How to make phase diagrams - Gattefossé

Summary

This video explains the process of creating phase diagrams for emulsions, micro-emulsions, and nano-emulsions. It covers the role of surfactants and co-surfactants in stabilizing emulsions by preventing droplet coalescence. The script details the preparation of pseudo ternary diagrams to identify the optimal ingredient ratios for different phases. The titration method is used to determine emulsion and micro-emulsion zones, and the results are plotted on the diagram. These diagrams are crucial for formulating drug delivery systems, especially in oral and dermal applications, ensuring the right balance of components for effective emulsification.

Takeaways

• 😀 Emulsions are dispersions of liquid droplets (e.g., oil in water) that can form stable systems depending on surrounding conditions.
• 😀 A surfactant helps prevent droplet coalescence by reducing surface tension in emulsions, making them more stable.
• 😀 When droplet sizes are smaller than 200 nm, emulsions are categorized as micro-emulsions or nano-emulsions, which are transparent and thermodynamically stable.
• 😀 Formulating emulsions, micro-emulsions, or nano-emulsions requires at least four key ingredients: an oily phase, an aqueous phase, a surfactant, and a co-surfactant.
• 😀 Phase diagrams are essential for determining the optimal ratio of components (water, oil, surfactant, co-surfactant) in emulsions.
• 😀 Pseudo ternary phase diagrams simplify the complex four-component system by fixing ratios between two components, often surfactant and co-surfactant.
• 😀 Pseudo ternary diagrams are developed under fixed temperatures, such as 25°C or 37°C for liquid excipients, and 45°C for semi-solid excipients.
• 😀 The phase diagram plots different zones of emulsions and micro-emulsions, using a titration method to add water to a surfactant-oil mixture until phases change.
• 😀 The process of titration involves adding water drop by drop to an initial mixture, and visually observing changes (turbid, opaque, or transparent) to identify emulsion and micro-emulsion phases.
• 😀 These phase diagrams are crucial for determining formulations for oral and dermal drug delivery, identifying self-emulsifying drug delivery systems (SEDDS) for both applications.
• 😀 By using the phase diagram, specific formulations can be selected to create either emulsions or micro-emulsions suitable for oral or dermal applications.

Q & A

What is an emulsion?

An emulsion is a dispersion of droplets of one liquid (like oil) within another immiscible liquid (like water). It is stabilized by the presence of a surfactant that reduces surface tension, preventing the droplets from coalescing.

How does the droplet size affect the appearance of emulsions?

When the droplet size is smaller than 200 nanometers, the system is considered a micro-emulsion or nano-emulsion, and it appears transparent. Larger droplets result in a turbid or opaque emulsion.

What is the role of a surfactant in an emulsion?

A surfactant stabilizes the emulsion by reducing the surface tension between the oil and water phases, preventing the droplets from merging or coalescing into larger droplets.

What are the basic ingredients needed to formulate an emulsion?

An emulsion requires at least three ingredients: an oily phase (oil), an aqueous phase (water), and a surfactant. A co-surfactant may also be added to improve the stability and properties of the emulsion.

What is the purpose of a phase diagram in emulsion formulation?

A phase diagram helps identify the optimal ratios of components (oil, water, surfactant, and co-surfactant) needed to create stable emulsions and micro-emulsions. It shows which phases form under different component ratios.

What is a pseudo ternary phase diagram?

A pseudo ternary phase diagram is a simplified version of a phase diagram, where one component’s ratio is fixed (often surfactant and co-surfactant), reducing the system from four to three variables, making the diagram easier to interpret.

What are the temperature considerations when developing phase diagrams?

Phase diagrams are developed at fixed temperatures, such as 25°C or 37°C for liquid excipients. For semi-solid excipients, like GATT FOSSA, the phase diagram is developed at 45°C as they need to be melted.

How is the titration process used to develop a phase diagram?

The titration process involves slowly adding water to a starting formulation (X), which consists of oil, surfactant, and co-surfactant. As water is added, the mixture changes from clear to turbid (emulsion phase) and then to transparent (micro-emulsion phase). These changes are recorded and plotted on the diagram.

What is the significance of the gridlines on a pseudo ternary diagram?

The gridlines represent the percentages of each component in the formulation. Each gridline indicates a 10% increase in the amount of the component, with the components' total always summing to 100%.

How do phase diagrams assist in the development of drug delivery systems?

Phase diagrams are used to identify formulations that can create stable emulsions or micro-emulsions under specific conditions, which is crucial for the development of self-emulsifying drug delivery systems (SEDs) for oral and dermal drug delivery.