Introduction
Biphasic liquids are systems consisting of two immiscible (non-mixing) liquid phases.
These systems are common in pharmaceutical, cosmetic, and chemical industries.
They are typically created when two liquids with different polarities, such as oil and water, are combined.
Due to their differences in polarity, these liquids do not mix and form separate layers, creating a biphasic liquid system.
When left undisturbed, biphasic liquids will separate into their respective layers.
Classification of biphasic liquids:
1) Emulsions:
Emulsions are mixtures of two immiscible liquids, such as oil and water, where one liquid (dispersed phase) is dispersed as small droplets within the other (continuous phase).
Emulsions can be further classified as:
a) Oil-in-water (O/W) emulsions:
Small droplets of oil are dispersed in an aqueous phase.
b) Water-in-oil (W/O) emulsions:
Small droplets of water are dispersed in an oil phase.
c) Multiphase emulsions:
Complex systems with multiple immiscible liquid phases, such as water-in-oil-in-water (W/O/W) or oil-in-water-in-oil (O/W/O) emulsions.
2) Suspensions:
Suspensions are mixtures in which solid particles are dispersed in a liquid medium without dissolving.
The solid particles do not dissolve in the liquid and remain suspended, often settling at the bottom over time.
Suspensions are common in pharmaceutical formulations, such as liquid oral medications or topical creams containing insoluble active ingredients.