Role of Statistics in Lyophilization or Freeze Drying
Role of Statistics in Lyophilization or Freeze Drying
Thomas A. Jennings, Ph.D.
January 2003
There is little doubt, at least in my mind, that lyophilization or freeze drying (see INSIGHT Vol. 2 No. 1) is a very complex and often confusing process. In our efforts to understand such a complex process we will tend to simplify rather than treat the subject in a rigorous manner. Even so, the process continues to offer us a real challenge in our efforts to reach some kind of general understanding.
But our efforts to simply do come at a price which often is a source of even more confusion. Take for example when one finds that less that 1 % of the product in a batch is defective in some way, e.g., partial meltback (see INSIGHT Vol. 1 No. 5). If our product is in vials, it represents less than 1 in a hundred but if the batch size is of the order of 50,000 there could be hundreds of defective product that will have to be removed from the batch by inspection. Now the defective product not only represents a loss in revenue but is a constant source of irritation because the defects are generally randomly scattered throughout the batch and there does not appear to be any pattern one can attribute to the process or the freeze drying equipment that can account for the defects. What makes this even more frustrating is that attempts to eliminate these defects often proves to be an exercise in futility.
The answer to such problems may often lie in the fact that not even the most fundamental aspects of statistics were applied to the process. This INSIGHT will therefore address two key parameters that need to be examined on a statistical basis in order to improve the reliability of the process.
Given the nature of this topic and troubled state that now seems to grip the world, what better way to commence this first issue of the sixth volume of INSIGHT but with a smile or two by paying a visit to our dear friends at the Surcure Company. Especially when it is the last day of the year and preparations are underway for the Annual Surcure New Year?s Eve Party. So let us begin our story.
Since it is the last day of the year and minds are now more focused with anticipation on the big party that evening than on the work at hand and given the fact that the following day is a paid holiday, it is of little wonder that, by the time the afternoon has arrived, interest in working is rapidly waning. It is at times like this that Armondo will retreat to the safety of his office and invite his friend and associate to join him in his office while the last minutes of the year slowly tick by. Armondo is relaxing behind his desk and he has some regrets about consuming another one of those huge sandwiches so apply named an ?Awful - Awful? for it seems that the sandwich is beginning to live up to its name as the afternoon wears on.
The room is quite for some time and it is Armondo who breaks the silence by stating ?I think I should have passed up on the ?Awful - Awful? at lunch. Especially since we will have a big meal tonight and I also guess I should not have eaten the apple pie but I do like apple pie so much.
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