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861.
建立高效液相色谱法同时测定食品中的安赛蜜、苯甲酸、山梨酸、苋菜红、脱氢乙酸、胭脂红、日落黄、诱惑红8种添加剂。样品采用Agilent zorbax sb–C_(18)色谱柱梯度洗脱,紫外检测器检测,外标法定量分析。结果表明,8种添加剂的质量浓度在0.5~20μg/m L范围内与其色谱峰面积线性关系良好,相关系数均大于0.999,方法检出限为0.06~0.18 mg/kg。样品的加标回收率为91.3%~101.1%,测定结果的相对偏差为0.47%~1.35%(n=6)。该方法操作简单,灵敏度高,结果准确可靠,适用于食品添加剂的常规分析。 相似文献
862.
An efficient and general selective method for the synthesis of 8-aminoquinoline derivatives has been disclosed through transition metal direct C–N coupling from fluoroquinolines and arylamines. Significantly, good chemo- and regio-selectivity was observed for polyfluoroquinolines in which only C–F bond on 8-substituted position was broken. Thus, this methodology proves its value as an inexpensive and efficient synthetic way to access quinolin-8amine derivatives in moderate to good yields. 相似文献
863.
Wei Li Jianling Zhang Dr. Yueju Zhao Minqiang Hou Dr. Buxing Han Prof. Dr. Cailan Yu Jianping Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(4):1296-1305
The study of the micelle‐to‐vesicle transition (MVT) is of great importance from both theoretical and practical points of view. Herein, we studied the effect of compressed CO2 on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactants in aqueous solution by means of direct observation, turbidity and conductivity measurements, steady‐state fluorescence, time‐resolved fluorescence quenching (TRFQ), fluorescence quantum yield, and template methods. Interestingly, all these approaches showed that compressed CO2 could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO2 can be used to switch the MVT reversibly by controlling pressure. Some other gases, such as methane, ethylene, and ethane, could also induce the MVT of the surfactant solution. A possible mechanism is proposed on the basis of the packing‐parameter theory and thermodynamic principles. It is shown that the mechanism of the MVT induced by a nonpolar gas is different from the MVT induced by polar and electrolyte additives. 相似文献
864.
Xiangyang X Ling L Jianping Z Shiyue L Jie Y Xiaojin Y Jinsheng R 《Colloids and surfaces. B, Biointerfaces》2007,55(2):222-228
N-Succinyl-N′-octyl chitosan (SOC) was prepared and characterized by elemental analysis, FTIR, 1H NMR, WAXD and TG. An anticancer drug, doxorubicin (DOX), was incorporated into polymeric micelles forming by SOC in aqueous solutions. Critical micelle concentrations (CMC) of SOC were determined by fluorescence spectroscopy. The DOX-loaded SOC micelles were characterized by measurement of size and drug loading. The loading content of DOX increased with increasing drug-to-carrier ratio, and the more amount of the octyl chain, the higher the drug loading content. The average size, which was affected by the amount of octyl chain and drug loading content, was in the range of 100–200 nm. The polymeric micelles containing doxorubicin in the core region exhibited a sustained release and more cytotoxic activity against HepG2, A549, BGC and K562 than doxorubicin alone, this can be attributed to an endocytosis mechanism rather than passive diffusion. 相似文献
865.
Jianping Ou 《Journal of mathematical chemistry》2007,42(3):423-432
Let G be an n-vertex unicyclic molecular graph and Z(G) be its Hosoya index, let F
n
be the nth Fibonacci number. It is proved in this paper that if G has girth l then Z(G) ≥ F
l+1+(n−l)F
l
+F
l-1, with the equality holding if and only if G is isomorphic to , the unicyclic graph obtained by pasting the unique non-1-valent vertex of the complete bipartite graph K
1,n-l
to a vertex of an l-vertex cycle C
l
. A direct consequence of this observation is that the minimum Hosoya index of n-vertex unicyclic graphs is 2n−2 and the unique extremal unicyclic graph is. The second minimal Hosoya index and the corresponding extremal unicyclic graphs are also determined. 相似文献
866.
Liquid chromatography/ultraviolet (LC/UV) and mass spectrometry/mass spectrometry (MS/MS) libraries containing 39 phenolic compounds were established by coupling a LC and an ion trap MS with an electrospray ionization (ESI) source, operated in negative ion mode. As a result, the deprotonated [M-H]- molecule was observed for all the analyzed compounds. Using MS/MS hydroxybenzoic acid and hydroxycinnamic acids showed a loss of CO2 and production of a [M-H-44]- fragment and as expected, the UV spectra of these two compounds were affected by their chemical structures. For flavonol and flavonol glycosides, the spectra of their glycosides and aglycones produced deprotonated [M-H]- and [A-H]- species, respectively, and their UV spectra each presented two major absorption peaks. The UV spectra and MS/MS data of flavan-3-ols and stilbenes were also investigated. Using the optimized LC/MS/MS analytical conditions, the phenolic extracts from six representative wine samples were analyzed and 31 phenolic compounds were detected, 26 of which were identified by searching the LC/UV and MS/MS libraries. Finally, the presence of phenolic compounds was confirmed in different wine samples using the LC/UV and LC/MS/MS libraries. 相似文献
867.
以末端含有炔基的2-十二烷基三硫代碳酸酯-2-甲基-丙酸丙炔醇酯(DMPE)为链转移剂(CTA),2,2′偶氮二异丁腈(AIBN)为引发剂,在N,N-二甲基甲酰胺(DMF)中,利用可逆加成-断裂链转移(RAFT)聚合反应制备了分子链末端带炔基的均聚物聚(N-丙烯酰基-L-缬氨酰甲胺)(PAVMA—C帒CH),然后与叠氮基封端的聚乙二醇单甲醚(MPEG-N3)进行"click"偶合反应,制备具有温敏特性的光学活性嵌段聚合物MPEG-b-PAVMA.利用1H-NMR和体积排阻色谱(SEC)等表征了所合成的均聚物和共聚物的结构和分子量分布.1H-NMR结果表明所合成的嵌段共聚物中MPEG和PAVMA链段的重复单元数分别为115和55.利用紫外分光光度计测试了均聚物及嵌段聚合物的温敏特性,结果表明均聚物和共聚物在水中的低临界溶解温度(LCST)分别为6.5℃和19.5℃.比旋光度测试结果表明,均聚物和共聚物具有旋光性,同时相比于单体,其旋光能力有所降低.圆二色谱法(CD)的测试结果显示,均聚物和嵌段共聚物在220nm和197nm附近分别有一个较弱的正Cotton效应峰和一个较强的负Cotton效应峰,并且在水溶液中主要以无规的二级构象结构存在。 相似文献
868.
采用ANSYS有限元分析软件中热分析结构单元,对聚合物电致发光二极管(PLED)在光强为1000cd/m2时的热特性进行模拟,获得其温度场、热流分布及温度梯度的分布图,从仿真结果知PLED器件的最高温度为45.968℃,处于PFO-BT发光层,最低温度为45.95℃,处于石英玻璃基底末端.计算得出聚合物发光器件总热阻为1305℃/W,聚合物发光层至石英玻璃基底末端热阻为1℃/W.通过改变PLED器件输入功率、基底材料以及基底厚度3个参数,分别模拟得出其对PLED器件热特性的影响,仿真结果表明器件最高温度TH与输入功率P显现良好的线性关系;不同基底材料对器件温度影响小,负极端为器件主要散热通径;当基底厚度不断增加时,PLED器件最高温度随着增加,而最低温度不断减少,器件总热阻基本不变,发光层至石英基底末端热阻线性增大. 相似文献
869.
870.
Sun S Cheng Z Xie J Zhang J Liao Y Wang H Guo Y 《Rapid communications in mass spectrometry : RCM》2005,19(8):1025-1030
A method incorporating headspace liquid-phase microextraction (HS-LPME) coupled to matrix-assisted laser desorption/ionization (MALDI) with Fourier transform mass spectrometry (FTMS) was established to analyze volatile basic components in tobacco. The sample preparation volume for MALDI-MS was compatible with the volume of the solvent microdrop in the HS-LPME procedure. The pH and the polarity of the solvent for HS-LPME were adjusted by choice of the MALDI matrix and matrix additive. Based on the elemental composition and tandem mass spectrometry information, 25 volatile nitrogenous compounds in tobacco were detected and identified. The approach is fast and sensitive, and has the potential for automation for high-throughput analysis. This approach offers an alternative method for analysis of trace volatile organic compounds in complex samples. 相似文献