Dear Folks/Experts,
I would like to know what are the factors may cause uneven or more water contents in lyophilized vials (most of the vials meeting acceptance limit few vials shown too higher water contents).
20mL vial size and 1/3rd is fill volume (Shelf temp vs set are meeting and vaccum found set limit)
Thanks in advance!
On the assumption that the content of all the vials is, truly, identical, i.e. no pipetting error, all fills assured by weight, then the are a few things to check:
1. distribution of the vials - are they edge or centre of the pack? Centre dry last so if all the problem vials are in the centre, then more time in primary drying is needed.
2. uniformity of the vials - moulded vials can have very variable bases, which can affect drying (heat transfer through the base from the shelf). If using a tubing type vial, should not be an issue. If moulded vials are the problem, again extending primary drying is needed.
3. if none of the above, then more time, and perhaps a higher temperature in secondary drying should solve the problem. That is, unless there has been some defect in primary drying like a vacuum excursion that caused meltback of the ice ...
A good overview on freeze dyring can be found here:
https://www.scientificproducts.com/resources/articles-tech-notes/basic-principles-of-freeze-drying
Kind regards
Rob
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