Nov. 21, 2020
Surfactant refers to a substance that can significantly reduce the surface tension of a liquid. Most are long-chain organic compounds with amphiphilic properties. Generally, it is composed of a non-polar hydrocarbon chain or a carbon chain containing heterocyclic or aromatic groups and more than one polar group. The phenomenon that Surfactant accumulate on the surface layer of the solution is called molecular adsorption or positive adsorption.
In medicaments, some poorly soluble vitamins, steroid hormones, volatile oils and many other poorly soluble drugs have very little solubility in water and cannot reach the concentration required for treatment. At this time, the solubilization effect of surfactants can be used to improve the solubility of the drug . This kind of solubilizing surfactant is called solubilizing agent.
(1) Cationic surfactants are not used as emulsifiers for oral emulsions due to their high toxicity and irritation.
(2) Anionic Surfactants are generally used as emulsifiers for external preparations.
(3) Zwitterionic surfactants, such as agar, gum arabic, etc. can be used as emulsifiers for oral preparations.
(4) Non-ionic surfactants are not only low in toxicity, but also have good compatibility, are not easy to change compatibility, are insensitive to pH changes and electrolytes, and can be used for external or internal preparations.
The function of promoting the spreading or penetration of liquid on the solid surface is called wetting, and the surfactant that can play the role of wetting is called wetting agent.
The substances that have the effect of generating foam and stabilizing foam are called foaming agents and foam stabilizers. Surfactants can reduce the surface tension of the liquid and stabilize the foam, so it has the function of a foaming agent and a foam stabilizer. They usually have a higher HLB value and stronger hydrophilicity. Surfactants as foaming agents are mainly used in cavity administration and skin medication.
Add some surfactants with HLB value of 1 to 3 in the stable foam solution, which can compete with the foam layer for the surface of the liquid film and adsorb on the surface of the foam instead of the original foaming agent to destroy the foam. This is used to eliminate the foam. The surfactant is called "defoamer".
Surfactants used to remove dirt are called detergents. Nonionic Surfactant have the strongest detergency, followed by anionic surfactants. Commonly used detergents are sodium soap, potassium soap, sodium oleate, sodium lauryl sulfate and other sodium alkyl sulfonates.
Most cationic and zwitterionic surfactants can be used as disinfectants, and a few anionic surfactants have similar effects. Different concentrations of surfactants can be used as needed, which can be used for skin disinfection, wound or mucous membrane disinfection, instrument disinfection and environmental disinfection lamps before surgery. Commonly used are benzalkonium bromide, 0.5% alcohol solution for skin disinfection, 0.02% aqueous solution for local wet compress, and 0.05% aqueous solution for instrument disinfection.