分子烙印聚合物固定相分离咖啡因和茶碱的研究

分子烙印是一种新兴的分子识别技术,利用该技术可制备对烙印分子具有“预定”识别能力的高分子聚合物,即分子烙印聚合物（MIP）,从而可以对性质和组成相近的组如对映体等进行分离^[1,2],咖啡因与茶碱的分子烙印聚合物的制备以及二者分析已有报道^[3-9],但存在两种完全相反的结论。一种观点认为,即使以咖啡因为烙印分子,所制备的聚合物对咖啡因分子的选择性吸附能力也小于茶碱^[3-6]。而另一种观点则认为,在一定条件下,如以咖啡因分子为烙印分子的烙印聚合物对咖啡因分子具有更强的吸附能力^[7-9]。本文分别采用茶碱和咖啡因作为烙印分子,以甲基丙烯酸等为功能单体,在不同条件下制备了多种非共价型分子烙印聚合物,并系统地考察了其作 为HPLC固定相对咖啡因和茶碱的分离能力,同时也对烙印分子应具备的条件加以探讨。     

Determination of Tetracyclines by Solid-Phase Extraction with a Molecularly Imprinted Polymer and High-Performance Liquid Chromatography

Tetracyclines are widely used antibiotics classified as emerging pollutants and may lead to an increase in bacterial resistance in the environment. In order to determine these compounds at low concentrations, a water-compatible molecularly imprinted polymer was developed for solid-phase extraction followed by high-performance liquid chromatography analysis. The monomers 2-hydroxyethyl methacrylate and glycerol dimethacrylate were added 1 h after the start of the synthesis to provide hydroxyl groups on the polymer surface. This hydrophilic layer established hydrogen bonds with water, minimizing interferences of this solvent in the analyte-polymer complex, increasing analyte adsorption. The polymer was then used for solid-phase extraction to preconcentrate the tetracyclines. The method provided low limits of quantification (5 µg L^?1), good linearity, precision, and accuracy for tetracyclines, with preconcentration factors of 14, 19, 29, and 41 for oxytetracycline, tetracycline, chlortetracycline, and doxycycline, respectively.     

Facile Preparation of an Ionic Liquid Composite Mesoporous Polymer as a Solid Phase Extraction Adsorbent for the Separation and Purification of Flavonoids from Chamaecyparis obtusa

A new ionic liquid composite mesoporous polymer (ILCMP) was synthesized by one-pot copolymerization. The obtained ILCMP with good morphology, good pore diameter distribution, and high adsorption capacity was successfully applied as the sorbent in solid-phase extraction (SPE) to extract and separate quercitrin and myricetin from Chamaecyparis obtusa. 87.8–101.8% of satisfactory recoveries were obtained with RSDs less than 6.2% and the amounts of quercitrin and myricetin in Chamaecyparis obtusa were 0.38 and 0.12 mg/g, respectively. The proposed ILCMP-SPE-HPLC method was applied for the separation, purification, and determination of flavonoids from natural products.     

Application of Ionic Liquid Modified Silica for Solid-Phase Extraction of Polysaccharides from Laminaria japonica

Silica-confined ionic liquids were synthesized for solid-phase extraction of polysaccharides, which was determined by high-performance liquid chromatography coupled with RI detection. The sorbent with amino-imidazolium groups was found to be the optimal material by a comparison of the adsorption capacity of fucoidan and laminarin onto different synthetic sorbents. The proper elution solvents for both laminarin and fucoidan were decided from practical tests. The sorbent performed stably and selectively, demonstrating potential applications in the separation of hydrophilic biomacromolecules, such as polysaccharides.     

Bamboo Charcoal as Solid-Phase Extraction Adsorbent for the Determination of Organophosphorus Pesticides in Water Samples by High-Performance Liquid Chromatography

In this paper, bamboo charcoal was successfully developed for the solid-phase extraction adsorbent for the determination of six organophosphorus pesticides in water samples. After the bamboo charcoal was pretreated and packed in the solid-phase extraction cartridge, the organophosphorus pesticides in water samples were carried out the solid-phase extraction. To establish a perfect solid-phase extraction procedure, the experimental conditions including the eluent, eluent volume, pH of the sample, flow rate of the sample, and loading volume of the sample were all investigated. When 100 mL water samples in the pH range of 6–7 were loaded with the flow rate of 2.5 mL · min^?1 and then eluted with 10 mL acetonitrile, the proposed extraction method was validated by the recovery, correlation coefficient (R²), repeatability (RSD, n = 7) and LODs, which were 69.6–93.4%, 0.9982–0.9998, 2.9–5.6%, and 0.08–1.04 µg · L^?1, respectively. Furthermore, the analysis of the tap, snow, and river water samples demonstrated the feasibility of the proposed SPE method for real water samples. Based on the aforementioned factors, it could be concluded that bamboo charcoal was a good solid-phase extraction adsorbent, and this proposed solid-phase extraction method was suitable for the effective enrichment and determination of the organophosphorus pesticides in water samples.     

Determination of Polysaccharides in Undaria pinnatifida by Ionic Liquid-Modified Silica Gel Size Exclusion Chromatography

Ionic liquid-modified silica particles with a large pore size were synthesized and used as the stationary phase for size exclusion chromatography coupled with a refractive index detector for the determination of polysaccharides, such as fucoidan, alginic acid, and laminarin from Undaria pinnatifida (seaweed). The molecular weight of polysaccharide was determined by a dextran standard curve (5–1100?kDa). The ionic liquid-modified silica column exhibited excellent size exclusion properties in separating laminarin from other components. The 1-butyl-3-methyl-imidazolium bis-(trifluoromethylsulfonyl)-amino silica column has superior resolution in laminarin separation than the other columns because the amino-group in ionic liquid provide π–π interactions due to aromaticity of the ring structure, which enhances the effect of the hydroxyl group in the target compound separation. The concentrations of polysaccharides were calculated using a standard linear equation to be 0.332–0.484?mg/g of fucoidan, 0.207–0.301?mg/g of alginic acid, and 0.154–0.297?mg/g of laminarin.     

离子液体-加速溶剂萃取-高效液相色谱法测定蜜饯中的有机酸类防腐剂

以离子液体氯化1-辛基-3-甲基咪唑盐([Omim]Cl)的水溶液为萃取剂,采用加速溶剂萃取结合高效液相色谱法测定了蜜饯中苯甲酸、山梨酸、肉桂酸等有机酸类防腐剂,优化了加速溶剂萃取实验参数,最佳萃取条件为:离子液体浓度为0.1mol/L,萃取时间为5min,萃取温度为80℃。在最佳条件下,有机酸类防腐剂的检出限为0.4～27.7μg/L。将本方法用于蜜饯样品的检测,回收率为78.2%～113.9%。实验结果表明:离子液体-加速溶剂萃取法快速、高效。     

Determination of Lignans in Schisandra sphenanthera and Schisandra chinensis Using Ionic Liquid-based Ultrasonic-assisted Extraction and High-performance Liquid Chromatography

A green, rapid and precise sample pretreatment technique, IL-based UAE(ionic liquid-based ultrasonic-assisted extraction), was coupled with high-performance liquid chromatographic separation to identify the main effective components in Schisandra sphenanthera(S. sphenanthera) and Schisandra chinensis(S. chinensis) including schisantherin A, schisandrin A, and deoxyschizandrin. Four different types of ionic liquids have been investigated, finally[C₆MIM] [BF₄] was used as the extraction solvent. A powder form of S. sphenanthera and S. chinensis was mixed with the[C₆MIM] [BF₄] to produce a suspension. This suspension was ultrasonically extracted in a water bath at room temperature. Several of the process parameters were optimized, including the type of ionic liquid used and its volume, the sample amount, the size of the sample particle, the extraction time, etc. HPLC calibration curves were established for all the analytes and proved to be linear(r>0.9999). The lowest detection level for schisandrin A was 0.12 μg/mL, for schisantherin A was 0.08 μg/mL, and for deoxyschizandrin was 0.10 μg/mL. The recoveries of the target compounds were from 74.19% to 109.33%. The standard deviations for detection were generally no more than 6.31%. In contrast to conventional extraction methods, the IL-based UAE did not involve volatile organic volatile solvents, and the analysis time, required sample and solvent volumes were also lower than those of the conventional techniques.     

咖啡因分子印迹固相萃取柱的制备及应用

以咖啡因作为模板分子,α-甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂,制备了咖啡因分子印迹聚合物(MIP)。与非印迹聚合物(NIP)相比,MIP对咖啡因具有更高的吸附容量和选择性,MIP和NIP对咖啡因的最大静态吸附量分别为28.1和16.5mg/g,相对选择因子为1.25。以咖啡因分子印迹聚合物为固相萃取填料,结合高效液相色谱(HPLC),建立了茶水中咖啡因浓度及人饮茶后血清中咖啡因浓度的检测方法。考察了洗脱剂种类和用量对咖啡因回收率的影响。当萃取柱依次以2mL水活化,水溶液上样,2mL水淋洗,6mL甲醇-乙酸(9∶1,V/V)洗脱,咖啡因在MIP固相萃取柱上的回收率达到97.5%,而在NIP柱上的回收率仅为54.9%。     

同时测定体液中咖啡因和茶碱的薄层色谱扫描法

研究了同时测定血清、尿样中的咖啡因和茶碱的薄层色谱定量法。在ＧＦ２５４硅胶板上，用乙酸乙酯－氨水（Ｖ乙酸乙酯∶Ｖ氨水＝９６∶４）的二元展开体系能将这两种生物碱有效地分离。其Ｒｆ值为咖啡因０．４６，茶碱０．１６。分离后的试样用薄层色谱扫描仪进行扫描定量，测定波长２７２ｎｍ，线性范围咖啡因０．００９７～１．９４μｇ，茶碱０．００９０～１．８０μｇ。血清及尿样的加标回收率在９５．８％～１０６．５％之间，相对标准偏差２．９５％～３．５０％。本法较为简便、快速、准确     

Extraction of Catechin Compounds from Green Tea with a New Green Solvent

An emerging green solvent called a deep eutectic solvent（DES） was applied to the extraction and determination of catechin（C）,（＋）epicatechin gailate（ECG） and （-）epigallocatechin gallate（EGCG） from Chinese green tea.After evaluating different combinations of them by extraction methods and DESs,a DES-based extraction method was established and optimized by a systematic investigation of the influencing factors.As a result,a total of 3.629,35.25 or 114.2 mg/g catechin,（＋）epicatechin gallate or （-）epigaliocatechin gallate were extracted respectively under optimal conditions with extraction efficiencies of 82.7％,92.3％ and 97.0％,respectively.By comparing with other common used solvents for extracting catechin compounds,DESs were proved to be potential extraction solvents for bioactive ingredients.     

Evaluation of Polyaniline as a Sorbent for SPE of a Variety of Polar Pesticides from Water Followed by CD-MEKC-DAD

A recently synthesized polyaniline (PANI) has been used and evaluated as a sorbent for solid-phase extraction of a variety of polar pesticides and some of their degradation products from water samples. Several classes of pesticides including phenoxy acids, triazines, ureas, oxime carbamates and carbamates were selected for this study. The determination of these pesticides was carried out using cyclodextrin modified micellar electrokinetic chromatography equipped with diode array detection. The recovery results using PANI were compared with those obtained by C₁₈, Isolute ENV+, Oasis HLB and LiChrolut EN. Effect of humic acid, as a major interference, on extraction recovery was also studied. The performance of the method was evaluated by analysis of tap and river water. The RSD of method was between 6 and 14% (n=3) and detection limits were in the range of 0.01–0.5 g L^–1 using 350-mL water samples.     

Synthesis and Characterization of a Molecularly Imprinted Polymer for Preconcentration of Clothianidin in Environmental Samples

A molecularly imprinted polymer for the selective solid-phase extraction of clothianidin was prepared using the analyte as a template, methacrylic acid and styrene as functional monomers, ethylene glycol dimethacrylate as the cross-linker, acetonitrile as a porogen, and 2,2-azobisisobutyronitrile as an initiator. The polymer was characterized by scanning electron microscopy and infrared spectroscopy. Adsorption measurements indicated that the molecularly imprinted polymers exhibited good recognition ability and fast dynamics toward clothianidin. Using this imprinted polymer as a sorbent, a new method of molecularly imprinted solid phase extraction coupled to high performance liquid chromatography for the determination of clothianidin residues was developed. The molecularly imprinted solid phase extraction procedure was optimized to purify and enrich clothianidin residues in river water, soil, tomatoes, grapes, and Chinese cabbage. The average recoveries of clothianidin spiked at 0.005 to 0.05 mg/L were 84.32 to 89.49% in river water with a relative standard deviation 2.22 to 4.79% (n = 3). The average recoveries of clothianidin spiked at 0.05 to 0.5 mg/kg were 85.49 to 96.36% in soil, grapes, Chinese cabbage, and tomatoes, with a relative standard deviation of 2.40 to 6.02% (n = 3). Overall, this study provides a sensitive and effective method for the accurate determination of clothianidin residues in environmental samples.     

Rapid Determination of Phenolics in Food Packaging by Magnetic Solid-Phase Extraction and High-Performance Liquid Chromatography

A method for magnetic solid-phase extraction was developed for the preconcentration of bisphenol A, bisphenol AF, tetrabromobisphenol A, and 4-tert-octylphenol from food containers and packaging materials. Cetyltrimethylammonium bromide was added to a solution of magnetic nanoparticles to enhance adsorption of the analytes prior to high-performance liquid chromatography. The effects of the amount of surfactant, the amount of magnetic nanoparticles, the pH, the adsorption time, the desorption solution, and the reuse of the extractant were optimized. The linear dynamic ranges were from 0.05 to 25 milligrams per liter. The limits of detection were between 1.21 and 2.48 micrograms per liter, the limits of quantification were from 4.03 to 8.27 micrograms per liter, and the relative standard deviations were between 2.2 and 4.1 percent. This magnetic solid-phase extraction approach was successfully employed for the analysis of plastics with recoveries from 88.0 to 101.1 percent and relative standard deviations between 2.3 and 5.4 percent.     

An Ionic Liquid Loaded β-Cyclodextrin-Cross-Linked Polymer as the Solid Phase Extraction Material Coupled with High-Performance Liquid Chromatography for the Determination of Rhodamine B in Food

A novel method for separation and determination of rhodamine B in food samples is described. The work is based on the utilization of an ionic liquid loaded β-cyclodextrin cross-linked polymer coupled with high-performance liquid chromatography for the determination of rhodamine B. The inclusion interaction of the ionic liquid-β-cyclodextrin cross-linked polymer with rhodamine B was studied by FTIR. Under optimum conditions, the preconcentration factor achieved for this method was approximately 20. The linear range, detection limit, and relative standard deviation were 0.80 to 130.0 µg L^?1, 0.09 µg L^?1, and 0.66% (n = 3, concentration = 10.0 µg L^?1), respectively. The technique was successfully applied for determination of rhodamine B in food samples.     

Selective Solid-phase Extraction of Aloe Emodin from Aloe by Molecularly Imprinted Polymers

The extraction and separation of aloe emodin were optimized via selective molecularly imprinted solid-phase extraction. Molecularly imprinted polymer was prepared from the functional monomer, methacrylic acid and a mixture of ethanol/dodecanol(90/10, volume ratio) as porogen. It overcomes the common problems of imprin-ting biological polar compounds and shows high selectivity compared favorably with those of non-imprinted polymer and commercially available C₁₈ and silica cartridges in similar aloe emodin tests. Good linearity was obtained between 0.002 and 2.5 mg/mL(r²=0.998) with relative standard deviations below 3.3%.     

固相萃取-高效液相色谱法测定水中BPA、NP和OP含量

采用国产新型D4020大孔吸附树脂自制固相萃取柱,研究了柱长、上样速度、样品溶液的pH、盐浓度等因素对壬基酚、辛基酚和双酚A吸附率的影响,确定了最佳固相萃取条件,建立了固相萃取-高效液相色谱测定水中痕量壬基酚、辛基酚和双酚A的分析方法.该法双酚A、壬基酚和辛基酚的检出限分别为0.432 μg/L、0.998 μg/L和1.336 μg/L,回收率为91%～96%,相对标准偏差(RSD)为1.5%～5.6%.方法简便快速、成本低廉,灵敏度高,准确度好,用于实际水样分析,取得满意结果.     

Simultaneous Voltammetric Determination of Theophylline and Guaifenesin Using a Multiwalled Carbon Nanotube‐Ionic Liquid Modified Glassy Carbon Electrode

A glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNTs) and a hydrophobic ionic liquid (IL), was used for the simultaneous voltammetric determination of theophylline (TP) and guaifenesin (GF). The results showed that the oxidations of TP and GF were facilitated at modified electrode and peak‐to‐peak separation at MWCNT? IL/GCE (252 mV) was larger than that observed at unmodified GCE (165 mV). Voltammetric signals for TP and GF exhibited linear ranges of 0.5 to 98.0 µM (R²>0.99) and 1.5 to 480.0 µM (R²>0.99), respectively. The method was used to estimate TP and GF contents in some real samples.     

Synthesis of surface molecularly imprinted silica micro-particles in aqueous solution and the usage for selective off-line solid-phase extraction of 2,4-dinitrophenol from water matrixes

Very severe reaction conditions are required in the conventional synthesis of molecularly imprinted polymers (MIPs), which is unfavorable to their applications in chemical separation and analysis. A simple surface molecular imprinting approach was developed to synthesize MIP-coated SiO₂ micro-particles in aqueous solutions. The ¹H NMR and UV-vis spectroscopic analysis indicated that via hydrogen bonding, the functional monomer (o-phenylenediamine) can associate with the target (template) 2,4-dinitrophenol (2,4-DNP), as a model compound of organic pollutants, to form a precursor in aqueous solution. The copolymerization of this precursor and the free monomer was performed in the aqueous suspension of surface modified SiO₂ particles, leading to the formation of MIP-coated SiO₂ micro-particles. The MIP-coated silica particles were characterized with FT-IR, TGA, and UV-vis solid-state reflection spectroscopy, and were further demonstrated to have high adsorption capacity, excellent selectivity and site accessibility for 2,4-DNP. The new absorbent was successfully used in solid-phase extraction (SPE) to selectively enrich and determine 2,4-DNP in aqueous samples. The experimental results indicated that the MIP-SPE column yielded recoveries higher than 92% with R.S.D. <2.8%, much better than the commercial C₁₈-SPE column, which produced a recovery less than 30% with R.S.D. <3.0%.     

Solid-Phase Extraction and High-Performance Liquid Chromatography for Simultaneous Determination of Important Bioactive Ginsenosides in Pharmaceutical Preparations

A robust method based on high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection has been developed for simultaneous determination of six important ginsenosides (Rg1, Re, Rb1, Rc, Rb2, and Rd) in pharmaceutical preparations. For sample preparation, simple and efficient extraction by ultrasonication, combined with solid-phase extraction (SPE) for clean-up, was effective without consuming large amounts of solvent. Chromatographic separation was performed on an ODS column with optimized gradient elution by means of a dual-solvent-pumping system. The validated method results in excellent separation, and quantitative determination is highly precise and accurate. The problem of co-elution of ginsenosides Rg1 and Re is also solved, with good resolution (R_S approx. 1.5). Intraday variation was between 0.2 and 4.4% and interday variation was between 0.4 and 6.5% (n=5 for both). The accuracy was satisfactory—in the range 93.9 to 103.4% from replicate evaluation at three different spiking concentrations. Overall limits of detection based on a typical injection volume of 5 μL were from 1.16 to 1.58 ng μL⁻¹. The validated method enabled complete assessment for quality control of ginseng samples. The technique may be performed with less sample preparation and, consequently, reduced possibility of sample loss.