Emulsifying agents help the production of a stable emulsion by reducing

Emulsifying agents help the production of a stable

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1.Emulsifying agents help the production of a stable emulsion
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3.If a substance is added which alters the solubility of the emulsifying agent, this balance may be altered and the emulsion may change type 4.An ideal emulsifying agent should be
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Naturally Occurring Emulsifying Agents 1. Polysaccharides Acacia is the best emulsifying agent as it forms a thick film at the oil-water interface to act as a barrier to coalescence 2. Semisynthetic polysaccharides Low-viscosity grades of methylcellulose and carboxymethyl-cellulose are used to form o/w emulsions 3. Sterol-containing substances These agents act as water-in-oil emulsifying agents. Examples include beeswax, wool fat and wool alcohols
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Synthetic Surfactants 1. Anionic surfactants a) These are organic salts which, in water, have a surface-active anion. b) They are widely used in external preparations as o/w emulsifying agents c) They must be in their ionized form to be effective d) Emulsions made with anionic surfactants are generally stable at more alkaline pH e) They are incompatible with some organic and inorganic cations (e.g. cetrimide) c) Examples are sodium stearate, calcium oleate, triethanolamine oleate, sodium lauryl sulphate COO -
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Synthetic Surfactants (Con’t) 2. Cationic surfactants a) These are usually quaternary ammonium compounds which have a surface-active cation b) They are used in the preparation of o/w emulsions for external use c) Emulsions formed by a cationic surfactant are generally stable at acidic pH d) Incompatible with anionic surfactants and drugs d) They usually have antimicrobial activity e) Examples are cetrimide and benzalkonium chloride N +
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Synthetic Surfactants (Con’t) 3. Non-ionic surfactants a) They are used to produce either o/w or w/o emulsions for both external and internal use b) They are highly resistant to pH change c) The non-ionic surfactants are compatible with both anionic and cationic substances c) The type of emulsion formed depends on the balance between hydrophilic and lipophilic groups which is given by the HLB (hydrophilic-lipophilic balance) number d) Examples are glycerol esters, sorbitan esters and polysorbates
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The HLB (hydrophilic-lipophilic balance) system a) An HLB number represents the relative proportions of the lipophilic and hydrophilic parts of the emulsifying agent b) High numbers (8-18) indicate a hydrophilic molecule, and produce an o/w emulsion c) Low numbers (3-6) indicate a lipophilic molecule and produce a w/o emulsion Emulsifying agent HLB value Glyceryl monosterate 3.8 Sorbitan monosterate 4.7 Polysorbate 20 16.7
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