【精品文档】24中英文双语外文文献翻译成品：基于共价有机框架的磁性吸附剂的多环芳烃固相萃取及其HPLC定量字符连接

此文档是毕业设计外文翻译成品（ 含英文原文+中文翻译），无需调整复杂的格式！下载之后直接可用，方便快捷！本文价格不贵,也就几十块钱！一辈子也就一次的事！外文标题：A covalent organic framework-based magnetic sorbent for solid phase extraction of polycyclic aromatic hydrocarbons, and and its hyphenation to HPLC for quantitation外文作者：Rong Wang ,Zilin Chen文献出处:Microchimica Acta , 2017 (5751) :1-8(如觉得年份太老，可改为近2年，毕竟很多毕业生都这样做)英文4589单词， 24889字符(字符就是印刷符)，中文7792汉字。Abstract A novel covalent organic framework based mag- netic adsorbent was developed for magnetic solid phase ex- traction (MSPE) of polycyclic aromatic hydrocarbons (PAHs). Covalent organic framework-LZU1 (= Lan Zhou University-1) was covalently immobilized onto polyethyleneimine-functionalized magnetic nanoparticles (COF-LZU1PEIFe3O4), and the resulting material was characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The effects of the pH value of sample solution, percentage of acetonitrile, ex- traction time and sampling volume on MSPE of six PAHs were investigated. The COF-LZU1PEIFe3O4 displays high extraction efficiency for the PAHs such as pyrene, benzoapyrene, fluoranthene, benzaanthracene, benzoafluorathene and dibenza,hanthracene. Following desorption with acetonitrile, the PAHs were quantified by HPLC. The MSPE-HPLC method shows low limit of detec- tion (0.220 pg mL1), wide linear range and good reproduc- ibility (relative standard deviations 4.4% for intra-day and inter-day precision). The method was successfully applied to determine PAHs in environmental samples. Good recoveries were obtained, ranging from 90.9 to 107.8% for water samples and 85.1 to 105.0% for soil samples.Keywords Covalent organic framework . COF-LZU1 . Magnetic solid phase extraction . Environmental analysis . Trace analysis . HPLCIntroductionCovalent organic frameworks (COFs) are a class of crystalline porous materials that consist of light elements (C, H, B, N, O etc.) and are connected through strong covalent bonds 17. These materials possess much fascinating properties including high specific surface area, excellent thermal stability, high porosity, and low density. With these unique properties, COFs have aroused intensive interest of scientists for the greatpotential application in diverse areas 2, 4, such as gas storage 810, gas adsorption 11, 12, photoelectricity 13, 14, ca- talysis 15, 16 and chromatographic separation 1719. However, there are still few reports focusing on their perfor- mance in the field of sample pretreatment. Metalorganicframeworks (MOFs) are another novel class of porous mate- rials similar to COFs, which have shown to be promising materials as sorbents for sample preparation in many pioneer works 2024. As the analogues of MOFs, COFs should possess great application potential in sample preparation.Hydrazone covalent organic frameworks have been synthe- sized and applied to the solid-phase microextraction (SPME) of pyrethroids 25 and pesticides 26 in vegetables. Therefore, it is possible to develop the application of COFs as promising adsorbent in sample pretreatment.Since the first discovery of COF materials in 2005 1, a variety of COFs have been reported. Imine-linked COF-LZU1 (Lan Zhou University-1) was first designed and synthesized by Wang group in 2011 15, which was constructed with 1,3,5-triformylbenzene and 1,4-diaminobenzene through Schiff base reaction. COF-LZU1 has a two-dimensional (2D) layered-sheet structure and possesses large number of benzene rings and imine groups. Unlike boron-containing COFs that linked by boroxine or boronate-ester groups, COF-LZU1 is highly stable in water and most organic sol- vents 15. Niu et al. explored its performance as the stationary phase of capillary electrochromatography for separating or- ganic molecules 19. The results indicated that COF-LZU1 can offer strong stacking interaction and hydrophobic effect with the analytes. This suggests that it may be an excellent enrichment media for compounds with abundant system.Sample preparation is a critical step prior to analysis, espe-cially when complex samples are present. Over the past few decades, many new sample pretreatment techniques with low solvent consumption and low sample handling have been de- veloped and applied to extract target compounds from different matrices 27, 28. Among these techniques, magnetic solid-phase extraction (MSPE) has attracted increasing atten- tion due to its large adsorption capacity and high extraction efficiency 29. Additionally, magnetic nanoparticles (MNPs) can be rapidly separated from sample matrix via an external magnet, which would simplify operation procedure and short- en analysis time. Considering of the features of COF-LZU1 and MSPE, we attempted to prepare a COF-LZU1 functionalized MNPs and apply to magnetic solid-phase extraction. In order to achieve the immobilization of COF-LZU1, polyethyleneimine-functionalized Fe3O4 nanoparticles (PEI Fe3O4) 30 were chosen as the magnetic support. With the numerous active amino groups in the structure of PEI, COF-LZU1 can be covalently bonded to the surface of PEIFe3O4 through Schiff base reaction.Polycyclic aromatic hydrocarbons (PAHs) are well-known environment pollutants, which are considered to be carcino- genic and mutagenic to human beings. It is of great impor- tance to monitor and control the amount of PAHs in environment. Since the concentration of PAHs in environmental samples is usually in trace levels, it is necessary to enrich PAHs by efficient sample pretreatment method before instrumental analysis 3134. Considering the properties of COF-LZU1 and PAHs, COF-LZU1 based MSPE method was expected to exhibit high extraction efficiency and capacity for analysis of PAHs in environment. Herein, in this work, we reported the fabrication of a novel COF-LZU1 functionalized MNPs (COF- LZU1PEIFe3O4) and its application for the MSPE of PAHs. Fe3O4 nanoparticles were first coated with PEI, then COF-LZU1 was grown on the surface of MNPs attributing to the covalent bonding between the PEI layer and COF- LZU1. The morphology and surface properties of nanoparticles were characterized by transmission electron microscopy (TEM) and Fourier-transformed infrared spectroscopy (FT-IR). COF-LZU1PEIFe3O4 were used as magnetic adsorbent for extraction of PAHs from environmental samples. The extraction performance was systematically investigated. To the best of our knowledge, it is the first time that COF-LZU1 is immobilized on solid support for sample preparation.ExperimentalChemicals and materials1,3,5-Triformylbenzene, 1,4-diaminobenzene, pyrene (PYR), benzoapyrene (BaPY), phenanthrene, anthracene, naph- thalene, 1-naphthol were purchased from SigmaAldrich (MO, USA, ). Fluoranthene (FLU), benzaanthracene (BaAN), benzoafluorathene (BaFL), dibenza,hanthracene (Da,hAN) were obtained from TCI (Shanghai, China, ). 4-Phenylphenol, 4-vinylbiphenyl and 1,4-dioxane, polyethyleneimine (PEI, Mw 70,000 g mol1, 50% (w/v) aqueous solution) were bought from Aladdin Reagent (Shanghai, China, www. ). Methanol and acetonitrile were HPLC grade (Tedia, OH, USA, ). Other reagents were analytical grade. Purified water was obtained from a Milli-Q system (MA, USA, / US/en).InstrumentationThe chromatographic analysis was performed by a Shimadzu 20A HPLC system (Tokyo, Japan, . cn), which equipped with two 20A pumps, a six-port valve, a 20A UV detector, and a 10A fluorescent detector. The chromatographic separation was carried out by a C18 column (150 mm 4.6 mm i.d., 5 m particle size, GL Science, Tokyo, Japan, ). The mobile phaseconsisted of methanol and water (89/11, v/v) and the flow rate was 1.0 ml min1. The detection wavelength of fluorescent detector was set at 290 nm (exiting wavelength) and 430 nm (emission wavelength), while the detection wavelength of UV detector was set at 254 nm. The column temperature for HPLC separation was set at 30 C.Fourier-transformed infrared spectroscopy (FT-IR) charac- terization was performed on Thermo Nexus 470 FT-IR system (MA, UAS, ). The transmission electron microscopy (TEM) image was obtained by a JEM-2100 (HR) transmission electron microscope (TEM) (JEOL, Tokyo, Japan, https:/www.jeol.co.jp/en/).Preparation of COF-LZU1PEIFe3O4PEIFe3O4 was prepared following Amals method 30. Briefly, FeCl24H2O (0.7 g) was firstly dissolved in 80 mL of distilled water. Then 10 mL of KNO3 (2.0 M), 10 mL of NaOH (1.0 M) and PEI (1.7 g) were added to this solution sequentially under nitrogen atmosphere. After being stirred for 2 h at 90 C, the synthesized nanoparticles were collected by a magnet, followed by washing with water for several times.1,3,5-Triformylbenzene (3 mg), 1,4-diaminobenzene(3 mg) were dissolved in 3 mL of 1,4-dioxane and followed by the addition of 60 L of 3 M aqueous acetic acid. PEI Fe3O4 (100 mg) were suspended in above solution with ultrasonication. For modification of COF-LZU1, the temper- ature was rose to 150 C and reacted for 24 h. Finally, the COF-LZU1PEIFe3O4 were washed with ethanol thor- oughly and dried in the oven (60 C).COF-LZU1PEIFe3O4 based MSPE proceduresPAHs standard were dissolved in 20 mM phosphate buffer (pH 9, containing 1% acetonitrile, v/v) at certain concentra- tion. COF-LZU1PEIFe3O4 (5 mg) were carefully weighed and mixed with 20 mL of sample solution. The mix- ture was stirring for 30 min with the assistant of a magnetic stirring apparatus (two bottles containing the mixture and stir ring bar were placed together and stirring). Before collection of nanoparticles, the stirring bar was removed by a magnet under stirring. After that, the nanoparticles were separated from the solution by an external magnet. The step of desorption was carried out by sonication for 3 min with 200 L acetonitrile. Then the eluent (20 L) was injected into the HPLC system for analysis.Sample preparationTo investigate the application in real samples of this method,water and soil samples were collected. Tap water was obtained from laboratory and lake water was from East Lake, Wuhan. Water samples were filtered through 0.45 m nylon membrane and then added 1% acetonitrile (v/v). Two soil samples were collected, one was from lakeshore of East Lake (soil A) and the other one was from the land beside a local road in Wuhan (soil B). The soil samples were firstly dried and grounded into powder. 5 g soil powder were mixed with 20 mL acetonitrile and ultrasonicated for 1 h. The supernatant was then collected after centrifuged at 10000 rpm (6932 g) for 10 min. The solution was con- densed to dryness through a rotary vacuum evaporation, followed by being redissolved in 20 mL acetonitrile for soil A sample and 1 mL for soil B sample. 50 L solution of soil A sample and 150 L acetonitrile were diluted to 20 mL with 20 mM phosphate buffer (pH 9) and loaded for MSPE. 20 L soil B sample solution and 180 L acetonitrile were diluted to 20 mL with 20 mM phosphate buffer (pH 9) and loaded for MSPE.Results and discussionChoice of materialsCOF-LZU1 possesses many remarkable characteristics: ex- cellent thermal stability, low density, high surface area, and permanent porosity. The high surface area and porosity can improve the loading capacity of adsorbent. It is highly stable in water and most organic solvents 15. COF-LZU1 is pre- pared from 1,3,5-triformylbenzene and 1,4-diaminobenzene through Schiff base reaction. There are rich benzene rings and imine groups in its structure. Thus it can offer strong stacking interaction and hydrophobic effect with compounds with abundant system. All these characteristics make it an attractive material for solid phase extraction. Moreover, as a new class of covalent porous crystalline polymers, it is significant to broaden the application of COFs.Preparation of COF-LZU1PEIFe3O4A COF-LZU1-modified magnetic nanoparticles was prepared in this work, as shown in Fig. 1. Fe2+ was firstly formed Fe(OH)2 in the presence of NaOH, then heated at 90 C after the addition of PEI solution. During the formation of Fe3O4 nanoparticles, PEI was self-assembled on the surface via elec- trostatic interaction. Amino groups of PEI layer were active to participate the formation of COF-LZU1 through the Schiff- base reaction, resulting in the immobilization and growth of COF -LZU1 on magnetic nanoparticles. The aromatic rings and imine groups of COF-LZU1 can offer strong stacking interaction and hydrophobic effect with the analytes. Therefore, COF-LZU1PEIFe3O4 can exhibit high extrac- tion efficiency for PAHs.The structure and the thickness of COF-LZU1 would affect the interaction between the target compounds and the COF-LZU1PEIFe3O4. Some parameters that can affect modi- fication of COF-LZU1 were investigated. These include the reaction temperature, the concentration of ligands and the volume of aqueous acetic acid as can be seen in the supporting information. The optimized conditions were selected for the coating of COF-LZU1 as follows: reaction temperature: 150 C, concentration of ligands: 1 mg mL1 and volume of 3 M aqueous acetic acid: 60 L.Characterization of COF-LZU1PEIFe3O4FT-IR spectroscopy was employed to characterize the functional moieties of the COF-LZU1PEIFe3O4 (Fig. 2). The absorption band at 581 cm1 is assigned to stretching vibration of Fe-O for Fe3O4 nanoparticles. The absorption bands at 3404 cm1,1688 cm1 are caused by stretching of N-H and C = O, respectively. The peak at 1614 cm1 corresponds to the C = N stretching for imine. The peaks at 614 cm 1 , 679 cm1,831 cm1 are characteristic absorption of C-H for substituted aromatic. The FT-IR analysis result indicates the formation of COF-LZU1, suggesting the COF-LZU1 has been successfully modified on the sur- face of Fe3O4.The morphology of PEIFe3 O4 and COF-LZU1PEIFe3O4 nanoparticles were investigated by TEM. As shown in Fig. 3, the obtain nanoparticles are cubic in shape and well-dispersed, with a mean diameter about 40 nm (average face-centered diagonal). It can be seen that the surface of PEIFe3O4 was smooth (Fig. 3b). After modification of COF-LZU1, a thin and rough polymer layer is observed (Fig. 3d), indicating that the COF-LZU1 is immobilized onto the surface of PEIFe3O4.Optimization of sampling conditionsAs mentioned above, the aromatic rings and imine groups of COF-LZU1 can offer strong -interaction and hydrophobic effect with the analytes. Therefore, six PAHs compounds were selected to test the enrich- ment performance of COF-LZU1PEIFe3O4 due to their hydrophobic properties and demands of low- content determination. To achieve higher extraction effi- ciency, the following parameters were optimized: (a) pH of sample solution; (b) acetonitrile content; (c) extrac- tion time; (d) sampling volume. Respective data and Figure are given in the Electronic Supporting Material. The following experimental conditions were found to give best results: (a) A sample pH value of 9.0; (b) acetonitrile content of 1%; (c) extraction time of 30 min; (d) sample volume of 20 mL.Enrichment performance of COF-LZU1PEIFe3O4Extraction performance of COF-LZU1PEIFe3O4 was evaluated under the optimized conditions. Sample solu- tion containing 0.5 ng mL1 was extracted by COF- LZU1PEIFe3O4, then analyzed with HPLC (Fig. 4b). For comparison, the six PAHs standard solution (0.5 ng mL1) was directly injected into HPLC system for analysis (Fig. 4a). Significant extraction efficiency is observed for COF-LZU1PEIFe3O4. Enrichment fac- tors (FE) of COF-LZU1PEIFe3O4 towards PAHs were determined and calculated by: FE = Cg/C0; where C0 is defined as the concentration of PAHs in the initial sample solution and Cg is the PAHs concentration in desorption solution after MSPE. FE for six PAHs are calculated to be 39 for FLU,40 for PYR,72 forBaAN,86 for BaFL,86 for BaPY, 90 for Da,hAN (theoretical enrichment factor is 100-fold), as shown in Table S1.To further understand the adsorption mechanism of COF-LZU1PEIFe3O4 for analytes, other PAHs and aromatic compounds were also loaded onto MSPE, the extraction factors are listed in Table S1. FE is positively related mostly to the number of condensed rings and log KOW of compounds, for example, FE(BaPY) FE(PYR) FE(phenanthrene), which suggests that the adsorption of COF-LZU1PEIFe3O4 is mainly attributed to stack- ing and hydrophobic interaction. However, 4- phenylphenol and 1-naphthol with lower log KOW value (3.20 and 3.09 respectively) shows more adsorption on COF-LZU1PEIFe3O4 than naphthalene, which pos- sesses a log KOW value of 3.33. It seems that the hydro- gen bonds interaction is involved in the adsorption of OH groups containing compounds by forming O- HN = C. BaFL and Da,hAN possess same log KOW value, while Da,hAN shows more adsorption on COF- LZU1PEIFe3O4 than BaFL, which suggests that molecular weight is also involved in the adsorption be- sides stacking and hydrophobic interaction.Reusability of COF-LZU1PEIFe3O4Reusability is an important factor for evaluating the efficiency of sorbents. In the process of MSPE, the coating of COF-LZU1PEIFe3O4 might be destroyed during stirring and ultrasonication, further affected the reuse of COF- LZU1PEIFe3O4. In order to investigate the reusability, COF-LZU1PEIFe3O4 were used six times for the extraction of PAHs (the nanoparticles were washed with ace- tonitrile for three times and dried in the oven before the next use). The conservation rate was calculated by the ratio of peak area after extraction to the peak area after first extraction. The co