Principle, Procedure, Merits, Demerits and Applications of Gaseous and Radiation Sterilization : Pharmaceutical Guidelines -->

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Principle, Procedure, Merits, Demerits and Applications of Gaseous and Radiation Sterilization

Sulphur dioxide and formaldehyde are both commonly used. Many materials cannot be removed from these gases after exposure as they are highly reactive.

Gas Sterilization

Sulphur dioxide and formaldehyde are both commonly used. Many materials cannot be removed from these gases after exposure since they are highly reactive chemicals. Because of this, they have a limited usefulness. HCHO and SO2 are inherently more disadvantageous than ethylene oxide and beta-propiolactone.
  • Sterilize plastic, optics, and electric objects that are sensitive to temperatures exceeding 60 °C and / or radiation with ethylene oxide gas.
  • There is no known resistance to its use, including bacterial spores, and it is compatible with most plastics (e.g., of medical devices), regardless of the frequency with which it is applied.
  • But it is highly flammable and toxic, as well as carcinogenic.
  • Sterilization processes generally begin with a preconditioning step, which is followed by the sterilization process and an aeration step to remove residual toxic materials, such as ethylene oxide.
Ethylene oxide can be sterilized in two ways:
  • The gas chamber method
  • The micro-dose method


  • Initiates the reproductive process by alkylating vital metabolites.
  • Sulfhydryl, amino, carboxyl, and hydroxyl groups are alkylated by replacing active hydrogens with hydroxyethyl radicals.
  • Microorganisms die without reproducing when their metabolites have been altered.
Beta propiolactone
  • At room temperature, it is not flammable.
  • Vapor pressure is low.
  • A variety of bacteria are susceptible to its bactericidal effects at relatively low concentrations.
  • Alkylating agents such as ethylene oxide use it.
  • When used in at least 2 hours at a temperature of 24 C and with a relative humidity of at least 70%, vapor concentrations of approximately 2-4mg/l of space are effective.

Radiation Sterilization

Use of UV rays

UV rays are used to kill bacteria on surfaces or penetrate clean air and water for their germicidal properties.

Lethal action
In bacteria, U.V light causes electrons within the molecules to be excited, altering their reactivity and causing them to pass through matter.

An organism dyes or becomes incapable of reproducing when the activity of essential atoms is altered in this way.

Intensity of radiation and duration of exposure determine germicidal effectiveness of ultraviolet radiation.

U.V LAMPs must be maintained free of dust, grease, and scratches in order to maintain maximum effectiveness.

When emission levels decrease substantially, they must be replaced.


  • Sterilization of packed pharmaceuticals is not possible due to their low penetration power.
  • Atmospheric organisms are less effective.


  • The process is used to sterilize air so that it does not cross-contaminate.
  • Before packing thermolabile substances, it is used to sterilize them.

Ionization Radiation

Gamma and Beta Rays are the result of accelerated electrons as they move to high speeds and energies from radioactive isotopes, such as COBALT 60 (GAMMA RAYS).

However, gamma rays are relatively expensive, although they have high penetration power.

The electron accelerator is divided into two types.
  • Linear acceleration
  • Van de Graff accelerator
Lethal Action
  • Mutation caused by radiation beam energy transfer to receptive molecules causes microorganisms to cease reproducing.
  • Through direct action, water molecules also become hydrogen and hydroxyl ions, causing mutations.
  • They modify nucleic acids to produce energy, and thus the bacterial cell can no longer utilize them for metabolism.


  • It is not necessary to take any aseptic precautions.
  • It can be used for all types of materials, including dry, moist, and frozen materials.
  • There is very little exposure time.


  • Plants used are very expensive.
  • It is very dangerous for workers to be exposed to radiation.


  • Syringes, hypodermic needles, scalpels and other plastic items can all be sterilized with this process.
  • The sterilization of bone and tissue transplants, tubing, and catheters is done using this method.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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