There are various things to consider when formulating W/O emulsions. I find this test to be easy and generally reliable. Pharmaceutical Emulsions (Dr.) Mirza Salman Baig Assistant Professor (Pharmaceutics) AIKTC, School of Pharmacy,New Panvel Affiliated to University of Mumbai (INDIA) 2 Definition: An emulsion is a thermodynamically unstable system containing mixture of two or more immiscible liquids which is stabilized by adding emulsifying agent Emulsion. If, on the other hand, it required quite a bit of mixing to incorporate the water and the viscosity actually increases, then the emulsion is W/O. If the water is readily incorporated and the viscosity drops, you can be quite certain that the emulsion is O/W. One tried-and-true way to determine which type of emulsion you have is to add water to it with propeller mixing. The type (O/W or W/O) of emulsion you wind up with is almost entirely dependent on the emulsifier.īancroft’s Rule tells us that wherever the emulsifier is most soluble will become the external/continuous phase. We should remember that if the internal phase ever exceeds 74%, we no longer have only spherical droplets.
As a general rule, the amount of water is approximately 60-80%. One thing that I have noticed in recent years as we have developed more efficient W/O emulsifiers is that the ratio of oil to water is basically the same whether we have a W/O or O/W emulsion. Oil-soluble drugs can be given parenterally in form of an oil-in-water emulsion. o/w emulsion facilitates the absorption of water-insoluble compounds comparing to their oily solution preparations (e.g. Another comment I hear is that I have more oil than water in my emulsion, so oil must be the external/continuous phase. o/w emulsion is convenient means of oral administration of water-insoluble liquids.
I can’t tell you how many times that chemists have told me that the emulsion they made must be water-in-oil since they’“added the water phase into the oil phase!“ This, of course, is nonsense. I have never heard a good explanation for this geographical discrepancy.
While water-in-oil emulsions have become more popular in the United States in recent years due to their rising popularity in the sunscreen arena, they have enjoyed widespread use in Europe for many years. While there are several reasons for this, probably the most important one is that these emulsions (usually) do not have a clearly defi ned electrical double layer surrounding the emulsion droplets thus there is a greater likelihood of coalescence. Formulating water-in-oil emulsions is inherently more difficult than oil-inwater emulsions.
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