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941.
Apeng Chen Kyle B. Lynch Xiaochun Wang Joann J. Lu Congying Gu Shaorong Liu 《Analytica chimica acta》2014
We integrate a high-pressure electroosmotic pump (EOP), a nanoflow gradient generator, and a capillary column into a miniaturized liquid chromatographic system that can be directly coupled with a mass spectrometer for proteomic analysis. We have recently developed a low-cost high-pressure EOP capable of generating pressure of tens of thousands psi, ideal for uses in miniaturized HPLC. The pump worked smoothly when it was used for isocratic elutions. When it was used for gradient elutions, generating reproducible gradient profiles was challenging; because the pump rate fluctuated when the pump was used to pump high-content organic solvents. This presents an issue for separating proteins/peptides since high-content organic solvents are often utilized. In this work, we solve this problem by incorporating our high-pressure EOP with a nano-flow gradient generator so that the EOP needs only to pump an aqueous solution. With this combination, we develop a capillary-based nano-HPLC system capable of performing nano-flow gradient elution; the pump rate is stable, and the gradient profiles are reproducible and can be conveniently tuned. To demonstrate its utility, we couple it with either a UV absorbance detector or a mass spectrometer for peptide separations. 相似文献
942.
A chemical investigation of AcOEt‐soluble portion of the 95% EtOH extract of the aerial parts of Clerodendranthus spicatus led to the isolation and characterization of a new diterpenoid, named clerospicasin J ( 1 ). Structure elucidation of 1 was achieved by spectroscopic analyses, including 2D‐NMR. The diterpenoid 1 exhibited significant inhibitory activity on the proliferation of the SKOV3 cell lines. Moreover, the cytotoxicity of 1 against SKOV3 cells was related to apoptotis as confirmed by DAPI (=2‐(4‐amidinophenyl)‐1H‐indole‐6‐carboxamidine) nuclear staining and flow cytometry. 相似文献
943.
Solid‐Phase Organic Synthesis of 1,4‐N‐Vinyl‐ and 1,4‐N‐Allyl‐Triazoles with the Sulfonate Linker 下载免费PDF全文
Aiying He Shouri Sheng Zhenzhong Huang Li Liu Mingzhong Cai 《Journal of heterocyclic chemistry》2014,51(6):1862-1865
Polymer‐supported 2‐azidoethyl sulfonate and 3‐azidopropyl sulfonate reagents have been developed and applied to the solid‐phase organic synthesis of 1‐vinyl‐ and 1‐allyl‐1,2,3‐triazoles, respectively, by CuI‐mediated azide‐alkyne cycloadditions and subsequent cleavage from the polymer support through elimination reaction promoted by DBU. The advantages of this new synthetic method include simple operation and high yield of the products, as well as good stability of the reagents. 相似文献
944.
Shouri Sheng Wusheng Sheng Qiaosheng Hu Hongen Qu Mingzhong Cai 《Journal of heterocyclic chemistry》2014,51(2):315-321
A regioselective 1,3‐dipolar cycloadditions of ionic liquid‐supported vinyl ethers, derived from ionic liquid‐supported α‐phenylselenomethyl ether, with ethyl cyanoformate N‐oxide gave supported isoxazoline derivatives, which were then cleaved from the ionic liquid support under mild acidic conditions to afford ethyl isoxazole‐3‐carboxylates. This new synthetic method is simple and efficient and the products are obtained in good yields. 相似文献
945.
Synthesis of 2,5‐Diketopiperazine Derivatives Using 2‐Isocyanophenyl 4‐Methylbenzoate as a Fragrant Convertible Isocyanide 下载免费PDF全文
A new protocol in which 2‐isocyanophenyl 4‐methylbenzoate is used as a convertible isocyanide for Ugi/deprotection + activation/cyclization synthesis of 2,5‐diketopiperazine derivatives has been developed. This operational simple procedure displays good functional group tolerance and avoids treatment of typically known offensive isocyanides. 相似文献
946.
Mn3O4资源丰富、结构稳定,具有较高的理论电容,是一种较有潜力的超级电容器材料,但其较差的导电性却阻碍了其在这方面应用。本论文以实心ε-MnO2微米粉体和具有亲水性的GO粉体为原料,在去离子水中通过磁力搅拌和冷冻干燥制备出具有良好接触的MnO2/GO复合粉体。然后经一步氢气还原处理,使实心ε-MnO2和GO同步转化为具有纳米多孔结构的多孔Mn3O4和RGO,从而获得分散均匀、具有高比表面积和优良导电性的高性能Mn3O4/RGO复合粉体。经电化学测试可知,Mn3O4/RGO复合粉体在2 mV/s的扫描速率下的比电容为25.2 F/g且具有较好的电容留存率。 相似文献
947.
Liqiang Tan Yeling Jin Xiaochun Cheng Jie Wu Wei Zhou Liangdong Feng 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(3):575-585
Batch sorption experiments were performed to remove Eu(III) ions from aqueous solutions by using attapulgite under ambient
conditions. Different experimental conditions, such as contact time, solid content, foreign ions, pH, ionic strength, fulvic
acid and temperature, have been investigated to study their effect on the sorption property. The results indicated that the
sorption of Eu(III) onto attapulgite was strongly dependent on pH, ionic strength and temperature. The sorption increased
from about 8.9 to 90% at pH ranging from 2 to 6 in 0.01 mol/L NaNO3 solution. The Eu(III) kinetic sorption on attapulgite was fitted by the pseudo-second-order model better than by the pseudo-first-order
model. The sorption of Eu(III) onto attapulgite increased with increasing temperature and decreasing ionic strength. The Langmuir
and Freundlich models were used to simulate the sorption isotherms, and the results indicated that the Freundlich model simulated
the data better than the Langmuir model. The thermodynamic parameters (∆G
o, ∆S
o, ∆H
o) were determined from the temperature dependent isotherms at 298.15, 318.15 and 338.15 K, and the results indicated that
the sorption reaction was an endothermic and spontaneous process. The results suggest that the attapulgite is a suitable material
as an adsorbent for preconcentration and immobilization of Eu(III) from aqueous solutions. 相似文献
948.
Zhenhu Cao Yan ZhangPingan Song Yuanzheng Cai Qi GuoZhengping Fang Mao Peng 《Journal of Analytical and Applied Pyrolysis》2011,92(2):339-346
A novel metal chelate complex containing phosphorus, nitrogen and zinc (II) ion was synthesized and used as the flame retardant of low density polyethylene (LDPE). The zinc chelate complex was synthesized by reacting zinc acetate with the ligand of tetraethyl (1,2-phenylenebis(azanediyl)) bis (2-hydroxylphenylmethylene) diphosphonate (TEPAPM). The chemical structure of the target Zn-TEPAPM was confirmed by FTIR, 1H NMR, 13C NMR and 31P NMR spectra. The flame retardancy and thermal behavior of LDPE containing various amount of Zn-TEPAPM were investigated by limiting oxygen index test, thermogravimetric (TG) analysis and cone calorimetry. The results show that Zn-TEPAPM can greatly increase the thermal stability, the char formation and smoke suppression ability of LDPE. The TG curves show that even when the filler content of Zn-TEPAPM is as low as 1 wt% in LDPE, the onset degradation temperature of LDPE is increased from 429 °C to 442 °C, and the maximum degradation temperature is increased from 469 °C to 488 °C. Also, a reduction of 32% for the peak heat release rate (PHRR) is obtained in the cone test. Moreover, Zn-TEPAPM is demonstrated to be a very effective synergist of ammonium polyphosphate (APP). When 1 wt% of Zn-TEPAPM was introduced into the LDPE/APP (mass ratio 80/19) blend, the PHRR value is reduced by 32%, compared with that of LDPE/APP blend without Zn-TEPAPM, and the char layer becomes more compact and intact. 相似文献
949.
A simple, rapid and sensitive CE-ESI-MS method for the simultaneous analysis of seven stimulants and narcotics (amphetamine, ephedrine, methadone, pethidine, tetracaine, codeine and heroin) was developed. The CE-ESI-MS experimental conditions were optimized as follows: 20?mmol/L ammonium acetate with pH 9.0 as running buffer, the separation voltage of 22?kV and the sheath liquid of isopropanol/water (1:1 v/v) containing 7.5?mmol/L acetic acid with 3.0?μL/min flow rate. Under the optimized conditions, the stimulants and narcotics were well separated within 4.6?min using a 70-cm length fused-silica capillary (50?μm id). The detection limits (S/N=3) of the CE-ESI-MS analysis were in the range of 0.40-1.0?ng/mL. Method repeatability of intra-day and inter-day was satisfactory. The recoveries obtained from the analysis of spiked urine samples were between 84.1 and 108%. The developed method was successfully applied for the simultaneous analysis of methadone, pethidine and codeine and their in vitro metabolites. 相似文献
950.
Cluster studies have attracted much interest in the past decades because of their extraordinary properties. To describe the interaction between atoms or molecules and predict the energies and structures, potential functions are developed. However, different potentials generally produce different structures and energies for a cluster. To study the effect of potentials on the structure of a cluster, He clusters in the size range of 13-140 are investigated by Lennard-Jones (LJ), Pirani, and Hartree-Fock-dispersion individual damping (HFD-ID) potential with dynamic lattice searching (DLS) method. Potential function curves, cluster structures, bonds, and energies of the global minima are compared. The results show that cluster energies decrease with the values of the potential functions, the differences between structures depend upon the disagreements of the potentials, and the preferable motif of a cluster changes from icosahedron to decahedron with the increase of the derivative of the short-range part of the potentials. 相似文献