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91.
92.
The surface pressure vs. mokcular surface area relations for dipalmitoyl phosphatidylcholine (DPPC) insoluble monolayer and sodium deoxycholate (SDC) adsorbed monolayer,L and D1, respectively, were obtained from the analyses of surface tensions measured by the Wilhelmy glass plate. Also, D1 was obtained by a drop-weight method. Next, the surface pressure time course,(t), of the SDC aq. was measured by the Wilhelmy plate before and after DPPC was spread on the liquid surface. At DPPC spreading,(t) jumped to a maximum,, and decreased along an exponential curve. The values of with various surface amounts of DPPC and bulk concentrations of SDC were analyzed using a dual surface-region model. The model enabled the estimation of. For better fitting, modified relations were constructed in place of D1. The exponential decrease of(t) was also observed on the SDC adsorbed monolayer which was rapidly compressed by a moving barrier. The(t) relaxation rate constants of the SDC monolayers which were compressed by DPPC spreading and the moving barrier agreed with each other, suggesting a desorption of SDC from the surface. 相似文献
93.
用在线萃取-流动注射分光光度法(FISP)测定了作为杂质与2,5-二羟基苯磺酸钙共存的对苯二酚。专门设计并制作了与流动注射分光光度测定单元组合在一起的在线萃取流路,对苯二酚用乙醚萃取进入有机相并在此相中于其吸收峰297.5 nm波长处测定其吸光度,通过萃取基体成分,即2,5-二羟基苯磺酸钙的干扰,由于其在乙醚中不溶解而得以消除。对苯二酚的吸光度与其相应浓度在3.5×10-6~5.0×10-4mol.L-1之间呈线性关系,相关系数达0.999 4。该方法的检出限为2.53×10-6mol.L-1。应用此方法分析了来自不同批次的3个试样,所得结果的RSD在0.69%~1.65%之间,且其值与药典法所测得结果相符。 相似文献
94.
Yong Zhong DU Fu Qiang HU Hong YUAN Shinzo OMI 《中国化学快报》2006,17(4):553-556
Stable poly(styrene-co-sodium styrene sulfonate) (P(St-NaSS) nanoparticles with broader size distribution were synthesized by thermal emulsion polymerization without any conventional initiators and emulsifiers. The obtained polymer nanoparticles have higher ξ potential, and the particle sizes have broad distribution. The stability of polymer particles originated from the addition of small amounts of ionic comonomer, NaSS, which can act as an emulsifier in somewhat. The monomer conversion could reach up to about 28 wt% in 48 h, and did not increase by further polymerization when higher polymerization temperature (120 ℃) was employed. This polymerization system may be give some further understand for mechanism of emulsion polymerization. 相似文献
95.
Summary It is demonstrated that magnesium can be titrated with EGTA in the presence of CaEDTA complex. On the basis of this substitution reaction, calcium and magnesium are successively titrated with EGTA, if an appropriate amount of CaEDTA is added after having reached the end point for calcium. Both end points are indicated amperometrically using a thallium oxide anode. The method has been tested for analysis of tap and mineral water. Larger amounts of manganese(II) render the calcium result too high. Moreover, the indication of both end points is affected by the electrode position of an inactive MnO2-layer onto the Tl2O3-layer. Reducing agents destroy the Tl2O3-layer. These interferences can be overcome by addition of an appropriate amount of manganate(VII) to the sample.
Sukzessive Substitutionstitration von Calcium und Magnesium mit ÄGTA, indiziert mit der Thalliumoxidelektrode
Zusammenfassung Magnesium kann mit ÄGTA in Gegenwart des CaÄDTA-Komplexes titriert werden. Auf der Grundlage dieser Substitutionstitration können Calcium und Magnesium nacheinander mit ÄGTA titriert werden, wenn nach dem Endpunkt für Calcium eine ausreichende Menge CaÄDTA zugesetzt wird. Beide Endpunkte werden amperometrisch mit Hilfe einer Thalliumoxidelektrode angezeigt. Die Methode wurde an Leitungswasser und Mineralwasser geprüft. Größere Mengen Mangan(II) bewirken zu hohe Calciumwerte. Darüber hinaus wird die Indikation beider Endpunkte dadurch beeinträchtigt, daß sich eine inaktive MnO2-Schicht auf der Tl2O3-Schicht elektrolytisch abscheidet. Reduzierende Stoffe zerstören die Tl2O3-Schicht. Diese Störungen können durch Zugabe von Permanganat vermieden werden.相似文献
96.
Usachev N. Ya. Belanova E. P. Krukovsky I. M. Kanaev S. A. Atal"yan O. K. Kazakov A. V. 《Russian Chemical Bulletin》2003,52(9):1940-1949
Thermal transformations in systems formed by interaction of Zn and Na nitrates with Y, X, and A zeolites were studied by TG—DTA technique. Temperature regions of existence of adsorbed water, water of crystallization, and decomposition of NO3
– anion were determined. These intervals depend on the composition, structure, method of preparation, and pre-treatment conditions of zeolite systems. The extent of NO3
– decomposition depends not only on the zinc and sodium content but also on the presence of ammonia involved in NO3
– reduction. The zeolite matrix strongly stabilizes the occluded NO3
– anions. A portion of zinc oxide formed by zinc nitrate decomposition is probably localized inside the zeolite cavities as the [Zn—O—(ZnO)
n
—Zn]2+ particles. The latter compensate charges of the isolated [AlO4]– tetrahedra. 相似文献
97.
不同介质凝胶体系中草酸钙结晶的研究 总被引:2,自引:0,他引:2
研究了五种不同介质(水、氯化钠、合成尿、正常人尿液和尿石患者尿液)的凝胶体系中草酸钙(CaC2O4)晶体的生长,及各种体系中防石药物柠檬酸钾(K3cit)对CaC2O4生长的影响.没有加K3cit时,CaC2O4晶体以一水草酸钙(calcium oxalate monohydrate, COM)为主要物相,但在氯化钠和合成尿的凝胶体系中同时出现了二水草酸钙(calcium oxalate dihydrate, COD)和三水草酸钙(calcium oxalate trihydrate, COT),肾结石患者尿液中出现COD,而正常人尿液中没有COD和COT生成.加入K3cit后,水、氯化钠和合成尿介质的凝胶体系中,COT的含量显著增加,患者尿液中产生大量COD,而正常人尿液中出现了少量的COD和极个别的COT.COT的增加与低温、体系中高的离子强度及金属离子等因素有关.K3cit具有诱导COD和COT的生成、减小COM晶体比表面积的作用,从而有利于防治草酸钙结石的形成. 相似文献
98.
J. -L. Fortier P. -A. Leduc P. Picker J. E. Desnoyers 《Journal of solution chemistry》1973,2(5):467-475
The enthalpies of dilution of NaCl, Me4NBr, andn-Bu4NBr were measured in water at 25°C with a new flow microcalorimeter. The data were analyzed with a polynomial equation, and the derived relative apparent molal enthalpies L are in good agreement with literature values. Provided care is taken that mixing is complete, flow calorimeters are as reliable and much less time-consuming than cell-type instruments for enthalpies of dilution measurements. 相似文献
99.
Two methods, e.g. initial rate method and thermokinetic reduced extent method were presented for studies on non-competitive
inhibition. Arginase-catalyzed the hydrolysis of L-arginine toL-ornithine and urea and the inhibition of this reaction by sodium fluoride were studied in the absence and presence of exogenous
of Mn2+at 37°C in 40 mM sodium barbiturate-hydrochloric acid buffer solution (pH 7.4). Both methods were successively used to determine
the values of K1. The advances and disadvantages of each method were compared in this paper. Exogenous Mn2+ could result in more sensitivity of arginase to F-1. Since the inhibition of arginase by F-1 depends on the pH values of the reaction system and behave as a non-competitive inhibition, it probably due to its small
volume and high electronic density allow it access to the activity site of the enzyme and replaces of μ-OH2 (or μ-OH) as the bridge ligand with Mn(II, II) cluster. However, further studies are necessary to determine the modes of
interaction of F-1 with bovine liver arginase.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
100.
水合硫酸氢钠催化合成2-乙氧基萘 总被引:2,自引:0,他引:2
以-水合硫酸氢钠为催化剂,β-萘酚和无水乙醇为原料合成了2-乙氧基萘。优化反应条件为:β-萘酚150mmol,无水乙醇900mmol,催化剂2.0g,回流反应时间5h,产率85.5%。 相似文献