Sodium Decyl Sulfate Research Articles

Characterization and quantitation of apolipoprotein B-100 by capillary electrophoresis

The interaction of low density lipoproteins (LDL) with different surfactants was studied by capillary electrophoresis (CE) and sucrose density gradient ultracentrifugation as part of developing a method for quantitation of apoB-100 in serum. A mixture of surfactants consisting of 70% sodium dodecyl sulfate (SDS), 25% sodium myristyl sulfate, and 5% sodium cetyl sulfate was found to delipidate LDL particles more effectively than pure SDS or sodium decyl sulfate. The delipidation products of LDL [apolipoprotein B-100 (apoB-100) and lipids] were resolved as two distinct peaks by CE when using a 3.5 mm 70% SDS mixture, 20% (v/v) acetonitrile, 50 mm sodium borate, pH 9.1 buffer. This CE method was also used to characterize apoB-100 derived from samples of lipoprotein [a] and very low density lipoproteins (VLDL). A CE-based quantitation method for apoB-100 was developed utilizing the observed linear relationship between apoB-100 concentration and its corrected 214 nm absorbance peak area measured on-line by CE. Concentration values of apoB-100 in LDL and VLDL samples were determined by CE and found to be accurate when compared to values obtained by immunoturbidimetric analysis and the Lowry method. Capillary electrophoresis can be used as a precise, accurate, and specific on-line method for the qualitative and quantitative analysis of the apoB-100 component of VLDL and LDL-related lipoproteins.—Cruzado, I. D., S. L. Cockrill, C. J. McNeal, and R. D. Macfarlane. Characterization and quantitation of apolipoprotein B-100 by capillary electrophoresis. J. Lipid Res. 1998. 39: 205–217.

Preparation of Sodium Decylphosphate: Physical Chemical Measurements and Elaboration of the Binary Lyotropic Phase Diagram

Preparation and analysis of sodium decylphosphate, and elaboration of the binary phase diagram with water as solvent are presented. Lyomesophases isotropic, nematic calamitic and hexagonal are present and were studied by polarizing microscopy, small angle x-ray scattering, densimetry and refratometry. The results are compared with a related surfactant system, sodium decylsulphate.

Preparation of Sodium Decylsulphonate: Physical Chemical Measurements and Elaboration of a Ternary and a Quaternary Lyotropic Phase Diagram

Preparation and analysis of sodium decylsulphonate (SDSNATE), as well as the elaboration of the ternary and quaternary phases diagram are here presented. The lyomesosphases were studied by: polarizing microscopy, small angle X-ray scattering, densimetry and refratometry. We compare the present results on the SDSNATE systems to sodium decylsulphate systems and perhaps the most important point is that the SDSNATE is free of hydrolysis for all mesomorphic purposes, i.e. the SDSNATE is thermally stable.

Preparation of Sodium Decylsulphate: Physical Chemical Measurements and Elaboration of a Ternary and a Quaternary Lyotropic Phase Diagram

Preparation and analysis of sodium decylsulphate, as well as the elaboration of a ternay and a quaternary phase diagram are here presented. The lyomesophases were studied by: polarizing microscopy, small angle X-ray scattering, densimetry and refractometry. The results will be used as basis of comparison in subsequent articles for the related surfactants sodium decylphosphate and sodium decylsulphonate in lyotropic systems.

Titration microcalorimetry of adsorption processes in aqueous systems Interaction of sodium dodecylsulfate and sodium decylsulfate with poly(N-vinylpyrrolidone)

Procedures are described for analysing enthalpograms characterising adsorption by macromolecules in solution recorded using a titration microcalorimeter. The experimental procedure involves injecting small aliquots of a solution containing adsorbate into a sample cell containing a solution of macromolecular adsorbent. Treatments based on both Langmuir and Frumkin adsorption isotherms are described. The procedures are illustrated by application of the derived equations to the interaction of micelles of sodium dodecylsulfate(aq) and of sodium decylsulfate(aq) with the water-soluble polymer, PVP. The dominant features in the recorded enthalpograms are described using equations developed from the Frumkin equation. In both cases the adsorption is endothermic attributed to hydrophobic interactions between polymer and surfactant. However, an important feature of the analysis is the characterisation of adsorbate–adsorbate interactions using enthalpic interaction parameters. The enthalpograms are characterised by three composition ranges: (i) micelle deaggregation and weak interaction of monomers with polymer, (ii) micelle adsorption on to the soluble polymer up to surface saturation and (iii) micelle dilution.

Extremely Strong Interaction of Sodium Decyl Sulfate and Decyltrimethylammonium Bromide in Molecular Aggregates

The thermodynamic behavior of a mixture of sodium decyl sulfate (SDeS) and decyltrimethylammonium bromide (DeTAB) in aqueous solution and in molecular aggregates such as surface adsorbed films and micelles was investigated by measuring the electric conductivity and surface tension of the aqueous solutions. The thermodynamic quantities in solution and those in the molecular aggregates were evaluated from the experimental conductivity and surface tension data. The results for molar conductivity showed that dimerization or ion-pair formation of the SDeS and DeTAB molecules does not occur in aqueous solution and the mixture behaves as uni–univalent strong electrolyte below the critical micelle concentration (CMC). Contrary to the results in the aqueous solution, we found significant nonideal behavior in the phase diagrams of surface adsorption; that is, equimolar mixture of SDeS and DeTAB exists in the adsorbed film at almost all compositions irrespective of the bulk composition in the solution. The same result was also observed in the phase diagram of micelle formation. There was no difference in phase diagrams between surface adsorption and micelle formation at the CMC. The great nonideal mixing of SDeS and DeTAB in the molecular aggregates is undoubtedly attributable to the extreme attractive interaction between oppositely charged polar head groups of surfactants as well as to cohesion between hydrophobic groups. Further, in a low concentration region, it turned out that equimolar composition is preserved in the film during phase transition of the mixed adsorbed film of SDeS and DeTAB from a gaseous state to an expanded state.

Demixing of Mixed Micelles. Thermodynamics of Sodium Perfluorooctanoate−Sodium Dodecanoate Mixtures in Water

Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water−sodium perfluorooctanoate (NaPFO)−sodium dodecanoate systems were carried out as functions of the surfactants' total molality (mt) at different mole fractions (XNaPFO). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization (β) of the micelles were derived. The cmc's of the micelles are higher than those of the pure surfactants while β depends linearly on XNaPFO. At a given mole fraction, the apparent molar volume (VΦ) and heat capacity (CΦ) of the mixture increases and decreases monotonically with mt, respectively. From data in the premicellar region, the standard (infinite dilution) partial molar properties (Yo) of the mixtures were calculated for both volume and heat capacity. Yo depends linearly on XNaPFO according to the ideal behavior. From data in the postmicellar region, the excess properties (Yexc) for the mixed micelles formation from pure micelles were calculated. The values of the excess volumes and heat capacities are positive and negative, respectively, in the whole range of composition. The excess free energy (Gexc) is negative while both enthalpy and entropy are positive. On the basis of the pseudophase transition model and experimental evidences, the Gexc vs composition profile was derived. This profile indicates the presence of a critical point for 0.4 ≤ XNaPFO ≤ 0.6. According to this approach, Gexc was calculated for some mixtures. It turned out that sodium dodecanoate and sodium dodecyl sulfate micelles are miscible in the whole range of composition while ammonium perfluorononanoate (NH4PFN) and ammonium dodecyl sulfate micelles are partially miscible, and the coexistence of the two mixed micelles pseudophases occurs in the range 0.43 ≤ XNH4PFN ≤ 0.75. In the case of the sodium decyl sulfate−sodium perfluorooctanoate system, only a critical point is present.

Investigation of the force–distance relationship for a small liquid drop approaching an adhesive liquid/liquid interface

We have used a novel apparatus to investigate the forces between two liquid surfaces which are mutually attractive. An oil drop is formed at the tip of a thin flexible micropipette and the force exerted on the oil drop as it is pressed up to an oil/water interface is determined from the vertical deflection of the pipette shaft. The disjoining pressure in the thin, oil–water–oil emulsion film, formed by contact of the drop with the oil/water interface, is determined by the hydrostatic pressure applied to the oil contained in the micropipette. The radius and the thickness of the film are derived from the optical interference pattern observed using a microscope. A theory is presented for the variation in force and film radius as the drop is moved up to and down from the interface. Experimental results are given for dodecane–water–dodecane emulsion films stabilised by the anionic surfactant sodium decyl sulfate (SDS) in the presence of different aqueous phase concentrations of NaCl, which modifies the attractive force between the monolayers. Data for the force and film radius as a function of the pipette position relative to the oil–water monolayer show qualitative agreement with theoretical predictions. It is shown that differences between theory and experiment are not due to the existence of a line tension at the perimeter of the thin emulsion film formed as the oil drop is pressed up to the oil/water interface. Discrepancies between theory and experiment may be due to imperfect ‘pinning’ of the three-phase contact line at the inner diameter of the micropipette.

Differential scanning calorimetric studies on bovine serum albumin IV. Effect of anionic surfactants with various lengths of hydrocarbon chain

Using defatted and SH-blocked bovine serum albumin (BSA), measurements of differential scanning calorimetry (DSC) have been made at pH 7 on the complexes of BSA and a series of sodium alkyl sulfates. Alkyl sulfates used were sodium decyl sulfate (SDeS), sodium octyl sulfate (SOS), sodium hexyl sulfate (SHS) and sodium ethyl sulfate (SES). Results obtained were compared with those on the system BSA-sodium dodecyl sulfate (SDS) studied previously. Two peaks P 1 and P2 existed in the DSC curve of BSA. These peaks originate in the heat-induced transition of BSA. The pattern of DSC curve changed with the amount of the ligand added, i.e. with the molar mixing ratio ligand/BSA (1). The change for systems BSA-SDeS, BSA-SOS and BSA-SHS was qualitatively the same as that for the system BSA-SDS (2). Interestingly, SES, which is not a surfactant, interacts with BSA. The change for the system BSA-SES was qualitatively the same as that for the system BSA-Na 2SO 4. All alkyl sulfates suppressed the heat-induced transition at lower concentrations. A linear relationship was obtained for the plots of log ( D A ) 1 versus log CMC, where ( D A ) 1 is the molar mixing ratio of anionic surfactant ( D) to BSA ( A) at which the most heat-stable complex is formed. This suggests that the hydrophobic force has a serious effect on the formation of heat-stable complexes.

Adsorption of amphiphilic mixtures and stabilization of suspensions of hydrophobic solids in water

The adsorption at the water/air and graphon/water interface of mixtures of an anionic surfactant (sodium decyl sulphate) and a non-ionic polymer (polyvinylpyrrolidone) has been studied by investigating the stabilization of hydrophobic solid suspensions in aqueous media. ESCA, viscosity, surface tension, zeta potential and adsorption kinetics measurements converge in demonstrating the presence of an associate in solution and on the solid surface. The maximum stability of the aqueous suspensions of carbons is reached for the adsorption from mixtures having a composition corresponding to that typical of the associate in solution.

Excess free energy, enthalpy and entropy of surfactant-surfactant mixed micelle formation

Enthalpies of dilution and osmotic coefficients of sodium decylsulfate (NaDeS)-dodecyldimethylamine oxide (DDAO) mixtures in water were determined at 298 and 310 K, respectively. From the enthalpies of dilution, the apparent and then the partial molar relative enthalpies of the surfactant mixtures were calculated. From the osmotic coefficients, calculated at 298 K, the non-ideal free energies were derived. The latter were combined with the partial molar relative enthalpies to obtain the non-ideal entropies. From the apparent molar properties, using a previously reported approach, the excess thermodynamic properties for the surfactant-surfactant mixed micelle formation in water were evaluated as functions of the mixture composition at some total micellized concentration. In the whole range of the mixture composition, the excess free energy is negative, indicating that the mixed micelle formation is favoured with respect to that of pure micelles. This process is governed by the enthalpy and/or the entropy, depending on the mixture composition. The effect of the alkyl chain length was also studied by comparing the present results to those of the sodium dodecylsulfate-DDAO mixture.

Nuclear Magnetic Resonance and X-Ray Study of a Rectangular Phase

The rectangular phase in the lyotropic system sodium decyl sulphate (SdS)–decanol–water was studied by2H NMR and small-angle X-ray scattering. To investigate the variation in unit cell dimensions, the shape of the ribbons, and molecular segregation within the ribbons with composition, nine samples were prepared. The aspect ratio of the ribbon cross section was found to be independent of composition, ρ = 1.42 ± 0.02, whereas the aspect ratio of the unit cell varied with composition,b/a= 2.7–3.0. In general, the molecular distribution of SdS and decanol is highly nonuniform; the decanol concentration is 2.5 to 3.0 times higher in the central lamellar region of the ribbons than in their curved edges, while SdS accumulates in the curved regions. On addition of SdS, a vertical compression of the unit cell occurs (adecreases andbremains unchanged). However, the absolute dimensions of the ribbons remain constant and the added SdS accumulates in the central lamellar region of the ribbons. Addition of decanol yields horizontal expansion of the unit cell (adecreases andbincreases) and the absolute dimensions of the ribbon cross section increase slightly. The added decanol distributes evenly in the aggregate.

Thermodynamic Studies of Sodium Dodecyl Sulfate–Sodium Dodecanoate Mixtures in Water

Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water–sodium dodecyl sulfate (NaDS)–sodium dodecanoate systems were carried out as functions of the surfactants total molality (mt) at different mole fractions (XNaDS). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization of the micelles (β) were calculated. The cmc vsXNaDSprofile deviates negatively from that predicted on the basis of the Clint approach, while the β vsXNaDSprofile deviates positively from the line correlating the values for pure surfactants. At a given mole fraction, the profiles of all the investigated properties as functions ofmtqualitatively do not differ from those for pure surfactants and lie between those for the two pure surfactants. By using a previously reported thermodynamic approach, from the apparent molar properties in the postmicellar region the excess properties for the mixed micelles formation were evaluated. The excess volumes and entropies are positive, while the excess heat capacities, enthalpies, and free energies are negative in the whole range of the mixtures composition. The absolute values of the excess properties are generally small with respect to those for other previously investigated systems, i.e., sodium dodecyl sulfate–dodecyldimethylamine oxide and sodium decylsulfate–dodecyldimethylamine oxide.

Miscibility of sodium dodecyl sulfate and sodium decyl sulfate in the adsorbed film and micelle

The interfacial tension of the aqueous solution of sodium dodecyl sulfate (SDS) and sodium decyl sulfate (SDeS) mixture against hexane was measured as a function of the total molality and composition of the surfactant mixture at 298.15 K under atmospheric pressure. The compositions of adsorbed film and micelle were evaluated numerically by applying the thermodynamic relations to the experimental results. These results were shown in the form of the phase diagrams of adsorption and micelle formation and compared with those of the aqueous solution of sodium perfluorooctanoate (SPFO) and SDeS mixture. It was found that the diagrams of SDS and SDeS system have swollen cigar shapes and are quite different from those of SPFO and SDeS system which show non-ideal mixing both in the adsorbed film and micelle. This finding was attributed to the fact that the interaction between fluorocarbon and hydrocarbon chains is weaker than that between hydrocarbon chains.

Effects of fluorocarbon and hydrocarbon anionic micelles on the kinetics of water replacement in the palladium(II) aquocomplex of 1,1,7,7-tetraethyldiethylenetriamine by monoalkylthioureas

The effect of sodium perfluorooctanoate (NaPFO), sodium perfluorononanoate (NaPFN) and sodium decyl sulfate (SDeS) micelles on the kinetics of water replacement in the cationic palladium(II) complex [Pd(Et4dien)(H2O)]2+, where Et4dien = Et2N(CH2)2NH(CH2)2NEt2, by the nucleophiles methyl-, ethyl- and butylthiourea has been studied in aqueous acidic solutions at 25 °C and ionic strength 0.03 mol dm–3(0.06 mol dm–3 with SDeS). The micellar aggregates promote the substitution reactions reaching a maximum rate just beyond the critical micelle concentrations, which have been estimated experimentally by surface tension and conductivity measurements. The binding constants of the nucleophiles calculated from the present kinetic data, together with those obtained previously in the presence of sodium dodecyl sulfate (SDS), indicate that the capacity of the micelles to solubilize the thioureas increases in the order SDeS < SDS ≈ NaPFO < NaPFN. Moreover, for each surfactant used, solubilization is favoured by an increase in the hydrophobic character of the substrates. The estimated free energies of transfer of the thioureas from aqueous to micellar pseudo-phase show that the affinity of the hydrogenated micelles toward the substrate CH2 group is larger than that of the fluorinated ones. The possible solubilization sites and reaction rates in the micellar pseudo-phases are also discussed.

Solubilization of N-Alkylpyridinium Ions in Anionic Nematic Lyomesophases

Deuterium quadrupole splittings from the aromatic ring of a series of linear N-alkylpyridinium-d5 ions, with alkyl chains from 1 to 16 carbon atoms, were measured using 2H-NMR spectroscopy. The pyridinium ions, 10% deuteriated in the aromatic ring, were dissolved in nematic anionic lyomesophases prepared from sodium decyl sulfate (SDS) and cesium decyl sulfate (CsDS). With these splittings, the two order parameters that completely describe the average orientation of the aromatic ring with respect to the magnetic field were calculated. The added pyridinium ions have a dramatic effect on the mobility of the CsDS mesophase components. The smaller N-methyl and N-ethylpyridinium ions, C1 and C2, have a disruptive effect on the integrity of the mesophase, C3 and C4 do not have an appreciable effect, and the larger ones, C5 to C12, show the opposite effect, increasing the order of the system with the length of the alkyl chain. This phenomenon, not observed in the SDS mesophase, may be attributed to differences in charge distribution between both surfaces. This interpretation is supported by estimation of the degrees of dissociation and first cmc of SDS and CsDS using conductometric measurements. The results could also be explained if the CsDS mesophase was near to a phase transition and stabilized by the added ions.

Kinetic Study of Sodium Decyl Sulfate Solutions by the Capillary Wave Method

The capillary wave method has been applied to aqueous solutions of sodium decyl sulfate (SDes). The damping coefficient increased monotonically with concentration below the critical micelle concent...

Effect of the addition of n-alkylamines on the growth of sodium decyl sulfate micelles

The effect of the addition of n-alkylamines [CH3(CH2)mNH2; m= 5, 6, or 7] on the growth of sodium dodecyl sulfate (SDS) micelles has been studied by small-angle neutron scattering (SANS) and viscosity measurements at 30 °C. The viscosities of SDS (0.3 mol l–1 in D2O) solutions show a distinct rise at a certain amine concentration (XC) which depends on the chain length of the amine. This has been attributed to a change in micellar shape. To corroborate our viscosity results, SANS experiments were carried out on 0.3 mol l–1 SDS–amine micellar systems. SANS distribution showed a well defined peak for 0.3 mol l–1 SDS which shifts towards low Q-values on addition of different amines. The SANS spectra were analysed using the Hayter–Penfold model and shape and size parameters were computed. The results are interpreted in the light of micellar growth caused by the addition of amines. The micelles are shown to be ellipsoidal with the length of the semi-major axis depending on the chain length of the amine.

Thermodynamic Study on the Miscibility of Sodium Perfluorooctanoate and Sodium Decyl Sulfate in the Adsorbed Film and Micelle

The interfacial tension against hexane of the aqueous solution of the mixture of sodium decyl sulfate (SDeS) and sodium perfluorooctanoate was measured as a function of the total molality and the composition of surfactants at 298.15 K under atmospheric pressure. The miscibility in the adsorbed film and micelle was examined on the basis of the composition data. The film composition was evaluated from the total molality vs bulk composition curve at a given interfacial tension; the two surfactants are miscible in all proportions and the adsorbed film abounds in SDeS. The micelle composition was evaluated from the critical micelle concentration (CMC) vs bulk composition curve; the two surfactants are partially miscible and the two kinds of micelles having different overall compositions coexist in the micellar solution at the bulk composition of the cusp of the curve. This conclusion was thermodynamically confirmed by evaluating the film composition at the CMC from the micelle composition.

Spontaneous Vesicle Formation from Aqueous Solutions of Didodecyldimethylammonium Bromide and Sodium Dodecyl sulfate Mixtures

Spontaneous vesicle formation in the aqueous mixture of didodecyldimethylammonium bromide (DDAB) and sodium dodecyl sulfate (SDS) has been investigated with differential interference microscopy, transmission electron microscopy, glucose trapping experiments, ζ potential measurements, and surface tension measurements. The micrographs of the DDAB-SDS mixtures confirm the spontaneous formation of polydispersed vesicles including giant vesicle with a diameter less 40 μm. The captured volume of the DDAB -SDS mixtures is 2.2 L/mol at the SDS mole fraction (X SDS ) of 0.64 and decreases with increasing X SDS . Vesicle formation in DDAB-SDS mixtures will occur in the X SDS range of 0.64-0.75, below the total surfactant concentration of 2.2 wt %. Surface tension measurements for the mixtures exhibit very low values, 23 mN/m, indicating the ion-pairing of DDAB and SDS, a pseudo-zwitterionic surfactant. This surfactant favors the morphology of a vesicle. The mechanism of vesicle self-formation is the penetration of SDS into the DDAB molecules. In addition, spontaneous vesicles are also formed in the mixture of DDAB and sodium decyl sulfate.