# EO (Ethylene Oxide) Residuals - EN ISO 10993-7:2008

I

#### Institute

Hello,
Can anyone help with the determination/calculation of EO, ECH residuals for limited exposure devices. We have determined (GC) amount of EO residuals, which is 1 ppm per product (extract) and now I have to establish limit for product according to TCL (tolerable contact limit) and A (surface area)....so I will calculate TCL x A and then justify that the product has (because of 1ppm) acceptable EO residuals according to EN ISO.

Am I right?

Thank you!
By!

#### Stijloor

Staff member
Super Moderator
Hello,
Can anyone help with the determination/calculation of EO, ECH residuals for limited exposure devices. We have determined (GC) amount of EO residuals, which is 1 ppm per product (extract) and now I have to establish limit for product according to TCL (tolerable contact limit) and A (surface area)....so I will calculate TCL x A and then justify that the product has (because of 1ppm) acceptable EO residuals according to EN ISO.

Am I right?

Thank you!
Bye!
Help anyone?

Thanks!!

Stijloor.

#### Qara123

##### Involved In Discussions
Institute,

The ISO specification for limited exposure devices is 20mg. You have tested your device and the EO result is 1ppm per product extract. However, the units "mg" and "ppm" are not directly comparable and you should convert your results to "mg" to determine whether you meet the ISO specification.

Q

I

#### Institute

Hy Q,
I think that you mentioned old requirement for EO residual (20 mg) that is the reason why I wrote ISO 10993:2008, nevertheless I will check once again...

Bye

#### Qara123

##### Involved In Discussions
Institute,

Regardless of the ISO specification, my point is that the units "mg" and "ppm" are not directly comparable. For example, if a specification states "50 mg or less" and the results provided is "10 ppm", a reviewer would not be able to determine whether the result meets the specification without additional information because "ppm" is a dimensionless quantity.

Q

S

#### sway123

Institute,

I realize this response is very late, but it may help others in the future.

The 2008 version of 10993-7 states that for limited exposure devices the maximum dose of EO to the patient shall not exceed 4 mg in the first 24 h, and that the Tolerable Contact Limit (TCL) shall not exceed 10 ug/cm2. If you have measured your residuals, you can divide the EO residuals (in milligrams) by the extracted surface area of the device, and get the TCL in units of ug/cm2 (be sure to convert mg of EO to ug during calculation). The ppm measurement is based on the weight of the device and weight of residue.

Hope that helps someone.

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