ANALYTICAL CHEMISTRY
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2015
·
IF 5.636
Jun-Hui Zhang,Sheng-Ming Xie,Ling Chen,Bang-Jin Wang,Pin-Gang He,Li-Ming Yuan
Porous organic molecular cages as a new type of porous materials have attracted a tremendous attention for their potential applications in recent years. Here we report the use of a homochiral porous organic cage (POC) (CC3-R) diluted with a polysiloxane (OV-1701) as a stationary phase for high-resolution gas chromatography (GC) with excellent enantioselectivity. A large number of optical isomers have been resolved without derivatization, including chiral alcohols, diols, amines, alcohol amines, esters, ketones, ethers, halohydrocarbons, organic acids, amino acid methyl esters, and sulfoxides. Compared with commercial β-DEX 120 and Chirasil-L-Val columns, the CC3-R coated capillary column offered more preeminent enantioselectivity. In addition, CC3-R also exhibits good selectivity for the separation of isomers, linear alkanes, alcohols, and aromatic hydrocarbons. The excellent resolution ability, repeatability, and thermal stability make CC3-R a promising candidate as a novel stationary phase for GC. The study described herein first proves useful commercially. This work also indicates that porous organic molecular materials will become more attractive in separation science.
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ANALYTICAL CHEMISTRY
·
2014
·
IF 5.825
Jun-Hui Zhang,Sheng-Ming Xie,Mei Zhang,Min Zi,Pin-Gang He,Li-Ming Yuan
Chiral nematic mesoporous silica (CNMS) has attracted widespread attention due to some unique features, such as its nematic structure, chirality, large pore size, high temperature resistance, low cost, and ease of preparation. We first reported the use of CNMS as a stationary phase for capillary gas chromatography (GC). The CNMS-coated capillary column not only gives good selectivity for the separation of linear alkanes, aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and isomers but also offers excellent enantioselectivity for chiral compounds. Compared with enantioseparations on commercial β-DEX 120 and Chirasil-l-Val columns, a CNMS-coated capillary column offers excellent enantioselectivity, chiral recognition complementarity, and the separation of analytes within short elution times. It can also be potentially applied in high-temperature GC at more than 350 °C. This work indicates that CNMS could soon become very attractive for separations.
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JOURNAL OF CHROMATOGRAPHY A
·
2014
·
IF 4.258
Juan Zhang,Wenpeng Zhang,Tao Bao,Zilin Chen
In this work, we fabricated a novel graphene-based capillary column for open-tubular capillary electrochromatography (OT-CEC) by a layer-by-layer strategy. To immobilize graphene onto the inner surface of silica capillary, a bio-inspired method was first used to functionalize the capillary surface with a layer of polydopamine (PDA). Graphene oxide (GO) was then introduced and can covalently react with polydopamine, realizing immobilization of graphene as a result. To enhance the modification efficiency of polydopamine, a conductive polymer, polyaniline (PANI) was introduced to be a sub-layer; polydopamine was then introduced following with GO , to generate a multilayer GO-PDA-PANI@capillary. Interestingly, separation efficiency of the graphene-based capillary was enhanced significantly by using conductive PANI as a sub-layer. The morphology of different layers modified on the capillary column was characterized by scanning electron microscopy (SEM). The electroosmotic flow (EOF) characteristics of capillaries modified with different layers were also investigated by varying the pH value of mobile phase. GO-PDA-PANI@capillary showed good separation efficiency towards alkylbenzenes by OT-CEC mode, with theoretic plate numbers up to 133,918 for benzene. The separation was found to follow a reversed-phase chromatographic retention mechanism. Repeatability of the GO-PDA-PANI@capillary was studied, with relative standard deviations for intra-day and inter-day runs less than 2.89%, and column-to-column runs less than 6.17%. The separation performance of GO-PDA-PANI@capillary was also compared with that of the reported graphene modified capillary.
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Analytical Methods
·
2015
·Vol. 7
·期 7
·3229-3237
·
IF 1.821
Xueyan Zhang,Hongyun Ji,Xudong Zhang,Zhen Wang,Dan Xiao
Graphene Quantum Dots (GQDs) have potential to be an excellent stationary phase because of their high surface area, adsorption affinities and rich functional groups. The rich functional groups of GQDs can form hydrogen bonding and π–π electrostatic stacking interactions with volatile aromatic compounds or unsaturated organic compounds. Herein, GQDs were explored as the stationary phase for gas chromatographic capillary column separation of alkanes and aromatic isomers with 3-aminopropyldiethoxymethyl silane (3-AMDS) as the coupling reagent. GQD coated capillary columns exhibit high separation efficiency for ethylbenzene, styrene, xylene, propylbenzene, alkanes, and dichlorobenzene isomers at low temperature. The elution sequence of the analytes follows an increasing order of their boiling points, even for p-dichlorobenzene and m-dichlorobenzene, which have close boiling points (p-dichlorobenzene, 173.4 °C, m-dichlorobenzene, 173 °C). The separation behavior of the column for different organic substances is related to van der Waals forces or π–π interactions between the test analytes and GQDs. Compared with the commercial HP-5 and HP-innowax capillary columns, GQD coated columns allowed fast and efficient separation of the analytes at low temperature without temperature-programming. The relative standard deviations (RSD) of five replicate separations for the test analytes on the GQD coated capillary column were 0.1–1.6%, 0.7–4.0%, 0.8–8.5%, and 1.2–2.2% for retention time, peak area, peak height, and half peak width, respectively.
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ANALYST
·
2013
·Vol. 139
·期 1
·242-250
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IF 3.969
Juan Zhang,Wenpeng Zhang,Tao Bao,Zilin Chen
A novel capillary with hydroxyapatite (HAP) as the stationary phase was prepared for open-tubular capillary electrochromatography (OT-CEC). To immobilize HAP, a mussel-inspired polydopamine method was utilized to modify the capillary firstly, generating a polydopamine layer; and then a layer of HAP would be formed on the polydopamine layer by a biomineralization process, to produce a HAP-modified capillary (HAP@capillary). Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) provided evidence of nanostructured HAP grown on the surface of the capillary wall. The electroosmotic flow (EOF) characteristic of the HAP@capillary was investigated by varying the percentage of acetonitrile and pH value of the buffer with thiourea as a marker, and a pH-dependent EOF from anode to cathode was observed. The HAP@capillary exhibits high column efficiency for methylbenzene, up to 151 138 plates per meter. Different kinds of compounds including alkylbenzenes, phenols and amines have been successfully separated by the HAP@capillary in CEC mode. The HAP@capillary also possessed good separation ability in capillary liquid chromatography (CLC) mode because of the relatively large ratio of HAP in the capillary; however, the separation efficiency was not as good as that in CEC mode. The reproducibilities of the HAP@capillary were evaluated, and the relative standard deviations were found to be lower than 5%.
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JOURNAL OF CHROMATOGRAPHY A
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2016
·
IF 3.926
Tao Bao,Pingxiu Tang,Deying Kong,Zhenkun Mao,Zilin Chen
Covalent-organic frameworks (COFs) are attractive materials for their fascinating properties, such as rigid structures, exceptional thermal stabilities, low densities, and permanent porosity with specific surface areas, which indicate potential for application in chromatography similar to related metal-organic frameworks (MOFs). However, the utilization of COFs in analytical chemistry is far behind as compared to that of the MOFs due to the challenging work of their immobilization. Here, we have successfully demonstrated the growth of the boron COF-5 on the inner wall of the fused silica capillary by a developed polydopamine-supported method. Combined with the layer-by-layer strategy, multilayer COF-5-coated capillary was obtained. The formation of COF-5 on polydopamine-coated substrate has been confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction. A novel stationary phase of COF-5 was developed on the basis of successful growth of COF-5 on polydopamine for open-tubular capillary electrochromatography (OT-CEC). Baseline separation of neutral, acidic and basic analytes was achieved on multilayer COF-5-coated capillary column. The fabricated capillary columns showed high column efficiency (154,060 plates/m for methylbenzene), excellent stability and repeatability. The precision (relative standard deviation (RSD), n = 3) of retention time, peak height, and peak area for tested neutral compounds were in the range of 1.2–1.3%, 1.8–4.2%, and 0.9–2.4%, respectively. To the best of our knowledge, it was the first demonstration that COF-5 was developed as a novel stationary phase.
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MICROCHIMICA ACTA
·
2017
·Vol. 184
·期 4
·1169-1176
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IF 4.58
Kong Deying,Bao Tao,Chen Zilin
The covalent organic framework LZU1 (Lan Zhou University-1) is one of the imine-based covalent organic frameworks (COFs) that possesses attractive properties such as structural regularity, stability and good porosity. This work reports on the in-situ synthesis of COF-LZU1 on the inner walls of capillary column for open-tubular capillary electrochromatography (OT-CEC). The fused-silica capillary was first modified with 3-aminopropyltriethoxysilane and glutaraldehyde. Epitaxial growth of COF-LZU1 on the inner walls was accomplished by Schiff base reaction. The formation of COF-LZU1 was confirmed by SEM and FT-IR. The COF-LZU1 coating increases the interactions between analytes and coating, which remarkably improves the CEC separation selectivity of neutral analytes, amino acids and nonsteroidal anti-inflammatory drugs. The COF-LZU1-modified column exhibits good stability and repeatability. The precisions (relative standard deviations) for intra-day, inter-day and column-to column are <1.6%, 5.6% and 6.8%, respectively. Hence, the imine-based COFs represent attractive stationary phase for application in CEC separations.
Covalent organic framework (COF-LZU1) was in situ synthesized on the inner wall of a capillary column for electrochromatographic separation of nonsteroidal drugs and amino acids.
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TALANTA
·
2016
·
IF 4.035
Tao Bao,Pingxiu Tang,Zhenkun Mao,Zilin Chen
A novel capillary column with metal-organic framework-5 (MOF-5) as the stationary phase was prepared for open-tubular capillary electrochromatography (OT-CEC). To grow MOF-5, the fused-silica capillary was functionalized firstly using 3-aminopropyltriethoxysilane and glutaraldehyde as covalent linkers; and then MOF-5 would be immobilized on the inner wall of COOH-terminated capillary by epitaxial growth , to produce a MOF-5-modified capillary. The successful growth of MOF-5 has been characterized and confirmed by scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectra . The influence of pH value and methanol on electroosmotic flow (EOF) of the MOF-5-modified capillary column was investigated. The EOF showed a pH-dependent from anode to cathode. The immobilization of MOF-5 improved the interactions between analytes and layer on inner wall of the capillary. Excellent separations of substituted benzenes and acidic and basic analytes were obtained on the fabricated capillary columns. The MOF-5-modified capillary columns exhibited good repeatability, with relative standard deviations for intra-day, inter-day runs and column-to-column less than 1.87%, 3.53%, and 8.49%, respectively. Our successful application of MOF-5 paved the way for introducing series of dicarboxylate-based isoreticular MOFs to OT-CEC as novel stationary phase.
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JOURNAL OF SEPARATION SCIENCE
·
2016
·Vol. 40
·期 4
·954-961
·
IF 2.741
Yilin Li,Tao Bao,Zilin Chen
In this work, we developed a capillary column modified with zeolitic imidazolate framework-8 as a novel stationary phase for open-tubular capillary electrochromatography. To immobilize zeolitic imidazolate framework-8 onto the inner surface of silica capillary, a bio-inspired polydopamine functionalization was used to functionalize the capillary surface with polydopamine. First, a polydopamine layer was assembled inside the capillary. Second, due to noncovalent adsorption and covalent reaction ability, polydopamine could attract and anchor zeolitic imidazolate framework-8 onto the inner surface of capillary. It has been demonstrated that zeolitic imidazolate framework-8 was successfully grafted on the inner wall of the capillary by scanning electron microscopy, and Fourier transform infrared spectroscopy. The electro-osmotic flow characteristics of capillaries were also investigated by varying the pH value and acetonitrile content of mobile phase. The zeolitic imidazolate framework-8 coating not only increased the phase ratio of open-tubular column, but also improved the interactions between tested analytes and the stationary phase. Three groups of isomers including acidic, basic, and neutral compounds were well separated on the zeolitic imidazolate framework-8 bonded column, with theoretic plate numbers up to 1.9 × 10 5 N for catechol. The repeatability of the prepared columns was also studied, and the relative standard deviations for intra- and interday runs were less than 5%.
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JOURNAL OF CHROMATOGRAPHY A
·
2016
·
IF 3.926
Xiaohong Yang,Changxia Li,Meiling Qi,Liangti Qu
This work presents the separation performance of graphene-ZIF8 (G-Z) composite material as stationary phase for capillary gas chromatography (GC). The G-Z stationary phase achieved high column efficiency of 5000 plates/m determined by n -dodecane ( k = 1.22) at 120 °C and showed weakly polar nature. Importantly, it exhibited high selectivity and resolving capability for branched alkane isomers and aromatic positional isomers, showing clear advantages over the reported neat graphene and ZIF8. In addition, it attained high resolution for geometric cis -/ trans -isomers. The G-Z column exhibited good column thermal stability up to 300 °C and column repeatability with RSD values of retention times in the range of 0.01–0.19% for intra-day, 0.05–0.88% for inter-day and 0.66–5.6% for between-column, respectively, Moreover, the G-Z column was employed for the determination of minor impurity isomers in real reagent samples, which demonstrates its promising potential in GC applications .
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JOURNAL OF SEPARATION SCIENCE
·
2017
·Vol. 40
·期 23
·4521-4529
·
IF 2.557
Haixia Lyu,Heqing Zhao,Wenfei Qin,Zenghong Xie
A simple “one-pot” approach for the preparation of a new vinyl-functionalized organic–inorganic hybrid monolithic column is described. In this improved method, the hydrolyzed alkoxysilanes of tetramethoxysilane and triethoxyvinylsilane were used as precursors for the synthesis of a silica-based monolith, while 1-hexadecene and sodium ethylenesulfonate were used as vinyl functional monomers along with azobisisobutyronitrile as an initiator. The effects of reaction temperature, urea content, and composition of organic monomers on the column properties (e.g. morphology, mechanical stability, and chromatographic performance) were investigated. The monolithic column was used for the separation of neutral solutes by reversed-phase pressurized capillary. Furthermore, the monolith can separate various aromatic amines, which indicated its excellent cation-exchange capability and hydrophobic interactions. The baseline separation of the aromatic amines was obtained with a column efficiency of up to 78 000 plates/m.
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RSC Advances
·
2016
·Vol. 6
·期 110
·108217-108228
·
IF 3.289
Lujiang Xu,Zheng Han,Ying Zhang,Yao Fu
The vapor phase hydrodeoxygenation (HDO) of lignin-derived phenols under H2 atmosphere has great significance for producing high-quality fuels and commodity chemicals. Herein, we reported a simple, green method to prepare molybdenum oxide@N-doped carbon (MoOx@NC) via in situ pyrolysis of molybdenum precursor preloaded cellulose and demonstrated its catalytic performance for vapor phase HDO of lignin-derived phenols. When the pyrolysis temperature was at 600 °C, the catalyst (MoOx@NC-600) exhibited the best catalytic performance in vapor phase HDO of guaiacol. Through systematically investigating the parameters, such as: reaction temperature, WHSV, residence time, and concentration, the optimal reaction conditions for vapor phase HDO of guaiacol were 450 °C and 1 h−1 with atmospheric H2. The concentration of the feed was 20% in mesitylene, and the residence time was about 3.3 s. The carbon yield of aromatic hydrocarbons was 83.3%, with 65.7% benzene, 15.5% toluene and 2.1% alkylbenzenes. In addition, other lignin-derived phenols were also investigated and desired results were achieved with the MoOx@NC-600 catalyst. Furthermore, MoOx@NC-600 showed good stability due to the N-doped carbon formed on the surface of the MoOx particles. The catalysts were characterized using elemental analysis, AAS, BET, XRD, XPS, TEM, and EDS mapping. The high catalytic performance of MoOx@NC-600 toward lignin-derived phenols HDO can be attributed to the synergistic effect of the carbon supports and Mo5+ (molybdenum oxynitrides), Moδ+ (Mo2N) and Mo4+ on the surface of the MoOx particles.
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