Stability study of W/O/W viscosified multiple emulsions

Stable multiple emulsions with a small proportion of primary emulsion containing different viscosifying agents in the outer aqueous phase were formulated. The multiple systems were assessed by evaluating several parameters, such as the macroscopic aspect, droplet size, release rate, and accelerated stability under elevated temperatures. The effect of different viscosifying agents at different concentrations on the stability and the multiplicity of the multiple emulsions was examined. The viscosity increased by increasing the concentration of the viscosifying agents. It also appeared that the viscosifying agents increased the temperature stability of the multiple emulsions. As a result, the formulation viscosified with Klucel was more stable, while the one prepared with carbomer viscosified the outer phase at much lower concentrations with much better skin feel.     

Effect of Dextrose in the Internal Aqueous Phase on Formation and Stabiblity of W/O/W Multiple Emulsions

The osmolarity of the internal aqueous phase of W/O/W multiple emulsions was varied by using different concentrations of dextrose in the internal phase. Evaluation of the stability of the emulsions was done by microscopic, viscometric and conductometric methods. Microscopic study indicated that as the dextrose concentration in the internal phase increased (0 - 2.50% W/V), the stability, in terms of coalescence of the internal droplets and rupture of the interfacial oily layer, increased from 12 hrs to 7-8 weeks. Viscometric evaluation showed the emulsions to exhibit Non-Newtonian flow and the apparent viscosities of freshly prepared emulsions increased from 8000 to 56,000 cps as the dextrose concentration was increased; the viscosity decreased as the emulsion aged. The amount of drug released as determined by the conductometric method, correlated with the viscosity and stability of the emulsions. The reduction of globule size of the primary (W/O) phase by use of a colloid mill increased the apparent viscosity significantly and thus improved the stability of the formulations.     

Effect of Dextrose in the Internal Aqueous Phase on Formation and Stabiblity of W/O/W Multiple Emulsions

Abstract

The osmolarity of the internal aqueous phase of W/O/W multiple emulsions was varied by using different concentrations of dextrose in the internal phase. Evaluation of the stability of the emulsions was done by microscopic, viscometric and conductometric methods. Microscopic study indicated that as the dextrose concentration in the internal phase increased (0 – 2.50% W/V), the stability, in terms of coalescence of the internal droplets and rupture of the interfacial oily layer, increased from 12 hrs to 7-8 weeks. Viscometric evaluation showed the emulsions to exhibit Non-Newtonian flow and the apparent viscosities of freshly prepared emulsions increased from 8000 to 56,000 cps as the dextrose concentration was increased; the viscosity decreased as the emulsion aged. The amount of drug released as determined by the conductometric method, correlated with the viscosity and stability of the emulsions. The reduction of globule size of the primary (W/O) phase by use of a colloid mill increased the apparent viscosity significantly and thus improved the stability of the formulations.     

Physicochemical characterization and in vitro release of salicylic acid from O/W emulsions prepared with Montanov 68: effect of formulation parameters

Montanovs® are surfactants consisting of a combination of alkylpolyglucosides and long chain saturated alcohols. They are used to formulated oil in water (O/W) emulsions where they generate liquid crystals. Emulsions containing 5% Montanov 68® with 40% Lanol 1688® were prepared and salicylic acid (SA) was incorporated at different stages of the O/W emulsion preparation. This study highlights the effects of formulation parameters on the microscopic characteristics, particle size and rheologic properties of Montanov 68® O/W emulsions. Diffusion studies with these emulsions showed the influence of SA incorporation at different steps on the release kinetics. Montanov® enabled the release of SA to be controlled when it was solubilized in the internal phase. The presence of a physical barrier formed by the Montanov® at the interface between the oil and water appeared to modulate the SA passage to the external phase.     

Effect of non-ionic surfactant concentration and type on the formation and stability of W/O/W multiple emulsions: Microscopic and conductometric evaluations

W/O/W multiple emulsions with sodium salicylate as a model drug were prepared and evaluated for the effect of surfactant concentration and type on stability using microscopic and conductometric methods. Primary (W/O) emulsions were prepared with lipophilic surfactants (2-31% W/W relative to the oily phase). W/O/W emulsions were formed by mixing the primary emulsions with solutions containing 0.5 to 2% W/V hydrophilic surfactants. Optimum concentration of the lipophilic surfactant was 26% W/W. The optimum hydrophilic surfactant concentration was 1% W/V. Best stability was achieved with HLB 3.7 lipophilic and HLB 15.6 hydrophilic surfactants.     

Effect of non-ionic surfactant concentration and type on the formation and stability of W/O/W multiple emulsions: Microscopic and conductometric evaluations

Abstract

W/O/W multiple emulsions with sodium salicylate as a model drug were prepared and evaluated for the effect of surfactant concentration and type on stability using microscopic and conductometric methods. Primary (W/O) emulsions were prepared with lipophilic surfactants (2-31% W/W relative to the oily phase). W/O/W emulsions were formed by mixing the primary emulsions with solutions containing 0.5 to 2% W/V hydrophilic surfactants. Optimum concentration of the lipophilic surfactant was 26% W/W. The optimum hydrophilic surfactant concentration was 1% W/V. Best stability was achieved with HLB 3.7 lipophilic and HLB 15.6 hydrophilic surfactants.     

Formation and Stability Studies of Multiple (w/o/w) Emulsions Prepared with Newly Synthesized Rosin-Based Polymeric Surfactants

The multiple (water-in-oil-in-water, w/o/w) emulsions were prepared using newly synthesized rosin-based polymeric surfactants. The oil phase used was liquid paraffin. These emulsions were evaluated for stability by various methods: conductivity, viscosity, particle size, and visual inspection. The stability studies were carried out at 37°C and 4°C for 1 month. The multiple emulsion prepared with polymer 7 was found to be more stable compared to the emulsions prepared with polymer 2.     

Formation and stability studies of multiple (w/o/w) emulsions prepared with newly synthesized rosin-based polymeric surfactants

The multiple (water-in-oil-in-water, w/o/w) emulsions were prepared using newly synthesized rosin-based polymeric surfactants. The oil phase used was liquid paraffin. These emulsions were evaluated for stability by various methods: conductivity, viscosity, particle size, and visual inspection. The stability studies were carried out at 37°C and 4°C for 1 month. The multiple emulsion prepared with polymer 7 was found to be more stable compared to the emulsions prepared with polymer 2.     

不同油相对负载茶多酚的多重乳液稳定性的影响

采用高压均质和高速剪切的方法,观察其制备的初乳对多重乳液稳定性的影响,并研究了大豆油、芥花油、油茶籽油和葵花籽油四种不同的植物油作为油相对多重乳液稳定性的影响,实验结果表明,用高压均质方法制备的初乳能够获得稳定的、外观细腻的多重乳液。四种不同的油相制备的多重乳液在4000r/min,15min的离心条件下不分层;大豆油作为油相制备的多重乳液在室温下放置两个月分层,芥花油、油茶籽油和葵花籽油,在室温下放置三个月不分层。对四种不同油相制备的多重乳液的粒径进行测量,实验结果表明,油茶籽油的D0.1,D0.5和D0.9三个数据的粒径的稳定性比较好。     

Preparation of monodisperse W/O emulsions using a stainless-steel microchannel emulsification chip

In this study, hydrophobically treated stainless-steel microchannel (MC) array chips were used for preparing monodisperse W/O emulsions. A water-saturated decane containing 5?wt% tetraglycerin monolaurate condensed ricinoleic acid ester was used as the continuous phase. A Milli-Q water containing 5?wt% polyethylene glycol (molecular weight 20,000) and 5?wt% NaCl was used as the dispersed phase. The stainless-steel MC array chips used for MC emulsification had a sufficiently high contact angle of the dispersed phase to their surface in the continuous phase. The resultant uniform-sized aqueous droplets with a coefficient of variation of <5% had average diameters of 100–300?µm, depending on the MC cross-sectional size. The maximum productivity of uniform-sized aqueous droplets reached higher than 1?mL?h^?1. The difference in the critical capillary number of the dispersed phase that flows in a 100-µm depth MC was 1.5 times greater than that in a 30-µm depth MC.     

Prolonged release of pentazocine from multiple O/W/O emulsions

Multiple O/W/O emulsions containing pentazocine were prepared and tested in vitro and in vivo. The effect of two different concentrations of three additives, viz. sodium chloride, glucose and glycerol, location of the drug either in one or any two phases of the O/W/O emulsions and pH of the receptor fluid on in vitro release characteristics of the drug was studied. All the parameters influenced the drug release. Multiple O/W/O emulsions gave higher extent of drug release than the simple O/W emulsions. The results of in vivo studies in mice showed prolonged tissue levels of pentazocine from the multiple O/W/O emulsions in comparison to aqueous drug solution and simple O/W emulsion.     

Design and development of multiple emulsion for enhancement of oral bioavailability of acyclovir

The objective of this investigation was to design and develop water-in-oil-in-water type multiple emulsions (w/o/w emulsions) entrapping acyclovir for improving its oral bioavailability. Multiple emulsions (MEs) were prepared and optimized using Span-80 and Span-83 as lipophilic surfactant and Brij-35 as hydrophilic surfactant. The physio-chemical properties of the w/o/w emulsions - particle size, viscosity, phase separation (centrifugation test) and entrapment efficiency were measured and evaluated along with macroscopic and microscopic observations to confirm multiple nature, homogeneity and globule size. Stability study, in vitro and ex vivo release studies were performed followed by in vivo studies in rats. Stable w/o/w emulsions with a particle size of 33.098 ± 2.985 µm and 85.25 ± 4.865% entrapment efficiency were obtained. Stability studies showed that the concentration of lipophilic surfactant was very important for stability of MEs. Drug release from the prepared formulations showed initial rapid release followed by a much slower release. In vivo studies in rats indicated prolonged release and better oral bioavailability as compared to drug solution. The overall results of this study show the potential of the w/o/w emulsions as promising drug delivery systems for acyclovir.     

Fabrication of polystyrene hollow spheres in W/O/W multiple emulsions

One mild multiple emulsions was used for the fabrication of hollow polystyrene (PS) spheres. Polystyrene was dissolved in a volatile organic solvent to form the O phase, then an aqueous phase containing a surfactant was transferred into above phase to form an oil-in-water (W_in/O) emulsion, followed by addition of W_in/O emulsion in the external W_out phase, and solvent evaporation. Final product with diameter of 150 μm, surface roughness of 30 nm, and sphericity of 98.0% was obtained. The possible influences on the formation of PS hollow sphere were also discussed.     

Stability of orange oil/water nanoemulsions prepared by the PIT method

This article reports the preparation and characterization of orange oil/water nanoemulsions stabilized by commercial nonionic surfactants based on ethoxylated lauryl ether (Ultrol line), by the phase inversion temperature (PIT) method. The orange oil/surfactant/water dispersions were prepared at different HLB values, by varying the concentrations of the surfactants as well as the concentration of the oil phase. The stability of the o/w nanoemulsions and the size distribution of the dispersed particles in these systems in general depended on the concentration of the oil phase used: the emulsions prepared with an oil phase of 14 wt% had smaller droplet size in the dispersed phase than the emulsions prepared in the presence of oil phases of 20 and 30 wt%. The nanoemulsions prepared with pure surfactants were more stable in the presence of Ultrol L60, but the surfactants' cloud point had a strong influence on the stability of the emulsions formed when this was very near room temperature. Because of this, we prepared systems containing mixtures of surfactants. Among these systems, the most stable nanoemulsions were those prepared with a Ultrol L100/Ultrol L20 mixture with HLB of 12.40. This behavior can be attributed to the complete solubilization in mixed micelles of the more hydrophobic surfactant.     

Correlation Between Nature of Emulsifier and Multiple Emulsion Stability

The effect of emulsifier type on the preparation and stability of multiple emulsions was studied. The influence on the yield of preparation and stability with regard to the HLB of emulsifier II was found to be different for each emulsifier. The best stabilities of the multiple emulsions were obtained when there is a similarity between the hydrophobic part of the emulsifier and the oil phase.     

铜与硅之间W/Mo-N薄膜的扩散阻挡层性能

研究了铜与硅之间W／Mo-N薄膜的扩散阻挡性能。在Si(100)基片上利用反应溅射沉积一层Mo-N薄膜,然后再利用直流溅射在Mo-N上面沉积Cu／W薄膜。样品在真空下退火,并利用四点探针、X射线衍射分析、扫描电镜分析、俄歇电子能谱原子深度剖析等测试方法研究了Cu／W／Mo-N／Si的热稳定性及W／Mo-N薄膜对铜与硅的扩散阻挡性能。实验分析表明,Cu／W／Mo-N／Si结构具有非常好的热稳定性,在600℃退火30min仍未发生相变,并能有效的阻挡铜与硅之间的扩散。     

Correlation Between Nature of Emulsifier and Multiple Emulsion Stability

Abstract

The effect of emulsifier type on the preparation and stability of multiple emulsions was studied. The influence on the yield of preparation and stability with regard to the HLB of emulsifier II was found to be different for each emulsifier. The best stabilities of the multiple emulsions were obtained when there is a similarity between the hydrophobic part of the emulsifier and the oil phase.     

W/O乳状液模板法制备纳米MnO2微球

以偏重亚硫酸钠（Na2S2O5）和高锰酸钾（KMnO4）为原料，通过W／O乳状液模板技术制备了纳米MnO2微球．用SEM、TEM、XRD、FT-IR等手段对产品的形貌、物相和成分进行了表征．结果发现用本方法制得的纳米MnO2微球，大小基本均匀，球形规整，纯度较高，且具有较高的反应活性．结合实验事实和产品特性，初步探讨了纳米MnO2微球的形成机理．     

A Novel Method for Rapid Non Destructive Determination of O/W Creams Stability

A nonconventional method for evaluation of emulsion stability was developed. The method was found to be valid for viscous emulsions and results obtained are in good correlation to conventional methods compared.

The technique is based on electrical conductivity measurements during nondestructive short heating-cooling-heating cycles carried out on cosmetic viscous emulsions. Conductivity curves were obtained on a recorder, where the second heating cycles were lower and almost parallel to the first heating curves. The bigger the conductivity differences between the two heating curves, the lower is the emulsion stability.

A relative Stability Index Δ/h, indicating relative change in conductivity between two cycles was elaborated. This index was usefull in finding out

- optimal required HLB values for required emulsion

- optimal amount of oily phase

- emulsifier concentration.     

Interaction between Re and W on the microstructural stability of Ni-based single-crystal superalloys

The influences of Re and W as well as their interaction on γ′ and topologically close-packed (TCP) phases have been investigated in seven kinds of Ni-based single-crystal superalloys. The results show that after full heat treatment, the γ′ size is reduced with increasing Re, but does not change with increasing W. After thermal exposure at 1000°C for 1000?h, the TCP phase is dramatically increased with increasing Re, but increased slightly with increasing W. The TCP phase volume fraction in higher Re alloys is much more than that in lower Re alloys which have the same total content of Re and W. This indicates that W instead of Re could effectively improve the microstructural stability of Ni-based single-crystal superalloys.