Optimization of nano-emulsion preparation by low-energy methods in an ionic surfactant system

7 pages, 8 figures, 3 tables.-- PMID: 16981744 [PubMed].-- Printed version Sep 26, 2006.The low-energy emulsification method Emulsion Inversion Point (EIP) was used to prepare O/W nano-emulsions in the W/potassium oleate−oleic acid−C12E10/hexadecane ionic system. This method had not practically been used in ionic systems up to now. The resulting droplet sizes, much smaller than those obtained with the high-energy emulsification methods, depend on the composition (formulation variables) and preparation variables (addition and mixing rate). Phase diagrams, rheology measurements, and experimental designs applied to nano-emulsion droplet sizes obtained were combined to study the formation of these nano-emulsions. To obtain small droplet sizes, it is necessary to cross a direct cubic liquid crystal phase along the emulsification path, and it is also crucial to remain in this phase long enough to incorporate all of the oil into the liquid crystal. When nano-emulsion forms, the oil is already intimately mixed with all of the components, and it only has to be redistributed. Results show that the smaller droplet sizes are obtained when the liquid crystal zone is wide and extends to high water content, because in this case, during the emulsification process, the system remains long enough in the liquid crystal phase to allow the incorporation of all of the oil. Around the optimal formulation variables, the liquid crystal zone crossed during emulsification is wide enough to incorporate all of the oil whatever mixing or stirring rate is used, and then the resulting droplet size is independent of preparation variables. However, when the composition is far from this optimum, the liquid crystal zone becomes narrower and the mixing of components controls the nano-emulsion formation. High agitation rates and/or low addition rates are required to ensure the dissolution of all of the oil into this phase.Peer reviewe

Nano-emulsions preparation by low energy methods in an ionic surfactant system

6 pages, 1 table, 9 figures.-- Printed version published Oct 5, 2006.-- Issue title: Papers from "Formula IV: Frontiers in Formulation Science", an International conference organised by the RSC, held in London, July 4-7th 2005.The emulsion inversion point method was used to form nano-emulsions in the ionic system water/oleic acid–potassium oleate–C12E10/hexadecane. Potassium hydroxide solutions were added to oleic acid–C12E10/hexadecane solutions at constant temperature (25 °C) in order to obtain nano-emulsions at 80% water concentration, with a stoichiometric relation of oleic acid and KOH at this point. So, the ionic surfactant (the potassium oleate) was formed along the emulsification path. The influence of the phases present during the emulsification process on nano-emulsion droplet size was analized. The results show that the smallest droplet size is obtained when along the emulsification path and near the nano-emulsion region the equilibrium is achieved with all the oil dissolved in a phase, in this case in a cubic liquid crystalline phase. It has also been found that the most probable breakdown mechanism of the nano-emulsions formed is Ostwald Ripening.This work was funded under Spanish MCYT Project No. PPQ2002-04514-C03-02.Peer reviewe

Una Mirada nueva a la química experimental de bachillerato

En esta publicación se proponen once prácticas de laboratorio relacionadas con distintos temas de los programas de química del bachillerato. Los experimentos se han diseñado de modo que, sin renunciar al rigor científico, resulten amenos y fácilmente comprensibles para los estudiantes. Se destacan también las aplicaciones de los productos obtenidos y su relación con la vida cotidiana. Se ha intentado que el volumen de residuos generados sea mínimo o, en su caso, se han planteado procedimientos para recuperar los productos obtenidos. Además, se ha hecho especial hincapié en las normas de seguridad personal y ambiental que el alumno debe seguir en todo momento en el laboratorio

Guía per a l'avaluació de les competències en els laboratoris de ciències i tecnologia (AQU)

Postprint (published version