Surfactant Concepts and Common Raw Materials
Concept of surfactant
Surfactant: Substances that have strong surface activity and can significantly reduce the surface tension of a liquid.
Surface Tension: The force that causes molecules on the surface of a liquid to shrink inward to a minimum area.
Nonpolar hydrocarbon chain: Hydrocarbon chain with more than 8 carbon atoms.
Polar group: Carboxylic acid, sulfonic acid, sulfuric acid, amino or amine group and their salts, also hydroxyl group, amide group, ether bond, etc.
Application range of HLB value of surfactants
HLB<=3: can be used as defoamer; HLB=3~8: can be used as W/O emulsifier; HLB=7~9: can be used as wetting agent; HLB=8~18: can be used as O/W emulsifier; HLB=15 or above: can be used as solubilizer.
Emulsifier: HLB=3~8, can be used as W/O type emulsifier; HLB=8~16, can be used as O/W type emulsifier.
Wetting agent: HLB=7~9, can be used as wetting agent.
Foaming agent: Foaming agent usually has strong hydrophilicity and high HLB value.
Defoamer: In case of stable foam, adding some surfactants with strong lipophilicity and HLB value of 1~3 can destroy the foam.
Decontaminant: The optimum HLB value is generally 13~16, nonionic surfactants are the strongest in decontamination, followed by anionic surfactants.
1 Disinfectants and bactericides: most cationic surfactants and amphoteric surfactants can be used as disinfectants, a small number of anionic surfactants also have a similar effect Inhibitors or other antimicrobial agents in the surfactant solution is easy to solubilize and reduce its activity, need to increase the dosage in order to achieve the same inhibition of the original effect.
Solubilization
Concept: After the surfactant reaches CMC in aqueous solution, the solubility of insoluble drugs increases significantly, forming a transparent colloidal solution, this effect is called solubilization. Solubilizer refers to surfactant with solubilizing ability, and the solubilized substance is called solubilizer.
The nature of solubilizing agent: the solubilizing agent of homologue increases with the increase of the number of carbon atoms, the CMC decreases, the number of aggregated micelles increases, and the amount of solubilization increases.
The order of solubilizer addition: usually solubilizers and solubilizers are mixed first than solubilizers mixed with water first.
The nature of solubilizer: when solubilizer and surfactant with opposite charge are mixed, solubilization, formation of soluble and insoluble complexes and other complex situations may occur under different ratios; solubilizer and nonionic surfactant pairing, pH can significantly affect the amount of solubilization. Weakly acidic drugs have greater solubilization under acidity; weakly alkaline drugs have more solubilization under alkalinity; amphoteric drugs have maximum solubilization at isoelectric point.
