top of page
  • Writer's pictureSanichem Resources

Ethylene Oxide Residual Analysis

Updated: Apr 1, 2022

Ethylene Oxide Sterilization For Medical Device

Ethylene Oxide (EO or EtO) is used to sterilize medical devices. Ethylene oxide gas (usually under pressure) may penetrate container boxes and packaging pouches made of certain materials and practically dissolve in medical devices which are generally made of various polymers such as plastic and rubber.

Ethylene Oxide (EO) is used to sterilize medical devices. Ethylene oxide gas (usually under pressure) may penetrate container boxes and packaging pouches made of certain materials and practically dissolve in medical devices which are generally made of various polymers such as plastic and rubber.

The amount of EO absorbed in the medical device material depends on several factors including material composition of the medical devices, packaging and shipping material and sterilization cycles.

Ethylene Oxide, Ethylene Chloride & Ethylene Glycol

Once dissolved in the material, EO gas permeate gradually depending on the solubility and diffusivity of EO in the material, packaging materials and aeration conditions.

If traces of chlorine or chloride ions are present in the device, they will quickly react with EO to form ethylene chlorohydrin (ECH). On a slower scale, traces of acid or moisture will convert EO into ethylene glycol (EG).

What Are the Dangers of Ethylene Oxide?

EO and ECH are found to be toxic to human and exposure to these chemicals is harmful to human health. Since these residues permeate gradually out of the EO sterilized devices, the patients and to a lesser extend the handler may be exposed when the device is used.

Ethylene Oxide Residual Limits for Medical Device ISO 10993-7

The permissible limits of these EO residues in medical devices will depend on the types of medical devices which have been categorized according to their duration of use on patients. The ISO 10993-7 (2008) on Biological evaluation of medical devices - Part 7: Ethylene oxide sterilization residuals is the guiding document generally accepted for the evaluation of EO residuals in medical devices.

Under this guideline, the allowable limit of each residue, the recommended method of extracting and analyzing the residues and stringent quality control on the analytical procedure is documented for the evaluation of EO residuals in medical devices.

(A) Limited exposure – devices which cumulative single, multiple or repeated use is up to 24 hours.

B) Prolonged exposure – devices which cumulative use is likely to exceed 24 hours but less than 30 days.

(C ) Permanent contact – devices which cumulative use exceeds 30 days.

Ethylene Oxide Residual Detection For Medical Device

SaniChem Resources has developed methods for analyzing EO residuals in various medical devices based on the ISO 10993-7 guideline. These methods has been validated and registered in our testing scope under the ISO/IEC 17025 accreditation.

There are three in-house methods for the analysis of EO residues. Method CH100 is the main method of determining the level of EO, ECH and EG in various medical devices. Basically this method involves total or exhaustive extraction of the residues from the medical devices and analyzing EO, ECH and EG by gas chromatography.

Method CH104 is a validated method for the analysis of EO in aqueous solution. Certain manufacturer and sterilization operators have facilities for extracting the residues on-site. It is less cumbersome to ship the extract which require cold shipment than to ship the medical devices which requires dry-ice frozen condition during transit.

Ethylene Oxide Dissipation Curve

Dissipation curves or decay curves is a tool recommended in the ISO 10993-7 to estimate the levels of each residue in a medical device at certain time after sterilization. This information is useful for product release date, for example.

We provide a package rate for developing dissipation curves for medical devices. A set of samples (normally 10 samples) which are isolated and frozen at various specified interval after sterilization are analyzed for the residual levels.

Normally, the medical devices are isolated and keep frozen at 0, 1, 3, 5, and 7 days after sterilization during the aeration process. At the end of the collection period, the level of EO residues are determined. Dissipation curves are generated based on first order decay rate of the total amount (dose) of the residue in the devices. Example of EO dissipation curve is shown on the right.

How to Send Samples For Analysis

Samples may be submitted to our laboratory either by hand or through a reliable courier service. We may be able to provide pick-up service with a minimal charge for samples from Malaysia. Please inquire about the pick-up rate and availability.

We also receive samples from other countries such as Singapore, Indonesia, Philippines, Vietnam, Saudi Arabia, United Arab Emirates, Pakistan, Egypt and Kenya. Send us an email to arrange for the analysis.

For sterilized medical devices, the samples must be placed in a Styrofoam box and filled with dry ice. A well-packed/insulated Styrofoam box may need about 1-2 kilograms of dry ice (pellet) to last 24-hour shipping.

ISO 10993-7 guideline states that there must be some dry ice still present when the shipment arrives at the laboratory to ensure that the samples were frozen during transit.

For aqueous extracts of EO residues, the sample may be placed in 2 mL GC sampler vials. Our experience showed that the solution must be almost full (with about 1-2% head-space), well capped, and insulated. An ice pack may be used to keep the solution cold (but not frozen) during transit.

Dry ice must NOT be used as the vial may break when the aqueous solution expands upon freezing. Please use the EO Test Request Form to record your submission. Sample submission must be accompanied by the test request form and official purchase order.

Our policy requires that we cannot provide the test report BEFORE a purchase order from the customer is received. We will provide a written quotation prior to sample submission. Please email or call us for a quotation stating the test required and the number of samples for each test.

Contact us if you have any questions regarding EO residual analysis.

2,044 views0 comments

Recent Posts

See All


Subscribe to our newsletter • Don’t miss out!

Thanks for subscribing!

bottom of page