Surfactants

What is the HLB value for a 100% hydrophilic molecule?

20

What is the HLB value of a surfactant acting as an emulsifying agent in W/O emulsions?

3-6

What is the HLB value of a surfactant acting as a wetting agent?

7-9

What is the HLB value of a surfactant acting as an emulsifying agent in O/W emulsions?

8-18

Where is the charge found on most cationic surfactants?

A nitrogen atom (for example; with amine and quaternary ammonium surfactants)

What is the most used class of surfactants?

Anionic surfactants

What are the four classifications for surfactants?

Anionic, cationic, zwitterionic/amphoteric, and nonionic

How are surfactants generally classified?

Based on the nature of their hydrophilic group

What is an example of a cationic surfactant? What is it used for?

Benzalkonium chloride Important preservative in the preparation of ophthalmic and nasal solutions

What do the most commonly encountered anionic surfactants contain?

Carboxylate, sulfate, sulfonate and phosphate polar groups in combination with counterions such as sodium and potassium (for water solubility) or calcium and magnesium (for oil solubility)

What is an example of a zwitterionic/amphoteric surfactant? What is it used for?

Cocamidopropyl betain (CAPB) Used in skin cleansers because of its thickening and foaming properties

What is the HLB value of a surfactant acting as a solubilizing agent?

High HLB value needed (15-18)

What is an example of a nonionic surfactant? What is it used for?

Polyoxyethylene sorbitan esters of fatty acids Used to solubilize steroids in ophthalmic formulations

What is a zwitterionic/amphoteric surfactant?

Possess polar head groups which on ionization can impart both positive and negative charges (with positive charge almost always carried by an ammonium group and the negative charge a carboxylate)

What is an example of an anionic surfactant? What is it used for?

Sodium lauryl sulfate Used as a wetting and emulsifying agent

What are surfactants?

Surfactants are amphiphiles (two distinct regions in their chemical structure: hydrophilic and hydrophobic) that are used as solubilizing, wetting and emulsifying agents

How can you tell the water soluble a nonionic surfactant is?

The longer the poly(oxyethylene) chain, the higher the aqueous solubility

In the hydrophilic-lipophilic balance (HLB) system, what does a higher number mean?

The surfactant is more hydrophilic

What are the most common nonionic surfactants?

Those with a poly(oxyethylene) chain as the hydrophilic group

Does the emulsifier have to be more soluble in the continuous phase than in the dispersed phase?

Yes

Which class of surfactants shows excellent compatibility with the other classes of surfactants?

Zwitterionic/amphoteric