what are all the limitations for freeze drying?

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Shruti Priya's picture

Answer: 
The probable limitations are:- 1.the product is prone to oxidationdue to high porosity and large surface area. 2.the period of drying is high(rarely less than 10 hrs) 3.this method cannot be adopted for solutions containing non aqueous solvents. 4.equipment and running costs are high. Reference: By Subrahmanyam's 'Pharmaceutical engineering',Vallabh prakashan. pg no.405

Shruti Priya

Ayman Waddad's picture

Answer: 

A very hygroscopic product will be obtained due to the porosity, fast solubilization and complete dryness as a result of the freeze drying process. So we need special packaging system (e.g. immediate collection of the freeze dried product in situ) to the final containers. The oxidation of the product is one of the possible results but could be avoided or minimized by the conducting the freeze druing process under highly vacuum pressure. The most common drawback is the expensive machine used specially on large scale production. Also the process itslef is very slow although this depend on many other factors. Since a sublimation process occured during the freeze drying a need to apply a radiant heat to equilibrate the latent heat of sublimation although a danger of melting the ice attached to the container wall.

References:

1. Aulton, M. E. (2002). Pharmaceutics The Science of Dosage Form Design.Edinburgh, Churchill Livingstone. 2nd. page 393.

2. Hickey, A. J. and D. Ganderton (2001). Pharmaceutical process engineering. New York, M. Dekker. page 105

Ayman Waddad

Ph.D Student

China Pharmaceutical University

Nanjing

China

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