Thursday, March 21, 2019

Lyophilizer Sterilization

Lyophilizer and freeze dryer are synonymous names for the same equipment. A lyophilizer (lyo) executes a water removal process typically used to preserve perishable materials, to extend shelf life or make the material more convenient for transport. It is usually decontaminated on a periodic basis and after each production batch. The standard process is to decontaminate by using steam to raise the temperature and hold it there until 6-log kill is attained. After the proper sterilization time is reached, the lyophilizer is then left to cool before product is brought in for another cycle. Because of the large thermal mass, this can take many hours. Lyophilizers also need to pull deep vacuums to perform the drying function. Heating and cooling with steam causes thermal expansion and contraction which compromises the tight tolerances required to keep the lyo sealed enough to reach deep vacuum levels. To mitigate these concerns and provide a faster sterilization cycle, chlorine dioxide gas can be used to decontaminate the components.

  • Quicker cycles with Chlorine Dioxide Gas than Steam or Vapor Phase Hydrogen Peroxide
    • 1.5 to 3 hours depending on desired level of kill and sensitivity of components versus 24 hours for steam or 8 to 12 hours for VPHP.

  • Less stress on the lyophilizer with Chlorine Dioxide Gas than Steam 
    • No thermal stresses with CD gas as there are with steam, because there are no heating and cooling requirements.
  • No cycle development required for Chlorine Dioxide Gas
    • CD: 1 mg/liter for 2 hours or 5 mg/liter for 30 minutes of exposure. 
    • VPHP: Cycle parameters must be developed for every specific application. If ambient temperatures change, the cycle parameters most likely need to be changed.

To learn more, read our Application Note about this specific use.

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