Solubilization In Microemulsions Research Articles

Rhodamine B for Probing the Effects of Modifications in Cetrimonium Bromide Counter-anions by Transition Metals on CTAB/Butanol/n-hexane/water Microemulsion.

Dye solubilization in microemulsion based on Cetyltrimethylammonium bromide (CTAB) and its modified forms (counter-anions based upon Zn2+, Cu2+ and Fe3+) is comparatively innovative and not explored in existing literature. Here, surfactant with modified counterions (SMCs) were used to study the effects of metal chlorides (ZnCl2, CuCl2 and FeCl3) modifications on the comparative solubilization of Rhodamine-B (RB) by Cetyltrimethylammonium bromide (CTAB) and its modified forms. The solubility of RB in different microemulsions were studied using UV-Visible spectroscopy and phase diagrams of CTAB with modified counter ions CTA+[ZnCl2.Br]- named as CZN-1, CTA+[CuCl2.Br]- named as CCU-1 and CTA+[FeCl3.Br]- named as CFE-1 based upon surfactant with modified counter ions (SMCs). Four different points in microemulsion region of phase diagram were selected with different percentage composition of Smix (surfactant and co-surfactant), oil and RB (taken as water component). The interaction of RB, CCU-1, CFE-1 and CZN-1 within microemulsion environment were studied using Fluorescence spectroscopy. Emission spectra of RB in CCU-1 and CFE-1 based microemulsion confirmed that RB formed complexes with Cu and Fe ions. It was also found that RB was less soluble in CTAB based microemulsion as compared to microemulsions based on SMCs. This novel research study will expose new path for future research work related to microemulsion.

Skin pigmentation improvement with resveratrol microemulsion gel using polyoxyethylene hydrogenated castor oil

Objective To investigate the safety and efficacy of resveratrol microemulsion gel in improving pigmentation. Methods Resveratrol microemulsion gel was prepared by the microemulsion solubilization method, and its quality was evaluated. The transdermal and drug retention rates of resveratrol in vivo were assessed using a transdermal test. The inhibitory effects of resveratrol suspension and microemulsion on tyrosinase activity and melanin production of A375 human melanocytes and zebrafish embryos were compared. A skin patch test was used to investigate the safety of the gel on 15 volunteers. Results The microemulsion gel was homogeneous and stable. Compared with suspension and microemulsion, the drug penetration rate and skin retention in the microemulsion gel group were significantly increased. Compared with the suspension group, the activity of melanocyte tyrosinase in A375 human melanocyte was significantly inhibited in the microemulsion group, and the melanin production rate of A375 human melanocyte and the melanin area of zebrafish yolk was decreased. All 15 volunteers tested negative for the human skin patch. Conclusions The microemulsion gel could significantly enhance the ability of resveratrol to inhibit the formation of melanin without causing side effects. These data provide the experimental basis for developing and applying the preparation for improving pigmentation.

Release of Tretinoin Solubilized in Microemulsion from Carbopol and Xanthan Gel: In Vitro versus Ex Vivo Permeation Study

Tretinoin (TRE) is, for its anti-comedogenic and comedolytic activity, widely used in the topical treatment of acne vulgaris. The effect lies in the regulation of sebum production and collagen synthesis. The study is devoted to the formulation of dermal gels containing TRE using microemulsion as the drug solubilizer. The aim was to evaluate the effect of the reference microemulsion (ME) and lecithin-containing microemulsion (MEL) on the release of TRE through the synthetic membrane (in vitro) and the pig's ear skin (ex vivo) through the Franz cell diffusion method. Subsequently, after an ex vivo study, the amount of the drug in the skin influenced by the applied formulation was determined. In addition, the impact of ME on the microscopic structure, texture, and rheological properties of gels was evaluated. On the basis of the analysis of texture, rheological properties, and drug release studies, Carbopol formulations appear to be more appropriate and stable. Considering the synthetic membrane as a stratum corneum, the Carbopol gel penetrated about 2.5-higher amounts of TRE compared to the Xanthan gel. In turn, ex vivo studies suggest that MEL slows the drug transfer to the dissolution medium, simulating absorption into the blood, which is a desirable effect in local treatment. The drug retention study proved the highest amounts of TRE in the skin to which microemulsion-Carbopol formulations were applied. The results confirm the benefit of TRE solubilization in ME due to its bioavailability from the tested dermal formulations.

Effect of alcohols on water solubilization in surfactant-free diesel microemulsions

Microemulsions are preferred over other methods of mixing two immiscible liquids as they are thermodynamically stable, but require a high percentage of surfactant. Surfactant-free microemulsions, on the other hand, use an amphisolvent instead of surfactants, making them an economical alternative. The current experimental investigation focuses on formulation of surfactant-free water-in-diesel microemulsions with the help of straight-chain aliphatic alcohols as diesel replacement for IC engines. Dynamic light scattering measurements revealed these microemulsions had average water droplets of less than 10 nm. The microemulsions were formulated using single-alcohol, two-alcohols, and three-alcohols. It becomes crucial to study the water solubilization of microemulsions as the addition of water in diesel improves combustion efficiency. The water solubilization in surfactant-free microemulsions was found to be dependent on the hydrophilic–lipophilic balance (HLB) of the alcohols, as it determined the solubilizing property of alcohol. The microemulsions could only be formulated in the HLB range of 6.27 to 7.76 and were found to have maximum water solubilization in the HLB range of 6.67 to 7.63. Butanol had the highest water solubilization in a single alcohol system, butanol–ethanol in the ratio of 3:1 for the two-alcohol system, and propanol–butanol–octanol in the ratio of 3:1:1 for three-alcohol systems. Alcohols with higher HLB were more hydrophilic, causing migration of alcohol from the interface to bulk water. In comparison, alcohol with a lower HLB caused the migration of alcohol from the interface to bulk diesel, which resulted in reduced water solubilizations. Hence, the microemulsions could not be formulated beyond specific HLB range. The formulated microemulsions could be a prospective substitute for diesel fuel as alcohols can be derived from renewable routes.

Preparation of ionic liquids microemulsion and its application for the treatment of oily sludge

The surface-active ILs [C16mim]Cl synthesized by combining imidazole group (C4H6N2) and 1-chlorohexadecane (C16H33Cl) was used as surfactant to prepare ILs microemulsions for sludge treatment. Meanwhile, the treatment conditions were optimized and the optimal conditions were obtained. Due to the strong interaction between ILs and asphaltenes as well as the solubilization of microemulsions, the residual oil rate of oily sludge decreased to 1.33%. The characterization of oily sludge was performed by scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR) and contact angle measurement. Results showed that [C16mim]Cl ILs microemulsions treatment could effectively promoted the desorption of asphaltenes from the surface of sludge solids, which provided a clear understanding of the mechanism for ILs microemulsions-enhanced oily sludge recovery.

The Oscillatory Spinning Drop Technique. An Innovative Method to Measure Dilational Interfacial Rheological Properties of Brine-Crude Oil Systems in the Presence of Asphaltenes

The oscillatory spinning drop method has been proven recently to be an accurate technique to measure dilational interfacial rheological properties. It is the only available equipment for measuring dilational moduli in low interfacial tension systems, as it is the case in applications dealing with surfactant-oil-water three-phase behavior like enhanced oil recovery, crude oil dehydration, or extreme microemulsion solubilization. Different systems can be studied, bubble-in-liquid, oil-in-water, microemulsion-in-water, oil-in-microemulsion, and systems with the presence of complex natural surfactants like asphaltene aggregates or particles. The technique allows studying the characteristics and properties of water/oil interfaces, particularly when the oil contains asphaltenes and when surfactants are present. In this work, we present a review of the measurements of crude oil-brine interfaces with the oscillating spinning drop technique. The review is divided into four sections. First, an introduction on the oscillating spinning drop technique, fundamental and applied concepts are presented. The three sections that follow are divided according to the complexity of the systems measured with the oscillating spinning drop, starting with simple surfactant-oil-water systems. Then the complexity increases, presenting interfacial rheology properties of crude oil-brine systems, and finally, more complex surfactant-crude oil-brine systems are reviewed. We have found that using the oscillating spinning drop method to measure interfacial rheology properties can help make precise measurements in a reasonable amount of time. This is of significance when systems with long equilibration times, e.g., asphaltene or high molecular weight surfactant-containing systems are measured, or with systems formulated with a demulsifier which is generally associated with low interfacial tension.

The phase behavior and solubilization ability of nonionic surfactant-distillate fraction of crude oil microemulsion system

In this paper, phase behavior in temperature scanning of E1305/distillate fractions/water/n-butyl alcohol microemulsion system were investigated. And the effect of surfactant concentration and oil type on microemulsion solubilization ability was studied. In the research, the content of saturates, aromatics, resins and asphaltenes in distillate fractions of crude oil was analyzed. The change of phase inversion temperature (PIT), solubilized ability and temperature caused by different compositions of distillate fraction was investigated. According to the experimental results, the phase behavior of temperature scanning was Winsor Ⅰ → Winsor Ⅲ → Winsor Ⅱ. The ability of solubilizing microemulsion was improved by increasing the surfactant content. The temperature of optimum solubilization was decreased with the increase of surfactant content. When the type of oil phase was changed, the solubilized ability of microemulsion was decreased with the increase of distillation temperature. And the optimum solubilization temperature was increased. According to the results, this phenomenon was caused by the increase of wax content and equivalent alkane carbon number.

Extended Surfactants Including an Alkoxylated Central Part Intermediate Producing a Gradual Polarity Transition—A Review of the Properties Used in Applications Such as Enhanced Oil Recovery and Polar Oil Solubilization in Microemulsions

AbstractThe research published in the past half century indicates that surfactant interfacial performance in producing low tension or high solubilization with polar oils is not generally attained with pure conventional species exhibiting well‐defined polar and nonpolar parts. The improvement trends reached with surfactant mixtures as well as the introduction of additives like cosurfactants and linkers lead to the introduction of the so‐called extended surfactants, whose structure includes an intermediate polarity spacer between the hydrophilic head and the lipophilic tail. Recent investigations on different kinds of surfactants in a variety of applications—such as detergency, cosmetics, enhanced oil recovery or crude demulsifying, and vegetable oil extraction—indicate that these extended surfactants are likely to be particularly performing with oils containing polar groups, such as triacylglycerols and asphaltenic crudes. Possible applications of extended surfactants in enhanced oil recovery, crude emulsion breaking, detergency and cleaning, medicine and cosmetics vehicles, and natural oil extraction as well as some other cases are quickly reviewed.

Phase Behavior and Solubilization of Microemulsions Containing C16mimBr with Different Oil-Water Ratios

Abstract The effects of oil-water ratios (α) on the composition of the balanced interfacial layer and the optimum solubilization of microemulsions C16mimBr/butan-1-ol/oil (octane, decane, dodecane)/5% NaCl solution were investigated. As α increases, the alcohol solubility in water and oil phases (Sa) in the microemulsions also tends to increase. The reason is the relatively high solubility of the alcohol in the oil phase compared to the solubility in water. When α increases, the number of surfactant ( n s s ${\rm{n}}_{\rm{s}}^{\rm{s}}$ ) and co-surfactant ( n a s ${\rm{n}}_{\rm{a}}^{\rm{s}}$ ) molecules required to balance the interface layer and the proportion of alcohol in the interfacial layer (AS) increase but the solubilization capacity (SP*) decreases. When the total mass of water and oil is unchanged, the solubilization capacity of the microemulsion systems is lower the higher the relative content of oil is. The effects of different oils, salinity and temperature on the composition of the balanced interfacial layer and the solubilization of microemulsions were also investigated.

Formulation, physicochemical characterization and stability study of lithium-loaded microemulsion system

Lithium biocompatible microemulsion based on Peceol®, lecithin, ethanol and water was studied in attempt to identify the optimal compositions in term of drug content, physicochemical properties and stability. Lithium solubilization in microemulsion was found to be compatible with a drug-surfactant binding model. Lithium ions were predominantly solubilized within lecithin head group altering significantly the interfacial properties of the system. Pseudo-ternary phase diagrams of drug free and drug loaded microemulsions were built at constant ethanol/lecithin weight ratio (40/60). Lithium loaded microemulsion has totally disappeared in the Peceol® rich part of phase diagram; critical fractions of lecithin and ethanol were required for the formation of stable microemulsion. The effect of lithium concentration on the properties and physical stability of microemulsions were studied using microscopy, Karl Fischer titrations, rheology analyses, conductivity measurements and centrifugation tests. The investigated microemulsions were found to be stable under accelerated storage conditions. The systems exhibited low viscosity and behaved as Newtonian fluid and no structural transition was shown.

Synergetic effect of cationic surfactive ionic liquid C 12mimBr and anionic surfactant SDBS on the phase behavior and solubilization of microemulsions

Synergistic effect of the surfactant mixture of ionic liquid 1-dodecyl-3-methylimidazolium bromide (C 12mimBr) and sodium dodecyl benzene sulfonate (SDBS) on the phase behavior and the solubilization ability of the microemulsion systems was studied with ɛ– β fishlike phase diagrams. The middle-phase microemulsion appears at the range of the mole ratios of C 12mimBr to SDBS 0–0.1 and 0.7–1.0. The solubilization ability (SP*) of the mixed surfactant based microemulsion systems increased markedly compared to the pure C 12mimBr or SDBS-based microemulsion systems. The mixture of C 12mimBr and SDBS also shows preferable synergism in the solubility of the alcohol and the composition of the interfacial layer. The effects of alcohols, alkanes and NaCl concentrations on the ɛ– β fishlike phase diagrams of C 12mimBr/SDBS (molar ratio = 8:2)/alcohol/alkane/brine microemulsion systems were also investigated.

Diclofenac Solubilization in Microemulsions Based on Mixed Nonionic Surfactants and R (+)-limonene

Diclofenac is a nonsteroidal anti-inflammatory drug that reduces inflammation and pain hormones in the body. Dispersing the drug in water is impossible and its solubility in oils is very limited. In this study, we solubilized sodium diclofenac in nanostructures of the constructed U-type water/sucrose laurate/ethoxylated mono-di-glyceride/oleic phase microemulsions. The mixing ratio (w/w) of sucrose laurate/ethoxylated mono-di-glyceride equals unity. The oleic phase was the pure R (+)-limonene or R (+)-limonene mixed with ethanol at a weight ratio equals unity. The solubilization capacity of the drug in these systems is many times higher than in either oil or water systems. The sodium diclofenac solubilized microemulsions are fully diluted with water without phase separation. The solubilization capacity decreases as the water content increases. The system free of alcohol solubilizes less amounts of drug over all the range of water contents compared to the system containing alcohol. Small angle x-ray scattering was used to evaluate the effect of solubilized sodium diclofenac on the microstructure and diffusion properties of the loaded microemulsions. From the periodicity and correlation length measured by small angle x-ray scattering, we learned that the drug affects the structure of loaded microemulsion droplets probably less spherical than the empty systems. The transition from water-in-oil to a bicontinuous phase occurs at the different water contents compared to the empty (i.e., without drug) microemulsions. The drug remains solubilized at the interface upon further dilution with water and is oriented with its hydrophilic part facing the water, and strongly affects the inversion to oil-in-water droplets.

Solubilization and interfacial curvature in microemulsions: I. Interfacial expansion and co-extraction of oil

We show that solubilization in microemulsion droplets is best described as a combination of interfacial adsorption and internal absorption. We progressively add solute to a Winsor type I system, and simultaneously measure the amount of solute at the oil–water interface and its effect on the interfacial curvature. We determine the relationship between the effective packing parameter and the amount of solute adsorbed at the oil–water interface. For four solutes, a significant amount of oil is co-extracted with solute into the interfacial film. Moreover, we show that solubilization in microemulsions can be characterized by two physical quantities with precise meaning: (1) the increase in interfacial area per molecule of adsorbed solute and (2) the number of oil molecules co-extracted with each solute molecule into the interfacial film. To quantify these effects, we introduce the constant interfacial thickness (CIT) model. It provides a general relationship between curvature, packing and interfacial composition in oil/water/surfactant/solute mixtures. Finally, we show that these results can be used to calculate the free energy of transfer of solute and oil from the droplet core to the interface.

Enhancing solubilization in microemulsions—State of the art and current trends

AbstractAlong a formulation scan, solubilization is maximal when a bicontinuous microemulsion is in equilibrium with both oil and water excess phases in a so‐called Winsor III system. The logical way to enhance solubilization is to increase the interaction of the surfactant for both the oil and water phases, which can be easily attained by increasing the size of both the head and tail groups. However, this approach is limited by solubility constraints. Additional solubilization enhancement can be attained by introducing a molecule(s) that bridge the bulk phase and the adsorbed surfactant layer; this can be accomplished by using the so‐called lipophilic and hydrophilic “linker effect” or by using block copolymer additives. In either case, the goal is to modify an extended zone in the oil and water domains close to their boundary. The intramolecular grafting of a linker group between the hydrophilic and lipophilic moieties in a surfactant results in a so‐called “extended” surfactant structure, which produces enhanced solubilization, as does the surfactant/linker combination, but with the added benefit that the self‐contained extended surfactant structure does not undergo selective partitioning. We conclude that an improvement in solubilization is directly related to the presence of a smooth, blurred, and expanded transition across the interfacial region from polar to apolar bulk phases.

A two-state model for selective solubilization of benzene-limonene mixtures in sodium dihexyl sulfosuccinate microemulsions.

When surfactants are used to solubilize oil, the oil to be solubilized is often a mixture of components with differing properties, for example, solubilization of drug molecules in microemulsion formulations, remediation of organic polluted aquifers using surfactants, and so forth. Previous research has demonstrated that selective solubilization of one organic component over the other may occur if the organic components are dissimilar. In this research, we investigated selective solubilization from benzene-limonene mixtures in Winsor type I and III microemulsion systems containing water, sodium di-n-hexyl sulfosuccinate, and NaCl. The effect of the oil phase composition and the electrolyte concentration on the selectivity was studied. It was found that the selectivity toward benzene was highest at low electrolyte and benzene concentrations, decreasing as the electrolyte or benzene concentration increased. The results are discussed on the basis of the two-state solubilization theory and by correlating the curvature of the surfactant film in the microemulsion with changes of the electrolyte concentration and the oil phase composition. A simple mathematical model is developed for the selectivity, which combines the two-state solubilization theory and the net-average curvature model of microemulsion solubilization to yield close agreement with the experimental data.

Compositions of Mixed Surfactant Layers in Microemulsions Determined by Small-Angle Neutron Scattering

Surfactant mixing in model water-in-heptane microemulsion interfaces has been investigated for blends of a cationic didodecyldimethylammonium bromide (DDAB) with poly(ethylene glycol) monododecyl ethers (C12EJ, J = 3, 4, 5, 6, 7, 8, and 23). Phase behavior studies, electrical conductivity, and contrast variation small-angle neutron scattering (SANS) have been employed to delineate the effects of systematic variation of ethylene oxide headgroup size. These mixtures are characterized by an overall surfactant concentration (0.10 mol dm-3) and mole fraction of nonionic, which was varied up 0.20. The larger ethylene oxide (EO) numbers of 5−7 and 23 lead to significant enhancements in the maximum microemulsion solubilization capacity compared to DDAB only, whereas the shortest surfactant employed, C12E3, caused a decrease in the phase stability. Microemulsion nanostructure and interfacial compositions were studied for the EO3, EO4, EO6, and EO7 systems in partial structure factor type SANS experiments, as descr...

Non-ionic sucrose esters microemulsions for food applications. Part 1. Water solubilization

Factors affecting water solubilization in four-component nonionic microemulsion systems stabilized by polyol nonionic surfactants (sucrose esters) have been investigated. The effect of changing the chain length of alcohol (used as cosurfactant) and the lipophilic moiety of surfactant have been explored. The maximum water solubilization in the isotropic region (at oil/ n-butanol ratio of 1) was 47, 23 and 55 wt.% for sucrose stearate (S-1570), sucrose laurate (L-1695) and sucrose palmitate (P-1570), respectively. Replacing the triglyceride oil (MCT) by dodecane caused a decrease in the water solubilization (40 wt.%) for sucrose stearate with an oil/ n-butanol ratio of 1. The empirical BSO (Bansal, Shah, O’Connell) [1] equation which was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths, i.e. N S= N O+ N A, where N S, N O, N A are the surfactant chain lengths, oil and alcohol, respectively, was re-examined for this type of surfactants. This study demonstrates that a maximum water solubilization is obtained when the N S=( N O±3)+ N A for N S is greater than 14; when N S is less than 14, this equation cannot predict the maximum water solubilization.

Improving solubilization in microemulsions with additives. Part III: Lipophilic linker optimization

AbstractPolar oil additives are able to substantially improve the solubilization in surfactant‐oil‐water microemulsions through the so‐called lipophilic linker effect. Long‐chain alcohols (above C8) and their low ethoxylation derivatives were found to produce such an improvement. A method is proposed to evaluate the lipophilic linker performance and to compare lipophilic linker candidates in different oil‐surfactant systems. The best lipophilic linker was found to have a hydrophobe chain length as an average between that of the surfactant tail and the n‐alkane oil. The experimental data agree with that obtained by using a simple model based on the estimation of molecular interactions.

Evidence for Synergism in Nonionic Surfactant Mixtures: Enhancement of Solubilization in Water-in-Oil Microemulsions

It is well-known that certain mixtures of surfactants can provide better performance than pure surfactants for a wide variety of applications,1,2 and thus it is expected that enhanced solubilization ofwater inwater-in-oil (w/o) microemulsions will also be achieved with certain surfactant mixtures. The formation of w/o microemulsions involves dissolving an aqueous phase into an oil phase, creating a transparent and thermodynamically stable suspension of dropletswith diameters in the range of 10100nm. It is desirable to accomplish thiswithaminimum amount of surfactant,3 and in order to achieve this goal, mixtures of surfactants canbeused. We intend toaddress different surfactant mixtures that exhibit synergism in the solubilizationofwater inw/omicroemulsions, showing the existence of at least two different mechanisms of synergism. Synergism in surfactants may be defined as any situation where mixtures of surfactants have superior properties when compared to the properties of any of the single components alone. Although certain mixtures of dissimilar surfactants canbe expected to showsynergism, enhancement in properties may also occur withmixtures of similar structures. Shinoda et al.4,5 havedemonstrated thatmacroemulsionsmadewithnonionic surfactants that have been purified to a single poly(ethylene oxide) chain length are generally less able to solubilize the dispersed phase into the continuous phase, when compared to macroemulsions made with surfactant having the same average length, but an ethylene oxide size distribution. Ordinarily, onewouldnot expect strong synergistic effects in mixtures of nonionic surfactants, as synergism in anionic/nonionic surfactantmixtures has beenattributed to Coulombic, ion-dipole, or hydrogen-bonding interactions among the polar groups. Nonionics, which have minimum intermolecular interactions, should have, by comparison, the lowest synergism of all mixtures.6 In light of this previous work, we are able to demonstrate strong synergism in nonionic surfactant mixtures. When formulating water-in-oil microemulsions, one mustaccount for several factors, including thepartitioning of thesurfactant (or its components)betweentheoil,water, and interfacial domains (Figure 1). For maximum solubilization it is desirable to have most of the surfactant at the interface between the oil and water, rather than dissolved in the oil or water phases. Increasing the interfacial area should also increase solubilization. Synergism in microemulsion solubilization has been previously reported for a nonionic-anionic system designed for pharmaceutical applications, using mixtures of AOT (sodium bis(2-ethylhexyl)sulfosuccinate) and Arlacel 20 (sorbitan laurate) in different proportions.7,8 The present paper reports similar improvements using nonionicnonionic surfactant mixtures for solubilization of water in water-in-oil microemulsions and provides evidence for two different synergism mechanisms.

Water Solubilization and Chain Length Compatibility in Nonionic Microemulsions

The BSO (Bansal, Shah, O'Connell) equation ( J. Colloid Interface Sci. 75, 462, 1980) was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths. The present study examines, for the first time, the applicability of this equation for nonionic microemulsions. By constructing pseudo-ternary phase diagrams and measuring the area of the single phase regions as well as the water contents at the boundary, we find that the solubilization capacity is directly related to the alcohol chain length only if the alcohol solubility in both the aqueous and oleic phases is limited. In addition, we try to integrate the concept of chain length compatibility with the competition between the natural curvature and the critical radius of the interface. The attempt to unify the experimental results may serve as a guideline for optimization of microemulsion systems.