Microemulsion Composition Research Articles

Application of microemulsions for the extraction, pre-concentration of PAHs as a tool for fast screening of perspective oil chemical markers

A simple method for the determination of 16 priority polycyclic aromatic hydrocarbons (PAHs) from geological cores as oil markers using microemulsion extraction, pre-concentration with following fluorometric detection was developed. Parameters, such as the composition of microemulsion (ME), temperature, pH, which affect the intensity of fluorescence were investigated and optimized. The potential of the developed technique has been demonstrated by the determination of these PAHs in oil and oil cores. The calculated pre-concentration factor using microemulsion (3.3% CTAB, 0.8% heptane, 8% n-butanol and 87.9% water) varies from 5 to 10. The main parameters that influence the intensity of fluorescence are the charge of a surfactant and the nature of the oil. The limits of detection ranged between 10–50 μg/kg.

Influence of pyridine oximate and quaternized pyridinium oximate ions on the hydrolysis of phosphate esters in cationic microemulsions

Kinetic studies have been performed to understand the hydrolytic potencies of oximate (2- and 4-pyridinealdoxime) and its functionalized oximate (4-(hydroxyiminomethyl)-1-alkylpyridinium bromide) ions (alkyl = C10H21 (4-C10PyOx-); alkyl = C12H25 (4-C12PyOx-)) in the cleavage of phosphate esters, diethyl p-nitrophenylphosphate (Paraoxon) and p-nitrophenyl diphenyl phosphate (PNPDPP) in a cationic (O/W) microemulsion system (ME) over a pH range 7.5 to 11.0 at 300 K. The kobs values for the reaction of paraoxon with oximate and its functionalized oximate were determined in different microemulsion composition and the kinetic rate data shows that kobs values increases with increasing water content. The specificity of different chain length of alcohols (n-butanol, n-pentanol, n-hexanol and n-octanol) was also investigated in hydrolytic reactions of paraoxon for different microemulsion composition.

Microemulsion and Microporation Effects on the Genistein Permeation Across Dermatomed Human Skin.

This study reports the microemulsion (ME) effects on the permeation of genistein across normal (intact) and microporated human skin. The genistein formulation was optimized to know the stable ME region in the pseudo-ternary phase diagrams and to maximize the skin permeation and retention of genistein. The phase diagrams were constructed with different oil phases, surfactants, and their combinations. The influence of formulation factors on the permeation through intact and microporated human skin was determined. Based on its wide ME region, as well as permeation enhancement effects, oleic acid was used as an oil phase with various surfactants and co-surfactants to further maximize the ME region and skin permeation. The water content in the formulation played an important role in the ME stability, droplet size, and flux of genistein. For example, the ME with 20% water exhibited 4- and 9-fold higher flux as compared to the ME base (no water) and aqueous suspension, respectively. Likewise, this formulation had demonstrated 2- and 4-fold higher skin retention as compared to the ME base (no water) and aqueous suspension, respectively. The skin microporation did not significantly increase the skin permeation of genistein from ME formulations. The ME composition, water content, and to a lesser extent the ME particle size played a role in improving the skin permeation and retention of genistein.

Slowing Down Kinetics in Microemulsions for Nanosegregation Control: A Simulation Study

The synthesis of bimetallic nanoparticles in microemulsions has been studied by simulation. The aim of this study was to understand the principles underlying kinetics in colloidal systems, which allowed us to further investigate the interaction between the intermicellar exchange rate and chemical reduction and ultimately to discover how these nanostructures may become. We present here results for three couples of metals with different reduction rates, the reduction rate of the faster metal being 10 times faster than the rate of the slower one in all cases. Under these conditions, the impact of slowing down chemical reductions on the final nanoarrangement can be studied. Our results show that a bimetallic nanostructure can be tuned by changing the microemulsion composition only when both metal reduction rates are quite fast in relation to the intermicellar exchange rate. If this is not the case, the compartmentalization of the reaction medium does not play any role because of chemically controlled kinetics...

Ruthenium silica nanoreactors with varied metal–wall distance for efficient control of hydrocarbon distribution in Fischer–Tropsch synthesis

We report here a new strategy for the control of hydrocarbon selectivity in Fischer–Tropsch (FT) synthesis using silica yolk–shell ruthenium nanoreactors prepared in water/oil (W/O) microemulsions. The sizes of nanoreactors have been varied by changing the microemulsion composition. Nanoreactors prepared with the smallest internal volume exhibited a restriction of hydrocarbon chain length growth during FT synthesis. An increase in the nanoreactor volume resulted in a gradual shift of the hydrocarbon distribution to longer-chain hydrocarbons till a distribution of hydrocarbons reached that observed over the reference catalysts prepared by deposition of non-encapsulated metal nanoparticles on silica supports. The observed remarkable modifications of hydrocarbon selectivity over Ru nanoreactors have been explained by shape selectivity effects on hydrocarbon growth due to decrease in entropy in comparison with infinite growth and increase in the Gibbs energy for growing hydrocarbon chains located inside the limited volumes of nanoreactors.

Bioadhesive polymeric film-based integrative platform for the unidirectional carbamazepine release from a volatile microemulsion.

Carbamazepine (CBZ) shows inconsistent absorption primarily due to its poor dissolution rate. In this study, we describe a bioadhesive polymeric film, embedded with microemulsion (ME), as a tool to enable improved CBZ dissolution and achieve sustained release. The ME was formulated using pseudo-ternary components; water, oil (n-butyl acetate), surfactant (tocopheryl polyethylene glycol 1000 succinate, TPGS) and cosurfactant (1,4-butanediol). The region at surfactant to co-surfactant ratio of 1:1 was characterized using dynamic light scattering, small angle neutron scattering and differential scanning calorimetry. Scattering studies showed that size distribution did not change upon water addition and temperature. Optimized ME composition containing CBZ was embedded into bioadhesive films composed with a backing layer. We successfully demonstrate the confinement of CBZ-ME into the film matrix and thereupon, the achievement of unidirectional sustained drug release up to 8 h. Our further investigations are directed over testing the system for localized drug delivery applications.

Effect of AOT Microemulsion Composition on the Hydrodynamic Diameter and Electrophoretic Mobility of Titanium Oxide Nanoparticles

The hydrodynamic diameter and electrophoretic mobility of titania nanoparticles in AOT microemulsions are studied depending on their water content (from 0 to 1.5 vol %), chloroform content in n-decane–chloroform mixture (from 0 to 30 vol %) and temperature (from 0 to 60°C). Considerable changes in diameter (from 20 to 400 nm) are detected upon adding water to the microemulsion. The electrophoretic mobility grows by 2–3 times upon adding chloroform, or as the temperature falls. The observed features allow us to halve the time of electrophoretic concentration for 140 nm TiO2 nanoparticles, and to concentrate 14 nm nanoparticles that do not exhibit electrophoretic mobility in the absence of chloroform.

Optimized Enzymatic Synthesis of Feruloyl Derivatives Catalyzed by Three Novel Feruloyl Esterases from Talaromyces wortmannii in Detergentless Microemulsions

Three novel feruloyl esterases (Fae125, Fae7262 and Fae68) from Talaromyces wortmannii overexpressed in the C1 platform were evaluated for the transesterification of vinyl ferulate with two acceptors of different size and lipophilicity (prenol and L-arabinose) in detergentless microemulsions. The effect of reaction conditions such as the microemulsion composition, the substrate concentration, the enzyme load, the pH, the temperature and the agitation were investigated. The type A Fae125 belonging to the subfamily 5 (SF5) of phylogenetic classification showed highest yields for the synthesis of both products after optimization of reaction conditions: 81.8% for prenyl ferulate and 33.0% for L-arabinose ferulate. After optimization, an 8-fold increase in the yield and a 12-fold increase in selectivity were achieved for the synthesis of prenyl ferulate.

Characterization of Complex Crude Oil Microemulsions-DSC Contribution

Surfactant flooding is a chemical enhanced oil recovery (EOR) process which consists in injecting optimized formulations of surfactants in the reservoir in order to remobilize the residual oil trapped in the pores of the rock. To do that, it is necessary to design specific formulations in order to get so-called Winsor III systems of very low interfacial tensions with the crude oil. Unfortunately, there is no well-established way to characterize and understand the physical properties and structures of microemulsions composed of crude oil and industrial surfactants due to their extreme complexity. In a previous work, we have developed a methodology based on the use of several techniques (DLS, MLS, SAXS, cryo-SEM, DSC, interfacial measurements, etc.) allowing physico-chemical and morphological characterization of these microemulsions in the case of a model system. In this article, we will demonstrate how DSC can be used to provide information on the physico-chemical composition of complex microemulsions (water and oil content, salinity, etc.) and on their morphology (continuous phase, dispersed phase, etc.).

Thermally stable microemulsions comprising imidazolium based surface active ionic liquids, non-polar ionic liquid and ethylene glycol as polar phase

Ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C2mim] [Tf2N], as a non-polar phase in conjunction with polar ethylene glycol (EG) forms microemulsions stabilized by surface active ionic liquids (SAILs), N-methyl-N-alkylimidazolium chlorides, [Cnmim] [Cl], where n = 8, 12 and 16 in conjunction with decanol as co-surfactant. The phase behaviour of the ternary systems has been investigated and three regions of microemulsions – polar-in-ionic liquid, bicontinuous and ionic liquid-in-polar, have been identified using electrical conductivity measurements. The effect of alkyl chain length on the phase behavior has been discussed in detail. The one-phase microemulsion region is found to decrease with the increase in the alkyl chain length of the SAILs. The microstructural characteristics have been investigated by using FTIR and NMR spectroscopy. The micropolarity of reverse micelles present in the microemulsions has been investigated using UV–Vis spectroscopy employing methyl orange as a polarity probe. The dynamics of solvent relaxation in microemulsions have been investigated by steady-state and time-resolved fluorescence spectroscopy using coumarin 153 (C-153) as fluorescence probe at different compositions of microemulsions. The dynamic light scattering measurements (DLS) reveals the expansion of reverse micelles formed by [Cnmim][Cl] in non polar [C2mim] [Tf2N] upon the addition of polar component. Interestingly, the microemulsions have been found to be thermally stable in a wide temperature range as revealed from temperature dependence UV–Vis, fluorescence and DLS measurements.

Controlling the composition, phase volume, and viscosity of microemulsions with cosolvent

Optimizing macroscopic properties of microemulsions (volume, composition, and viscosity) is tedious and often involves the use of an alcohol. We show that this optimization is possible when the alcohol acts as cosolvent (rather than a cosurfactant) to partition between the interface and bulk phases(s). Herein presented a phase behavior study of water, crude oil, tridecyl alcohol propoxy sulfate (C13-13PO-SO4), internal olefin sulfonate (C20-24IOS), and ethoxylated phenol (phenol-2EO) mixtures, rationalized by pseudophase theory and pseudoternary phase diagram. The detailed phase behavior study involved varying the surfactant concentration, cosolvent concentration, brine salinity, and oil content. High-performance liquid chromatography (HPLC) was used to determine the interfacial composition and steady and dynamic rheology to characterize the bicontinuous middle-phase samples. Measurements confirmed that phenol-2EO acted as cosolvent. A systematic shift of phase type is observed by increasing the cosolvent-to-surfactant content in the initial water/surfactant solution. Furthermore, it was observed that the interfacial ratio of cosolvent to surfactant controls the microemulsion composition, viscosity, and volume. This ratio is highly tunable, but when too high, a distortion of the middle phase is observed. The experimental results provide a methodology to tailor the composition of amphiphile mixture for optimizing microemulsion properties.

Specific efficiency of microemulsion matrix transdermal delivery system of insulin (experimental model of diabetes mellitus typeI)

Aim. To study the specific activity of the microemulsion form of the matrix insulin transdermal delivery system in vivo on the experimental streptozotocin model of type I diabetes.Materials and methods.Male rats (n = 25) were randomized to the experimental and control groups. TDS insulin with a microemulsion composition was applicated to the animals of the experimental group (n = 15) for 4 days with daily replacement of TDS and control of the glycemia level. The glycemia level of the control group rats (n = 10) was determined throughout the experiment. The blood glucose concentration was measured using glucometer One Touch Select (USA). Results.The average blood glucose level in experimental group was 28.4 ± 2.3 mmol/l before application of TDS insulin. The average glycemic index was 21.2 ± 3.1 mmol/l (p < 0.001) during of TDS application. The blood glucose decrease was 26 ± 8% relative to baseline values. The glycemia was 28.4 ± 1.4 mmol/l in the control group rats throughout the experiment.Conclusion.A significant decrease of blood glucose level with TDS insulin application in rats with experimental type 1 diabetes demonstrates the existence of the specific activity of the microemulsion matrix transdermal delivery system of insulin.

Ion-Exchange Processes between Surface Layer and Core of Reverse Micelles of NaAOT+Tergitol NP-4 during Evaporation Crystallization of KNO3

Liquid extraction and microdroplet probing of the composition of reverse microemulsions (NaAOT+Tergitol NP-4, NaAOT, and Tergitol NP-4 in n-decane) with aqueous salt solutions (KNO3, NaNO3, and KNO3+NaNO3) were used to determine the distribution of Na+ and K+ between the surface layer and the micelle core in the processes of evaporation crystallization of KNO3 and NaNO3 salts. It is shown that, at high content of NaAOT, K+ cations in micelle core are virtually completely replaced by Na+ and no crystallization of KNO3 in NaAOT micelles is observed. At low content of NaAOT in mixed micelles and small solubilization capacity (less than 1 vol %) partial exchange takes place and crystallization of KNO3 begins from a mixture of KNO3+NaNO3 salts. During crystallization, micelle cores become depleted in potassium nitrate, which causes reverse exchange of K+ cations, associated with AOT–, for Na+ contained in the micelle core. As a result, mainly KNO3 crystallizes in mixed micelles.

Novel microemulsion-based gels for topical delivery of indomethacin: Formulation, physicochemical properties and in vitro drug release studies

HypothesisMicroemulsion-based semisolid systems may be considered as an interesting alternative to the traditional dosage forms applied in topical drug delivery. Mechanical properties of topical products are important both in terms of application and dosage form effectiveness. In this study we designed and evaluated novel microemulsion-based gels with indomethacin and analyzed the factors affecting their mechanical characteristics and drug release. ExperimentsThe impact of the microemulsion composition on the extent of isotropic region was investigated with the use of pseudoternary phase diagrams. Selected microemulsions were analyzed in terms of electrical conductivity and surface tension in order to determine the microemulsion type. Microemulsions were transformed into polymer-based gels and subjected to rheological and textural studies. Finally, the indomethacin release from the analyzed gels was studied and compared to commercially available product. FindingsThe extent of isotropic domain in pseudoternary phase diagrams seems to be dependent on the polarity of the oil phase. The surface tension and conductivity monitored as a function of water content in microemulsion systems revealed possible structural transformations from w/o through bicontinuous systems into o/w. The mechanical properties of semisolid microemulsion-based systems depended on the composition of surface active agents and the drug presence. The drug release profiles observed in the case of the investigated gels differed from those recorded for the commercially available product which was most probably caused by the different structure of both systems.

Phase equilibria, interfacial, and bulk compositions of microemulsions containing short-chain alcohols studied by an optimum microemulsion dilution method

An optimum microemulsion dilution method was presented to explore the phase behavior of imidazolium type surfactant 1-alkyl-3-methylimidazolium bromide (C12mimBr, C14mimBr, and C16mimBr)/short-chain alcohol (butan-1-ol, propan-1-ol)/oil/water systems. The dilution method was obtained based on the geometrical consideration in the composition tetrahedron phase diagram. Two dilution equations were deduced. The solubilities of the alcohol in oil and water phases were calculated, respectively. The composition of the surfactant-and-alcohol interfacial layer, represented by the mass fraction of alcohol in the interfacial layer, A S , and the maximum solubilization ability of the microemulsion phase, SP*, were also obtained.

An analytical GC-MS method to quantify methyl dihydrojasmonate in biocompatible oil-in-water microemulsions: physicochemical characterization and in vitro release studies

Microemulsions (MEs) loaded with methyl dihydrojasmonate (MJ) were developed to improve the aqueous solubility of this drug. The composition of the formulations ranged according to the oil/surfactant ratio (O/S). The MEs were characterized according to diameter of droplets, X-ray diffraction and polarized light microscopy. The MJ identification and quantification was performed by gas chromatography-mass spectrometry (GC-MS). The MJ showed a retention time of ∼16.7 min for all samples. The obtained correlation coefficient from the calibration graph was 0.991. The developed analytical method was effective enough to quantify low and high concentrations of MJ. The increase of the O/S ME ratio led to a reduction of the droplet diameter. All formulations showed an amorphous structure and the behavior varied between isotropic and anisotropic systems. A decrease in the release of MJ with the increase of the O/S ratio in the formulations was observed. The analytical method developed for the quantitative determination of MJ is suitable to detect and quantify the drug compound from different compositions of MEs in the in vitro release test, and by analogy in other prolonged effects related to the drug reservoir effect of these systems was observed, revealing that ME can be a promising nanocarrier for MJ delivery to tumor cells.

Study of the Electrochemical Behavior of Biodiesel Microemulsion

AbstractMicroemulsions have become a widely employed technique for the control of biodiesel quality but are still poorly understood as regard to their electrochemical behavior. In this work, we report the fundamental importance associated with the knowledge of electrochemical behavior of microemulsions composed of water in the presence of a supporting electrolyte, soybean biodiesel and propan‐1‐ol as consolute, along with the ferrocyanide–ferricyanide redox system applied as probe. The voltammetric results showed that for different compositions of microemulsions, variation in peak currents and change in system reversibility as well as in the electron transfer process were clearly noted. Furthermore, through the study of the diffusion coefficient, three different types of microemulsions including Oil/Water, Bicontinuous, and Water/Oil were successfully identified. Electrochemical impedance spectroscopy studies were also carried out aiming at obtaining more information regarding the electrode/solution interface. All the studies performed demonstrated that different types of microemulsions were formed upon exerting a direct influence on the electrochemical behavior of the redox probe. These results, in essence, point to the possibility of choosing a more suitable and advantageous microemulsion type for the development of an analytical method, as in the case, for example, of the microemulsions ME‐2 and ME‐3 which presented high voltammetric response in redox probe oxidation.

Nanoparticle Size Control in Microemulsion Synthesis.

Quasi-monodisperse populations of (H3O)Y3F10·xH2O nanocrystals of varying size are prepared in Igepal-stabilized microemulsions. Correlations between microemulsion composition, micelle hydrodynamic radius, and final nanoparticle size are established and shed light on the mechanism of particle size control. Under the conditions considered here, size control appears to be primarily governed by the number of micelles and the quantities of precursor ions. More specifically, the number of NPs formed can be successfully correlated with the number of micelles present and final NP size is, in turn, determined by the number of nuclei and the total amount of material available for nanocrystal formation. This insight into nanoparticle formation facilitates the selection of appropriate synthetic conditions for the preparation of populations of a targeted size.

Analysis of phenolic acids by ionic liquid-in-water microemulsion liquid chromatography coupled with ultraviolet and electrochemical detector

An environmentally friendly ionic liquid-in-water (IL/W) microemulsion was established and applied as mobile phase in microemulsion liquid chromatography (MELC) with ultraviolet (UV) detection or electrochemical detector (ECD) for analysis of phenolic compounds in real samples. The optimal condition of the method was using the best composition of microemulsion (0.2% w/v [HMIM]PF6, 1.0% w/v SDS, 3.0% w/v n-butanol, 95.8% v/v water, pH 2.5) with UV detection. The validation results indicated that the method provided high degree of sensitivity, precision and accuracy with the low limit of detections ranged from 17.9–238ng/mL, satisfactory mean recovery values in the range of 80.1–105% and good linearity (r2>0.9994). Additionally, this method exhibited high selectivity and resolution for the analytes and was more eco-friendly compared with traditional MELC method. Consequently, the established IL/W MELC method was successfully applied to simultaneously separate and determine target compounds in Danshen sample and its preparation.

Preparation and Oxidation Stability Evaluation of Tea Polyphenols-Loaded Inverse Micro-Emulsion.

Compared to synthetic antioxidants, tea polyphenols (TPs) has its own advantages in edible oil industry, however, the hydrophilic properties have restricted its applications. In this study, the ternary phase diagram of TPs-loaded micro-emulsion (ME) system was constructed, in which glyceryl monooleate (GMO), Tween80, linoleic acid as the surfactants, ethanol as the co-surfactant and soybean, corn, sunflower oil as the oil phase, have been used for the preparation of ME. The results indicated that a composition of ME (57.5% oil, 18% Tween80, 18% GMO, 4% Linolic acid, and 2.5% water+ethanol) could dissolve maximum water and could stable for 2 mo at room temperature with an average diameter of 6 to 7 nm, as detected by means of dynamic light scattering (DLS). The loaded of TPs into ME led to an increase of particle size to 15 to 16 nm, due to increased polarity of the water phase. The antioxidant capacity of TPs in ME was characterized by the peroxide value (POV) method. The addition of 1% water phase with 0.1 g/mL TPs could retain the POV at low value for 30 d at accelerating temperature 50 °C. Meanwhile, comparing the three edible oil, ME with corn oil has lower conductivity and higher value of POV during the storage. This work provides an efficient and environmentally friendly approach for the preparation of TPs-loaded ME, which is beneficial to the application of TPs in edible oil.