Physicochemical parameters influencing the emulsion drop size

The stirring-mixing energy is the most obvious factor in the drop size reduction process, but it is not necessarily the most important one. Both the physicochemical formulation and the composition variables are shown to play a determinant role, at constant stirring condition.The generalized formulation versus water/oil ratio diagram allows to map emulsion properties such as emulsion type, stability and viscosity. It is used to discuss the combined effect of the formulation and composition upon the emulsion drop size, through their influences on the interfacial tension, and the emulsion viscosity and stability.     

Analysis of the Phase Changes During Evaporation of Emulsions with Different Oil Phases

Emulsions surfer alterations in their microstructure after applied on the skin, because of the interaction with skin constituents and mainly by the evaporation of volatile components. These alterations are not even considered by cosmetic formulators, but they are extremely important because they can act on formulation stability, on delivery and on permeation of actives and also on the ability to build the occlusive film, responsible for skin's moisturization. This research studied the phase changing during evaporation of emulsions made with three different oil phase: mineral oil, avocado oil, and isocethyl/stearoil stearate, as a function of the decrease on water ratio, using phase diagrams and evaporation test. It was observed the formation of liquid crystalline phases and their transition along the evaporation path for emulsions with the three different oil phases. It was also observed that these transitions occurred in different water ratios.     

Study of the polymer concentration and polymer/crosslinker ratio effect on gelation time of a novel grafted polymer gel for water shutoff using a central composite design method

In this research article, a hydrogel was prepared by crosslinking of carboxymethyl cellulose‐g‐polyacrylamide copolymer aqueous solution with chromium(III) acetate for the purpose of a water shutoff job in the oil reservoir. The experiments were conducted to investigate the main effects of copolymer concentration and crosslinker/copolymer ratio on gelation time of the hydrogel system. Then the effects of these two factors and their interactions on the gelation time were determined by using a central composite design (CCD) of the response surface method. CCD was used to generate the quadratic mathematical model for the gelation time response as a function of copolymer concentration, crosslinker/copolymer ratio, and their interaction. Furthermore, the analysis of variance (ANOVA) was used to evaluate the quality of the quadratic model. The ANOVA result of the developed model showed that the model was highly significant. The result also showed that the crosslinker/polymer ratio had more effects on the gelation time than did the polymer concentration and their interaction. A response surface method provides an optimum gel formulation. Core flooding experiments reveal that a significant permeability reduction on the sand pack cores can be achieved at reservoir conditions, when it is treated with an optimum gel formulation. Hence, this gel system may be suitable in the water shutoff job required for enhanced oil recovery from the oil fields. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of interfacial and structural properties of CTAB at the oil/water interface using dissipative particle dynamics simulations

We have used dissipative particle dynamics (DPD) to simulate the system of cetyltrimethylammonium bromide (CTAB) monolayer at the oil/water interface. The interfacial properties (interfacial density, interfacial thickness, and interfacial tension), structural properties (area compressibility modulus, end to end distance, and order parameter), and their dependence on the oil/water ratio and the surfactant concentration were investigated. Three different microstructures, spherical oil in water (o/w), interfacial phase, and water in oil (w/o), can be clearly observed with the oil/water ratio increasing. Both the snapshots and the density profiles of the simulation show that a well defined interface exists between the oil and water phases. The interface thickens with CTAB concentration and oil/water ratio. The area compressibility modulus decreases with an increase in the oil/water ratio. The CTAB molecules are more highly packed at the interface and more upright with both concentration and oil/water ratio. The root mean square end-to-end distance and order parameter have a very weak dependence on the oil/water ratio. But both of them show an increase with CTAB concentration, indicating that the surfactant molecules at the interface become more stretched and more ordered at high concentration. As CTAB concentration increases further, the order parameter decreases instead because the bending of the interface. At the same time, it is shown that CTAB has a high interfacial efficiency at the oil/water interface.     

Poly(lactic-co-glycolic acid) microspheres for the controlled release of huperzine A: in vitro and in vivo studies and the application in the treatment of the impaired memory of mice

Huperzine A loaded poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres were prepared by an oil/water (o/w) solvent evaporation technique. With a decrease of the ratio of o/w from 1 : 100 to 1 : 50, the encapsulation efficiency was reduced about 4%. Increasing the PVA concentration from 0.5 to 2% reduced the percentage encapsulation efficiency of huperzine A from 60.7 to 47.4% and the particle size of microspheres from 84.2 to 26.2 microm. The addition of stearic acid improved the encapsulation efficiency, but also accelerated the in vitro release of hupezine A from microspheres. After i.m. administration of huperzine A loaded microspheres in mice, huperzine A was sustained released from the PLGA microspheres up to 12 d with a low initial burst. Passive avoidance test of mice showed that the microspheres formulation offered an improved therapeutic efficiency in the treatment of the impaired memory of the mice superior to injection gastric (i.g.) administration of huperzine A suspension at the same dose, whose therapeutic efficiency was similar as that of a 50% reduced dose of the microspheres formulation.     

Conductive Flow Parameters of Mixed Nonionic Surfactants Microemulsions

This article focuses on the electrical conductivity study of the brine solution/sucrose laurate/ethoxylated mono-di-glyceride/oil + ethanol system. The oils were R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride. The mixing ratio (w/w) of ethanol/oil and that of sucrose laurate/ethoxylated mono-di-glyceride equal unity. The brine solution was 0.01 M aqueous sodium chloride solution. No observable effect was observed on the phase boundaries by replacing pure water with brine solution in the case of R (+)-limonene based microemulsions. In the systems based on isopropylmyristate and caprylic-capric triglyceride, the replacement of pure water by brine significantly affected the phase boundaries, the microemulsion region shrink and the total monophasic area of microemulsions decreased. Electrical conductivity increases with the increase in the water volume fraction and percolation thresholds were observed. The critical volume fractions where the percolation thresholds appear depend on the type of oil used in the microemulsion formulation. Electrical conductivity was measured at different temperatures and the activation energy of conduction flow was evaluated. At the percolation threshold the activation energy of conduction flow reaches a minimum value. Beyond the percolation threshold, a small increase is observed in the activation energy of conduction flow then it decreases with the increase in the water volume fraction indicating structural transitions.     

Study of the preparation of sustained-release microspheres containing zedoary turmeric oil by the emulsion-solvent-diffusion method and evaluation of the self-emulsification and bioavailability of the oil

The purpose of this study was to design a sustained-release formulation of an oily drug. The sustained-release microspheres with self-emulsifying capability containing zedoary turmeric oil (ZTO) were prepared by the quasi-emulsion-solvent-diffusion method. The micromeritic properties, the efficiency of emulsification and the drug-release behavior of the resultant microspheres were investigated. The bioavailability of the microspheres was compared with conventional ZTO self-emulsifying formulations for oral administration using 12 healthy rabbits. An HPLC method was employed to determine the concentration of germacrone in plasma, which was used as an index of ZTO. Spherical and compacted microspheres with average diameters of 100-600 microm have been prepared, and their release behavior in distilled water containing 1.2% (w/v) of polysorbate-80 can be controlled by the ratio of polymer/Areosil200 in the microspheres. The resultant emulsions with mean droplet sizes of 200-500 nm are produced when the microspheres are immersed in phosphate buffer (pH 6.8) under gentle agitation. The stability and the droplet size of the resultant emulsions are also affected by the polymer/Areosil200 ratio in the formulation, while the amount of talc has a marked effect on the self-emulsifying rate. The plasma concentration-time profiles with improved sustained-release characteristics were achieved after oral administration of the microspheres with a bioavailability of 135.6% with respect to the conventional self-emulsifying formulation (a good strategy for improving the bioavailability of an oily drug). In conclusion, the sustained-release microspheres with self-emulsifying capability containing ZTO have an improved oral bioavailability. Our study offers an alternative method for designing sustained-release preparations of oily drugs.     

Initial inter-phase transport of compounds in a model emulsion system

Three-phase geranyl acetate emulsions stabilized by a non-ionic surfactant, Laureth 4, were prepared with a constant weight fraction of a lamellar liquid crystal and varied aqueous to oil phase weight ratios according to the phase diagram. The appearance and micrographs of the drop pattern versus time were recorded. As expected, emulsions with the lower values of the water to oil (W/O) ratio appeared to be of the W/O variety while the two more stable emulsions with the highest W/O ratio appeared as oil to water (O/W). Considering the surfactant exclusive solubility in the oil, this result was unexpected and the emulsions were investigated as to their structure. Unpredictably, all the emulsions were of the O/W kind; including the highest ratio of oil to water. The reason for this unanticipated outcome was the lamellar liquid crystal being dispersed into the aqueous phase at the slightest perturbation.     

Submicron Size Formulation of Linseed Oil Containing Omega-3 Fatty Acid for Topical Delivery

The aim of the present study was to design and develop topical submicron size gel formulation of linseed oil with enhanced permeation through the skin for the management of psoriasis. Linseed oil contains significant amount of α-linolenic acid (ALA) an omega-3 fatty acid, which is responsible for its pharmacological actions. In order to enhance permeation through skin, microemulsion based gel formulation was prepared and characterized. Microemulsions were prepared by aqueous phase titration method, using linseed oil, Unitop 100, PEG 400, and distilled water as the oil phase, surfactant, cosurfactant and aqueous phase, respectively. Selected formulations were subjected to physical stability studies and consequently in vitro skin permeation studies. Surface morphology studies of optimized formulation were done by transmission electron microscopy (TEM). The droplet size of microemulsions ranged from 70 to 500 nm with average particle size 186 nm. The optimized microemulsion was converted into hydrogel using carbopol 971 which had a viscosity of 498 ± 0.04 cps. During in vitro permeation study the flux of microemulsion formulation and gel was found to be 19.05 and 10.2 µg/cm²/hr, respectively, which indicated better penetration of linseed oil through the skin. These result indicated that the developed ME formulation may be a good approach for topical therapy for the management of psoriasis.     

Study on the formation and rheological properties of sucrose stearate lamellar liquid crystals

The phase diagrams of S1570–Brij 97/oleic acid/water system at two different S1570/Brij 97 mass ratios of 1/1 (system S) and 7/3 (system P) were determined at 37°C, respectively. The microstructures and rheological properties of liquid crystals at constant surfactants/water mass ratio of 1/1 were studied with increase in oil content. Small-angle x-ray scattering measurements showed that system S exhibited a typical lamellar liquid crystals and the repeat distance (d) decreased as oil content increased. While for system P, two couples of scattering peaks were observed when oil content reached 28 wt%. This indicated that adding oil content may give rise to a multilamellar structures in the higher S1570/Brij 97 mass ratio system. The rheological tests indicated that a transition from elastic gel-like properties to viscoelastic liquid-like properties appeared in both system S and P when oil content reached 20 wt%, corresponding to the polarizing optical microscopy textures changing from oily streak to cruciate flower. This supplies a way to adjust structure, rheological properties, and even phase transition by altering the S1570/Brij 97 mass ratio and oleic acid content in system.     

FORMULATION OF MODEL CUTTING-OIL WATER EMULSIONS USING PARAFFINIC OIL AND IONIC/NONIONIC SURFACTANT MIXTURE.

Cutting-oil emulsions are marketed under the shape of concentrates that the user has to dilute. More often these concentrates are monophasic microemulsions. We show that this kind of microemulsions may be obtained while relying on the generalized concept of Winsor, which guides the manipulation of three formulation parameters, which in turn rationally modify the surfactant interactions with the oily and the aqueous phases.

The model concentrates that we have formulated contain six constituents. The oily phase is constituted of paraffinic oil and normal decanol. The aqueous phase is a solution of monoethanolamine borate in water whose hardness is fixed at 40°f. The active mixture contains a hydrophilic surfactant and a lipophilic surfactant.

We have formulated concentrates presenting an excellent ability to dilution, a very good stability to the hardness of water and pHs in agreement with the cutting fluid specification sheets, while identifying the formulation parameters to the mass ratio of normal decanol in the oily phase, to the mass ratio of monoethanolainine borate in the aqueous phase and to the mass ratio of the hydrophilic surfactant in the active mixture.     

Catastrophic phase inversion of abnormal emulsions in the vicinity of the locus of transitional inversion

This paper deals with the phase behaviour of model abnormal emulsions of cyclohexane/water/polyethoxylated surfactant in the vicinity of the locus of transitional inversion (optimum formulation). Abnormal emulsions are formed under dynamic conditions if the phase containing the soluble surfactant becomes the dispersed phase. Phase maps have been suggested in the literature that define the boundaries of emulsion morphologies. On these maps, only one transformation can be observed for any formulation scan. Furthermore, the morphology of emulsions in the vicinity of the locus of transitional inversion is rather vague. One might assume that by changing the HLB of the surfactant used in an abnormal emulsion to favour the continuous phase, that abnormal emulsion will gradually transform to a normal emulsion of the same type. A new experimental procedure was adopted in which emulsification was started with abnormal emulsions. To transform the abnormal emulsions to the normal emulsion of the same type, they were exposed to variations in temperature, the surfactant HLB, or water–oil phase ratio. As the optimum formulation was approached, the abnormal emulsions became so unstable that could not exist anymore in the un-favoured morphology and inverted to the normal emulsion of the opposite type. Further variation in the formulation along the route led to a transitional inversion to the normal emulsion of the original type. The result indicates an important finding that the transformation of abnormal emulsions to normal ones of the same type occurred via two successive inversions of catastrophic and transitional nature. It appears that the boundaries of catastrophic inversion correspond to the emulsions with the finest drop size. A modification to the phase behaviour maps, to include the locus of catastrophic phase inversion in the vicinity of the transitional inversion, was thus suggested.     

Adsorption of bituminous components at oil/water interfaces investigated by quartz crystal microbalance: implications to the stability of water-in-oil emulsions

Silica-gel-coated QCM crystals oscillating in a thickness shear mode are used to measure adsorption of bituminous components in water-saturated heptol (1/1 vol ratio of a heptane/toluene mixture) at the oil/water interface. In addition to the viscoelasticity of the adsorbed film, the effects of the bulk liquid density and viscosity as well as the liquid trapped in interfacial cavities are taken into account for the calculation of adsorbed mass. Asphaltenes in heptol adsorb continuously at the oil/water interface, while resins (the surface-active species in maltenes) show adsorption saturation in the same solvent. For Athabasca bitumen in heptol, two adsorption regimes are observed depending on concentration. At low concentrations, a slow, non-steady-state, and irreversible adsorption takes place. At high concentrations, a steady-state adsorption with limited reversibility results in a quick adsorption saturation. The threshold concentration between these adsorption regimes is 1.5 wt % and 8 wt % for oil/water and oil/gold interfaces, respectively. The threshold concentration, the total adsorbed amount, and the flux of non-steady-state adsorption depend on the resin-to-asphaltene ratio. The threshold concentration is related to the earlier reported critical bitumen concentration characterizing the rigid-to-flexible transition of the interfacial film. We propose a new mechanism based on the change of the effective resin-to-asphaltene ratio with dilution to explain both the adsorption behavior and emulsion stability.     

阴阳离子表面活性剂混合体系对原油的乳化及增粘行为

利用阴阳离子表面活性剂复配技术,实现了高含水量原油体系的乳化及增粘.通过调整表面活性剂分子结构,解决了阴阳离子表面活性剂复配体系在油田模拟水中的溶解度问题.确定了相关体系高含水量油包水(W/O)乳状液的表面活性剂浓度,研究了可以产生高含水量油包水乳状液的油水混合体积比范围,并研究了温度、pH值、油水混合比例和离子强度对乳化及增粘作用的影响.获得了一系列具有优良乳化效果和乳状液稳定性的体系,其中部分体系粘度可增大80倍.这对于三次采油提高采收率有重要意义.     

阴阳离子表面活性剂混合体系对原油的乳化及增粘行为

利用阴阳离子表面活性剂复配技术,实现了高含水量原油体系的乳化及增粘. 通过调整表面活性剂分子结构,解决了阴阳离子表面活性剂复配体系在油田模拟水中的溶解度问题. 确定了相关体系高含水量油包水（W/O）乳状液的表面活性剂浓度,研究了可以产生高含水量油包水乳状液的油水混合体积比范围,并研究了温度、pH值、油水混合比例和离子强度对乳化及增粘作用的影响. 获得了一系列具有优良乳化效果和乳状液稳定性的体系,其中部分体系粘度可增大80倍. 这对于三次采油提高采收率有重要意义.     

Stability versus phase ratios of geranyl acetate three-phase emulsions

Three-phase geranyl acetate emulsions stabilized by a non-ionic surfactant, Laureth 4, were prepared with a constant weight fraction of a lamellar liquid crystal and varied aqueous to oil phase weight ratios according to the phase diagram. The appearance and micrographs of the drop pattern versus time were recorded. As expected, emulsions with the lower values of the water to oil (W/O) ratio appeared to be of the W/O variety while the two more stable emulsions with the highest W/O ratio appeared as oil to water (O/W). Considering the surfactant exclusive solubility in the oil, this result was unexpected and the emulsions were investigated as to their structure. Unpredictably, all the emulsions were of the O/W kind; including the highest ratio of oil to water. The reason for this unanticipated outcome was the lamellar liquid crystal being dispersed into the aqueous phase at the slightest perturbation.     

Formulation development of a filter-sterilizable lipid emulsion for lipophilic KW-3902, a newly synthesized adenosine A1-receptor antagonist

KW-3902 (a newly synthesized adenosine A1-receptor antagonist) has potent diuretic and renal protective activities. The objective of the present study was to develop an injectable formulation of KW-3902, that was water-insoluble and less than 1 microg/ml, and so lipid emulsion was selected as a favorable formulation. Changing the mixing ratio of oil to lecithin, the particle size of the lipid emulsion was controlled, and by adjusting the mixing ratio of oil/lecithin=1:1, the weight ratio, a lipid emulsion with a mean particle size of 130 nm was prepared. This small particle size makes this emulsion filter-sterilizable, which is a favorable feature for heat labile products. The stability of the KW-3902 lipid emulsion was assessed from the viewpoint of the electrostatic repulsion, and by including the oleic acid a stable lipid emulsion was developed, which was stable for at least 12 months at 10 and 25 degrees C and for 3 months at 40 degrees C. The feature of this small particle size emulsion was also characterized by comparing it with a conventional emulsion (oil/lecithin=1:0.12, the weight ratio, particle size is 220 nm). The release of KW-3902 from the oil particles was measured and the apparent permeability of KW-3902 was calculated from the equation according to Fick's theory. The apparent permeability, P, of KW-3902 was not affected by the particle size of the emulsion (1.78x10(-11) cm/s for the small emulsion and 1.76x10(-11)cm/s for the conventional emulsion). The distribution mode of KW-3902 in the lipid emulsion was also discussed by considering the findings of the permeability and solubility of KW-3902.     

Phase Transitions in Emulsions Formed by Aqueous Emulsifier and its Action on Improving Mobility in Oil Recovery

Transition from oil-in-water (O/W) emulsions to water-in-oil (W/O) emulsions and its action on enhanced oil recovery was investigated by viscosity, morphology, and simulated flooding experiments. This transition can be realized by increasing the volume ratio of oil to water or decreasing the emulsifier concentration. At a mass concentration of 0.3 wt%, the self-developed emulsifier FJ-1 mainly forms O/W emulsions at a volume ratio (oil to water) of 1:1. The emulsions behave as O/W emulsions with a low viscosity when the volume ratio of oil to water is below 2:1. Above 2:1, increasing volume ratio leads to the O/W emulsions transferring into W/O emulsions with high viscosity. For example, at a volume fraction of 4:1, the viscosity of W/O emulsions reaches 229.1 mPa · s, and separated water can hardly be detected. Transition from O/W emulsions to W/O emulsions with high viscosity can also be realized by decreasing the concentration of emulsifier to 0.05 wt% or lower at a volume ratio of 1:1. These may be the critical factors leading to transition from O/W emulsions to W/O emulsions at core conditions. Simulated flooding experiments show that emulsifier fluids can act as an in situ mobility improver and make an improvement of oil recovery even by 20.4%. The results indicate that the water-in-crude-oil emulsions possess great potential in enhancing oil recovery.     

Impact of the state of water on the dispersion stability of a skin cream formulation elucidated by magnetic resonance techniques

This study investigated the relationship between the state of water and the dispersion stability of a skin cream formulation. Hydrophilic ointments treated with a high-pressure wet-type jet mill were used as model formulations. Spin-lattice relaxation times (T(1)) were measured by magnetic resonance techniques to estimate the state of water in samples. A shorter T(1) relaxation time was obtained from samples with higher surfactant content, whereas the processing pressure of the jet mill and 1-week storage at 40 °C did not influence the T(1) relaxation time. Observations using scanning electron microscopy (SEM) showed that coalescence occurred in samples with lower surfactant contents (1.0% by weight) following 1-week storage at 40 °C. We also investigated samples prepared using a hydrophilic surfactant with a short polyethylene glycol (PEG) chain and with PEG-4000. From the change in T(1) relaxation times after removing the oil phase from samples by centrifugation, it was clarified that most of the surfactant was located on the surface of oil droplets. Furthermore, SEM observations showed that phase separation was facilitated as the PEG chain length of the surfactant shortened. Thus, a thin water layer over oil droplets is the most important factor for stabilizing their dispersion. This study provides proof-of-principle results on the contribution of the state of water to the dispersion stability of a skin cream formulation.     

Dependence of the activity of a rhizopus lipase on microemulsion composition

Enzymatic hydrolysis of a model triglyceride, palm oil, was carried out with lipase fromRhizopus sp. in microemulsions with varying water content. The microemulsions were based on a nonionic surfactant, pentaethylene glycol monododecyl ether (C12 EO5), buffered water solution and an oil component consisting of isooctane and palm oil at a weight ratio of 20:1. The structure of the microemulsions was characterized using Fourier transform pulsed-gradient spin-echo¹H NMR. The rate of reaction decreased as the water content of the reaction medium was increased. The self-diffusion coefficient of water, D_w was found to be constant within the interval 1–20% water. The difference in reactivity is believed to be due to a difference in structure of the palisade layer between water and hydrocarbon microdomains. The nonionic surfactant was demonstrated to be unsuitable for enzymatic reactions since only partial hydrolysis was obtained in all experiments. The surfactant, however, did not cause enzyme deactivation, even at very high concentrations.