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Composition of Cleaning Agents for Pharmaceutical Industries 61
Anionic:
Cationic:
Nonionic:
Amphoteric:
With alkaline pH
With acidic pH
The active part is:
Negative
Positive
Neutral
?
Anionic
Cationic
FIGURE 9 Classification of surfactants.
Adistinction can be made between anionic (e.g., soaps), cationic (mainly
quaternary ammonium compounds), and amphoteric surfactants. Its almost
exclusively nonionic and anionic surfactants that are used as components for
detergents, whereas cationic and amphoteric surfactants are used to formulate
disinfectants due to their microbicidal effect.
The Chemical Structure of Nonionic Surfactants
Nonionic surfactants are produced by reactions of fatty alcohols or fatty amines
(both made from natural oils) with ethylene oxide (EO) alone, EO plus propylene
oxide (PO), or PO alone (Fig. 10).
Ethylene and PO are two very reactive gases. The ring-shaped connection of the
oxygen with the two neighboring carbon atoms is extremely instable. When these
substances are brought together with, for example alcohols under suitable conditions,
the ring-shaped bonds are broken. The hydrogen atom of the alcoholic
hydroxyl-group (–OH) binds to the oxygen of the ethylene or PO respectively.
CH3 -(CH2 ) n -CH2 -OH +H2C CH2 H 2 C CH-CH3 O
Fatty alcohol Ethylene oxide and/or Propylene oxide
CH 3 -(CH 2 -) n CH 2 -O –CH 2 -CH 2 -OH
CH 3 -(CH 2 ) n -CH 2 -O CH 2 -CH-CH 3
O H
O
Formation of adducts
poly addition
CH3 -CH2 -(CH2 ) n -CH2 -CH2 - -O-CH2 -CH2 (CH2 -CH2 -O) n -CH2 -CH2 -OH
Hydrophobic
FIGURE 10 Nonionic surfactants.
Hydrophilic