Oil Emulsion System Research Articles

Hydrogen formation by the photodecomposition of water over Pt/TiO 2 suspended in a water in oil emulsion

Hydrogen formation by the photodecomposition of water has been successfully achieved in a water in oil emulsion (w/o emulsion) system containing Pt/TiO2. The hydrogen formation rate was affected by the amount of water added to the emulsion. It was concluded that water in the w/o emulsion containing Pt/TiO2 was more active than free water for the photodecomposition to form hydrogen.

Fat Reduces Volatiles Production in Oil Emulsion System Analyzed by Purge‐and‐Trap Dynamic Headspace/Gas Chromatography

ABSTRACTRelease of volatiles in oil emulsion systems containing various fat contents was determined using purge‐and‐trap dynamic headspace/gas chromatography. Oil emulsions were prepared using 0, 0.5, 1, 2, 4, or 8% oil, and a standard mixture was prepared using hydrocarbons, aldehydes, ketones, and alcohols. Fat content in oil emulsions reduced the volatility of added volatile standards, and the amount of volatiles released from oil emulsion correlated negatively with fat content (r2= 0.92 in total volatiles). Among these tested, the volatilization of ketones was least influenced by fat content. The release of nonpolar hydrocarbons was not influenced but polar compounds (aldehydes, ketones, and alcohols) were greatly influenced by water.

Direct Observation of Water−Oil Emulsion Systems in the Liquid State by Environmental Scanning Electron Microscopy

Environmental scanning electron microscopy is a technique capable of imaging fluid systems in their natural state without prior specimen preparation. As such, it is potentially a very powerful tool for studying emulsion structures at a resolution significantly higher than that for conventional optical microscopy. We present data on several water−oil emulsions that demonstrate the capability of the instrument. Separate preparations of vegetable oil and polybutene were used, emulsified with nonionic polysaccharide surfactants. Rather large contrast variations were found between the oil and water phases, with water always appearing brighter whether it was in the dispersed or continuous phase. The observed contrast is attributed to variations in the secondary electron emission characteristics arising from the dielectric response function of water compared with hydrocarbons. We propose that delocalized electrons in π-bonds provide an energy-absorbing mechanism that leads to a reduction in secondary electron emission from unsaturated hydrocarbon oils, relative to that of water, by lowering the energy gap. We present a qualitative description of an “energy window” model, affording secondary electrons a range of energies over which interactions with the sample are minimal, and discuss how variations of the energy window are likely to influence secondary electron emission.

Oil–water–oil multiple emulsions for prolonged delivery of hydrocortisone after topical application: comparison with simple emulsions

Multiple emulsions show a high potential for prolonged delivery of drugs. In multiple emulsions, the entrapped substance can be transfered from the internal phase to the external phase through the middle phase, i.e. the membrane phase. These systems could be used for prolonged delivery of drugs. The present study was aimed to assess the suitability of oil–water–oil emulsions as prolonged release topical formulations of hydrocortisone. In order to avoid any influence of the composition of the formulation and to study only the effect of the emulsion type, a multiple emulsion as well as a simple emulsion were prepared with exactly the same composition. The percutaneous absorption of hydrocortisone from these two emulsion types was studied. At a finite dose, the percentage of hydrocortisone absorbed from the simple emulsion was 1.5-fold greater than that observed from the multiple emulsion, and the drug was kept longer in the epidermis and dermis from this galenic form. It was concluded that the multiple oil–water–oil emulsion systems may be used for obtaining a prolonged topical release of hydrocortisone.

Interaction of Gelatin and Sodium Dodecyl Benzene Sulphonate at Oil and Water Interfaces

Interaction between sodium dodecyl benzene sulphonate (SDBS) and gelatin ivas studied in relation to emulsification behaviour and emulsion stability. We chose two different oils to study influences of oil phase characteristics, namely, tricresyl phosphate (TCP) as an oil with polar and slightly hydrophilic nature, and n-dodecane (n-C12) as its apolar contrast. Our interfacial tension measurements showed that both TCP and n-C12 give critical values (i.e., cac and cmc) very close to I hose of surface tension measurement. This result indicates that the complexation behaviour in bulk solution is independent of the presence or the nature of the oil phase. Absolute tension values above the cmc and slope value at the cmc in gelatin free systems, however, imply SDBS’s weaker adsorption to TCP than to n-C12 Our emulsification results for the TCP system revealed the existence of an optimal point for emulsion stability in the SDBS concentration region between the cac and the cmc. Above this point, emulsion stability deteriorates remarkably. The behaviour is in line with our findings from the dynamic sorption experiments (ellipsomelry, TIRF, and SPR) reported elsewhere, which showed a rapid desorption of gelatin from the hydrophobic surfaces above the cac. The results suggest that the adsorption of gelatin/surfactant complexes at the interface is a key factor for stability of the polar oil emulsion system. Contrary to that, the n-C12 system did not show any deterioration, even above the cmc, which is presumably due to a strong double layer effect from the firmly adsorbed layer of SDBS at the interface.

Effect of Demulsifier Partitioning on the Destabilization of Water-in-Oil Emulsions

The factors affecting the demulsification and interfacial behavior of water-in-oil emulsions in the presence of oil-soluble demulsifiers were investigated. Using both model water-in-oil and water-in-crude oil emulsion systems with demulsifiers with different chemical structures, the effects of demulsifier partitioning on the interfacial and film rheological properties were studied. The experimental results were compared and related with the demulsifier performance. There is a one-to-one correlation between the performance of demulsifier and the interfacial activity of the partitioned demulsifier; the partitioned demulsifier components exhibit an increase in static and dynamic interfacial activity, low dynamic interfacial and film tension, and a low film dilational modulus with a high adsorption rate−low interfacial tension gradient (Marangoni−Gibbs stabilizing effect) and have excellent demulsification performance.