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41.
Zeta-potentials of self-assembled surface micelles of ionic surfactants adsorbed at hydrophobic graphite surfaces 总被引:1,自引:0,他引:1
Vamsi K. Paruchuri Anh V. Nguyen Jan D. Miller 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,250(1-3):519-526
The zeta-potentials of the self-assembled surface ionic surfactants (sodium dodecyl sulfate—SDS and hexadecyltrimethyl ammonium bromide—CTAB) on graphite surfaces were determined both from streaming potential and electrophoretic mobility measurements. The adsorption of the surfactants at graphite–liquid interfaces has been studied using atomic force microscopy (AFM) soft-contact imaging which shows the formation of linear, parallel hemicylinders with headgroups oriented towards the solution. The magnitude of the zeta-potential increased with an increase in surfactant concentration, reaching a constant value at a concentration corresponding to the point of surface micelle formation as confirmed from AFM imaging. The streaming potential and electrophoretic mobility measurements showed that the zeta-potentials of SDS and CTAB surface micelles adsorbed at the graphite surface were about −75 and +70 mV, respectively, well in agreement with the values reported for bulk phase micelles in the literature. 相似文献
42.
以紫外光谱法研究了青霉素G钾盐(Pen-K)在十六烷基三甲基溴化铵(CTAB)胶束体系中的水解反应, 并探讨了水解反应机理.结果表明, CTAB胶束对Pen-K的水解具有抑制作用; Pen-K在CTAB胶束体系水解时,体系pH值的变化与在水中相似, 表明H+浓度对这种抑制作用影响较小.红外光谱和微极性研究表明,部分Pen-K钾盐定位于CTAB胶束栅栏层中, 增加了其稳定性. 相似文献
43.
A new, simple, and selective method has been presented for the separation and preconcentration of inorganic arsenic (As(III)/As(V)) and selenium (Se(IV)/Se(VI)) species by a microcolumn on-line coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES). Trace amounts of As(V) and Se(VI) species were separated and preconcentrated from total As and Se at desired pH values by a conical microcolumn packed with cetyltrimethylammonium bromide (CTAB)-modified alkyl silica sorbent in the absence of chelating reagent. The species adsorbed by CTAB-modified alkyl silica sorbent were quantitatively desorbed with 0.10 ml of 1.0 mol l−1 HNO3. Total inorganic arsenic and selenium were similarly extracted after oxidation of As(III) and Se(IV) to As(V) and Se(VI) with KMnO4 (50.0 μmol l−1). The assay of As(III) and Se(IV) were based on subtracting As(V) and Se(VI) from total As and total Se, respectively. All parameters affecting the separation/preconcentration of As(V) and Se(VI) including pH, sample flow rate and volume, eluent solution and volume have been studied. With a sample volume of 3.0 ml, the sample throughput was 24 h−1 and the enrichment factors for As(V) and Se(VI) were 26.7 and 27.6, respectively. The limits of detection (LODs) were 0.15 μg l−1 for As(V) and 0.10 μg l−1 for Se(VI). The relative standard deviations (RSDs) for nine replicate determinations at 5.0 μg l−1 level of As(V) and Se(VI) were 4.0% and 3.6%, respectively. The calibration graphs of the method for As(V) and Se(VI) were linear in the range of 0.5–1000.0 μg l−1 with a correlation coefficient of 0.9936 and 0.9992, respectively. The developed method was successfully applied to the speciation analysis of inorganic arsenic and selenium in natural water samples with satisfactory results. 相似文献
44.
阳离子表面活性剂与溴酚红的显色反应及其分析应用 总被引:15,自引:0,他引:15
黄传敬 《光谱学与光谱分析》2000,(2)
研究了阳离子表面活性剂 (CSAA)溴化十六烷基三甲铵 (CTAB)、溴化十六烷基吡啶 (CPB)在水溶液中与溴酚红 (BPR)的显色反应。发现在pH 5 0~ 6 0范围内 ,CSAA单体与BPR形成离子缔合物(缔合比为 3∶2 ) ,可用于微量CSAA及CSAA的临界胶束浓度 (CMC)的测定。本文还研究了显色反应的适宜条件、分析特征 ,并讨论了反应机理 相似文献
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48.
Different Aggregation Behaviors of Tetra- (4-hydroxyphenyl) Porphyrin (THPPH2) in the Inner Core and on the Surface of CTAB Micelles 总被引:2,自引:0,他引:2
It is hard to study the effects of different microenvironments on porphyrin aggregation because of its complex substituted groups. A trans-membrane process was realized by controlling bulk pH values for an amphiphilic porphyrin from the inner core to the surface of CTAB micelles1. Thus it is posible to study the different aggregation actions of the porphyrin in the inner core and on the surface of micelle. Results and DiscussionThe absorption spectra of THPPH2 at pH 7.2 have four Q bands… 相似文献
49.
以氯化亚锡(SnCl2.2H2O)和硫代乙酰胺(TAA)为前驱物,十六烷基三甲基溴化铵(CTAB)为表面活性剂,采用微波水热法控制合成花簇状SnS微球。采用XRD和FESEM等分析手段对制备的样品进行表征。结果表明:合成的产物为正交晶系的SnS微晶,且结晶性良好;SnS微晶是由长方形纳米片自组装而成的花簇状微球。通过改变CTAB用量,可以实现花簇状SnS微晶的形貌和尺寸的调控,并初步分析了其形成过程。利用紫外-可见吸收光谱分析,产物的光学带隙约为1.51 eV;室温光致发光光谱表明,产物在832 nm处具有近红外发光特性。 相似文献
50.
A transient micellar phase extractor using CTAB was described for the online sample concentration of various anionic analytes (drugs and herbicides) in CE. Stacking and separation was performed at neutral pH in coelectroosmotic flow in a hexadimethrine bromide coated fused‐silica capillary. A micellar plug (e.g. 10 mM CTAB) was injected prior to hydrodynamic injection of the analytes prepared in aqueous organic solvent (e.g. with 30% ACN). In the presence of an electric field, the micelles interacted with the anions inside the capillary. This was followed by selective analyte focusing via the mechanism of micelle to solvent stacking. The micelles acted as transient extractor because the stacking ends when the injected micelles completely migrated through the boundary between the sample and micellar plug. Fundamental studies were performed (effect of surfactant concentration, etc.) and the technique yielded 13‐ to 30‐fold improvements in peak height. A stacking CE method in conjunction with liquid–liquid extraction was also tested for the detection of the herbicides fenoprop and mecoprop in fortified drinking water at analyte concentration levels relevant to Australian Drinking Water Guidelines. 相似文献