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31.
María?Belén?Sierra Marcela?A.?Morini Pablo?C.?SchulzEmail author María?Luján?Ferreira 《Colloid and polymer science》2005,283(9):1016-1024
Following the studies on the effect of double bonds in the surfactant hydrophobic tail on the formation of mixed surfactant aggregates, we studied the viscosity and density of the system Sodium 10-undecenoate (SUD)–decyltrimethylammonium bromide (DTAB)–water. We found that the partial molar volume (pmv) and intrinsic viscosity of both, micellised and unmicellised mixtures, are non-ideal, dependent on the mixture composition and related to structural changes in micelles. These phenomena are caused by the presence of the double bond at the distal extreme of the SUD molecule, which has some affinity with water by formation of hydrogen bonds. In particular, as far as we know, this is the first report on non-ideal behavior of the pmv in mixed micelles. 相似文献
32.
The aqueous cationic system sodium undecenoate-dodecyltrimethylammonium bromide at low concentration
Maria?Belén?Sierra Marcela?A.?Morini Pablo?C.?SchulzEmail author 《Colloid and polymer science》2004,282(6):633-641
The aqueous sodium undecenoate (SUD) –dodecyltrimethylammonium bromide (DTAB) catanionic system was studied at low concentration. The system did not precipitate, even at a 1:1 SUD:DTAB proportion, but showed the formation of a coacervate in a range of surfactant mixture compositions. Micelles have a preferential composition of 0.37 mole fraction of SUD. This behavior is attributed to the presence of the double bond at the distal extreme of the SUD molecule, which can form hydrogen bonds with water. Consequently, the –CH=CH2 group is situated at the interface between the hydrocarbon micelle core and water, reducing the interfacial free energy. Structural computations demonstrate that the mentioned SUD proportion produces complete coverage of the micelle surface by the double bonds. 相似文献
33.
本文对微型管状离子选择电极在流动条件下的电化学特征进行了研究,并设计了新的集成微管路离子选择以电极功能块。用此微型装置测定了土壤、血清、水和药物中的K~+、Na~+、pH、Cl~-、F~-、阿托品、东茛菪碱,并和各种标准方法作了比较,获得满意分析结果。 相似文献
34.
甲基紫共振瑞利散射光谱法测定透明质酸钠 总被引:1,自引:0,他引:1
在pH5的乙酸盐缓冲介质中,甲基紫与透明质酸钠作用形成结合产物时将导致溶液共振瑞利散射(RRS)大大增强并产生新的RRS光谱,其最大散射峰位于341 nm处。透明质酸钠在0~2.5 mg.L-1范围内其浓度与RRS强度成正比。该法具有高灵敏度,对透明质酸钠的检出限(3σ)为20.1μg.L-1,选择性较好。此法用于测定从鸡冠组织中提取的透明质酸的粗品,测定结果的平均相对标准偏差为2.3%,加标平均回收率为98.9%。 相似文献
35.
36.
A background-free, fast protein staining method in polyacrylamide gel electrophoresis using an acidic dye, zincon (ZC) and a basic dye, ethyl violet (EV) is described. It is based on the counterion dye staining technique that employs two oppositely charged dyes to form an ion-pair complex in staining solution. The selective binding of free dye molecules to proteins in acidic solution produces bluish violet-colored bands. It is a rapid and end-point staining procedure, involving only fixing and staining steps that are completed in 1-1.5 h. The detection limit of this method is 8-15 ng of protein that is comparable to the sensitivity of the colloidal Coomassie Brilliant Blue G (CBBG) stain. Due to its sensitivity and speed, this stain may be more practical than any other dye-based stains for routine laboratory purposes. 相似文献
37.
During attempts to synthesize rare‐earth nitride tellurides black and bead‐shaped single crystals of the title compound sodium praseodymium(III) ditelluride (NaPrTe2) were obtained as a by‐product by reacting a mixture of praseodymium, sodium azide (NaN3) and tellurium at 900 °C for seven days in evacuated torch‐sealed silica vessels. NaPrTe2 crystallizes cubic (space group: Fd3¯m, Z = 16; a = 1285.51(9) pm, Vm = 79.96(1) cm3/mol, R1 = 0.028 for 146 unique reflections) and exhibits the Na+ and Pr3+ cations in slightly distorted octahedra of six telluride anions (d(Na—Te) = 325 pm, d(Pr—Te) = 317 pm) each. The main characteristics of this new structure type for alkali‐metal rare‐earth(III) dichalcogenides can be derived from the rock‐salt type structure (NaCl, cubic closest‐packed Te2— arrangement, all octahedral voids occupied with Na+ and Pr3+) with alternating layers consisting of Na+ and Pr3+ cations in a ratio of 3:1 and 1:3, respectively, piled along the [111] direction. 相似文献
38.
Summary In this paper, polymeric hollow fibers prepared from pH-stable polypropylene were used as columns for micellar electrokinetic
capillary chromatography (MECC). The electroosmotic flow (EOF) for polypropylene hollow fibers was evaluated in the pH range
of 5.0–12.0. With untreated polypropylene hollow fibers a stabilized but enhanced EOF was achieved when SDS was used in the
buffer, decreasing the separation window for uncharged substances in MECC to impractical levels. Uncharged acrylamide and
charged 2-acryloylamido-2-methylpropane sulfonic acid surface modifications were used to lower the strength of the EOF, increase
the separation window and prevent local overheating that could melt the column wall. 相似文献
39.
Uranium(VI) complexed with aluminon (3-[bis(3-carboxy-4-hydroxy-phenyl)methylene]-6-oxo-1,4-cyclohexadiene-1-carboxylic acid triammonium salt) was determined by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode. Trace uranium(VI) and zinc(II) can be simultaneously determined in a single scan in the presence of aluminon and urea. Optimal conditions were found to be: accumulation time; 180–200 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s−1, supporting electrolyte; 0.1 M sodium acetate buffer at pH 6.5–7.0, and concentration of aluminon; 1×10−6 M. The linear range of uranium(VI) and zinc(II) were observed over the concentration range 2–33 and 30–120 ng ml−1, respectively. The detection limit (S/N=3) are 0.2 ng ml−1 (uranium) and 30 ng ml−1 (zinc). A good reproducibility shows RSDs of 2.5–4.0% (n=10). The procedure offers high selectivity, with the presence of urea masking some metal ions. 相似文献
40.
In the presence of copper(I) iodide as catalyst, a variety of carbonyl compounds, such as aldehydes, ketones and acid anhydrous, could be trifluoromethylated with sodium trifluoroacetate to give the corresponding alcohols in moderate to high yields, and a possible mechanism was proposed to explain the roles of catalyst and solvent in the reaction system. 相似文献