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31.
32.
反相高效液相色谱法测定3种中成药中的葛根素 总被引:7,自引:0,他引:7
建立了测定小儿清感灵片、步长新脑心通胶囊和感冒清热颗粒 3种中成药中葛根素含量的反相高效液相色谱方法。采用APEXODS色谱柱 ,以醋酸铵缓冲液 (10 0mmol/L ,pH 5 0 ) 甲醇 (体积比为 75∶2 5 )的混合溶液为流动相 ,检测波长为 2 5 0nm ,流速为 0 8mL/min。葛根素在 2mg/L~ 2 0mg/L时其色谱峰面积与质量浓度的线性关系良好 (r =0 9999) ;上述 3种中成药中的葛根素含量分别为 3 48mg/g ,1 0 8mg/ g及 1 5 2mg/ g(蔗糖型 ) ;其加样回收率分别为 99 0 % ,93 4%和 97 5 %。该法简便、快速、专属性强 ,可以作为多种中药制剂中葛根素含量的测定方法。 相似文献
33.
Complexes [ML3]2+ of the bidentate ligand 2‐(1H‐imidazol‐2‐yl)pyridine were prepared with iron(II), cobalt(II), and ruthenium(II). The electronic spectra suggest the ligand to be a weaker σ‐donor and π‐acceptor than the closely related 2,2′‐bipyridine. The complexes are readily deprotonated by addition of base, and the effect of the deprotonation is to lower the MIII/MII redox potential by roughly 900 mV. This is roughly 75% of the drop observed for related complexes of 2,6‐di‐1H‐imidazol‐2‐ylpyridine, and suggests the effect to be largely coulombic in origin. 相似文献
34.
Kinetics of poly(ethylene terephthalate) glycolysis by diethylene glycol. I. Evolution of liquid and solid phases 总被引:1,自引:0,他引:1
The kinetics of uncatalysed glycolysis, at 220 °C, of poly(ethylene terephthalate) (PET) by diethylene glycol (DEG) in high excess has been studied. An experimental device allowing good separation, at reaction temperature, of the solid and liquid phases was set up.The results suggest that PET is initially depolymerized in the slightly swollen solid phase, by glycolysis of the amorphous interlamellar chains. This mechanism continues until a solid phase of highly crystallized polyester is obtained.The internal tensions engendered by this chemical modification cause cracks, delamination and mechanical disintegration of the polymer. The transfer towards the liquid phase is then strongly accelerated and the solvolysis of the depolymerization products continues in the liquid phase, up to equilibrium. 相似文献
35.
New transesterification reaction between acetylated wood and tetramethoxysilane: A feasibility study 总被引:1,自引:0,他引:1
Novel transesterification of acetylated maritime pine sapwood (Pinus pinaster Soland) reaction was performed with tetramethoxysilane (TMOS) in presence of dibutyltin oxide as a catalyst. Transesterification was confirmed by weight percent gain calculations (WPG), infrared spectroscopy (FTIR) as well as 13C and 29Si NMR CP-MAS analysis. The results showed that transesterification indeed occurs via exchange of acetate groups from acetylated wood and methoxysilane groups from TMOS. The effect of temperatures and reaction time upon transesterification efficiency was also investigated. 相似文献
36.
In this paper, we report the synthesis of carbohydrate-derived 1,7-enynes and subsequent metathesis to yield polyhydroxylated 1-vinylcyclohexenes. For example, we converted D-glucose 2 to the (6,7)-dideoxy-D-gluco-hept-6-ene-pyranose 7, which led to the desired 1,7-enyne 16. The ring-closing metathesis of this 1,7-enyne 16 with the second generation Grubbs catalyst, under Mori's conditions, gave the corresponding polyhydroxylated 1-vinylcyclohexene 25 in 76% yield. The conversion of several aldohexoses into polyhydroxylated 1-vinylcyclohexenes was carried out with satisfying yields. We report also the synthesis of two carbohydrate-derived ethyl 8-yn-2-enoates from D-glucose derivatives. 相似文献
37.
Jian Zhi SUN Xiao Chuan DENG Shu Bin WEI Fa Qiang LI Pei Hua MA 《中国化学快报》2005,16(10):1401-1404
A new kind of adsorbent Li(1+x)AlxTi(2-x)(PO4)3 was synthesized by solid state reaction method. The influence of the content of doping aluminum on the adsorbent Li(1+x)AlxTi(2-x)(PO4)3 was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the adsorption properties showed that the adsorbent can selectively adsorb sodium with the adsorption capacity of 11.76 mg/g. The optimum conditions of adsorption are at pH 10.0-11.0 in LiCl solution. 相似文献
38.
Cappa CD Smith JD Wilson KR Messer BM Gilles MK Cohen RC Saykally RJ 《The journal of physical chemistry. B》2005,109(15):7046-7052
Measurements of the oxygen K-edge X-ray absorption spectrum (XAS) of aqueous sodium halide solutions demonstrate that ions significantly perturb the electronic structure of adjacent water molecules. The addition of halide salts to water engenders an increase in the preedge intensity and a decrease in the postedge intensity of the XAS, analogous to those observed when increasing the temperature of pure water. The main-edge feature exhibits unique behavior and becomes more intense when salt is added. Density functional theory calculations of the XAS indicate that the observed red shift of the water transitions as a function of salt concentration arises from a strong, direct perturbation of the unoccupied molecular orbitals on water by anions, and does not require significant distortion of the hydrogen bond network beyond the first solvation shell. This contrasts the temperature-dependent spectral variations, which result primarily from intensity changes of specific transitions due to geometric rearrangement of the hydrogen bond network. 相似文献
39.
Euzenat L Horhant D Ribourdouille Y Duriez C Alcaraz G Vaultier M 《Chemical communications (Cambridge, England)》2003,(18):2280-2281
Thermal decomposition of hindered amine-borane adducts leads in high yields to monomeric (dialkylamino)boranes R1R2N-BH2 (R1 and R2 = alkyl) that are new and efficient boron-sources in the Pd0 catalyzed borylation reaction affording monomeric aryl(dialkylamino)boranes R1R2N-BHR3 (R3 = aryl). 相似文献
40.
Ben Salah M Vilminot S Richard-Plouet M André G Mhiri T Kurmoo M 《Chemical communications (Cambridge, England)》2004,(22):2548-2549
The synthetic mineral Co(II)5(OH)6(SO4)2(H2O)4 (1), obtained by hydrothermal reaction of CoSO4.7H2O and NaOH at 165 degrees C and consisting of brucite-like Co4(OH)6O2 layers pillared by OSO3-Co(H2O)4-O3SO, is a ferromagnet (T(Curie)= 12 K, Hc= 580 Oe). 相似文献