Monday 15 June 2020

Endotoxin control in depyrogenation tunnels

Understanding the way glassware is depyrogenated and how high concentrations of endotoxin can be used to assess how well depyrogenation tunnels are functioning is key to quality control.

In a new article, Tim Sandle explains:

Sandle, T. (2020) Endotoxin control in depyrogenation tunnels, Cleanroom Technology, February 2020. At:

Here is an extract:

“The regulatory standard for validation of an endotoxin inactivation (depyrogenation) process is that it should be capable of reducing an endotoxin challenge through 3 log10 reduction. To ensure this limit works, it is required to clean materials before dry heat depyrogenation with WFI. Otherwise, at least in theory, you could have an item contaminated with 10,000 endotoxin units (EU) entering a validated endotoxin inactivation process and still emerging with 10 EU intact and ready to contaminate your product.

Dry heat depyrogenation is a complex process and is still poorly understood with contradictory research data. The phenomenon that complicates the picture is that inactivation may approximate to Second Order chemical kinetics with a high initial rate of inactivation, then tail off to nothing. In practice, this means that at any particular depyrogenating temperature you will get some degree of inactivation in some period of time or other, but beyond that point, you will get no further inactivation by holding the material at that temperature.”

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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