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排序方式: 共有194条查询结果,搜索用时 171 毫秒
91.
气相-质谱法测定孜然芹挥发油的化学成分 总被引:13,自引:0,他引:13
采用水蒸气蒸馏法从孜然芹中提取挥发性成分,并用气相 质谱法(GC MS)联机分析,共分离出60余峰,鉴定出了49种物质,用面积归一法确定了相对含量。在所分离出的化合物中,碳氢化合物16种,烃类含氧衍生物32种。主要成分为枯茗醛和藏花醛,它们分别占测得组分的32 26%和26 49%。另有9种含量在1%以上的物质,主要是萜类中的单萜、倍半萜和芳香族醛、酮醚类物质。低含量组分主要为萜烯类的醇、醛、酮、酯和部分芳香族化合物。在气相分析中,选择了合适的条件,采用中等极性的DB 210柱,对孜然芹挥发油中的中等极性和非极性成分有较好的分离效果。 相似文献
92.
Dehydrated ammonium carnallite was synthesized with bischofite from salt lake and ammonium chloride solution in a 1:1 molar
ratio of MgCl2:NH4Cl, dehydrated at 160°C for about 4 h. The yield was above 85%. The product was then mixed with solid-state ammonium chloride
with a 1:4 mass ratio for the further dehydration at 410°C. The decomposition of NH4Cl made a pressure of NH3 at 30.5 kPa to prevent the hydrolysis of ammonium carnallite. The anhydration of magnesium chloride was achieved at 700°C.
The results showed that anhydrous magnesium chloride contains magnesium oxide in an amount that was less than 0.1% by weight.
XRD pattern and SEM micrograph showed a good dispersion of ammonium carnallite and anhydrous magnesium chloride crystals with
well-distributed big grains, just enough to meet the need for the production of magnesium metal in the electrolysis process.
__________
Translated from Chinese Journal of Applied Chemistry, 2005, 22(8) (in Chinese) 相似文献
93.
利用共沉淀法和固相法制备出SrZr0.95Y0.05O3微粒,采用溶胶包覆法使其与含氮TiO2溶胶复合,并原位光沉积Pt颗粒组装成异质结复合催化剂,采用XRD、TG-DTA、紫外可见漫反射光谱(UV-Vis DRS)和荧光光谱(FS)等技术对其进行了表征和分析,以草酸为牺牲剂,模拟太阳光下光催化产氢为探针,评价了催化剂的光催化活性。研究了不同氮源剂、烧结温度、载铂含量对催化剂光催化产氢活性的影响。结果表明,在模拟太阳光照射下,单独的SrZr0.95Y0.05O3和TiO2几乎不产生氢气;而将两者采用溶胶包覆法复合并掺氮后,所制备出的复合催化剂表现出一定程度的产氢活性,在氮源剂为三乙胺、400 ℃焙烧下具有最佳的产氢活性,催化活性的提高源于复合催化剂中形成的异质结抑制了光生载流子的快速复合以及氮掺杂引起对可见光的响应;进一步负载铂后,其产氢量得到大幅度的提高,其最佳负载量为1wt%,6 h内产氢量达到12.5 mmol,是未负载的样品的22倍多,这是由于铂负载进一步抑制了光生载流子的复合,从而大大地提高了光催化活性。 相似文献
94.
95.
In this paper, we use the abstract theory of semilinear parabolic equations and a priori estimate techniques to prove the
global existence and uniqueness of smooth solutions to the Cauchy problem for the following system of parabolic equations:
Supported by National Science Fundation of China. 相似文献
96.
Russian Journal of Organic Chemistry - 相似文献
97.
Jian Min Yi Sai Jin Huang Yu Ren Jiang Ke Wen Tang 《Journal of inclusion phenomena and macrocyclic chemistry》2010,68(3-4):271-275
To establish an extraction method for fenvaleric acid (FA) enantiomers using l-iso-butyl-l-tartaric esters and hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral selector, the distribution of FA enantiomers was examined in methanol aqueous solution containing HP-β-CD and 1,2-dichloroethane organic solution containing l-iso-butyl-l-tartaric esters. The influences of the concentration of l-iso-butyl-l-tartaric esters and HP-β-CD, organic diluent, pH, extraction temperature and the concentration of methanol aqueous solution on the partition coefficient (k) and separation factor (α) of FA were investigated. The experiment results showed that the complex formed by l-iso-butyl-l-tartaric esters with S-enantiomer is stabler than that with R-enantiomer. With the increase of the concentration of l-iso-butyl-l-tartaric ester, k and α increased; With the increase of the concentration of HP-β-CD, k increased firstly, and then decreased, but α increased all the while, k was the highest when the concentration of HP-β-CD was 4 mmol L?1. 1,2-dichloroethane organic diluent was better than the others. With the increase of pH, k and α decreased; with further increasing concentration of methanol aqueous solution, k and α decreased, k and α were the highest when the concentration of methanol aqueous solution was 10%. The extraction temperature had a great influence on k and α, too. 相似文献
98.
<正>The separation of enzymatic hydrolysis products of yeast RNA by ion-pair HPLC was studied.A modified chromatographic response function(MCRF) was proposed to appraise the effectiveness of chromatographic separation.This function takes the number of peaks,resolution and the retention time of the last peak into consideration.It shows advantages for optimization of HPLC separation of complex mixtures.An orthogonal array design was used to separate the hydrolysate of yeast RNA and the optimal chromatographic conditions were obtained. 相似文献
99.
研究项链李代数的结构,定义了箭图Q的重箭图Q循环上的映射σ,证明了这是一个李运算.引入左右指标数组概念,利用它们把项链李代数N_Q的基分成了5类,并构造了项链李代数的一些有趣的子代数. 相似文献
100.