Sterilization ethylene oxide gas

Sterilization of UHMWPE is accomplished by diffusion of EtO into the near-surface regions during several hours (Bruck and Mueller 1988, Ries, Weaver, and Beals 1996). After sterilization, residual EtO is then allowed to diffuse out of the UHMWPE to reduce the likelihood of an adverse topical reaction (Bruck and Mueller 1988). In a study by Ries and colleagues (1996), which provided details of a validated EtO sterilization cycle for UHMWPE, the following protocol was employed 18 hours of preconditioning at 65% relative humidity, followed by 5 hours of exposure to 100% EtO at 0.04 MPa, followed by 18 hours of forced air aeration. Thus, the entire sterilization cycle with EtO took a total of 41 hours. Preconditioning, exposure, and aeration were conducted at46°C. 

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Such sterilization procedures (see also Chapter 20) may include heat treatment, filtration, irradiation, recrystallization flxm a bactericidal solvent such as an aleohol, or for dry products where eompatible, ethylene oxide gas. If the raw material is only a minor constituent and the final product is adequately preserved either by lack of chemically... 

Closure liners of pulpboard or cork, unless specially treated with a preservative, foil or wax coating, are often a source of mould contamination for liquid or semi-solid products. A closure with a plastic flowed-in linear is less prone to introduce or support microbial growth than one stuck in with an adhesive, particularly if the latter is based on a natural product such as casein. If required, closures can be sterilized by either formaldehyde or ethylene oxide gas. 

The British Pharmacopoeia (1993) recognizes five methods for the sterilization of pharmaceutical products. These are (i) dry heat (ii) heating in an autoclave (steam sterilization) (iii) filtration (iv) ethylene oxide gas and (v) gamma or electron radiation. In addition, other approaches involving steam and formaldehyde and ultraviolet (UV) light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability... 

Ethylene oxide gas is highly explosive in mixtures of >3.6% vN in air, in order to reduce this explosion hazard it is usually supplied for sterilization purposes as a 10% mix with carbon dioxide, or as an 8.6% mixture with HFC 124 (2 chloro-1,1,1,2 tetrafluoroethane) which has replaced fluorinated hydroearbons (freons). Alternatively, pure ethylene oxide gas can be used at below atmospheric pressure in sterihzer chambers from which all air has been removed. 

The operation of an ethylene oxide sterilizer should be monitored and controlled automatically. A typical operating cycle for pure ethylene oxide gas is given in Fig. 20.7, and general eonditions are summarized in section 10. 

Ethylene oxide Gas concentration 800-1200 mgl 45-63°C 30-70% relative humidity 1-4 hours sterilizing time... 

L. Gramiccioni, M. Milana, and S. DiMarzio, A head space gas chromatographic method for the determination of traces of ethylene oxide in sterilized medical devices, Microchem. J., 32 89-93 (1985). 

Ethylene oxide, a sterilizing gas, may be used to sterilize rubber components when they are part of a medical device however, the gas is readily absorbed by the rubber and sufficient time must be allowed after sterilization for the concentration of residual ethylene oxide to dissipate to acceptable levels. ... 

Ethylene oxide gas is highly explosive in mixtures of >3.6% v/v in air in order to reduce this explosion hazard it is usually supplied for sterilization purposes as a 10% mix with carbon dioxide, or as an... 

Z. Zhu, I. P. Matthews, and W. Dickinson, Specificity, accuracy, and interpretation of measurements of ethylene oxide gas concentrations during sterilization using a microwave spectrometer. Rev. Sci. Instrum. 68(7), 2883-2890 (1997). 

Heat-sensitive materials may be sterilized by radiation, providing the product and its container are not radiation sensitive. It is particularly used with plastics, and more widely used with containers than with products. An alternative is ethylene oxide gas. This presents problems in that the gas must be brought into contact with the cell walls of contaminating bacteria. Ethylene oxide is highly reactive and can only be used when it can be proved not to react with the product. 

Sterihzabflity of biomedical polymers is an important aspect of the properties because polymers have lower thermal and chemical stability than other materials such as ceramics and metals, consequently, they are also more difficult to sterilize using conventional techniques. Commonly used sterilization techniques are dry heat, autoclaving, radiation, and ethylene oxide gas [ Block, 1977]. 

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