Document Detail


Reduced pressure ice fog technique for controlled ice nucleation during freeze-drying.
MedLine Citation:
PMID:  19937284     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A method to achieve controlled ice nucleation during the freeze-drying process using an ice fog technique was demonstrated in an earlier report. However, the time required for nucleation was about 5 min, even though only one shelf was used, which resulted in Ostwald ripening (annealing) in some of the vials that nucleated earlier than the others. As a result, the ice structure was not optimally uniform in all the vials. The objective of the present study is to introduce a simple variation of the ice fog method whereby a reduced pressure in the chamber is utilized to allow more rapid and uniform freezing which is also potentially easier to scale up. Experiments were conducted on a lab scale freeze dryer with sucrose as model compound at different concentration, product load, and fill volume. Product resistance during primary drying was measured using manometric temperature measurement. Specific surface area of the freeze-dried cake was also determined. No difference was observed either in average product resistance or specific surface area for the different experimental conditions studied, indicating that with use of the reduced pressure ice fog technique, the solutions nucleated at very nearly the same temperature (-10 degrees C). The striking feature of the "Reduced Pressure Ice Fog Technique" is the rapid ice nucleation (less than a minute) under conditions where the earlier procedure required about 5 min; hence, effects of variable Ostwald ripening were not an issue.
Authors:
Sajal M Patel; Chandan Bhugra; Michael J Pikal
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Publication Detail:
Type:  Journal Article     Date:  2009-11-24
Journal Detail:
Title:  AAPS PharmSciTech     Volume:  10     ISSN:  1530-9932     ISO Abbreviation:  AAPS PharmSciTech     Publication Date:  2009  
Date Detail:
Created Date:  2010-01-21     Completed Date:  2010-02-23     Revised Date:  2013-05-31    
Medline Journal Info:
Nlm Unique ID:  100960111     Medline TA:  AAPS PharmSciTech     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1406-11     Citation Subset:  IM    
Affiliation:
School of Pharmacy, University of Connecticut, Storrs, Connecticut 06269, USA.
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MeSH Terms
Descriptor/Qualifier:
Freeze Drying / methods*
Ice
Pressure
Surface Properties
Technology, Pharmaceutical*
Temperature
Chemical
Reg. No./Substance:
0/Ice
Comments/Corrections

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