Gravimetric measurement of momentary drying rate of spray freeze-dried powders in vials.
The profile of drying rate versus primary drying time for a spray freeze-dried trehalose aqueous solution is much different from that determined for regular freeze-drying. Drying rate declines very rapidly, attributed to rate-limiting heat transfer through the packed bed of frozen microparticles contained in a vial. The inter-particulate spaces appear to be the cause of this rate limitation. Use of either liquid nitrogen or liquid propane as a cryogenic produced strong differences in both SFD particle morphology and drying rate using trehalose, sucrose, or mannitol. The lack of any evident correlation supports the argument that the inter-particulate voids determine drying behavior.
Gieseler
Henning
H
Division of Pharmaceutics, Friedrich-Alexander-University Erlangen, Erlangen, Germany.
Lee
Geoffrey
G
D002241:Carbohydrates / Q000737:chemistry*; D004867:Equipment Design; D005612:Freeze Drying / Q000295:instrumentation* / Q000379:methods*; D007700:Kinetics; D014199:Trehalose / Q000737:chemistry
D002241:Carbohydrates; D014199:Trehalose