Residual Testing

What it is
When a product is sterilized with ethylene oxide (EO), some of the gas may be absorbed by the product and/or its packaging and retained after sterilization. There may also be traces of EO bi-products present after sterilization. The extent of degassing and aeration used during the sterilization process will have a significant effect in reducing these residue levels. Also influential are the number of hours or days between sterilization and testing. Residual testing is your assurance that your product is safe to market.

Why you need it
Determining the levels of EO and its by-products is a requirement for many medical devices. The International Standard (ISO) 10993-7 describes the categorization of products, methods of residual testing and allowable limits of residues.

How it is done
Residues can be extracted from product for residual testing in two ways:

• The Simulated Use Method extracts residues over a set time based on the maximum time the device would be exposed to a patient, and the route by which any dose would be administered.
• The Exhaustive Extraction Method extracts residues by heating the product in a sealed system and testing the vapor above it, or by repeated aqueous extraction of the samples.