In general, for drugs that are not very hydrophobic, ethanol, propylene glycol, glycerin, etc. are usually ground to achieve wetting. For drugs or medicinal materials that are highly hydrophobic, surfaces with HLB values between 6 and 15 are generally used Active agent. You can also choose from any of the following indicators:
1. Contact angles: It is the angle between the droplet and the spreading surface. The selected wetting agent should reduce the contact angle of the hydrophobic drug to less than 90 °. When the contact angle is 0, it can be completely wet; when the contact angle is 0 to 90 °, it can be wet and is a hydrophilic drug; when the contact angle is greater than 90 ° and less than 180 °, it cannot be wet; It is completely non-wetting and is a hydrophobic drug.
2. Interfacial tensions: Some wetting agents change the interfacial tension between hydrophobic drugs and solvents.
3. Wetting point: Wetting point refers to the amount of solvent needed to wet 100g of hydrophobic drug. Adding a wetting agent can reduce the wetting point, that is, reduce the amount of solvent.