Ethylene Oxide Sterilant Residual Tests

What is ethylene oxide (EO)?

Ethylene Oxide (EO) is known to exhibit a number of biological effects including:

• Irritation

  - Skin irritation, erythema, blisters and burns

  - Eye irritation, cataracts after repeat exposure

• Organ damage

  - Lungs: bronchitis, pulmonary edema, and emphysema

  - Central nervous system: nausea, vomiting, headaches

• Mutagenicity

  - Induces chromosomal aberrations

• Cancer in animals and humans

  - Lymphatic and other types of cancer

• Reproductive effects in animals

What is EO Test Sterilization Residuals Test?

Ethylene Oxide (EO) Residuals Analysis is used in the identification and quantification of EO and ECH by gas chromatography. This test can prove the safety of individual EO-sterilized medical devices by determining accepted residual limits.

"Ethylene Oxide Sterilization Residuals", part seven of the Biological evaluation of medical devices standards(ISO 10993-7), gives out the general considerations that should be taken into account when evaluating the levels of EO and ECH that may remain on medical devices, specifies allowable limits and compliance methods for residual ethylene oxide and ethylene chlorohydrin in individual EO-sterilized medical devices. It also outlines the specific limits of EO and ECH that must not be exceeded in order to ensure product and patient safety.

The Ethylene Oxide (EO) Residuals Analysis general procedures including:

Determining patient exposure; selecting appropriate test methods; preparing samples for testing; Sterilizing product; Performing test. Test samples are prepared according to applicable pre-use instructions on the product label, if available unless sponsor instructions for extraction specify otherwise. There are two methods of product extraction for residual EO analysis which are employed with medical device products, depending on intended device use: exhaustive extraction and simulated-use extraction.

Exhaustive extraction is used if all residual EO is potentially accessible to the user. In an exhaustive extraction, the device must be extracted in increments until no significant increase in cumulative residue level is detected upon re-extraction or until the amount extracted is less than 10% of what was detected in the first extraction. Limited use extraction is used to duplicate patient/user contact with the device. The patient or user would only be exposed to a part of the residual EO during normal product use.

Most devices are extracted by submersion in water. A certain amount of purified water is added to the extraction container. The ratio of device size to extraction fluid is prepared to maximize extraction efficiency and also allow for adequate detection sensitivity. Some devices can be extracted by filling the contacting portion of the patient or patient fluid with water. Components of the device that do not come in contact with the patient or patient fluid may be removed from the device. The device is first accurately weighed and then completely filled with a known amount of purified water. After extraction, the devices are cooled and stored to prepare for the gas chromatographic analysis.

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