Emulsifying agents, emulsion formulations

Soluble oils are delivered, concentrated , to the user and contain an emulsifying agent to ensure that a stable emulsion forms when added to water. This additive does not mix readily with mineral oil, however, so to overcome this a coupling agent is included in the formulation. 

Emulsifiers. Natural lecithin is one of the most widely used emulsifiers because it is metabolized in the body. However, type I allergic reaction to soybean lecithin emulsified in lipid solutions has been observed [195], Among the synthetic emulsifying agents, block copolymers of polyoxyethylene-polyoxypropylene (poloxamer) have attracted increasing interest for parenteral emulsions. Other examples of emulsifiers commonly found in parenteral formulations are given in Table 9 [190]. 

The following factors (which depend on the nature of the emulsifying agent and/or on a suitable choice of formulation and manufacturing conditions) favour emulsion stability ... 

In view of the high oil-water interfacial area which must be created, the fraction of emulsifying agent in microemulsion formulations tends to be significantly higher than that in ordinary emulsions. A typical microemulsion formulation would be 10-70 per cent oil, 10-70 per cent water and 5-40 per cent emulsifying agent48. 

Very finely divided wax emulsions are effective concrete dampproofing agents and are formulated so that the emulsion breaks down after contact with the alkaline concrete environment and forms a hydrophobic layer. Waxes of melting point 57-60°C are used with an emulsifying agent based on sorbitan monostearate or ethoxylated sorbitan monostearate [2], The properties of a commercial product are given in Table 4.4 [5],... 

Cetyl alcohol is also used for its water absorption properties in water-in-oil emulsions. For example, a mixture of petrolatum and cetyl alcohol (19 1) will absorb 40-50% of its weight of water. Cetyl alcohol acts as a weak emulsifier of the water-in-oil type, thus allowing a reduction of the quantity of other emulsifying agents used in a formulation. Cetyl alcohol has also been reported to increase the consistency of water-in-oil emulsions. 

The nonemulsifying grade is used in topical formulations as an emollient and as an emulsifying agent for water-in-oil emulsions. It is also a stabilizer for oil-in-water emulsions. The self-emulsifying grade is used as a primary emulsifier for oil-inwater systems." ... 

Linoleic acid is used in topical transdermal formulations, in oral formulations as an absorption enhancer, and in topical cosmetic formulations as an emulsifying agent. It is also administered in parenteral emulsions as a dietary supplement. 

Polyoxyethylene alkyl ethers are nonionic surfactants widely used in topical pharmaceutical formulations and cosmetics, primarily as emulsifying agents for water-in-oil and oil-in-water emulsions and the stabilization of microemulsions and multiple emulsions. 

Sorbitan esters are widely used in cosmetics, food products, and pharmaceutical formulations as lipophilic nonionic surfactants. They are mainly used in pharmaceutical formulations as emulsifying agents in the preparation of creams, emulsions, and ointments for topical application. When used alone, sorbitan esters produce stable water-in-oil emulsions and microemulsions but are frequently used in combination with varying... 

Anionic emulsifying wax is used in cosmetics and topical pharmaceutical formulations primarily as an emulsifying agent. The wax is added to fatty or paraffin bases to facilitate the production of oil-in-water emulsions that are nongreasy. In concentrations of about 2%, emulsions are pourable stiffer emulsions, e.g., aqueous cream BP, may contain up to 10% of anionic emulsifying wax. 

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