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EO Sterilant Residual Tests

Ethylene Oxide (EO) Residuals Analysis is used in the identification and quantification of ethylene oxide, ethylene chlorohydrin, and ethylene glycol by gas chromatography. This test helps manufacturers demonstrate the safety of products sterilized by EO by determining compliance with accepted residual limits.

Nelson Labs performs this analysis on products such as hospital surgery packs, gowns, drapes, catheters, and stent delivery systems. We follow the ANSI/AAMI/ISO 10993-7 Consensus Standard recognized by the FDA.

Applicable Standards

  • ISO 10993-7
  • ISO 11135

Testing Locations

  • Salt Lake City, UT, USA
  • Itasca, IL, USA
  • Ontario, CA, USA
  • Mexico City, Mexico
  • Shanghai, China
  • Petit-Rechain, Belgium
  • Somercotes, England
  • Rantigny, France
  • Wiesbaden, Germany
  • Espergaerde, Denmark

Study Outline

The Ethylene Oxide (EO) Residuals Analysis procedure is as follows:

Sample Preparation
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 available to the patient or user. In an exhaustive extraction, all residual EO available must be extracted from the device. This means that the device must be extracted in increments (usually 24 hours) 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. The usual extraction temperature is 35 – 39°C, unless otherwise requested by the sponsor.

Limited use extraction is used to duplicate patient/user contact with the device. The patient or user would only be exposed to part of the residual EO during normal product use. Unless directed otherwise, the default extraction method will be a water extraction using purified water, USP for 24 +/- 1 hours in a 35 – 39°C incubator.

In any case, the samples should be extracted for a time period and under conditions that equal or exceed the maximum use conditions. The following should be taken into consideration:

  • Duration of intended use
  • Temperature of the environment in which the product will be used
  • Fluid or tissue contact with the device
  • Fluid flow across critical surfaces
  • Other applicable use or pre-use conditions

Extraction by Submersion
Most devices are extracted by submersion in water. If the devices are very large, a representative portion may be selected. A known amount of purified water is added to the extraction vessel. The ratio of device size to extraction fluid is prepared to maximize extraction efficiency and also allow for adequate detection sensitivity.

Extraction by Fluid Path
Some devices may be extracted by filling the patient or patient fluid contacting portion 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 (to minimize any potential loss upon transfer to sampling vials) and stored at 2 – 8°C until gas chromatographic analysis.

The total extracted residue in mg for EO and ECH is reported in order to satisfy the ANSI/AAMI/ISO requirements. ANSI/AAMI/ISO does not specify any guidelines for EG levels.

Shipping requirements: To ensure that samples received by Nelson Labs are representative of product, please be sure to include complete information on sterilization, aeration, and proper handling of the device. Samples MUST be shipped on dry ice. Dry ice shall remain in the shipping container and be present when the package is opened in the laboratory. The means of shipping the samples will be noted in the final report.

Nelson Labs places EO residual samples on test within 24 hours (weekends excluded). This is contingent upon receipt of a completed Sample Submission Form and completed EO Residuals Extractions form.