperature ionic liquid-mediated in situ molecular imprinting technique, using norfloxacin (NOR) as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker. The optimal synthesis conditions and recognition properties of NOR-imprinted monolithic column were investigated. The results indicated that the imprinted monoliths exhibited good ability of selective recognition against the template and its structural analog. Using the fabricated material as solid-phase extraction sorbent, a sample pre-treatment procedure of molecularly imprinted solid-phase extraction coupling with HPLC was developed for determination of trace quinolone residues in animal tissues samples. The recoveries ranging from 78.16 to 93.50% for eight quinolones antibiotics such as marbofloxacin, NOR, ciprofloxacin, danofloxacin, difloxacin, oxolinic acid, flumequine and enrofloxacin were obtained.     

Determination of lipid oxidation level in broiler meat by liquid chromatography

An assay was conducted for the determination of malondialdehyde (MDA) levels in broiler meat. The method involves extraction of tissues with trichloroacetic acid (TCA) and reaction of the TCA extract with 2,4-dinitrophenylhydrazine (DNPH). After separation of the MDA-DNPH complex using a solid-phase extraction C18 column, samples were eluted with 1 mL acetonitrile. Aliquots of 20 microL acetonitrile were analyzed by liquid chromatography on reversed-phase C18 column (3 microm) with UV detection. The products were eluted isocratically with the mobile phase containing acetonitrile-water-acetic acid (39 + 61 + 0.2, v/v/v). The retention time for MDA-DNPH was 6.5 min, and the detection limit was 3.5 microg/kg. Two extraction methods (cold and hot) were also used in the study. The results showed that hot extraction increased results about 55.8% and recovery from samples spiked with 116.6 microg/kg was lower (74.6%) in comparison with cold extraction (94.7%).     

Development of an improved method for trace analysis of chloramphenicol using molecularly imprinted polymers

A confirmatory method is described for the determination of the illegal antibiotic chloramphenicol using a specifically developed molecularly imprinted polymer (MIP) as the sample clean-up technique. The newly developed MIP was produced using an analogue to chloramphenicol as the template molecule. Using an analogue of the analyte as the template avoids a major traditional drawback associated with MIPs of residual template leeching or bleeding. The MIP described was used as a solid-phase extraction phase for the extraction of chloramphenicol from various sample matrices including honey, urine, milk and plasma. A full analytical method with quantification by LC-MS/MS is described. The method was fully validated according to the European Union (EU) criteria for the analysis of veterinary drug residues.     

Molecular imprinting solid phase extraction for selective detection of methidathion in olive oil

A specific adsorbent for extraction of methidathion from olive oil was developed. The design of the molecularly imprinted polymer (MIP) was based on the results of the computational screening of the library of polymerisable functional monomers. MIP was prepared by thermal polymerisation using N,N’-methylene bisacrylamide (MBAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The polymers based on the itaconic acid (IA), methacrylic acid (MAA) and 2-(trifluoromethyl)acryl acid (TFMAA) functional monomers and one control polymer which was made without functional monomers with cross-linker EGDMA were also synthesised and tested. The performance of each polymer was compared using corresponding imprinting factor. As it was predicted by molecular modelling the best results were obtained for the MIP prepared with MBAA. The obtained MIP was optimised in solid-phase extraction coupled with high performance liquid chromatography (MISPE-HPLC-UV) and tested for the rapid screening of methidathion in olive oil. The proposed method allowed the efficient extraction of methidathion for concentrations ranging from 0.1 to 9 mg L⁻¹ (r² = 0.996). The limits of detection (LOD) and quantification (LOQ) in olive oil were 0.02 mg L⁻¹ and 0.1 mg L⁻¹, respectively. MIPs extraction was much more effective than traditional C18 reverse-phase solid phase extraction.     

Syntheses of molecularly imprinted polymers: Molecular recognition of cyproheptadine using original print molecules and azatadine as dummy templates

The use of custom-made polymeric materials with high selectivities as target molecules in solid-phase extraction (SPE), known as molecularly imprinted solid-phase extraction (MISPE), is becoming an increasingly important sample preparation technique. However, the potential risk of leakage of the imprinting molecules during the desorption phase has limited application. The use of a mimicking template, called a dummy molecular imprinting polymer (DMIP), that bears the structure of a related molecule and acts as a putative imprinting molecule may provide a useful solution to this problem.In the current study, cyproheptadine (CPH) and azatadine (AZA) were used as templates in the development of an MIP and DMIP for acrylic acid and methacrylic acid monomers. Our results indicate that DMIPs have equal recognition of CPH, avoiding the problem of leakage of original template during the desorption phase relative to MIPs synthesized in presence of the print molecule CPH. Examination of the surface structure of the two polymer products by SEM shows appreciable differences in structural morphology and function of the monomers employed. These results are well supplemented by data obtained for swelling ratios and solvent uptake. Molecular modelling of CPH and AZA suggests that both substrates are similar in shape and volume.     

Comparison of normal and reversed-phase solid phase extraction methods for extraction of beta-blockers from plasma using molecularly imprinted polymers

A molecularly imprinted polymer (MIP) prepared using propranolol as template, methacrylic acid (MA) and ethylene glycol dimethacrylate (EGDMA) was used to develop SPE methods in "reversed-" and normal phase mode for an analogue of propranolol (M47070) with another analogue (M45655) used as an internal standard. The compounds were also extracted in reversed-phase mode onto a non-imprinted polymer. It was necessary to employ a protein precipitation step ahead of MIP-SPE in order to facilitate downstream analysis. High extraction efficiencies and linear calibration ranges were achieved using both reversed-phase (RP) and normal phase (NP) MIP-based methods. Extraction efficiencies were lower on the non-imprinted polymer indicating stronger retention by the MIP. This stronger retention was attributed to selective imprint-based binding by the MIP that was not available for the non-imprinted polymer. Although clean extracts were obtained in both RP and NP modes, low level interference from template-related impurities or degradation products compromised detection of M47070 at low concentrations for the MIP-based methods. This interference made accuracy of the MIP-based methods poorer at low concentrations. The reversed-phase method showed marginally better accuracy and precision than the normal phase method.     

High-performance liquid chromatographic determination of sotalol in plasma. I. Application to the disposition of sotalol enantiomers in humans.

Two high-performance liquid chromatographic analytical methods have been developed for the measurement of dl-sotalol or d-sotalol and l-sotalol in plasma, using dl-atenolol as internal standard. Quantitation of dl-sotalol was carried out, following solid-phase extraction, on a 5-microns C18 reversed-phase column, with a mobile phase containing acetonitrile, ion-pairing reagent and distilled water, using ultraviolet detection at 235 nm. Quantitation of d-sotalol and l-sotalol was based on derivatisation with the chiral agent S-(-)-alpha-methylbenzyl isocyanate, followed by chromatographic separation on a 3-microns C18 reversed-phase column, with a mobile phase containing methanol, glacial acetic acid and distilled water, with fluorimetric detection at 220 nm excitation and 300 nm emission. A preliminary application of the latter method suggests that the disposition of sotalol in humans is not enantioselective.