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991.
采用高温固相反应法、Pechini合成方法和柠檬酸配位法,制备了系列锂锰复合氧化物LiMn2O4催化剂,应用于NH3-SCR反应,并与固相反应法合成的MnO2进行了比较。采用N2吸附-脱附、扫描电镜、X射线衍射、H2程序升温还原、NH3程序升温脱附、NO程序升温脱附和X射线光电子能谱对LiMn2O4催化剂进行表征。结果表明,引入Li有利于提高锰基催化剂的SCR活性和抗硫性。Pechini法制备LiMn2O4的NO转化率可在130~260℃达到90%以上;固相反应法制备LiMn2O4的NO转化率大于90%的温度为90~310℃;MnO2的温度窗口则仅为140~280℃。与MnO2相比,引入Li可形成LiMn2O4结构,因此,催化剂中更多的锰离子保持在相对较低的价态Mn3+,并调整表面活性氧含量;同时,Li的存在调变了LiMn2O4表面的酸位,从而减少高温下MnO2表面容易发生的NH3非选择性氧化,改善其催化NH3-SCR反应的温度窗口,也增强了抗硫性。 相似文献
992.
993.
Qiang Zhang Chen‐Gang Guo Fan‐Zhi Kong Cheng‐Xi Cao Liu‐Yin Fan Xin‐Qiao Jin 《Journal of separation science》2014,37(11):1359-1363
Uneven flow in free‐flow electrophoresis (FFE) with a gravity‐induced fraction collector caused by air bubbles in outlets and/or imbalance of the surface tension of collecting tubes would result in a poor separation. To solve these issues, this work describes a novel collector for FFE. The collector is composed of a self‐balance unit, multisoft pipe flow controller, fraction collector, and vacuum pump. A negative pressure induced continuous air flow rapidly flowed through the self‐balance unit, taking the background electrolyte and samples into the fraction collector. The developed collector has the following advantages: (i) supplying a stable and harmonious hydrodynamic environment in the separation chamber for FFE separation, (ii) effectively preventing background electrolyte and sample flow‐back at the outlet of the chamber and improving the resolution, (iii) increasing the preparative scale of the separation, and (iv) simplifying the operation. In addition, the cost of the FFE device was reduced without using a multichannel peristaltic pump for sample collection. Finally, comparative FFE experiments on dyes, proteins, and cells were carried out. It is evident that the new developed collector could overcome the problems inherent in the previous gravity‐induced self‐balance collector. 相似文献
994.
Quantitative analysis and pharmacokinetics study of tigecycline in human serum using a validated sensitive liquid chromatography with tandem mass spectrometry method
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Jiao Xie Taotao Wang Xue Wang Xiaoliang Cheng Haiyan Dong Yan Wang Xiaowei Zheng Liang Zhou Jianfeng Xing Yalin Dong 《Journal of separation science》2014,37(12):1396-1403
Tigecycline, a novel intravenously administered glycylcycline antibiotic, currently plays a key role in the management of complicated multiorganism infections. However, current liquid chromatography with tandem mass spectrometry methods briefly describe parameters and the only reported internal standard was sometimes difficult to obtain. In our study, an updated liquid chromatography with tandem mass spectrometry method for the quantitative analysis of tigecycline in human serum was developed. Sample preparation involved precipitation with 20% trichloroacetic acid. Chromatographic separation of tigecycline and tetracycline (internal standard) was achieved on a Hypersil GOLD C18 column using gradient elution. The selected reaction monitoring transitions were performed at m/z 586.1→513.2 for tigecycline and m/z 445.1→410.2 for tetracycline. The assay was linear over the concentration range of 5–2000 ng/mL. The intra‐ and interday precisions at three concentration levels (10, 100, and 1600 ng/mL) were <15% and their accuracies were within the range of 95.1–106.1%. The mean recovery ranged from 94.3 to 105.6% and the matrix effect from 92.1 to 97.6%. Tigecycline was stable under all tested conditions. This validated method was successfully applied to a pharmacokinetic study in critically ill patients. The data demonstrated that our method allows quantification of tigecycline in serum in a quick and reliable manner for widespread application. 相似文献
995.
Simultaneous determination of ten organophosphate pesticide residues in fruits by gas chromatography coupled with magnetic separation
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In this study, γ‐Fe2O3/chitosan magnetic microspheres were synthesized and evaluated by X‐ray diffraction, SEM, thermogravimetric analysis, and static and kinetic adsorption experiments. Results showed that the magnetic microspheres exhibited good adsorption ability, and offered fast kinetics for the adsorption of trichlorfon, methamidophos, malathion, methyl parathion, dimethoate, omethoate, phosphamidon, phorate, isocarbophos, and chlorpyrifos. Based on magnetic separation, a simple method of magnetic SPE coupled to GC for the simultaneous determination of ten trace organophosphate pesticide residues was developed. Under the optimal conditions, the enrichment factor for ten organophosphorus pesticides was 10.1–364.7 and linear range was 0.001–10.0 mg/L. The LOD (S/N = 3) of the method for the ten pesticides was 0.31–3.59 μg/kg. The RSD for three replicate extractions of spiked samples was between 2.5 and 6.3%. The pear and apple samples spiked with ten organophosphate pesticides at 20 and 200 μg/kg levels were extracted and determined by this method with good recoveries ranging from 79.9 to 98.7%. Moreover, the method has been successfully applied for the determination of the ten organophosphate pesticide residues in peach samples. 相似文献
996.
Mass‐spectrometry‐directed analysis and purification of pyrrolizidine alkaloid cis/trans isomers in Gynura japonica
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Lianxiang Fang Aizhen Xiong Xiao Yang Wenzhi Cheng Zhengtao Wang 《Journal of separation science》2014,37(15):2032-2038
Pyrrolizidine alkaloids are highly hepatotoxic natural chemicals that produce irreversible chronic and acute hepatotoxic effects on human beings. Purification of large amounts of pyrrolizidine alkaloids is necessary for toxicity studies. In this study, an efficient method for targeted analysis and purification of pyrrolizidine alkaloid cis/trans isomers from herbal materials was developed for the first time. Targeted analysis of the hepatotoxic pyrrolizidine alkaloids was performed by liquid chromatography with tandem mass spectrometry (precursor ion scan and daughter ion scan), and the purification of pyrrolizidine alkaloids was achieved with a mass‐directed auto purification system. The extraction and preparative liquid chromatography conditions were optimized. The developed method was applied to analysis of Gynura japonica (Thunb.) Juel., a herbal medicine traditionally used for detumescence and relieving pain but is potentially hepatotoxic as it contains pyrrolizidine alkaloids. Twelve pyrrolizidine alkaloids (six cis/trans isomer pairs) were identified with reference compounds or characterized by liquid chromatography with tandem mass spectrometry, and five individual pyrrolizidine alkaloids, including (E)‐seneciphylline, seneciphylline, integerrimine, senecionine, and seneciphyllinine, were prepared from G. japonica roots with high efficiency. The results of this work provide a new technique for the preparation of large amounts of pyrrolizidine alkaloid reference substances, which will also benefit toxicological studies of pyrrolizidine alkaloids and treatments for pyrrolizidine alkaloid‐induced toxicity. 相似文献
997.
998.
Jing Liu Fangjun Wang Jun Zhu Jiawei Mao Zheyi Liu Kai Cheng Hongqiang Qin Hanfa Zou 《Analytical and bioanalytical chemistry》2014,406(13):3103-3109
Conventional N-glycoproteome analysis usually applies C18 reversed-phase (RP) adsorbent for sample purification, which will lead to unavoidable sample loss due to the high hydrophilicity of N-glycopeptides. In this study, a porous graphitized carbon (PGC) absorbent was combined with a C18 adsorbent for N-glycopeptide purification in comprehensive N-glycoproteome analysis based on the hydrophobic and polar interactions between carbon and N-glycans. It was observed that the small hydrophilic N-glycopeptides that cannot retain onto C18 adsorbent can be captured by the graphitized carbon, while the large hydrophobic N-glycopeptides that cannot retain onto the graphitized carbon can be feasibly captured by the C18 adsorbent. Comparing with sample purification by using C18 adsorbent only, 28.5 % more N-glycopeptides were identified by combining both C18 and PGC adsorbents. The C18-PGC strategy was further applied for both sample purification and pre-fractionation of a complex protein sample from HeLa cell. After hydrophilic interaction chromatography enrichment, 1,484 unique N-glycopeptides with 1,759 unique N-glycosylation sites were finally identified. Online Abstract Figure
The overlap of identified N-glycosylation sites by different SPE strategies 相似文献
999.
Photofragment translational spectroscopy at 304 nm from C-H symmetric stretch excited CH3I [v
1 = 1]
ZHOU ZhiMin HU LiLi DONG ChangWu ZHANG LiJuan LIU Sheng DU YiKui CHENG Min ZHU QiHe 《中国科学:化学(英文版)》2014,57(6):902-910
The 304 nm photodissociation of the C-H symmetric stretch excited CH3I[v1=1,v2=0](v1 denotes the C-H symmetric stretch mode,and v2 denotes the umbrella mode)is studied with our simple photofragment translational spectrometer.An IR laser is used to excite the ground state CH3I[0,0]to the C-H symmetric stretch excited CH3I[1,0].With IR laser OFF and ON,the fractions of photofragments CH3(ν1,ν2)from the 304 nm photodissociation of CH3I[1,0]have been determined through the photofragment translational spectra(PTS)from measuring I and I*and also through the PTS from measuring CH3(0,0)(1,0)(0,1)and(1,1).The experimental results show that the C-H symmetric stretch vibration(v1=1)in parent molecules is about 66%retained in the photofragments in the I channel,but only 24%in the I*channel.The populations of photofragments CH3(0,2)and(0,3)are higher than CH3(0,0)and(0,1),showing strong inverted population both in I and I*channels. 相似文献
1000.
In Situ Facile Synthesis of Ru‐Based Core–Shell Nanoparticles Supported on Carbon Black and Their High Catalytic Activity in the Dehydrogenation of Amine‐Boranes
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Well‐dispersed core–shell Ru@M (M=Co, Ni, Fe) nanoparticles (NPs) supported on carbon black have been synthesized via a facile in situ one‐step procedure under ambient condition. Core‐shell Ru@Co NPs were synthesized and characterized for the first time. The as‐synthesized Ru@Co and Ru@Ni NPs exhibit superior catalytic activity in the hydrolysis of ammonia borane compared with their monometallic and alloy counterparts. The Ru@Co/C NPs are the most reactive, with a turnover frequency (TOF) value of 320 (mol min?1) molRu?1 and activation energy (Ea) of 21.16 kJ mol?1. Ru@Ni/C NPs are the next most active, whereas Ru@Fe/C NPs are almost inactive. Additionally, the as‐synthesized NPs supported on carbon black exhibit higher catalytic activity than catalysts on other conventional supports, such as SiO2 and γ‐Al2O3. 相似文献