Microemulsion Composition Research Articles

Size‐controlled synthesis of Ni‐B nanoparticles by applying statistical experimental design in reverse micelles technique

This work focuses on the size‐controlled preparation of Ni‐B nanoparticles by chemical reduction of nickel acetate with sodium borohydride in the ternary reverse micelles of cetyl trimethyl ammonium bromide (CTAB)/n‐hexanol/water. A response surface methodology (RSM) with four factors: CTAB/water (0.5–3.5 g/g); CTAB/n‐hexanol (0.2–0.8 g/g); B/Ni molar ratio (1–4); and nickel salt concentration (0.075–0.525 mol/L) was used to study the mean size of nanoparticles. Based on the central composite design (CCD), a total of 32 experimental tests were performed to correlate both reagent concentrations (Ni2+ and BH4−) and microemulsion compositions (surfactant/oil/water) to the size of to‐be‐obtained nanoparticles. The Ni‐B nanoparticles were obtained with a narrow size distribution of average diameter in the range of 4.5–30.6 nm. The quadratic model developed explained adequately the non‐linear nature of the modelled response (R2 = 0.97, precision = 33.19). Also the influence of effective variables on the mean size of Ni‐B nanoparticles was examined simultaneously and discussed theoretically by using 3D‐surface and 2D‐contour plots. Finally optimization of CCD based on desirability function was performed. The optimal conditions were found to be at the surfactant/oil/water mass ratio of 34/55/11, nickel salt concentration of 0.24 mol/L, and B/Ni molar ratio of 2.23 with desirability factor of 0.98. Moreover, validation of the optimization showed that the model predictions were very close to the experimental results with slight errors (7–10 %). Finally, TEM micrographs of Ni‐B nanoparticles at optimum conditions showed that by applying statistical experimental design in reverse micelle technique, not only particle size but also agglomeration could be effectively controlled.

A Novel Microemulsion System for Ocular Delivery of Azithromycin: Design, Characterization and Ex-Vivo Rabbit Corneal Permeability

Background: The poor bioavailability of ophthalmic drops is mainly due to the rapid nasolacrimal drainage of the drug and very low permeability of corneal epithelium. Hence, there is an interest to find an effective system to improve drug permeability and bioavailability. Objectives: The aim of the present study was to design and characterize a novel microemulsion system as an ocular delivery system for Azithromycin and evaluate its physicochemical characteristics and rabbit corneal permeability in order to enhance the penetration of the drug. Methods: The prepared microemulsions (MEs) were assessed for their viscosity, pH, particle size, surface tension, DSC, stability, in vitro drug release, and corneal rabbit permeability. In this study, a full factorial design was employed with 3 variables at 2 levels for preparing 8 formulations and data analysis. Results: The results showed that the average droplet size of ME formulations was in the range of 6.78 to 26.65 nm while pH values were 5.1 to 5.7 and viscosity range was 115 - 361 cps. Drug release profile revealed that 79.066% of the drug released in 24 hours of the experiment. The maximum and minimum percentages of drug permeated through rabbit cornea were observed in MEA-7 (12.87%) and MEA-2 (0.909%), respectively. All ME formulations with different compositions and properties significantly increased partitioning, flux, and permeability coefficient from rabbit cornea. Dapp and Papp parameters in MEA-1 and MEA-7 formulations were 0.00882 cm2h-1 and 2.391 cmh-1, which were 17.65, 35.17 times higher than those of control (AZ suspension, 1%), respectively. The flux (Jss) of Azithromycin in MEA-7 was 11.958 mg cm-2h-1, which was 39.86 times higher than that of control. Conclusions: The present study showed that any change in the content and composition of ME could change physicochemical properties and permeability parameters during drug permeation of ME formulations. The phenomenon may be due to the cornea structural changes in presence of ME components.

Determination of Iron, Copper, Zinc, Aluminum, and Chromium in Biodiesel by Flame Atomic Absorption Spectrometry Using a Microemulsion Preparation Method

This work proposes a flame atomic absorption spectrometry (FAAS) method for Fe, Cu, Zn, Al, and Cr determination in biodiesel using water in oil (w/o) microemulsion (ME) as a sample preparation method. A less toxic solvent (n-propanol), instead of those used in the standard method (ABNT NBR 15556), the absence of surfactant, and calibration using inorganic reference standards were investigated. A ternary phase diagram of biodiesel as oil, water, nitric acid, and n-propanol showed a single-phase ME region. The composition of ME adopted for analysis was 1.7 g of biodiesel and 1.1 mL of 1.4 mol L–1 HNO3, completed with n-propanol to 10 mL volume. Linear calibration graphs with R > 0.99 were obtained using ME prepared with oleic acid and inorganic standards. Analytes were stable for at least 3 days both in sample and in metallic standards MEs. The limits of detection obtained were 0.3, 0.1, 0.07, 1.7, and 1.0 mg kg–1 for Fe, Cu, Zn, Al, and Cr, respectively. These limits of detection were lower than those obt...

On Metal Segregation of Bimetallic Nanocatalysts Prepared by a One-Pot Method in Microemulsions

A comparative study on different bimetallic nanocatalysts prepared from microemulsions using a one-pot method has been carried out. The analysis of experimental observations, complemented by simulation studies, provides detailed insight into the factors affecting nanoparticle architecture: (1) The metal segregation in a bimetallic nanocatalysts is the result of the combination of three main kinetic parameters: the reduction rate of metal precursors (related to reduction standard potentials), the material intermicellar exchange rate (determined by microemulsion composition), and the metal precursors concentration; (2) A minimum difference between the reduction standard potentials of the two metals of 0.20 V is needed to obtain a core-shell structure. For values ∆ε0 smaller than 0.20 V the obtaining of alloys cannot be avoided, neither by changing the microemulsion nor by increasing metal concentration; (3) As a rule, the higher the film flexibility around the micelles, the higher the degree of mixture in the nanocatalyst; (4) A minimum concentration of metal precursors is required to get a core-shell structure. This minimum concentration depends on the microemulsion flexibility and on the difference in reduction rates.

The effect of microemulsion composition on the morphology of Pd nanoparticles deposited at the surface of TiO2 and photoactivity of Pd-TiO2

A series of microemulsion (ME) system, constituted by different water to surfactant molar ratios (Wo) and oil to surfactant mass ratios (S), have been applied for Pd-TiO2 preparation. The effect of ME properties on the morphology of Pd nanoparticles formed at TiO2 surface and an effect of Pd size and distribution on the surface and photocatalytic properties of Pd-TiO2 were investigated. Microemulsion systems were characterized by means of viscosity, density, dynamic light scattering as well as surface tension measurements to find a correlation between the conditions of Pd nanoparticles formation, their morphology and photocatalyst features. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), UV–vis diffuse-reflectance spectroscopy (DRS), BET surface area and elemental analysis. The photocatalytic properties of Pd-modified TiO2 particles were studied in a model reaction of phenol photodegradation under Vis irradiation, as well as active species involved in the photocatalytic reaction were determined. Microemulsion composition was found to be a crucial parameter in determining the features of the TiO2-based photocatalysts covered by metallic nanoparticles. The highest photocatalytic activity under Vis radiation was observed for the Pd-TiO2 sample (average diameter 2.4nm) obtained using 0.1mol% Pd in the ME system containing 1.5wt% of water and 82.8wt% of cyclohexane with average droplet size of 2.83±0.18nm. In this regard, synthesis of such metal-semiconductor composites through the microemulsion route should always be preceded by investigation of ME properties in order to the eliminate the inhibitory effect of ME internal structure.

Transungual Gel of Terbinafine Hydrochloride for the Management of Onychomycosis: Formulation, Optimization, and Evaluation.

The present study was aimed to optimize, develop, and evaluate microemulsion and microemulsion-based gel as a vehicle for transungual drug delivery of terbinafine hydrochloride for the treatment of onychomycosis. D-optimal mixture experimental design was adopted to optimize the composition of microemulsion having amount of oil (X 1), Smix (mixture of surfactant and cosurfactant; X 2), and water (X 3) as the independent variables. The formulations were assessed for permeation (micrograms per square centimeter per hour; Y 1), particle size (nanometer; Y 2), and solubility of the drug in the formulation (milligrams per milliliter; Y 3). The microemulsion containing 3.05% oil, 24.98% Smix, and 71.96% water was selected as the optimized formulation. The microemulsion-based gel showed better penetration (∼5 folds) as well as more retention (∼9 fold) in the animal hoof as compared to the commercial cream. The techniques used to screen penetration enhancers (hydration enhancement factor, ATR-FTIR, SEM, and DSC) revealed the synergistic effect of combination of urea and n-acetyl cysteine in disruption of the structure of hoof and hence, leading to enhanced penetration of drug.

Hydrolytic Cleavage of Paraoxon by Octanohydroxamate Ion in Cationic Microemulsions

ABSTRACTThe hydrolysis reaction of O,O‐diethyl O‐p‐nitrophenylphosphate (Paraoxon) with the octanohydroxamate ion (OHA−) was studied in a cationic oil‐in‐water (O/W) microemulsion system over a pH range 7.5–12.0 at 300 K. The O/W systems are stabilized by using cationic surfactant, cetyltrimethylammonium bromide (CTAB), and n‐butanol as cosurfactants. In a microemulsion, the rate enhancement by OHA− is greater toward the cleavage of paraoxon than its spontaneous (2.1 × 107 s−1) hydrolysis. The kobs values for the reaction of paraoxon with OHA− were determined in different microemulsion compositions with varying chain length of alcohols (n‐butanol, n‐pentanol, n‐octanol, and n‐dodecanol) and alkanes (n‐hexane, n‐heptane, and n‐decane). The effects of water content, pH, and size of the oil pool have been discussed.

Pore Scale Dynamics of Microemulsion Formation.

Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (<10(-2) mN m(-1)) that is required for miscibility to occur. Many studies focus on microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound consequences on the pore scale mixing behavior and resulting microemulsion properties.

Fischer–Tropsch synthesis in the presence of ultrafine iron-containing catalysts derived from reverse microemulsions

It is shown that active catalysts for Fischer–Tropsch synthesis with a controlled size of the particles of the dispersed phase may be formed on the basis of reverse microemulsions in a slurry reactor. After optimization of the composition of the reverse microemulsion (iron nitrate nonahydrate as a precursor of the active metal and SPAN-80 as a surfactant, 5 wt %), the size of the microemulsion droplets decreases to 130 nm. The chosen method for the synthesis of catalytic systems makes it possible to introduce promoters without any marked enlargement of the dispersed phase (130–160 nm). High-temperature Fischer–Tropsch synthesis is performed in a slurry reactor using catalysts prepared from reverse iron-containing microemulsions. The tested iron-containing catalytic systems feature high selectivity (up 73 wt %) in the formation of gasoline fractions (the C5–C10 fraction) that contain an abnormally high (up to 77 wt %) level of unsaturated hydrocarbons.

Microemulsion electrokinetic chromatography as a suitable tool for lipophilicity determination of acidic, neutral, and basic compounds.

In the present work, several MEEKC systems are studied to assess their suitability for lipophilicity determination of acidic, neutral, and basic compounds. Thus, several microemulsion compositions over a wide range of pH values (from 2.0 to 12.0), containing heptane, 1-butanol and different types and amounts of surfactant (SDS or sodium cholate: from 1.3 to 3.3%) are characterized using Abraham's solvation model. The addition of acetonitrile (up to 10%) is also studied, since it increases the resolution of the technique for the most lipophilic compounds. The system coefficients obtained are very similar to those of the 1-octanol/water, used as the reference lipophilicity index, allowing simple and linear correlations between the 1-octanol/water partition values (log Po/w ) and MEEKC mass distribution ratios (log kMEEKC ). Variations in the microemulsion composition (aqueous buffer, surfactant, concentration of ACN) did not significantly affect the similarity of the MEEKC systems to log Po/w partition.

Microemulsion synthesis method for preparation of mesoporous nanocrystalline γ-Al2O3 powders as catalyst carrier for nickel catalyst in dry reforming reaction

Three large mesoporous alumina powders were prepared by microemulsion (ME) method with different microemulsion structures and compositions (various surfactants and oil phases) and employed as catalyst carrier for preparation of mesoporous nanocrystalline Ni/Al2O3 catalysts. The prepared catalysts were used in dry reforming reaction for production of synthesis gas. The samples were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller surface area analysis (BET), temperature programmed reduction (TPR) and scanning electron microscopy (SEM) techniques. The results showed that the prepared γ-Al2O3 with different microemulsion compositions possessed mesoporous structure with high surface area from 239.7 to 277.7 m2 g−1. In addition, the prepared 10wt.% Ni/γ-Al2O3 catalysts exhibited high activity and stability in dry reforming reaction. The results also revealed that the microemulsion composition have a significant effect on the textural properties and affected the catalytic performance.

Development of intranasal nanovehicles of itraconazole and their immunological activities for the therapy of rhinovirus infection

Itraconazole (ITZ)-loaded microemulsion (ME) systems for intranasal (IN) delivery were developed for the treatment of human rhinovirus serotype 1B (HRV1B) infection. ITZ was incorporated into the oil-in-water (o/w) ME formulation composed of benzyl alcohol (oil), Cremophor EL (surfactant), Solutol HS15 (cosurfactant), and water. The optimized composition of ME was determined by constructing pseudo-ternary phase diagram. ITZ ME formulation with about 150nm mean diameter and spherical shape was prepared and the solubility of ITZ in blank ME was markedly improved (up to 13.9mg/mL). The initial value of droplet size was maintained with four times dilution in the aqueous buffer and 72h incubation. Released amounts of drug from ME formulation were significantly enhanced compared to drug suspension group (p<0.05). Particularly, ITZ ME group displayed lower levels of inflammatory markers in the lung compared to ITZ suspension group after their IN administration in the HRV1B-infected mouse model (p<0.05). Developed ITZ ME formulation via IN route can be a promising candidate for the treatment of rhinovirus infection.

Antimicrobial properties of microemulsions formulated with essential oils, soybean oil, and Tween 80

It was previously found that blending soybean oil with cinnamon bark oil (CBO), eugenol or thyme oil, Tween 80, and equal masses of water and propylene glycol could be used to prepare microemulsions. In the present study, the objective was to determine the antimicrobial activity of the microemulsions in tryptic soy broth (TSB) and 2% reduced fat milk. In TSB, the minimum inhibitory concentration (MIC) of CBO solubilized in microemulsions was up to 625ppm against cocktails of Listeria monocytogenes, Salmonella enterica or Escherichia coli O157:H7, which was equal to or higher in concentration than free CBO dissolved in ethanol. However, MICs of eugenol or thyme oil in microemulsions were much higher than that of free antimicrobials. Therefore, microemulsions of CBO were chosen to do further study. Inactivation curves of L. monocytogenes or E. coli O157:H7 in TSB or 2% reduced fat milk were tested and fitted using the Weibull model. In TSB, a gradual decrease in cell viability of L. monocytogenes and E. coli O157:H7 was observed with the microemulsion treatments at 625ppm CBO, which was in contrast to the more rapid and greater inactivation by free CBO. Gradual inactivation of L. monocytogenes in 2% reduced fat milk was also observed in the treatment with 10,000ppm free or microemulsified CBO. When fitted using the Weibull model, the predicted time to obtain a 3-log decrease of L. monocytogenes and E. coli O157:H7 in TSB or 2% reduced fat milk increased with an increased amount of soybean oil in microemulsions. Additionally, increasing the amount of Tween 80 in mixtures with different mass ratios of Tween 80 and essential oils significantly decreased the log reductions of L. monocytogenes in TSB. Our study showed that microemulsions can be used to dissolve EOs and control the rate of inactivating bacteria, but the composition of microemulsions is to be carefully chosen to minimize the reduction of antimicrobial activities.

Single crystalline rhabdophane-type CePO4 nanoparticles as efficient UV filters

Cerium-based materials have shown good results when applied as inorganic UV filters, either absorbing and/or scattering light. Although most papers report the use of Ce(IV), Ce(III) has shown better results for UV protection applications, confirmed by photocatalysis involving the degradation of castor oil, and UV–vis reflectance and absorbance spectroscopies. Reverse microemulsions have been widely employed to obtain nanosized particles with controlled morphology, thus water-in-oil microemulsion syntheses of cerium(III) orthophosphates using cetyltrimethylammonium bromide and 1-butanol as surfactant and co-surfactant are reported. Cerium(IV) oxide particles have been synthesized by the same way for concrete comparisons. The variations in the microemulsion compositions and their effects in the morphology and UV filter efficiency have been investigated. Electron micrographs evidence the formation of well dispersed and singly crystalline rhabdophane-type CePO4 nanorods, which display longer lengths as the surfactant amount decreases. The observation of 2D←2F5/2 Ce3+ transitions, ideal optical band gap energies (2.7–2.8eV) and, the formation of nanosized particles support the applicability of CePO4 for UV protection.

Solubility dynamic of methyl yellow and carbon black in microemulsions and lamellar liquid crystal of water, non ionic surfactants and cyclohexane system

Solubility dynamics of methyl yellow and carbon black in microemulsions and liquid crystals of water, non-ionic surfactants and cyclohexane system, have been investigated. Actually, solubility dynamics of these dyes both in microemulsion (w/o microemulsions) and the lamellar liquid crystal (LLC) were strongly related to the chemical composition, nature and characteristics of microemulsions and the lamellar liquid crystals.

D-optimal Design and Development of Microemulsion Based Transungual Drug Delivery Formulation of Ciclopirox Olamine for Treatment of Onychomycosis

The objective of the present study was to design and develop a microemulsion based transungual drug delivery formulation of ciclopirox olamine using colloidal carrier for treatment of onychomycosis. Capmul PG8 was selected as oil phase due to the high solubility of ciclopirox in it as compared to other oils and Cremophor EL and Transcutol P were used as surfactant and cosurfactant respectively. Pseudoternary phase diagrams were constructed using different ratio of Smix (surfactant:cosurfactant). The phase diagram obtained from 1:3 ratio showed largest microemulsion region. The construction of microemulsion was further optimized by D-optimal mixture design, taking oil, Smix and water as independent variables and globule size, transungual flux, and nail drug loading as response variables. Mathematical equations and response surface plots were used to correlate the dependent and independent variables. The optimized composition of microemulsion was predicted by numerical optimization technique on the basis of the highest desirability value. The predicted optimized microemulsion which contained 2% oil, 40% Smix, and 58% water was incorporated into Carbopol 940 gel base and evaluated for transungual drug permeation. The optimized microemulsion based gel formulation showed globule size (25.8±1.2 nm), transungual flux (0.436±0.014 μg/cm2/h), and drug loading in nail plate (82.89±5.74 μg) which was in close agreement with the predicted value of response variable by the optimization software, i.e. 26.145 mm, 0.431 μg/cm2/h, and 81.023 μg, respectively. These results confirmed that the D-optimal mixture design can be successfully employed for designing and development of microemulsion based formulation of ciclopirox olamine.

Peroxyl radical reactions with carotenoids in microemulsions: Influence of microemulsion composition and the nature of peroxyl radical precursor

The reactions of acetylperoxyl radicals with different carotenoids (7,7′-dihydro-β-carotene and ζ-carotene) in SDS and CTAC microemulsions of different compositions were investigated using laser flash photolysis (LFP) coupled with kinetic absorption spectroscopy. The primary objective of this study was to explore the influence of microemulsion composition and the type of surfactant used on the yields and kinetics of various transients formed from the reaction of acetylperoxyl radicals with carotenoids. Also, the influence of the site (hydrocarbon phases or aqueous phase) of generation of the peroxyl radical precursor was examined by using 4-acetyl-4-phenylpiperidine hydrochloride (APPHCl) and 1,1-diphenylacetone (11DPA) as water-soluble and lipid-soluble peroxyl radical precursors, respectively. LFP of peroxyl radical precursors with 7,7′-dihydro-β-carotene (77DH) in different microemulsions gives rise to the formation of three distinct transients namely addition radical (λmax=460nm), near infrared transient1 (NIR, λmax=700nm) and 7,7′-dihydro-β-carotene radical cation (77DH•+, λmax=770nm). In addition, for ζ-carotene (ZETA) two transients (near infrared transient1 (NIR1, λmax=660nm) and ζ-carotene radical cation (ZETA•+, λmax=730–740nm)) are generated following LFP of peroxyl radical precursors in the presence of ζ-carotene (ZETA) in different microemulsions. The results show that the composition of the microemulsion strongly influences the observed yield and kinetics of the transients formed from the reactions of peroxyl radicals (acetylperoxyl radicals) with carotenoids (77DH and ZETA). Also, the type of surfactant used in the microemulsions influences the yield of the transients formed. The dependence of the transient yields and kinetics on microemulsion composition (or the type of surfactant used in the microemulsion) can be attributed to the change of the polarity of the microenvironment of the carotenoid. Furthermore, the nature of the peroxyl radical precursor used (water-soluble or lipid-soluble peroxyl radical precursors) has little influence on the yields and kinetics of the transients formed from the reaction of peroxyl radicals with carotenoids. In the context of the interest in carotenoids as radical scavenging antioxidants, the fates of the addition radicals (formed from the reaction of carotenoid with peroxyl radicals) and carotenoid radical cations are discussed.

Preparation of Pt‐B/Al2O3 amorphous alloy catalysts via microemulsion methods and application into hydrogenation of m‐chloronitrobenzene

AbstractPt‐B/Al2O3 catalysts were prepared through chemical reduction of platinum ions with borohydride in a water/oil (W/O) microemulsion system comprising cetyltrimethyl ammonium bromide (CTAB), n‐butanol, cyclohexane, and H2PtCl6 solution. Transmission electron microscope (TEM) and selected‐area electron diffraction (SAED) analyses show that the active Pt particles on the catalysts are uniformly distributed as a Pt‐B amorphous alloy. We studied the effects of microemulsion composition, reduction conditions, and preparation methods on the catalysts applied into m‐chloronitrobenzene (m‐CNB) hydrogenation. We also investigated the kinetics of m‐CNB hydrogenation. The catalyst prepared via a single‐microemulsion method exhibited much higher activity and even higher selectivity than that prepared with the aqueous solution method. Finally, we propose the mechanism for Pt‐B effects on the catalytic performance of Pt‐B/Al2O3 in m‐CNB hydrogenation.

Selection of microemulsion composition via study of phase behavior for synthesis of stable monodisperse platinum nanoparticles and optimization of experimental parameters

ABSTRACTMonodisperse platinum nanoparticles were synthesized by microemulsion technique. Feasibility of formation of microemulsion with chosen proportions of components is a common problem with this method. Here, prior to preparation of microemulsion for synthesis purpose, systematic study was carried to check the suitability of selected microemulsion system by establishing phase diagram for ternary system at constant temperature on triangular coordinates. Temperature dependency of microemulsion was studied by preparing phase diagram of temperature against mass fraction of aqueous phase in ternary mixture. Both these triangular coordinate diagram at constant temperature and temperature dependency plots helped to choose proper concentrations of components in the system. Effects of molar concentration of water-to-surfactant ratio, platinum salt concentration, continuous oil phase concentration, and presence of cosurfactant with surfactant on particle size were investigated for selected system of components. Synthesized platinum nanoparticles were characterized by dynamic light scattering and transmission electron microscope. Light backscattering profiles obtained by Turbiscan were used to judge the stability of microemulsions. Further, partial weightage of affecting parameters on size of synthesized particle were studied by Taguchi orthogonal array method.

Application of water-in-oil microemulsions in microemulsion electrokinetic chromatography and as extractants of polar substances

We studied the use of water-in-oil (W/O) microemulsions as new pseudophases in microemulsion electrokinetic chromatography (MEEKC). It is shown that the method is suitable for the separation of complex mixtures of polar compounds. The effect of the microemulsion composition on the selectivity of separation of inorganic anions is examined. A new rapid method of sample preparation is proposed, which includes the complete dissolution of a mayonnaise sample in a reverse microemulsion for 2 min in an ultrasonic bath. Preservatives are determined by the MEEKC analysis of W/O microemulsion (MEEKC W/O). The developed procedure for determining preservatives in mayonnaise is simple and rapid: the duration of separation is 8 min and sample preparation takes 5 min. The repeatability of measurements is from 5.8 to 2.3%, and the intermediate precision is from 7.5 to 5.7%. The detection limit is 3.0 mg/kg for sorbic acid and 3.3 mg/kg for benzoic acid.