Permeability alterations in unilamellar liposomes due to betaine-type zwitterionic and anionic surfactant mixed systems

The alterations caused by betaine-type zwitterionic and anionic surfactant mixed systems in the permeability of unilamellar liposomes have been investigated. The partition coefficient of these systems, at different molar fractions, between the aqueous phase and the lipid bilayer of liposomes has been determined. These surfactant mixed systems were formed byN-dodecyl-N,N-dimethylbetaine (C₁₂-Bet) and sodium dodecyl sulfate (SDS) in the presence of 20 mM PIPES buffer and 110 mM Na₂SO₄, at pH 7.21. Unilamellar liposomes were prepared from egg phosphatidylcholine and phosphatidic acid (9:1 molar ratio). The release of the fluorescent agent 5-(6)-carboxyfluorescein induced by the systems has been studied at sub-solubilizing concentrations. When the molar fraction of C₁₂-Bet/SDS is about 0.4, the critical micelle concentration values of these systems exhibit a minimum, whereas their partition coefficient between the aqueous phase and lipid bilayer of lipid bilayers shows a maximum. There is a consistent correlation between the partition coefficient and the ability of the different systems of surfactants to modify the permeability of liposomes.     

Oxidative stability of sunflower oil bodies

This study investigates the oxidative stability of sunflower oil body suspensions (10 wt‐% lipid). Two washed suspensions of oil bodies were evaluated over 8 days at three temperatures (5, 25 and 45 °C) against three comparable sunflower oil emulsions stabilized with dodecyltrimethylammonium bromide (DTAB), polyoxyethylene‐sorbitan monolaurate (Tween 20) and sodium dodecyl sulfate (SDS) (17 mM). The development of oxidation was monitored by measuring the presence of lipid hydroperoxides and the formation of hexanal. Lipid hydroperoxide concentrations in the DTAB, SDS and Tween 20 emulsions were consistently higher than in the oil body suspensions; furthermore, hexanal formation was not detected in the oil body emulsions, whereas hexanal was present in the headspace of the formulated emulsions. The reasons for the extended resistance to oxidation of the oil body suspensions are hypothesized to be due to the presence of residual seed proteins in the continuous phase and the presence of a strongly stabilized lipid‐water interface.     

Effect of different antioxidants on lycopene degradation in oil‐in‐water emulsions

There is interest in incorporating lycopene into foods because it is a natural pigment and can also play a role in preventing disease. Therefore, the effect of the addition of various antioxidants in lycopene containing oil‐in‐water emulsions stabilized with Tween 20 at acidic pH was studied in order to determine protection systems against lycopene oxidation. In this model, EDTA showed pro‐oxidant activity while other chelators like citric acid and tripolyphosphate showed no effect. The free radical scavengers, propyl gallate (PG), gallic acid (GA), and α‐tocopherol all had the ability to decrease lycopene oxidation with α‐tocopherol being the most effective. The combination of 1 µM α‐tocopherol and 10 µM GA was more effective than the individual antioxidants. Addition of ascorbic acid to the combination of α‐tocopherol and GA system accelerated lycopene loss. These results suggest that by the proper selection of free radical scavenging antioxidants, lycopene stability in oil‐in‐water emulsions could be significantly improved. Practical applications: Evidence that dietary lycopene decreases the risk for a number of health conditions has generated new opportunities for addition of lycopene to functional foods. A successful strategy to deliver lycopene into foods is by means of oil‐in‐water emulsions. However, lycopene may decompose thus causing nutritional loss and color fading. In order to prevent this, the effectiveness of various antioxidants and their combinations in Tween 20 stabilized oil‐in‐water emulsions was studied. Overall, lycopene oxidation in oil‐in‐water emulsions could be significantly reduced by the proper selection of free radical scavengers. This fact is of interest to food industry for increasing the shelf‐life of lycopene containing functional foods where the lycopene is dispersed in the food in the form of an oil‐in‐water emulsion.     

Phase inversion of polyacrylamide‐based inverse‐emulsions: Influence of inverting‐surfactant type and concentration

The phase inversion of polymeric water‐in‐oil emulsions has been systematically studied by employing nonylphenol and alcohol ethoxylates with various chemistries as well as physical chemical characteristics. A combination of thermodynamics, phase diagrams, and rheometry were used to investigate the behavior of the inverting surfactants as well as the inverted, acrylamide‐based, cationic emulsions. Polymeric inverse‐emulsions containing the inverting surfactant showed no evidence of low‐shear thinning, though they did thin as hydrodynamic forces increased (0.01 to 100 s^?1) prior to reaching a chemistry‐ and concentration‐independent plateau, as is typical for emulsions. The viscosity of emulsions containing inverting surfactants reached a minimum at 1.2% of the “emulsion breaker”. The efficiency of inversion was optimized at 2 wt % of nonylphenols, expressed as a percentage of the total emulsion mass, and increased with the degree of ethoxylation. Interestingly, the viscosity of the polymer inverted in water was maximized at an inverting‐surfactant level corresponding to the CMC of the pure surfactant in water. The alcohol ethoxylates required a higher concentration for inversion (3 wt %), though they provided a higher ultimate inverse viscosity of the polymeric emulsion in water. Therefore, while the inversion process was less efficient with alcohol ethoxylates, the ultimate dilution solution properties of the polyelectrolytes liberated were improved relative to the nonylphenols. Overall, the process of adding a water‐in‐oil emulsion, containing an emulsion breaker, to an excess of water involves a catastrophic inversion mechanism. To be effective under such circumstances, an inverting surfactant should have a partition coefficient between the aqueous an organic phases greatly exceeding unity as well as a hydrophilic–lipophilic balance (HLB) above 12. Effectiveness increases linearly with the partition coefficient. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3567–3584, 2007     

Alkyd emulsions

Various aspects of alkyd emulsion technology have been investigated. The influence of alkyd oil length, acid value and hydroxyl number and type of surfactant used as emulsifier, on shear stability of alkyds emulsions have been studied. It was found that the acid value was the most important alkyd parameter, the stability increasing with increasing oil length. It is also shown that anionic surfactants give emulsions with small droplet sizes at lower concentrations than do nonionics. Polymerizable nonionic surfactants have been tested as emulsifiers and compared with conventional surfactants of the same hydrophilic lipophilic balance (HLB). It was found that surfactants capable of participating in the autoridative curing process give faster drying and improved film hardness compared with nonreactive surfactants. The distribution of driers between the alkyd phase and the water phase has been investigated. It was found that low pH and the use of hydrophilic anionic surfactants, such as sodium dodecyl sulphate, favour partitioning of cobalt into the aqueous phase which is unfavourable with respect to drying properties.     

Effect of the initial concentration of emulsifying agents on the ultracentrifugal stability of oil-in-water emulsions

The rate of loss of oil from 50% Nujol-50% water emulsions stabilized with varying concentrations of Tween 20 or Triton X-100, and from 50% olive oil-50% water emulsions stabilized with sodium dodecyl sulfate (SDS), was determined by ultracentrifugation at 39,460 rpm. In all cases the ultracentrifugal stability increased with increasing initial concentration of emulsifier, although, unlike the behavior of Nujol-water-SDS emulsions, the rate of separation of oil decreased with time. The quantity of olive oil separated after a given time of centrifugation decreased linearly with increasing concentration of SDS, reaching zero at a concentration of SDS somewhat below the critical micelle concentration, and at adsorption of SDS corresponding to only about half the saturation capacity. The ultracentrifugal stability of Nujol emulsions with Tween 20 or Triton X-100 continued to increase slowly with increasing concentration of emulsifier, even at concentrations far greater than the critical micelle concentration.     

The effect of shear and oil/water ratio on the required hydrophile-lipophile balance for emulsification

Required hydrophile-lipophile balance (HLB) values were examined in terms of the nature of kerosene-water, both oil-in-water (O/W) and water-in-oil (W/O), emulsions formed using Span 80/Tween 80 surfactant blends. Both the nature of the emulsification method and the oil/water ratio were critical in determining the resulting emulsion type. Both high- and low-shear conditions were investigated. Under high shear, low internal phase emulsions formed using the surfactant mixtures that corresponded to the required HLB values for emulsification involving kerosene (6 for W/O and 14 for O/W). However, at low shear, high internal phase (concentrated) emulsions resulted. Furthermore, depending on the oil/water ratio, some of the high internal phase emulsions were opposite to the type expected, given the HLB of the surfactant blend used. From these results, it appears that the emulsification technique (applied shear and oil/water ratio) used can be of greater importance in determining the final emulsion type than the HLB values of the surfactants themselves.     

Antioxidant activity of phenolic compounds in sunflower oil‐in‐water emulsions containing sodium caseinate and lactose

The aim of this work was to study the evolution of oxidation and the efficiency of phenolic antioxidants in sunflower oil‐in‐water emulsions containing sodium caseinate and lactose (Cas‐Lac) or stabilized by Tween‐20 (T‐20). Two groups of phenolic antioxidants which are structurally similar were tested, i.e. (1) α‐tocopherol and its water‐soluble analogue, Trolox; and (2) gallic acid and its ester derivatives propyl gallate and dodecyl gallate. Emulsion samples were oxidized at 40 °C and the progress of oxidation was followed through quantitation of oxidized triacylglycerol monomers, dimers and oligomers. Results showed that Cas‐Lac emulsions were more stable to oxidation than T‐20 emulsions. In both types of emulsions, the most protective antioxidants were the compounds of lower polarity, namely, α‐tocopherol and dodecyl gallate. It was also found that substantial amounts of α‐tocopherol coexisted with significant polymerization, which was indicative of the heterogeneity of oxidation, i.e. differences of oxidation rate in oil droplets.     

The effect of type of self-assembled system and pH on the efficiency of corrosion inhibition of carbon-steel surfaces

In this work, three surfactants were used in the preparation of self-assembled systems to inhibit acidic corrosion on API5LX Gr X52 carbon-steel surfaces: CTAB (a cationic surfactant), SDS (an anionic surfactant), and C₁₂E₉ (a non-ionic surfactant). These surfactants were used in the form of aqueous solutions and in microemulsions. Pseudoternary diagrams were constructed using aqueous phases consisting of 0.5 M NaCl at pH = 2, 4 and 7, butan-1-ol as co-surfactant and kerosene as oil phase. The values of c.m.c., maximum surface excess, minimum surfactant cross-sectional area and free energy of micellization were determined using surface tensiometry. The distinct effects of pH and type of self-assembled system on the efficiency of corrosion inhibition have been elucidated by electrochemical techniques (polarization and Tafel curves). It has been demonstrated that these parameters can significantly affect the results, which depend largely on the mechanism of aggregate adsorption on the metal surface and droplet stability. By establishing the optimal conditions, excellent corrosion efficiencies were found for these systems, even at low surfactant concentrations.     

Destabilization of Emulsion Formed During Aqueous Extraction of Peanut Oil: Synergistic Effect of Tween 20 and pH

To destabilize the emulsion formed during aqueous extraction processing (AEP) of peanuts, Tween and Span series surfactants (Tween 20, Tween 80, Span 20, and Span 80) were used alone or in combination to break the emulsion. Results indicate that only Tween surfactants had a pronounced demulsifying effect that was dependent on Tween concentration and system pH. When 1.2 wt% Tween 20 aqueous solution was used for oil extraction at pH 10.0, the highest free oil yield was achieved at 76.1 %, which was similar to the oil recovery of using proteases as a destabilization agent. The results obtained using a model emulsion system containing peanut oil and Tween 20/peanut protein isolates (PPI) showed that when Tween 20 and PPI coexisted in extraction medium at pH 10.0, the dynamic interfacial tension and droplet size distribution curves were very similar to those when Tween 20 was used alone, suggesting that Tween 20 dominated at the interface, instead of PPI. Destabilization of the model emulsions relied on three important factors: inclusion of Tween 20 at the initial mixing stage, high pH, and a gentle mixing speed. A synergistic destabilization mechanism of using Tween 20 at high pH during AEP was proposed. The discovery of Tween 20 as an effective demulsifier significantly contributes to the development of AEP of oilseeds.     

Microemulsion formation and detergency with oily soils: I. Phase behavior and interfacial tension

The ultimate objective of the project was to investigate the relationship between microemulsion phase behavior and detergency for oily soils. In this study, surfactant phase behavior was evaluated for hexadecane and motor oil as model oily soils. Producing microemulsions with these oils is particularly challenging because of their large hydrophobic character. To produce the desired phase behavior we included three surfactants with a wide range of hydrophilic/lipophilic character: alkyl diphenyl oxide disulfonate (highly hydrophilic), dioctyl sodium sulfosuccinate (intermediate character), and sorbitan monooleate (highly hydrophobic). This mixed surfactant was able to bridge the hydrophilic/lipophilic gap between the water and the oil phases, producing microemulsions with substantial solubilization and ultralow interfacial tension. The effects of surfactant composition, temperature, and salinity on system performance were investigated. The transition of microemulsion phases could be observed for both systems with hexadecane and motor oil. In addition, the use of surfactant mixtures containing both anionic and nonionic surfactants leads to systems that are robust with respect to temperature compared to single-surfactant systems. Under conditions corresponding to “supersolubilization”, the solubilization parameters and oil/microemulsion interfacial tensions are not substantially worse than at optimal condition for a middle-phase system, so a middle-phase microemulsion is not necessary to attain quite low interfacial tensions. A potential drawback of the formulations developed here is the fairly high salinity (e.g., 5 wt% NaCl) needed to attain optimal middle-phase systems. The correlation between interfacial tension and solubilization follows the trend predicted by the Chun-Huh equation.     

Effect of Electrolyte and Temperature on Volatile Organic Compounds Removal from Wastewater Using Aqueous Surfactant Two-Phase System of Cationic and Anionic Surfactant Mixtures

Abstract

Benzene, toluene, ethylbenzene, and xylene are frequently observed contaminants in industrial wastewaters causing concerns about environmental and health effects. An aqueous surfactant two-phase (ASTP) extraction system using mixtures of cationic and anionic surfactants have been shown to be a promising surfactant-based separation technique to concentrate solutes such as proteins and dyes from aqueous solution. A phase separation of a surfactant solution occurs at certain surfactant compositions and concentrations, forming two isotropic phases. One is rich in surfactant aggregates (surfactant-rich phase) and the other is lean in surfactant aggregates (surfactant-dilute phase). Most of the organic contaminants tend to solubilize and concentrate in the surfactant-rich phase, leaving the surfactant-dilute phase containing only small amounts of contaminants as remediated water. The effect of NaCl addition on the critical micelle concentration (CMC) and the extraction ability of ASTP formed by mixtures of cationic surfactant (dodecyltrimethylammonium bromide; DTAB) and anionic surfactant (alkyl diphenyloxide disulfonate; DPDS) at 50 mM total surfactant concentration with a 2:1 molar ratio of DTAB:DPDS was investigated; the CMC of the mixture slightly decreases with increasing NaCl concentration. The extraction and preconcentration of benzene are greatly enhanced by added NaCl. The higher the degree of hydrophobicity of contaminants, the greater the extraction into the surfactant-rich phases. At 1.0 M NaCl addition, about 95% of xylene, 92% of ethylbenzene, 90% of toluene, and 79% of benzene are extracted into the surfactant-rich phase within a single stage extraction and the contaminant partition ratios can be as high as 395 for xylene, 273 for ethylbenzene, 206 for toluene, and 84 for benzene, which are greater than those obtained from the conventional ASTP extraction system using nonionic surfactants.     

钻井液增黏剂的反相乳液制备及性能评价

以丙烯酰胺和丙烯酸为共聚单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,Span 60/Tween 80为复合乳化剂,在白油中进行反相乳液聚合,制备出了稳定的“油包水”型乳液,并初步评价了其在不同的钻井液中的性能.结果表明:该乳液在淡水、盐水以及饱和盐水钻井液中随着质量分数的增加具有较明显的增黏性能,但其在高温下的老化性...     

Mass transfer studies on multiple emulsion as a controlled mass release system

A novel type of multiple emulsions which contain a microemulsion in macrodroplets, was prepared by a two-step emulsification procedure. Mineral oil was used as the oil phase with a mixture of Aerosol OT and Span 20 as primary emulsifiers. A water-in-oil microemulsion was prepared by gradual addition of water in oil containing both these emulsifiers. This microemulsion system, when dispersed in an aqueous solution containing secondary emulsifier, produces water-in-oil-in-water (W/O/W) multiple emulsions. The release rate of solute dissolved in the internal aqueous phase was measured using the dialysis technique. A theoretical model describing the diffusion of a multiple emulsion system was developed, which predicts the half-life for 50% of the internal solute to diffuse to the external phase. Experimental results showed the stability of multiple emulsions improved significantly upon using a thermodynamically stable microemulsion as a primary emulsion and a polymeric surfactant as a secondary emulsifier. As a resull, half-life of these multiple emulsions is greater than that of conventional multiple emulsions.     

Insights Into Molecular Interaction of Antitumor Drug Mitoxantrone With Anionic Surfactant Sodium Dodecyl Sulfate at Different Temperatures

A study of the interaction of antitumor drug mitoxantrone with anionic surfactant sodium dodecyl sulfate (SDS) has been carried out by UV–Vis absorption spectroscopy at submicellar and micellar surfactant concentrations, pH 7.4 and 10, and over a temperature range of 293.15–323.15 K. The variation of the monomer drug absorbance as a function of SDS concentration indicates, at pH 7.4 and all investigated temperatures, two definite processes: process I in the submicellar range, attributed to the electrostatic interaction between mitoxantrone and SDS monomers; and process II in the micellar range, when the drug is incorporated into SDS micelles in monomer form. At pH 10, the results have indicated only the process II at micellar SDS concentrations. The monomer absorbance changes occurring as a result of the interactions between mitoxantrone and SDS were rationalized in terms of binding constant, micelle/water partition coefficient, and the corresponding thermodynamic parameters for binding and partitioning processes. Thermodynamic parameters indicate that at pH 7.4 both binding process of mitoxantrone to SDS and partition process of mitoxantrone between micellar and bulk aqueous phases are spontaneous and enthalpy controlled, while at pH 10 both processes are spontaneous and entropy controlled.     

Making homogeneous and fine droplet O/W emulsions using nonionic surfactants

In many emulsion systems, creaming occurs during the first stage of emulsion breakdown. To reduce the rate of creaming, emulsions having small and uniform droplets are desirable. In this work, types and HLB of nonionic surfactants, emulsification methods, and combinations of oils and nonionic surfactants were investigated in order to make stable and homogeneous emulsions. Emulsification was attained by dissolving the surfactants in the oil phases. The addition speed and volume of water to the oil phases were important factors affecting the emulsion droplet size. The change of the solute state in the process of emulsification was observed stage by stage, and the mechanism of emulsification was elucidated. Homogeneous emulsions were formed in the HLB region, showing liquid crystalline and gel phases in the emulsifying process. The addition speed of water to the oil phase was very important in forming the liquid crystalline and gel phases. Polyoxyethylene(n)sorbitan monostearate could emulsify three kinds of oils (hydrocarbon, fatty acid ester and triglyceride). Polyoxyethylene(n)alkyl ether could emulsify hydrocarbon and fatty acid ester. Polyoxyethylene(n)-monostearate could emulsify only hydrocarbon. Surfactants with proper HLB which were soluble in the oil phase and in the presence of a very small amount of water formed a stable emulsion. The solubility state of oil and surfactant was the key to making a fine emulsion.     

Effect of emulsifiers on the preparation of food‐grade oil‐in‐water emulsions using a straight‐through extrusion filter

This paper describes the preparation characteristics of food‐grade soybean oil‐in‐water (O/W) emulsions using a novel straight‐through extrusion filter, named a silicon straight‐through microchannel (MC). Polyglycerol fatty acid ester (PGFE), polyoxyethelene sorbitan monolaurate (Tween 20), and sucrose fatty acid ester were tested as emulsifiers. Optical observations of the emulsification process exhibited that monodisperse oil droplets were stably formed from an oblong straight‐through MC for PGFE and Tween 20. The effect of the emulsifier on the straight‐through MC emulsification behavior is discussed. The selected PGFE‐ and Tween 20‐containing systems enabled us to prepare monodisperse O/W emulsions with droplet diameters of 38—39 μm and coefficients of variation below 3% using an oblong straight‐through MC with a 16 μm‐equivalent channel diameter.     

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

In this study the effect of an anionic surfactant (sodium dodecyl sulfate SDS) and oils (hydrocarbons: C12–C16) on the formation and phase behavior of the systems of oil/monoacylglycerols (MAG):SDS/propylene glycol/water has been investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C). Electrical conductivity measurement, FT-IR spectroscopy and differential scanning calorimetry methods were applied to determine the structure and type of the microemulsions formed. The dimension of microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of SDS has a strong influence on the shape and extent of the microemulsion areas. Addition of an ionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of the isotropic region change with the temperature. It was shown that the presence in the systems of a surfactant more hydrophilic than MAG caused an increase in water content in the microemulsions. It was found that, depending on temperature and concentration of the surfactant mixture, it was possible to obtain a W/O type microemulsion with a dispersed particles size distribution ranging from 20 to 50 nm and containing about 17–38% water in the system. Among different alkanes (from C12 to C16), hexadecane embedded microemulsions showed a maximum water solubilization capacity.     

不同表面活性剂对单相微乳液特性的影响

表面活性剂是影响微乳液特性的关键因素之一。本文选取聚氧乙烯脱水山梨醇单油酸酯（Tween 80）、烷基糖苷1214（APG 1214）、十二烷基苯磺酸钠（SDBS）、脂肪醇聚氧乙烯醚硫酸钠（AES）、十二烷基硫酸钠（SDS）和95%纯度鼠李糖脂（R-95%）这6种表面活性剂,通过对其乳化性能和临界胶束浓度进行筛选,结合其形成微乳液的拟三元相图、粒径分布和界面张力分析其特性,并提出微乳液增溶油能力和增溶油成本。研究表明：APG 1214、SDBS、Tween 80乳化性能好、临界胶束浓度低具有更易形成微乳液的优势;5种表面活性剂（Tween 80、SDBS、APG 1214、SDS、AES）均可与正丁醇、水和3号白油自发形成单相微乳液,单相区面积大小为AES型>SDS型>APG 1214型>Tween 80型>SDBS型,最大增溶油能力大小为SDS型>AES型>APG 1214型>Tween 80型>SDBS型,最低增溶油成本大小为AES型相似文献   

Constant vapour pressure evaporation from a fragrance emulsion—effect of surfactant content in the liquid crystal

The evaporation paths for constant fragrance vapour pressure were calculated in a model emulsion system of water, surfactant, and linalool. It was found that the water content of the liquid crystal had a moderate effect on the time during which the fragrance vapour pressure was constant; significantly less of a consequence than the fraction of surfactant in the oil phase in equilibrium with the aqueous and liquid crystal phases. The results will serve as a guidance for the formulation of optimal fragrance emulsions for the mass market.