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1.
Solubilization of cholesterol by mixed micelles of sodium chenodeoxycholate with sodium ursodeoxycholate was investigated in carbonate-tetraborate buffer (Kolthoff) solution at pH 10 and 37°C. It was found that the mixing of the two bile salts gives a negatively synergetic effect on solubilization of cholesterol. The solubilizing power of bile salts for cholesterol was remarkably influenced with the change in mole fraction of sodium ursodeoxycholate (X UDC).The behavior of bile salt solutions saturated with cholesterol was examined by measuring the surface tension. Two break points were observed in the curves of surface tension vs. concentration. The break points seem to correspond to a CMC in the absence of solubilized cholesterol and another CMC in the presence of solubilized cholesterol inside bile salt micelle.  相似文献   

2.
The critical micelle concentration (CMC) for bile salts or other surfactants is defined as that solute concentration at which appreciable changes in such phenomena as light scattering, surface tension, or solubilization of other organic molecules occur, these changes indicating appearance of surfactant aggregates. The CMC thus reflects hydrophobic interactions of the surfactant with itself. The self-association of hydrophobic molecules resembles the partition of a solute into the lipophilic phase in reversed-phase high performance liquid chromatography (RPLC): Both processes can be considered as transfers of a molecule from an aqueous to a lipophilic medium. The critical micelle concentration of a particular bile salt, being a measure of its hydrophobic self-association, should therefore be correlated with its Chromatographic mobility since they are fundamentally related phenomena. Experimentally, significant correlations between these quantities are obtained, both for bile salts andn-alky1 sulfonates, and only microgram amounts of sample are required for RPLC measurements. Among three homologous series of bile salt surfactants, CMC values predicted from RPLC measurements agree, within a standard error of 7%, with CMC values determined directly. This suggests the applicability of reversed-phase liquid chromatography to the micro-scale determination of critical micelle concentrations of bile salts,n-alkyl sulfonates, and other homologous series of surfactants.This work was supported in Part by NIH Grants HL-07878 (W.H.E.) and AI-21873 (B.G.B.) and by a Fulbright Senior Fellowship (B.G.B.). This is paper LXXX in the series Bile Acids by W.H.E.Deceased March 29, 1986  相似文献   

3.
The micellar properties of aqueous binary mixed solutions of sodium glycocholate, NaGC, and octa-oxyethylene glycol mono-n-decyl ether, C10E8, have been studied on the basis of surface tensions, the mean aggregation number and the polarity of the interior of the micelles. The mean aggregation number, measured by steady state quenching method, decreased with the increase of the mole fraction of NaGC in the mixed system. The polarity of the interior, estimated by the ratio of first and third vibronic peak in a monomeric pyrene fluorescence emission spectrum, suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of NaGC in the mixed system. These are considered to be caused by the differences in the chemical structure and the hydrophobic nature between NaGC and C10E8. The mean aggregation number and the polarity of the interior for each micelle near the CMC in lower total concentration of surfactants showed the tendency approaching those of pure micelle of the nonionic surfactant. This suggests that the ratio of NaGC in the initial micelles in the range of lower total concentration near the CMC is lower than that of the corresponding prepared mole fraction in the mixed system. This lower value was confirmed also from theoretical calculation of the ratio of NaGC at the CMC in the mixed micelle by regular solution treatment of Rubingh in the solution.  相似文献   

4.
Abstract

The surface properties of the mixtures of zwitterionic surfactants derived from olive oil (carboxylbetaine-OCB and sulfobetaine-OSB) and anionic surfactant-sodium dodecylbenzene sulfonate (SDBS) at different mole fractions were investigated by surface tension measurement. The influences of the addition of inorganic salts (NaCl, MgCl2) on the surface activities in OCB/SDBS and OSB/SDBS systems were also studied. The result shows that the two mixed systems possess lower CMC values and higher surface activities over all mole fractions studied than their individual components. Meanwhile, the noticeable synergistic interactions of OCB/SDBS and OSB/SDBS were determined by the micelle interaction parameter (βm) according to regular solution theory. It is observed that the mixed OCB/SDBS system at αOCB?=?0.6 and the mixed OSB/SDBS system at αOSB?=?0.6 exhibit the strongest synergism. In addition, the binary surfactant mixtures performed better surface activities upon addition of inorganic salts and the different valence state of mental ions of the inorganic salts had different surface ability effect on the mixed system: Mg2+?>?Na+.  相似文献   

5.
The present research work is associated with the fluorescence investigations of binary aqueous mixed surfactants solutions of anionic bis-sulfosuccinate gemini surfactant (BSGSMA1,8) and three different conventional surfactants—anionic viz. sodium dodecyl sulfate (SDS), cationic viz. cetyl trimethyl ammonium bromide (CTAB), and nonionic surfactant viz. Triton X 100. Steady-state fluorescence spectroscopy technique has been utilized to examine the micellization behavior of aqueous solution of pure myristyl alcohol-based BSGSMA1,8 having flexible methylene chain [(CH2)8] as spacer group. Critical micelle concentration (CMC), aggregation number (N), and micropolarity of pure and mixed surfactants systems were explored during the investigations. The results revealed the best synergism behavior of prepared gemini BSGSMA1,8 with SDS as compared to CTAB and Triton X 100. The maximum reduction in the value of pyrene intensity ratio (I1/I3) was observed for gemini and SDS mixed surfactant solution. On the other hand, the increased I1/I3 value of mixed gemini with Triton X 100 exhibited that mixed surfactant system of anionic gemini BSGSMA1,8 with non-ionic Triton X 100 is not as compact as other mixed surfactant systems. Aggregation number increased and micropolarity decreased with increased concentration of gemini surfactants.  相似文献   

6.
Sodium 10-undecenyl sulfate (SUS), sodium 10-undecenyl leucinate (SUL) and their five different mixed micelles at varied percent mole ratios were prepared. The critical micelle concentration (CMC), C20, γCMC, partial specific volume, methylene group selectivity, mobilities and elution window were determined using a variety of analytical techniques. These surfactant systems were then evaluated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC). As a commonly used pseudostationary phase in MEKC, sodium dodecyl sulfate (SDS) was also evaluated. The CMC values of SUS and SUL were found to be 26 and 16 mM, respectively, whereas the CMC of mixed surfactants was found to be very similar to that of SUL. The C20 values decreased dramatically as the concentration of SUL is increased in the mixed micelle. An increase in SUL content gradually increased the methylene group selectivity making the binary mixed surfactants more hydrophobic. Linear solvation energy relationships (LSERs) and free energy of transfer studies were also applied to predict the selectivity differences between the surfactant systems. The cohesiveness and the hydrogen bond acidic character of the surfactant systems were found to have the most significant influence on selectivity and MEKC retention. The SUS and SDS showed the strongest while SUL showed the weakest hydrogen bond donating capacity. The basicity, interaction with n and π-electrons of the solute and dipolarity/polarizability were the least significant factors in LSER model for the surfactant systems studied. Free energies of transfer of selected functional groups in each surfactant systems were also calculated and found to be in good agreement with the LSER data.  相似文献   

7.
The interaction in two mixtures of a nonionic surfactant Triton-X-100 (TX-100) and different ionic surfactants was investigated. The two mixtures were TX-100/sodium dodecyl sulfate (SDS) and TX-100/cetyltrimethylammonium bromide (CTAB) at molar fraction of TX-100, αTX-100 = 0.6. The surface properties of the surfactants, critical micelle concentration (CMC), effectiveness of surface tension reduction (γCMC), maximum surface excess concentration (Γmax), and minimum area per molecule at the air/solution interface (A min) were determined for both individual surfactants and their mixtures. The significant deviations from ideal behavior (attractive interactions) of the nonionic/ionic surfactant mixtures were also determined. Mixtures of both TX-100/SDS and TX-100/CTAB exhibited synergism in surface tension reduction efficiency and mixed micelle formation, but neither exhibited synergism in surface tension reduction effectiveness.  相似文献   

8.
Micellar-enhanced ultrafiltration (MEUF) was used to remove cadmium ions from wastewater efficiently. In this study the nonionic surfactants polyoxyethyleneglycol dodecyl ether (Brij35) and polyoxyethylene octyl phenyl ether (TritonX-100) were for micellar-enhanced ultrafiltration to lower the dosage of the anionic surfactant sodium dodecyl sulfate (SDS). The surfactant critical micelle concentration (CMC) and the degree of micelle counterion binding were investigated. The effects of nonionic surfactant addition on the efficiency of cadmium removal, the residual quantities of surfactant, the permeate flux and the secondary membrane resistance were investigated. A comparison between MEUF with SDS and MEUF with mixed anionic–nonionic surfactants was undertaken. The results show that the addition of Brij35 or TritonX-100 reduced the CMC of SDS and the degree of counterion binding for the micelles. Due to these variations the Cd2+ rejection efficiency was at a maximum when the Brij35:SDS and the TritonX-100:SDS molar ratio was 0.5. The Cd2+ rejection efficiency in MEUF with SDS is higher than for MEUF with mixed surfactants when the total dose of surfactant is constant. The permeate flux of MEUF with SDS is higher than that for MEUF with mixed surfactants while the secondary resistance of MEUF with SDS is less than that of MEUF with mixed surfactants.  相似文献   

9.
Summary Capillary electrophoresis has been investigated as a novel experimental method for determination of the aggregation constants of surfactants. The tendency of sodium cholate and sodium taurodeoxycholate to associate was studied in phosphate buffers of pH 8.0 and pH 7.0, respectively. Stepwise aggregation equilibria of bile salt monomers has been described in terms of massbalance equations. The Offord equation was used to model the electrophoretic mobility of the bile salt associates, and the experimental mobility values could be fitted to the model. Interestingly, only even-membered aggregates-dimers and tetramers-besides the monomers were proposed from the results of the curve-fitting for both bile salts. The aggregation constants calculated were (in molar units): cholate logK A2=1.37, logK A4=4.98 taurodeoxycholate logK A2=1.68, logK A4=6.46. From these values, more pronounced aggregation of taurodeoxycholate starting at lower concentrations has been deduced, supporting the back-to-back association model of bile salts.  相似文献   

10.
The binding of mixed surfactants of cationic cetyltrimethylammonium bromide (CTAB) and nonionic octaethylene glycol monododecyl ether (C 12E 8) on anionic polyelectrolyte poly[2-acrylamido-2-methylpropanesulfonic acid (PAMPS)] and fluorophore-labeled copolymers containing about 40 mol% of AMPS was investigated at different mole fractions, Y , of CTAB in the surfactant mixture. The excimer emission of the cationic probe 1-pyrenemethylamine hydrochloride (PyMeA·HCl), nonradiative energy transfer (NRET) between pyrene and naphthalene labels and I 1/ I 3 of the pyrene label were determined by varying the total surfactant concentration, c Surf. The I E/ I M value of PyMeA·HCl firstly increases and then decreases to 0 with c Surf, showing a maximum on every curve. The critical aggregation concentration of the mixed surfactants determined from the I E/ I M maximum decreased from 5×10 -5 to 1×10 -5 mol/l as Y increased from 0.1 to 0.50, and then leveled off as Y increased up to unity. And at least 5×10 -6 mol/l CTAB was required for the mixed surfactants to bind on the PAMPS cooperatively. Equimolar binding of CTAB on AMPS was formed at I E/ I M=0 when Y =0.25, while at Y =0.1 some CTAB molecules in the mixed micelle were directed to the water phase without binding with AMPS. Both the intramolecular and the intermolecular NRET increased and then decreased with c Surf, having a maximum on each curve corresponding to the equimolar binding of CTAB and AMPS so long as Y >0, indicating the coiling of the chain and interchain aggregation upon bound surfactants. The I Py/ I Np value at the maximum decreased with decreasing Y because more nonionic surfactant C 12E 8 participated into the polyelectrolyte-mixed surfactant complexes together with bound CTAB.  相似文献   

11.
The interaction of fluorocarbon‐ containing hydrophobically modified sodium polyacrylic acid (FMPAANa) (0.5 wt%) with various surfactants (anionic, nonionic and cationic) has been investigated by rheological measurements. Different rheological behaviors are displayed for ionic surfactants and nonionic surfactants. Fluorinated surfactants have stronger affinity with polyelectrolyte hydrophobes comparing with hydrogenated surfactants. The hydrophobic association of FMPAANa with a cationic surfactant (CTAB) and a fluorinated nonionic surfactant (FC171) is much stronger than with a nonionic surfactant (NP7. 5) and an anionic surfactant (FC143). Further investigation of the effects of temperature on solution properties shows that the dissociation energy Em is correlated to the strength of the aggregated junctions.  相似文献   

12.
13.
Dependences of the surface tension of aqueous solutions of ionic (dodecylpyridinium bromide, sodium dodecylsulfonate) and nonionic (Triton X‐100) surfactants and their mixtures on total surfactant concentration and solution composition were studied, and the surface tension of the mixed systems were predicted using different Miller's model. It was found that how to select the model for calculation of ω is corresponding to the degree of the deviation from the ideality during the adsorption of mixed surfactants. The compositions of micelles and adsorption layers at air‐solution interface as well as parameters (βm, βads) of headgroup‐headgroup interaction between the molecules of ionic and nonionic surfactants were calculated based on Rubingh model. The parameters (B1) of chain‐chain interaction between the molecules of ionic and nonionic surfactants were calculated based on Maeda model. The free energy of micellization calculated from the phase separation model (ΔG 2 m ), and by Maeda's method (ΔG 1 m ) agree reasonably well at high content of nonionic surfactant. The excess free energy ΔG ads E and ΔG m E (except α=0.4) for TX‐100/SDSn system are more negative than that TX‐100/DDPB system. These can be probably explained with the EO groups of TX‐100 surfactant carrying partial positive charge.  相似文献   

14.
The interactions between the anionic surfactant di-(2-ethylhexyl) phosphate sodium salt (DEP) and two nonionic surfactants, dimethyldecyl phosphineoxide (DDPO) and dimethyltetradecyl phosphineoxide (DTPO), at the interface and in the micellar phases were investigated in the absence and presence of adenosine-5-monophosphoric acid disodium salt (AMP). The mixed systems were DEP–DDPO, DEP–DDPO/AMP (0.001 mol⋅L−1), DEP–DTPO, and DEP–DTPO/AMP (0.001 mol⋅L−1) at different bulk mole fractions of the anionic component (α 1=0.9,0.8,0.6,0.4,0.2). The mixed systems studied were investigated based on the theoretical models of Rubingh and Clint. The results showed surface tension reduction efficiency. The adsorbed mixed monolayer demonstrated stronger interactions than the mixed micelles, whereas AMP increased the interfacial interactions more than those in the micellar phase. The Gibbs energy of mixing suggests that the stability of the mixed micellar phase is greater than that of the micellar phases of the individual components. The synergism that occurred in the different mixed phases is discussed.  相似文献   

15.
The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C8PO6EO3S (6-3) and C8PO6EO6S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface.  相似文献   

16.
The counterion binding behaviour of micelles of sodium dodecyl sulphate (SDS) and several bile salts in the pure state have been studied, as well as in mutually mixed states, and in a mixed state with polyoxyethylene sorbitan monolaurate (PSML) as a nonionic surfactant. Electrochemical measurements have shown no counterion binding by the pure bile salt micelles and their mixtures with PSML; they can bind counterions when mixed with SDS, whereas the surfactant anions of SDS micelles bind counterions in the pure state and/or in mixed states with PSML. In the SDS-PSML and SDS-bile salts combinations, the counterion association is decreased by the increased proportions of the second component. The extent of counterion binding by the different systems is presented.  相似文献   

17.
The micellization process of binary surfactant mixtures containing cationic surfactants viz. dodecyl pyridinium halide (C12PyX; X=Cl, Br, I), tetradecyl pyridium bromide (C14PyBr), and hexadecyl pyridium halide (C16PyX; X=Cl, Br) and a nonionic surfactants viz. dodecyl nonapolyethylene glycol ether (C12E9), dodecyl decapolyethylene glycol ether (C12E10), dodecyl dodecapolyethylene glycol ether (C12E12), and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0–1) were studied by surface tension method. The composition of mixed micelles and the interaction parameter, β evaluated from the CMC data obtained by surface tension for different systems using Rubingh's theory were discussed. Activity coefficient (f1 and f2) of cationic surfactant (CnPyBr)/C12Em (n=12, 14, 16 and m=10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda's approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.  相似文献   

18.
1-Alkyl-3-(2-oximinopropyl)imidazolium chlorides were prepared with different alkyl chain lengths (Alk = C12H25, C14H29). Some physicochemical indices (CMC and pK aapp) were determined. The reactivity of these compounds was studied in the dissociation of 4-nitrophenyl esters of diethylphosphonic, diethylphosphoric, and toluenesulfonic acids. The times for 50% conversion of the substrates into reaction products decrease in the series: C12H25 > C14H29 >C16H33. In selecting the direction of modification of the supernucleophilic functional surfactants, we should take into account not only their hydrophobic properties but also the efficiency of substrate solubilization as well as the reactivity of the oximate group in the surfactant micelles.  相似文献   

19.
The hydrolysis reaction rate of p‐nitrophenyl benzoate (p‐NPB) has been examined in aqueous buffer media of pH 9.18, containing surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), or sodium dodecyl sulfate (SDS) at 35°C. Although the rate constant [log (k /s−1)] of p‐NPB hydrolysis has once decreased slightly below the critical micelle concentration (CMC) value for CTAB and CTAC, it has begun to increase drastically with micellar formation. With increasing concentrations larger than the CMC value, the log (k /s−1) value has reached the optimal value, i.e., a 140‐ and 200‐fold rate acceleration for CTAB and CTAC, respectively, compared to that without a surfactant. Whereas the anionic surfactant, SDS, has caused only a gradual rate deceleration in the whole concentration range (up to 0.03 mol dm−3). Increases in pH of the buffer have resulted in increases of the hydrolysis rate. In the CTAB micellar solution, the remarkably enhanced rate has been retarded significantly by the addition of only 0.10 mol dm−3 bromide salts. The effects of rate retardation caused by the added salts follows in the order of NaBr > Me4NBr > Et4NBr > Pr4NBr > n‐Bu4NBr. In the absence of surfactant, however, the addition of the bromide salts has accelerated the hydrolysis rate, except for the metallic salt of NaBr, with the order of Me4NBr < Et4NBr < Pr4NBr < n‐Bu4NBr. In the CTAC micellar solution, similar rate retardation effects have been observed in the presence of chloride salts (NaCl, Et4NCl, and n‐Bu4NCl). The effects of added salts have been interpreted from the viewpoints of the changes in activity of the OH ion and/or the nucleophilicities of the anions from the added salts.  相似文献   

20.
The interaction energy between hydrophobic SiO2 particles in aqueous solutions of a cationic surfactant (dodecylpyridinium bromide, DDPB), a nonionic surfactant (Triton X-100, TX-100), and their mixed solutions was measured as a function of concentration. Synergism has been observed in mixed surfactant solutions: the surfactant concentration required for achieving the set interaction energy in the mixed solutions was lower than in the solutions of the individual surfactants. The molecular interaction parameters in surfactant mixtures were calculated using the Rosen model. Chain-chain interactions between nonionic and cationic surfactants were suggested as the main reason for the synergism.  相似文献   

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