Surface Active Agent

Md. Istiqur Rahman.ID: 111-29-269.5th Batch, Section: A.

DefinitionA surface active agent (surfactant) is

a substance which lowers the surface tension of the medium in which it is dissolved, and/or the interfacial tension with other phases.

The term surfactant is also applied correctly to sparingly soluble substances, which lower the surface tension of a liquid by spreading spontaneously over its surface.

ExampleSoap, a salt of a fatty acid (saturated or unsaturated), is a surface active agent.A detergent is a surfactant (or a mixture containing one or more surfactants) having cleaning properties in dilute solution.An emulsifier is a surfactant which when present in small amounts facilitates the formation of an emulsion.

A foaming agent is a surfactant which when present in small amounts facilitates the formation of foam.

Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents and dispersants.

Classification

1. Non Ionic SAA2. Ionic SAA

Non Ionic SAA

I. Simple estersII. Polyoxyethylene (POE)

compoundIII. Sorbitan & mannitan

derivatives

Ionic SAA

I. CationicII. AnionicIII. Ampholytic

Cationic

a) Sulphatesb) Sulfonatesc) Alkanoates & Carboxylates

Anionic

a) Heterocyclic compoundsb) Quarternary ammonium

salt

Alkanoates & Carboxylates(i) Cations of strong metallic base

(ii) Cations of weak metallic base

(iii) Cations of weak organic base

Mechanism

Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads).

A surfactant contains both a water insoluble (or oil soluble) component and a water soluble component.

Surfactants will diffuse in water and adsorb at interfaces between air and water or at the interface between oil and water, in the case where water is mixed with oil.The insoluble hydrophobic group may extend out of the bulk water phase, into the air or into the oil phase, while the water soluble head group remains in the water phase.

This alignment of surfactants at the surface modifies the surface properties of water at the water/air or water/oil interface.

Sodium stearate, the most common component of most soap, which comprise about 50% of commercial surfactants.

Pharmaceutical Use of Surfactants SAA used in emulsions as an emulsifying agent. SAA used in suspensions as a flocculating agent. SAA as a wetting agent. SAA as a bactericidal agent. SAA as a solubilizing agent. To modify the properties of membranes. Enhancement of percutaneous absorption. Enhancement of transport across mucosal

membranes (rectal, vaginal, ophthalmic, nasal). SAA as a foaming agent.