Chapter 3 Flashcards
Define surfactants
solute that are adsorbed at the surface or interface of liquid and reduce the surface or interfacial tension and therefore termed Surface active agent, surfactants or amphiphile.
Surface active agents consists of two parts:
1-A lipophilic (hydrophopic) group
consisting of a long carbon chain which has little affinity for aqueous solvents
2 -A lipophopic (hydrophilic) group
consisting of polar group such as COOH, OH,…which has high affinity for polar solvents
Due to presence of both polar and non-polar groups within surfactant structure…….
surfactants have affinity for polar and non-polar solvents, so surfactant also termed Amphiphiles.
Most surfactants have ……..
a proper balance between their hydrophilic and lipophilic properties so that they can stay at the interface.
high number of polar groups e.g
OH, COOH. (hydrophilic SAA)
high number of non-polar groups e.g
hydrocarbon chain (lipophilic SAA)
Surfactants are arranged according to their HLB into:
Hydrophilic SAA (HLB > 10)
Lipophilic SAA ( HLB 1-10)
HLB = 20 implies……..
100% hydrophilic.
HLB =1 implies
100% hydrophobic
Why the HLB value of surfactants is between 0-20?
All surfactants combine hydrophilic and lipophilic groups in one molecule and that the ratio between the weight percentages of these two groups is HLB. The highest ratio is 20.
HLB of 0-3
Pharmaceutical use…
Antifoaming
HLB of 4-6
Pharmaceutical use…
w/o emulsifier
HLB of 7-9
Pharmaceutical use…
Wetting agent
HLB of 8-16
Pharmaceutical use…
o/w emulsifier
HLB of 13-15
Pharmaceutical use…
Detergent
