Interfacial Phenomena Specific Aims PDF

[Interfacial phenomena -- specific aims] Please pay extra attention to the highlighted questions. 1. Be able to describe to which dosage forms is interfacial phenomena relevant. 2. Be able to describe interface, surface and the main difference between them. Can two gases form an interfa...

[Interfacial phenomena -- specific aims] Please pay extra attention to the highlighted questions. 1. Be able to describe to which dosage forms is interfacial phenomena relevant. 2. Be able to describe interface, surface and the main difference between them. Can two gases form an interface? Is every surface an interface? Is every interface a surface? 3. Be able to describe surface- and interfacial tension. 4. Be able to define surfactants, and describe their unique feature and their orientation at interfaces; what is the main action of surfactants? \[answer: reduce the interfacial tension by their presence in the interface\] Why is it important that the molecule has both a hydrophilic and a hydrophobic portion? 5. Be familiar with the characteristics of the (4) main classes of surfactants. In which dosage forms can anionic surfactants be used? Which type of surfactants can be used as disinfectants and preservatives? Are cationic surfactants compatible with anionic agents? Which group of compounds is the most important among cationic surfactants? Which types of surfactants are sodium lauryl sulfate and benzalkonium chloride? 6. Be able to describe the main difference between the chemical compositions of tweens and spans, which of them is more hydrophilic and which is more hydrophobic? Are tweens and spans anionic, cationic, non-ionic or amphoteric surfactants? What are the advantages and disadvantages of non-ionic surfactants, and in particular of tweens? 7. Be able to describe regarding surfactants, which type of surfactants is the most commonly used in pharmaceutical dosage forms, and which type of surfactants is the most appropriate for dosage forms used orally and through parenteral administration? Are amphoteric surfactants used in many products? 8. Be able to describe the solid/liquid interface. When is the drug anticipated to come into contact with a liquid phase? 9. Be able to define wetting of solid particles, contact angle, and wetting agents; which contact angles may show complete wetting, good wetting, poor wetting and non-wetting? Do wetting agents increase or decrease the contact angle between the surface and the wetting liquid? What are the (3) types of wetting agents? Which water-miscible solvents can be used as wetting agents? 10. Be able to describe the HLB system and its advantages. What does this system reflect and based on what is the HLB number assigned to each surfactant? How are higher and lower HLB values associated with hydrophilicity and lipophilicity? Would an increase in polyoxyethylene chain length increase or decrease the HLB? At constant polar chain length would an increase in alkyl chain length or number of fatty acid groups increase or decrease polarity and HLB value? What would be approaches to determine HLB values for non-ionic surfactants and for surfactants other than non-ionic? Are HLB values of different surfactants algebraically additive? Can non-ionic surfactants have HLB values \> 20? Can other types of surfactants have HLB values \> 20? 11. Be able to describe the main applications of surfactants. Is it possible to assume the main applications of a surfactant based on its HLB value?