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May 2006


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The Pharmaceutical Microbiology Forum Email List <[log in to unmask]>
Tue, 23 May 2006 17:45:46 EDT
text/plain (79 lines)
Based on the PPM you listed (if indeed this is accurate), I would expect a  
D-value anywhere from 7 to 14 minutes using the Steris Cycle Development Guide, 
 with an average D-value around 11 minutes.  This range in D-values has to  
do with the percent saturation of hydrogen peroxide, with the lower D-value  
having a higher percent gram saturation (closer to the point of  condensation).  
In other words, at 700 PPM and 65% gram saturation one  would expect a 
D-value of approximately 14 minutes, and at 95% gram saturation  one would expect a 
D-value of approximately 7 minutes.  This is why  temperature and humidity are 
so important in this process.  Given your BI  log of approximately 6.28 log, 
your cycle should be GREATER than  approximately 44 minutes (7 minutes/log 
reduction x 6.28  log).   Truthfully, you may see positives even at 44  minutes.  
So to answer your question, I do not find it at all  surprising that you did 
not see total kill at 35 minutes.
On a side note, my firm now fabricates condensation sensor technology  
coupled with or without high concentration hydrogen peroxide monitoring to aid  in 
performing D-values, cycle development qualification, etc.  Please email  me 
directly if interested and I will send you the appropriate information.   As you 
can imagine, demand has been very strong.
Yours in  Service,

The Barrier Isolation Technology  Specialists
Serving the Pharmaceutical Industry Since 1994

Rick Nieskes - Barrier Isolator  Consultant
825 Lynnewood Drive
Waukesha, Wisconsin  53188
Tel: 262.548.9748
Fax: 262.548.9758
Mobile:  262.853.9748
Email: [log in to unmask]

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