Conductometric study of antidepressant drug-cationic surfactant mixed micelles in aqueous solution

Conductivity measurements have been carried out on aqueous solutions of two antidepressant drugs (nortriptyline hydrochloride and clomipramine hydrochloride) with four cationic surfactants (monomeric: cetyltrimethylammonium bromide, tetradecylammonium bromide; dimeric: 1,5-pentanediyl-alpha-omega-bis(hexadecyldimethylammonium bromide), 1,4-butanediyl-alpha,omega-bis(hexadecyldimethylammonium bromide) as well as with sodium chloride. Counterions from NaCl adsorb to the charged headgroup of the drug molecules and reduce the repulsion, hence cmc decreases. cmc values decreased with the addition of surfactants indicating mixed micelle formation. Experimental mole fraction of surfactants in micelle (X1) and their ideal values (X1 id) also support this explanation. Interaction parameter, beta, and excess free energy of micellization are negative suggesting synergism in mixed state. Activity coefficients are less than unity which means non-ideal mixing.     

多种类表面活性剂临界胶束浓度定量构效关系

表面活性剂的临界胶束浓度(CMC)是个非常重要的物质特性参数, CMC在研究表面活性剂的工业应用和生物利用方面发挥着关键作用. 本工作提出了一个新的拓扑指数—扩展距离矩阵, 建立了一个稳定的构效关系模型, 并对175种表面活性剂的临界胶束浓度进行了计算预测. 结果表明, 基于新的拓扑指数建立的构效关系模型计算临界胶束浓度能给出稳定可靠的预测结果, 其预测结果相关性系数R²(training set)=0.9295, 相对标准偏差ARD(training set)=8.20%, R²(testing set)=0.9257, ARD(testing set)=6.76%. 与文献中模型预测结果的对比表明, 本工作在稳定性和可靠性上均有显著改善.     

Rapid determination of surfactant critical micelle concentrations using pressure-driven flow with capillary electrophoresis instrumentation

This work demonstrates a novel, convenient utilization of capillary electrophoresis (CE) instrumentation for the determination of critical micelle concentrations (CMCs). Solution viscosity differences across a range of surfactant concentrations were monitored by hydrodynamically forcing an analyte towards the detector. Upon reaching the surfactant's CMC value, migration times were observed to change drastically. CMC values for four commonly employed anionic surfactants were determined—sodium dodecyl sulfate: 8.1 mM; sodium caprylate: 300 mM; sodium decanoate: 86 mM; sodium laurate: 30 mM; and found to be in excellent agreement with values previously reported in the literature. The technique was then applied to the less well-characterized nonionic surfactants poly(oxyethylene) 8 myristyl ether (CMC ∼ 9 M), poly(oxyethylene) 8 decyl ether (CMC ∼ 0.95 mM) and poly(oxyethylene) 4 lauryl ether.     

表面活性剂胶束化物理化学性质研究

通过电导法考查温度和盐浓度对十二烷基硫酸钠(SDS)临界胶束浓度(CMC)的影响,研究表面活性剂形成胶束过程的物理化学性质。根据拟相分离模型求得胶束化热力学函数,并讨论体系电导活化能随温度和SDS浓度变化关系。结果表明:SDS的CMC随温度升高而增加,随氯化钠浓度增大而减小。在热力学上SDS在水溶液中形成胶束是一个自发、放热、熵增的过程;在动力学上,SDS溶液电导率与温度关系符合Arrhenius公式,通过电导活化能信息可揭示离子型表面活性剂形成胶束的机理特征。     

荧光探针法测定甜菜碱cmc的研究

荧光探针法测定甜菜碱ｃｍｃ的研究任学贞，李干佐，王弘立，翟立民，隋卫平，徐欣艳（山东大学化学系，济南，２５０１００）关键词甜菜碱，芘，临界胶束浓度Ｅｋｗａｌｌ等［１］发现，表面活性剂的溶液能够增溶多环芳烃并发射较强的荧光．在常用的测定表面活性剂临界胶...     

Interfacial and aggregation properties of some anionic/cationic surfactant binary systems II. Mixed micelle formation and surface tension reduction effectiveness

Mixed micelle formation and surface tension reduction effectiveness (γ_cmc) were investigated for the following systems: triethanolammonium dodecylpoly(oxyethylene)sulfate (TADPS, containing about two ethylene oxide units)/dodecyltrimethylammonium bromide, TADPS/hexadecyltrimethylammonium bromide and TADPS/hexadecylpyridinium chloride. For all these anionic/cationic systems, the mixed critical micelle concentration (cmc) values reflect a strong synergism in mixed micelle formation, with β^M values ranging from −13.8 to −18.3. The mixed micelle composition is mixing-ratio dependent and, for equimolar mixtures, the mixed micelle is richer in the surfactant with the lower cmc. Precipitation is inhibited to a certain extent, thanks to the presence of ethylene oxide groups in the anionic species. The conditions for synergism in γ_cmc, differently expressed in the literature, can be derived from the surface tension equations established in our previous article. They can be conveniently described by a few characteristic constants: Γ _i ^∞ (saturated Gibbs excess), K _i (constant in the Szyszkowski equation), the cmc of the individual surfactants and the interaction parameters, β^S and β^M, of their mixtures. Excellent agreement between theoretically predicted and experimental results is obtained. With the increase in surfactant chain length, the β^M values decrease faster than the β^S ones and this can result in the loss of synergism in γ_cmc. Received: 11 June 2000 Accepted: 4 September 2000     

Electrochemical behavior of anthraquinone in aqueous solution in presence of a non-ionic surfactant

Cyclic voltammetric behavior of anthraquinone in aqueous medium has been studied in presence of a non-ionic surfactant, Triton X-100 (TX-100) using sodium salt of anthraquinone-2-sulphonic acid (AQS) as the electro-active species. When cathodic potential is applied, the anthraquinone (AQ) group of AQS is reduced to its dianion. In the reverse scan, the oxidation of AQ²⁻ gives AQ. The electrochemical behavior shows a profound influence from the dissolved state of TX-100 in aqueous media. Spectrophotometric results indicate interaction between AQ and TX-100. A CEC (chemical–electrochemical–chemical) mechanism with the electrochemical reaction coupled with preceding interaction of AQS with TX-100 and following protonation reaction of reduced AQ has been proposed.     

A Monomer‐Micelle Model for the Formation of Simple Taurocholate Micelles

A kinetic dialysis technique was used to validate a relationship between monomer taurocholate (TC) concentration and total TC concentration in TC solutions containing 0.15 M NaCl and 0.01 M buffer (pH = 7.4). Based on the experimental data and Mukerjee's equations, the number average degree and the weight average degree of TC aggregates were estimated to be nearly the same (～5), indicating that simple TC micelles were the only aggregates. Furthermore, the TC dimer concentration was quantified to be negligible. According to the validated relationship, aggregation number of 5 for simple TC micelles, and the definition of critical micelle concentration (CMC), a modified monomer‐micelle model was used for describing simple TC micelle formation. Moreover, the CMC value was estimated to be ～6.3 mM, which is consistent with the reported value of ～6.0 mM.     

Micelle formation of ethoxylated nonyl-phenols in aqueous solutions

The micelle formation of nonyl-phenols with various numbers of ethoxy groups (n _EO=10–40) was investigated in aqueous solutions and the study was focussed on the effect of temperature (293–323 K), the chain length and the inorganic electrolyte (NaCl) on the critical micelle concentration (c.m.c).The c.m.c. was determined by surface tension and interfacial tension measurements in a water/n-octane system. On the basis of the actual c.m.c. and its temperature dependence the thermodynamic functions of micelle formation (H° _m,S°_m,G°_m) were also calculated. The latter study comprised the determination of the thermodynamic function for unity ethoxy groups ((Y° _m)) as a function ofn _EO.According to the experimental results the micellar solutions are the more stable, the smaller the number of ethoxy groups in the tenside molecule and the higher the temperature as well as the electrolyte content of the system.     

Determination of the critical premicelle concentration, first critical micelle concentration and second critical micelle concentration of surfactants by resonance Rayleigh scattering method without any probe

The purpose of this work is to determine the values of critical premicelle concentration (CPMC), first critical micelle concentration (FCMC) and second critical micelle concentration (SCMC) of surfactants using a common spectrofluorophotometer by recording resonance Rayleigh scattering (RRS) signal without any probe. The plot of the RRS intensities at the maximum scattering wavelength (I(RRS)(max)) versus surfactant concentrations (c) was constructed to obtain the I(RRS)(max)-c curve. From the inflexions in I(RRS)(max)-c curve, the CPMC, FCMC and SCMC values of a surfactant can be obtained sensitively. The FCMC of some anionic, cationic and nonionic surfactants such as sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), Tween-20, and Tween-80 were determined by RRS method and the values are in good agreement with those obtained from conductivity and surface tension measurements and literature values. The CPMC and SCMC of SDS and CTAB were also determined by RRS method respectively and the values conform to literature values too. Furthermore, RRS method can also be used to determine the FCMC of an amphiphilic macromolecule-hemoglobin, whose structure resembles a surfactant. From the experimental results, it is concluded that RRS method can be applied to the simultaneous determination of the CPMC, FCMC and SCMC values in a sensitive, accurate and no probe way.     

Interactions between cationic gemini/conventional surfactants with polyvinylpyrrolidone: Specific conductivity and dynamic light scattering studies

The interaction between bis(hexadecyldimethylammonium)hexane dibromide (16-6-16), bis(tetradecyldimethylammonium)hexane dibromide (14-6-14), their conventional counterparts cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) with polyvinylpyrrolidone (PVP) was investigated using the conductivity technique. The results show that gemini surfactants interact strongly with PVP as compared to conventional surfactants. The results also reveal that the surfactants with shorter hydrocarbon chain interact weakly as those of longer hydrocarbon chain. The interactions of 16-6-16 and 14-6-14 and their conventional counterparts with PVP were also studied using dynamic light scattering (DLS) measurements. We have also highlighted the effect of surfactant–polymer interactions on the dispersion force in the solution. Critical aggregation concentration (cac) and critical micelle concentration (cmc) were obtained using the conductivity data. The degrees of micelle ionization and free energies associated with aggregation, micellization, and transfer have also been evaluated and discussed.     

壬基酚聚氧乙烯醚在油相中的CMCo及相关问题研究

对壬基酚聚氧乙烯醚在油相中的临界胶束浓度(CMC_o)及与之相关的问题进行了研究,并获得了部分CMC_o值.对CMC_o与表面活性剂自身结构的关系进行分析和数学处理后,发现CMC_o与活性物质自身结构间仍为对数关系.同时在对某些具体体系的界面张力随表面活性剂不同而发生的变化进行了详细分析,发现CMC_w和CMC_o是评价表面活性剂性能的有效工具.     

Adsorption of phenol and benzyl alcohol onto surfactant modified silica

The adsorption of the surfactant, dodecyltrimethylammonium bromide, DTAB, and the co-adsorption of the additives phenol and benzyl alcohol, onto silica from aqueous solutions are investigated. The adsorption of DTAB is found to increase with increasing alcohol concentration in solutions where the DTAB concentration is below the cmc. Moreover, the corresponding adsorption of DTAB decreases when the DTAB concentration is above the cmc. The co-adsorption of the alcohol is found to increase with increasing alcohol concentration, and benzyl alcohol co-adsorbs more strongly than phenol. The surfactant modified silica shows a very high ability to incorporate phenol and benzyl alcohol. The results are discussed in relation to solubilization site and surfactant aggregate shape.     

Formation and coexistence of the micelles and vesicles in mixed solution of cationic and anionic surfactant

In the aqueous mixtures of sodium alkylcarboxylate and alkyltrimethylammonium bromide, large unilamelar vesicles can be formed spontaneously or by sonication as the total carbon number in the HC chains is 19 (or larger). Vesicle formation can be influenced by changes of pH, molar ratio of the two surfactant components, and the polar head group of cationic surfactant. Micelles may coexist with the vesicles in these mixed systems. The larger hydrodynamic radius (200 nm) and aggregation number (800) illustrate that the shape of the micelle in 1:1 C₉H₁₉COONa–C₁₀H₂₁N(CH₃)₃Br is rod-like. In some mixed systems, the micelles can be transformed into stable vesicles by sonication — a phenomenon revealed for the first time. The surface-chemical properties of these catanionic surfactant solutions and the stabilities of vesicle have been studied systematically.     

The interaction of isomeric hexanediols with sodium dodecyl sulfate and dodecyltrimethylammonium bromide micelles

The micelle formation process for a typical anionic surfactant, sodium dodecyl sulfate, and a typical cationic surfactant, dodecyltrimethylammonium bromide, has been investigated in a series of mixed solvents consisting of different concentrations of isomeric hexanediols (1,2-hexanediol and 1,6-hexanediol) in water. The critical micelle concentrations and the degrees of counterion dissociation of the mixed micelles were obtained from conductance experiments. Luminescence probing experiments have been used to determine the concentration of micelles in solution and, hence, the micellar aggregation numbers of the surfactants in the mixed solvent systems. The alcohol aggregation numbers were determined by combining the partition coefficients (obtained using NMR paramagnetic relaxation enhancement experiments) with the micellar concentrations from the luminescence probing experiments. All these results are interpreted in terms of the difference in the interaction of the isomeric hexanediols with the surfactant as a function of the position of the hydroxyl groups on the six-carbon chain of the alcohol. Received: 28 June 2000/Accepted: 5 July 2000     

Determination of the Critical Micelle Concentration of Cationic Surfactants by Capillary Electrophoresis

The determination of the critical micelle concentration (CMC) of cationic surfactants by capillary electrophoresis was demonstrated. In this study, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DoTAB) were selected as cationic surfactants and propazine was chosen as test solute. In the evolution of the effective electrophoretic mobility of propazine as a function of surfactant concentration, a dramatic change in slope at a particular concentration is a good indication of the CMC of this surfactant. The CMC values determined experimentally were further confirmed by a curve-fitting approach. Simulation of the electrophoretic mobility curves as a function of surfactant concentration in both micellar electrokinetic chromatography and capillary zone electrophoresis using cationic surfactants as an electrolyte modifier was performed for propazine, and the intersection of these two mobility curves allowed us to precisely predict the CMC of the surfactant. The CMC values determined for TTAB and DoTAB are 1.6 ± 0.1 and 11.0 ± 0.1 mM, respectively, in the case of an electrolytic solution consisting of 70 mM phosphate buffer at pH 6.0. Moreover, the applicability of the electroosmotic mobility as a parameter for the determination of the CMC was examined.     

DMABN测定含溴化钠或正丁醇水溶液中表面活性剂的临界胶团浓度

以对二甲氨基苯甲腈(DMABN)为探针, 测定它在含NaBr或n-C4H9OH的表面活性剂十二烷基三甲基溴化铵(C12TABr)、季铵盐Gemini表面活性剂C12-3-C12·2Br和十二烷基硫酸钠(SDS)水溶液中的第二重荧光对应的强度(Ia)和特征波长(λa)对表面活性剂浓度(c)曲线. 由Ia-c曲线的转折点或λa-c曲线对应的一阶导数极小点可以获得临界胶团浓度(cmc), 扩展了DMABN探针测定表面活性剂cmc的适用性.     

Synthesis and characterization of a novel double-tailed cationic surfactant

A novel double-tailed cationic surfactant, N,N′-didodecylacetamidinium bicarbonate, was prepared by reacting dimethylacetamide dimethyl acetal with dodecylamine, followed by reacting with dry ice. MSD, FTIR, ¹H NMR, ¹³C NMR, 2D-NMR were used to confirm its structure. The surfactant reduced the surface tension of pure water to 24.7 mN m⁻¹ and its critical micelle concentration was 8.75 × 10⁻⁵ M. Formation of vesicle was also observed.     

Solution behaviour of a formate capped surfactant—the oxidation product of an alcohol ethoxylate

The solution behaviour has been investigated for an alcohol ethoxylate terminated with a formic acid ester. This compound has previously been reported to be an important degradation product in the auto-oxidation of alcohol ethoxylates. In this work we have investigated the solution behaviour of the formic acid ester surfactant C₁₂H₂₅(OCH₂CH₂)₄OCHO (C12E4---OCHO). The pure formate was found to be sparsely soluble in water with no clear point at 0.1%. The critical micelle concentration was found to be 129 μM at 35°C, compared to 50 μM for the parent surfactant C₁₂H₂₅(OCH₂CH₂)₅OH (C12E5). To mimic the behaviour of the oxidised surfactant, the formate was mixed in different ratios with C12E5 and the cloud point, surface tension and critical micelle concentration (cmc) of these mixtures were studied. The gradual increase of formate was found to shift the cloud point and isotropic regions to lower temperatures. The cmc of the mixture was found to be lower than for the pure surfactant. The favourable interaction was analysed according to the non-ideal model by Rubingh and the interaction parameter, β, was determined to be −4±0.53, which is unusually large for a mixture of two non-ionic surfactants. These results indicate that the reduction of cloud point observed during oxidation of non-ionic surfactants can in part be attributed to the formation of formate esters.