EN ISO 10993-7:1995

SLOVENSKI STANDARD
01-januar-2000
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Biological evaluation of medical devices - Part 7: Ethylene oxide sterilization residuals
(ISO 10993-7:1995)
Biologische Beurteilung von Medizinprodukten - Teil 7: Ethylenoxid-
Sterilisationsrückstände (ISO 10993-7:1995)
Evaluation biologique des dispositifs médicaux - Partie 7: Résidus de stérilisation a
l'oxyde d'éthylene (ISO 10993-7:1995)
Ta slovenski standard je istoveten z: EN ISO 10993-7:1995
ICS:
11.100.20 %LRORãNRRYUHGQRWHQMH Biological evaluation of
PHGLFLQVNLKSULSRPRþNRY medical devices
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL
IS0
STANDARD
10993-7
First edition
1995-l O-l 5
Biological evaluation of medical devices -
Part 7:
Ethylene oxide sterilization residuals
cvalua tion biologique des dispositifs m6dicaux -
Par-tie 7: R6sidus de s t6rilisa tion ;i I’oxyde d ‘6 th ykne
Reference number
IS0 10993-7:1995(E)
IS0 10993=7:1995(E)
Contents
Page
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative references
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Requirements
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4.2 Categorization of devices
4.3 Allowable limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4.3.1 Permanent contact devices
4.3.2 Prolonged exposure devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3’
4.3.3 Limited exposure devices
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.3.4 Special situations
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.4 Determination of EO and ECH residuals
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.4.1 Safety considerations
4.4.2 Determination of residue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.4.3 Product sampling
4.4.4 Sample/fluid ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.45 Extraction time and conditions
4.4.6 Product extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.4.7 Data analysis and interpretation
..*......................................................................
5 Product release
. . . . . . . . . . . . . . 7
5.1 Release of products without dissipation curve data
5.2 Procedure for product release using residue dissipation curves
Annexes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
A Evaluation of gas chromatograms
0 IS0 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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IS0 10993=7:1995(E)
B Gas chromatographic determination for EO and ECH
........... 12
C Factors influencing product residuals .
D Extraction conditions for determination of residual EO
. . . . . . . . 23
E Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
F Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0 IS0
IS0 10993=7:1995(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 10993-7 was prepared jointly by Technical
Committees lSO/rC 194, Biological evaluation of medical devices and
lSO/TC 198, Sterilization of health care products.
IS0 10993 consists of the following parts, under the general title Biological
evaluation of medical devices:
- Part I: Evaluation and testing
- Part 2: Animal welfare requirements
- Part 3: Tests for genotoxicity, carcinogenicity and reproductive
toxicity
- Part 4: Selection of tests for interactions with blood
- Part 5: Tests for cytotoxicity: in vitro methods
- Part 6: Tests for local effects after implantation
- Part 7: Ethylene oxide sterilization residuals
- Part 9: Degradation of materials related to biological testing
[Technical Report]
- Part 10: Tests for irritation and sensitization
- Part 1 I: Tests for systemic toxicity
- Part 12: Sample preparation and reference ma teriak
- Part 13: /den tification and quantification of degradation products
from polymers
0 IS0 IS0 10993=7:1995(E)
- Part 14: Identification and quantification of degradation products
from ceramics
- Part 15: Identification and quantification of degradation products
from coated and uncoated metals and alloys
- Part 16: Toxicokinetic study design for degradation products and
leachables
- Part 17: Glutaraldehyde and formaldehyde residues in industrially
sterilized medical devices
Annexes A and B form an integral part of this part of IS0 10993. Annexes
C, D, E and F are for information only.

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IS0 10993=7:1995(E)
Introduction
Requirements for the quality system for validation and routine monitoring
of sterilization of medical products with gaseous ethylene oxide are given
in International Standards developed by lSO/TC 198. Certain requirements
relating to medical devices for biological testing, selection of tests and the
allocation of devices to categories are dealt with in a variety of Inter-
national Standards under development by lSO/TC 194. The specific re-
quirements for ethylene oxide and other sterilization process residuals was
referred to lSO/TC 194. Other International Standards delineate particular
requirements for biological testing for specific products.
When determining the suitability of ethylene oxide (EO) for sterilization of
medical devices, it is important to ensure that the levels of residual EO
and ethylene chlorohydrin (ECH) pose a minimal risk to the patient in
normal product use. EO is known to exhibit a number of biological effects.
In the development of this part of IS0 10993, consideration was given to
these effects, which include irritation, organ damage, mutagenicity and
carcinogenicity in humans and animals, and reproductive effects in ani-
mals. Similar consideration was given to the harmful effects of ECH and
ethylene glycol (EG). In practice, for most devices, exposure to EO and
ECH is considerably lower than the maximum values specified in this part
of IS0 10993.
Product development and design should have considered the use of
alternative materials and sterilization processes with the aim of minimizing
exposure to residuals. Requirements herein are in addition to the biological
testing requirements for each individually designed medical device as in-
dicated in IS0 10993-I. The biological testing requirements, combined
with the EO-sterilization process residue limits, form the justification that
an EO-sterilized device is acceptable for use.
vi
IS0 10993=7:1995(E)
INTERNATIONAL STANDARD * IS0
Biological evaluation of medical devices -
Part 7:
Ethylene oxide sterilization residuals
3 Definitions
1 Scope
For the purposes of this part of IS0 10993, the defi-
This part of IS0 10993 specifies allowable limits for
nitions given in IS0 10993-I and the following defi-
residual ethylene oxide (EO) and ethylene
nitions apply.
chlorohydrin (ECH) in individual EO-sterilized medical
devices, procedures for the measurement of EO and
ECH, and methods for determining compliance so
3.1 simulated-use extraction: Extraction to dem-
that devices may be released. Additional background
onstrate compliance with the requirements of this
and guidance also is included in informative annexes part of IS0 10993, by evaluating residue levels avail-
able to the patient or user from devices during the
EO-sterilized devices that have no patient contact (e.g.
routine use of a device using an extraction method
in vitro diagnostic devices) are not covered by this
using water that simulates product use.
International Standard.
NOTE 1 The burden of validation on the analytical lab-
oratory is to demonstrate that the simulated-use extraction
is carried out under conditions that provide the greatest
2 Normative references
challenge to the intended use. Product use simulation
should be carried out assuming the device is assigned to
The following standards contain provisions which,
the most stringent category probable for duration of ex-
through reference in this text, constitute provisions posure and should take into consideration both tissue(s)
exposed and temperature of exposure.
of this part of IS0 10993. At the time of publication,
the editions indicated were valid. All standards are
subject to revision, and parties to agreements based 3.2 exhaustive extraction: Extraction until the
on this part of IS0 10993 are encouraged to investi- amount of EO or ECH in a subsequent extraction is
less than 10 % of that detected in the first extraction,
gate the possibility of applying the most recent edi-
or until there is no analytically significant increase in
tions of the standards indicated below. Members of
IEC and IS0 maintain registers of currently valid the cumulative residue levels detected.
International Standards.
NOTE 2 As it is not possible to demonstrate the exhaus-
tive nature of residual recovery, the definition of exhaustive
IS0 10993-I : 1992, Biological evaluation of medical
extraction adopted is as above.
devices - Part I: Guidance on selection of tests.
IS0 10993-3: 1992, Biological evaluation of medical
devices - Part 3: Tests for geno toxicity,
4 Requirements
carcinogenicity and reproductive toxicity.
NOTE 3 Information on the derivation of the limits in this
IS0 10993-I 0: 1995, Biological evaluation of medical
part of IS0 10993 as well as other important background
devices - Part IO: Tests for irritation and
information and guidance relevant to the use of this part of
sensitization. IS0 10993 are contained in informative annexes.
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IS0 10993=7:1995(E)
NOTES
4.1 General
4 If a material or device may be placed in more than one
This clause specifies maximum allowable residues for
duration category, the more rigorous testing requirements
ethylene oxide (EO) for each individual medical device
should apply. With multiple exposures, the decision into
sterilized with EO. Maximum allowable residues for
which category a device is placed should take into account
ethylene chlorohydrin (ECH) when ECH has been
the potential cumulative effect, bearing in mind the period
found to be present in medical devices sterilized with of time over which these exposures occur.
EO also are specified.
5 As it is applied in this part of IS0 10993, “multiple
use” is defined to mean repeated use of the same device.
No exposure limits are set for ethylene glycol (EG)
because risk assessment indicates that when EO
residues are controlled as required by this part of
4.3 Allowable limits
IS0 10993, it is unlikely that biologically significant
residues of EG would be present (see E.l).
For each medical device, the maximum allowable
doses of EO and ECH that are delivered to patients
The requirements in this part of IS0 10993 are in ad-
shall not exceed the values given below for the ex-
dition to the biological testing requirements set out in
posure category that the device has been placed into,
IS0 10993-I. For devices sterilized by ethylene oxide,
in accordance with 4.2.
attention shall be paid in particular to IS0 10993-3 and
IS0 10993-I 0. All applicable requirements of
NOTE 6 The limits for permanent contact and prolonged
IS0 10993-I shall take into account EO residual level
contact devices are expressed as maximum average daily
at time of release for each individually designed
doses. These limits also carry additional constraints for the
medical device.
first 24 h of the exposure period and, in the case of the
permanent contact devices, for the first 30 days. These
Results of the biological assessment of the device
constraints place limitations on the amount of EO and ECH
may dictate more stringent limits than those specified that can be delivered to the patient during these early time
periods. The procedure that was used to establish the al-
in 4.3, which are designed to protect against systemic
lowable limits is described in E.2.
effects. For example, irritation effects shall be con-
sidered for all devices, particularly small devices (see
E.2). This International Standard does not take ac-
4.3.1 Permanent contact devices
count of the possibility of acute localized effects, for
which insufficient data are available. Particularly for
The average daily dose of EO to patient shall not ex-
small devices, attention should be paid to the poten-
ceed 0,l mg/day. In addition, the maximum EO dose
tial for such effects and the concentration of EO per
shall not exceed
unit of surface area.
20 mg in the first 24 h;
60 mg in the first 30 days;
4.2 Categorization of devices
2,5 g in a lifetime.
In establishing the maximum daily doses of EO and
The average daily dose of ECH to patient shall not
ECH that a medical device is allowed to deliver to
exceed 2 mg/day. In addition, the maximum ECH
patients, devices shall be categorized according to
dose shall not exceed
duration of contact.
12 mg in the first 24 h;
Devices shall be placed into one of three exposure
categories in accordance with IS0 10993-I : 1992,
60 mg in the first 30 days;
subclause 5.2:
50 g in a lifetime.
a) limited exposure: devices whose single or mul-
tiple use or contact is likely to be up to 24 h;
4.3.2 Prolonged exposure devices
b) prolonged exposure: devices whose single, mul-
tiple or long-term use or contact is likely to exceed The average daily dose of EO to patient shall not ex-
24 h but not 30 days; ceed 2 mg/day. In addition, the maximum EO dose
shall not exceed
c) permanent contact: devices whose single, mul-
tiple or long-term use or contact exceeds 30 days. 20 mg in the first 24 h;

IS0 10993-7:1995(E)
0 IS0
4.4.1 .l Ethylene oxide
60 mg in the first 30 days.
The average daily dose of ECH to patient shall not
This is a flammable gas that is irritating to body sur-
exceed 2 mg/day. In addition, the maximum ECH
faces and highly reactive. It is mutagenic under many
dose shall not exceed
conditions, has fetotoxic and teratogenic properties,
can adversely affect testicular function and can pro-
12 mg in the first 24 h;
duce injury to many organ systems in the body. In
cancer studies in animals, inhalation exposure pro-
60 mg in the first 30 days.
duced several types of neoplastic changes including
leukaemia, brain tumours and mammary tumours,
4.3.3 Limited exposure devices
while ingestion or subcutaneous administration pro-
duced tumours only at the site of contact. One in-
The average daily dose of EO to patient shall not ex-
vestigator has reported higher cancer and mortality
ceed 20 mg.
rates in exposed workers. However, the results or
several recent studies in workers have not been con-
The average daily dose of ECH to patient shall not
sistent with this finding.
exceed 12 mg.
NOTE 7 The simultaneous use of more than one device
4.4.1.2 Ethylene chlorohydrin
or the use of devices in the treatment of neonates may re-
sult in additional exposure as described in E.2.1 .I.
This is a flammable liquid that is irritating to body
surfaces, acutely toxic and readily absorbed through
4.3.4 Special situations
the skin in toxic amounts. It has weak mutagenic po-
tential, has some potential to produce fetotoxic and
For multi-device systems, the limits shall apply to
teratogenic changes and can produce injury to several
each individual device.
organ systems in the body including lungs, kidneys,
central nervous system and cardiovascular system. It
Residue of EO in intraocular lenses shall not exceed
was negative in cancer bioassays in animals.
0,5 pg EO per lens per day, nor I,25 pg per lens
For blood oxygenators and blood separators, the
4.4.2 Determination of residue
average daily dose of EO to patient shall not exceed
60 mg.
A validated method of extraction and measurement
shall be used to determine the amount of EO and,
For extracorporeal blood purification set-ups, the EO
where necessary, ECH delivered to the patient.
and ECH limits specified above for the prolonged and
limited duration category apply, but the allowable EO
NOTE 9 If ECH is not detected based on the results of
dose for a lifetime may be exceeded.
analyses performed using the methods given in B.5.2 and
B.5.7, no further monitoring for ECH is required.
NOTE 8 The rationale for specifying EO limits for certain
devices that are at variance with the general requirements
Validated methods that meet this requirement are
appears in E.2.1.3.
described in annex B. However, any method which
has been shown to be analytically sound may be used
4.4 Determination of EO and ECH residuals
provided it has been validated by demonstrating that
the system meets the requirements set out in
The procedure for determining compliance with 4.3
annex A, and has been evaluated against the referee
consists of extracting the residue from samples, de-
methods contained in annex B.
termining the amount of residue, and analysing and
interpreting the data.
The guiding principle in selecting appropriate ex-
traction methods (4.4.6) for the quantitative deter-
4.4.1 Safety considerations
mination of EO and, where necessary, ECH is the
evaluation of dose to the patient in order to show
DANGER - Analysts and others obtaining sam-
compliance with requirements set out in 4.3.
ples should perform all work involving the use of
Where residues are shown to be within the require-
the chemicals and solvents required for these
methods under the fume hood with appropriate ments for products tested by exhaustive extraction,
protective clothing, and should review the Ma- there is no need further to challenge the device by
terial Safety Data information for each chemical simulated-use extraction, provided all applicable limits
prior to such use. in 4.3 are met. When exhaustive extraction is used,
0 IS0
IS0 10993=7:1995(E)
particular attention shall be paid to the limits ex- product load (see also C.1.5). In addition, operator and
pressed for the first 24 h and for the first 30 days in analyst safety shall be ensured.
43 . .
Samples should remain with the product load until the
Many analytical methods for these EO-sterilization re- day of analysis. The time between removal of sam-
siduals have been described and reviewed in the ples from a controlled aeration area and the beginning
literature (see annex F). Those methods that have of extraction should be held to a minimum.
been compared and evaluated in interlaboratory stud-
Samples shall be sealed, shipped and stored frozen
ies conducted by knowledgeable individuals in well-
when analysis is delayed. Samples shall be shipped in
equipped laboratories are described in annex B.
dry ice by overnight delivery service. Dry ice shall re-
However, the enormous diversity of materials and
main in the shipping container throughout the ship-
methods of construction of sterile medical devices
ment and be present when the package is opened in
may, in certain cases, still present problems in deter-
the laboratory. As an alternative, test samples may be
mining residual EO and ECH levels using the methods
taken directly from the product load at the desired
in annex B.
aeration interval and immediately placed into an ap-
Therefore, any method which has been shown to be
propriate extraction fluid or head space vial, which is
analytically sound (i.e. demonstrated accuracy, pre- sealed and then shipped to the laboratory for analysis.
cision, linearity, sensitivity and selectivity) may be
Samples shall be prepared according to any applicable
used, provided that it has been validated. Annex A
pre-use instructions in the product labelling.
contains general validation requirements, and the an-
nex B methods can be used as referee methods
Samples to be analysed should be placed in a fume
against which to evaluate alternative methods.
hood and removed from the packaging. Extractions
should be started as soon as possible after the device
4.4.3 Product sampling
has been removed from the packaging, or pre-use
preparations have been completed.
4.4.3.1 Representative samples
4.4.3.3 Sample “blank”
Samples intended to be used for residual analysis
shall be selected in such a manner as to be truly rep- To ensure that no other sample matrix components
resentative of the product. When selecting samples, with the same retention time as any of the residues
being determined are present, a “blank” sample shall
attention shall be given to the many factors described
be evaluated for the possible presence of such inter-
in annex C. Since many of these factors influence not
ferences by the extraction of a non-sterilized sample
only the initial levels of residuals in device com-
using the identical procedure being applied to the
ponents but also the rate of residue dissipation, they
EO-sterilized samples. In the event of materials being
shall also be considered when test samples are drawn
extracted from such a “blank” with conflicting or
from a processed load and sent to the laboratory for
analysis. overlapping retention times in the gas chroma-
tography analysis, chromatographic conditions shall
Removal of the product samples from the processed
be modified to separate the interfering peak from the
load soon after a sterilization cycle is completed and
analyte peak, or an alternative analytical procedure
shipment to a laboratory far from the sterilization site
shall be used.
or storage in the laboratory for later analysis can
jeopardize correlations of residual levels on the sam-
4.4.4 Sample/fluid ratios
ples with those on the rest of the load. Moreover, if
samples cannot be drawn from the load and handled
The volume of fluid used to extract residues from
so that the effect on aeration conditions for the sam-
devices, or representative sections of them, shall be
ple will be negligible, an experiment to establish the
sufficient to maximize extraction efficiency while
relationship between the sample aeration and load
maintaining detection sensitivity. The nature and size
aeration at various seasons of the year shall be carried
of the device sample therefore determines what con-
out.
stitutes the optimal fluid volume for extraction.
Sample/extraction fluid ratios for various devices typi-
4.4.3.2 Handling samples cally range from I:2 to 1 :I0 (i.e. 1 g in 2 ml to 1 g in
10 ml). Devices composed of highly absorbent ma-
Precautions shall be taken to minimize or control the
terials or those from which residues are extracted by
effects of laboratory conditions on the rate of aeration filling may require sample/extraction fluid ratios re-
for test samples that have been removed from a
flecting increased fluid volume. In any case,
0 IS0
IS0 10993=7:1995(E)
sample/extraction fluid ratios shall not undermine de- for a time equivalent to or exceeding the maximum
tection sensitivity. time for single use (or that ensures total extraction),
and at temperatures that provide the greatest realistic
4.4.5 Extraction time and conditions simulated challenge. An alternative is to prepare a
series of extracts (a minimum of three is suggested)
The aim of product extraction is to indicate the representing various shorter periods of time from
worst-case amount that could be delivered to the pa- which extraction rates can be used to calculate ef-
tient in actual use of the device: on a daily basis for fects of longer or daily repeated exposure.
limited exposure items, on a daily and up to monthly
To determine the dose of EO and, where necessary,
basis for prolonged exposure items, and on a daily,
ECH delivered to the patient or user over the course
monthly and up to a lifetime basis for permanent
of normal product use, simulated-use aqueous ex-
contact items. As indicated in annex E, exhaustive
traction procedures are employed. A simulated-use
extraction as described below can be a useful
extraction procedure shall be validated to demon-
alternative for permanent contact devices, given that
strate the actual exposure level to patients.
shorter-term constraints are ensured.
NOTE 10 The amounts of EO (or ECH) extracted by sim-
4.4.6 Product extraction
ulating normal product use are not necessarily similar to the
total product residual content.
There are two basic extraction methods employed for
the determination of EO-sterilization residuals in
Water or other aqueous systems (Kroes et al., 1985)
medical devices: simulated-use extraction, which is
are commonly used as extraction fluids for the recov-
the reference method, and exhaustive extraction,
ery of residual EO and ECH in simulated-use ex-
which represents an acceptable alternative in certain
tractions. These aqueous fluids are used for elution
situations. The choice of extraction method shall be
of EO residuals from the sample rather than to dis-
based on the intended use of the device. Examples
solve the sample material itself. If the intent is to
of suggested extraction methods are shown in
simulate product use by filling the device, the device
annex D.
should be filled so as to eliminate any air pockets. If
the assay is not performed immediately, the extract
The extraction method chosen shall represent the in-
should be decanted from the sample and sealed in a
tended use of the product with the greatest challenge
poly(tetrafluoroethylene) (PTFE)-lined, septum-capped
to the patient and not solely expeditious analysis or
to minimize the apparent concentration of residuals.
The headspace in the vial of any standard solution or
Extraction temperatures and times shall be deter-
extract shall be less than 10 % of the total volume.
mined based on the nature of the patient’s exposure
The extract may be stored in the refrigerator for sev-
and the patient’s duration of contact with the device
eral days (see annex E) but, where water extraction
as described in 4.2 and 4.3.
is used, caution shall be taken, as EO may convert to
ethylene glycol (EG) or ethylene chlorohydrin (ECH) (or
4.4.6.1 Simulated extraction (reference
both) during storage of the extract (Chesler et a/.,
method)
1985). It is incumbent upon the analyst to evaluate the
possibility of conversion on storage at the analysis
4.4.6.1.1 Simulated-use aqueous extraction is the
I
site.
reference method in that it is the only method which
produces results directly comparable to limits speci-
4.4.6.1.2 Exhaustive extraction represents an ac-
fied in 4.3. These limits are expressed in terms of
ceptable alternative and can provide useful infor-
delivered dose of EO and ECH to patients.
mation. It produces results which would tend to
represent a dose greater than or equal to one the pa-
Since it is necessary to evaluate the residue levels
tient may receive. Because such an extraction pre-
available to the patient or other end-user from devices
cludes measurement of dose as a function of time, it
during their routine use, extraction methods which
does not ensure that the mass of residue is not de-
simulate use are required. Simulated-use extraction
livered to the patient on the first day or during the first
shall be carried out under conditions which provide
month of exposure. However, when all applicable
the greatest challenge to the intended use.
limits in 4.3 are met and residues are shown to be
For example, many blood-contacting and parenteral
within the requirements for products tested by ex-
devices can be extracted with water or other aqueous
haustive extraction, there is no need further to chal-
fluids by filling or flushing the blood or fluid path
lenge the device by simulated-use extraction. When
(whichever is appropriate). Samples shall be extracted
exhaustive extraction is used, particular attention shall
0 IS0
IS0 10993=7:1995(E)
be paid to the limits expressed for the first 24 h and devices containing a relatively small amount of re-
for the first 30 days in 4.3. sidual EO, the commonly used methods may not be
capable of extracting these small amounts, even after
4.4.6.2 Exhaustive extraction (acceptable relatively long extraction times.
alternative method)
b) Residual ethylene chlorohydrin
4.4.6.2.1 Exhaustive extraction methods are in-
Water is typically used to extract residual ECH from
tended to recover the entire residual content of a de-
medical devices.
vice. For EO determination, extraction procedures
used include thermal extraction
followed by
4.4.6.2.2 Small devices shall be placed in a vial and
headspace gas analysis; solvent extraction pro-
subjected to extraction in their entirety, whereas for
cedures, with either headspace gas analysis of the
larger devices representative portions of the com-
solvent extract, chromatography of the solvent ex-
ponent materials may be selected when it is neces-
tract, or preparation of the bromohydrin derivative of
sary to determine EO residues in part of the device.
EO which is determined using a more sensitive GC
Caution shall be exercised in the latter case. It may
detector.
be necessary to take several representative portions
Residual ethylene oxide of the device in order to ensure confidence in the data
a)
derived from the small samples of larger devices.
A variety of extraction fluids have been used for the
These representative portions may be selected in one
exhaustive recovery of residual EO. Thermal
of two ways. If several varied materials are employed,
desorption followed by headspace gas analysis, as
the proportion of each component, as compared with
described in B.5.3, is an example of a procedure that
the total sample mass, should parallel the ratio of that
does not use an extraction fluid. When conducted as
component to the total mass of the device being
described, headspace methods are considered ex-
tested. An alternative method would be to select one
haustive since they are designed to recover all of the
of the components for testing, subsequent to an
residual EO from the sample. However, headspace
evaluation demonstrating that it represented the
methods may not be feasible or preferred for intact
worst case with regard to residual content. The
testing of large or complex devices. The analyst shall
method chosen shall be validated.
exercise caution in the execution of headspace
methods when evaluating residue levels in polymer
materials such as poly(methylmethacrylate) to ensure
4.4.7
Data analysis and interpretation
total recovery of EO.
4.4.7.1 ‘Calculation of amount of residue
For solvent extraction procedures, selection of a suit-
extracted
able extraction fluid depends on the material compo-
sition of the device and its components. To facilitate
The concentration of residue observed in the extracts,
complete recovery of EO from the sample, fluids that
is converted to a mount, in milligrams, as follows:
AE,
dissolve the sample material are generally preferred
in an exhaustive extraction, provided that interfering
substances are not also put into solution by the pro-
AE = F, ER x EV
cedure. Solvent extraction procedures that are com-
bined with headspace gas analysis are described in
Residue extracted by simulated use may be calcu-
B.5.4 and such procedures may be able to separate
EO from co-extracted interfering chemicals from the lated as follows:
sample matrix. The extraction fluids described in 8.3.2
ER x m
AR= *
were evaluated through interlaboratory comparison
testing (Marlowe, 1983; Marlowe et a/., 1986a;
Marlowe et a/., 1986b). The extraction efficiency of
Residue extracted by exhaustive extraction may be
other fluids shall be evaluated against one or more of
calculated as follows:
the methods described in this part of IS0 10993 in
Rs x mD
order to establish their suitability in exhaustive ex-
AE=
ms
traction procedures.
Prudent analytical procedure dictates that, in the initial
analysis of a given material, more than one procedure
is the extract residue, in milligrams;
AE
shall be used to validate quantitative recovery, when-
ever an exhaustive extraction is to be performed. For
n is the number of extractions;

0 IS0 IS0 10993=7:1995(E)
cable, ECH. If sufficient experimental data on residue
ER is the milligrams of EO per millilitre of ex-
diffusion kinetics are available, it may be possible to
tract as derived from the standard curve;
group devices for quality assurance testing based on
is the extract volume, in millilitres;
EV
similarity of materials, manufacturing processes and
use (see annex C).
is the mass of residue recovered, in milli-
AR
grams;
For release of batches of sterilized product, one of the
two methods in 5.1 and 5.2 shall be used.
m is the mass of extract, in grams;
is the density of water, in grams per milli-
5.1 Release of products without dissipation
e
litre;
curve data
is the residue extracted from the sample,
RS
When dissipation curve data are not available on a
in milligrams;
product, the product may be released if it is in corn-
pliance with this part of IS0 10993 and the data were
is the entire device mass, in grams;
mD
obtained from testing carried out according to appro-
priate procedures delineated in annex B and meet the
is the mass of sample, in grams.
mS
requirements for EO and, if applicable, ECH set out in
43 . .
4.4.7.2 Calculation of average delivered dose
(ADD) for comparison to allowable limits in 4.3
5.2 Procedure for product release using
For permanent contact devices the average delivered
residue dissipation curves
dose, ADD, in milligrams per day, is as follows:
Dissipation curves are used to estimate the post-
ADD = AE
sterilization time required for products or families of
25 000
similar products to reach residue limits, principally for
EO, in compliance with 4.3. Products shall be released
to the market-place according to predetermined post-
25 000 is the days per lifetime;
sterilization times and conditions defined by exper-
imental dissipation curves so that the target EO
AE is as above.
residue levels for the device as set out in 4.3 are en-
sured. The product aeration concerns documented in
Permanent contact devices shall also meet the pro-
annex C are to be considered by pooling data from
longed exposure and limited exposure limits as cal-
sterilization loads taken from aeration of quarantine
culated below.
storage at different times of the year if aeration tem-
For prolonged exposure devices, peratures differ. The presence of other EO-sterilized
medical devices in adjacent areas shall also be con-
=-
ADD $;
sidered when obtaining experimental data to generate
such dissipation curves.
where
Release of products manufactured and sterilized un-
der controlled conditions, as described in IS0 11135
30 is the days per month;
or EN 550 ([I] and [2]), may be carried out if data are
AE
is as above. pooled from a minimum of three sterilization lots run
at different times. Dissipation of EO from most ma-
Prolonged exposure devices shall also meet the limi-
terials and devices follows first-order kinetics, i.e. In
ted exposure limits as calculated below.
[EO] a Time after sterilization. A plot of the natural
logarithm of the experimentally determined EO con-
For limited exposure devices,
centration against time after sterilization is linear. Re-
ADD = AE
lease shall then be based on the time after
sterilization when the mean regression line intersects
where AE is as above.
the maximum allowable residue. This approach may
be used for products which are not sterilized in suf-
5 Product release ficient quantity (numbers of sterilization runs) for the
procedure described below to be applied, or may be
A product is in compliance with this part of IS0 10993 used while the dissipation curve data described is
when it meets the requirements for EO and, if appli- being collected.

IS0 10993=7:1995(E) 0 IS0
Regression analysis of pooled data from sufficient
PL is the prediction limit for a single indi-
time points for at least three lots of the same product vidual of the product;
to establish the nature of the dissipation curve will
is the student-t value at significance a
enable product to be released at the calculated upper
with yt - 2 degrees of freedom;
95 % prediction limit, PL, for the allowed residue limit
for the product. Time-concentration curves for devices
is the residual variance of the re-
( TX )
made from combinations of dissimilar materials may
gression line;
not fit this simple pattern over the entire range and
may need to be handled differently.
is the average of log EO values;
Formulae for calculating prediction limit, PL:
n is the number of values;
Yo - a
=-
is the individual time after sterilization
xi
xO
b
at which measurements are made;
is the avera ge of the times after
( ) 00 - YJ
Sol
PL = x0 + ta x x I+;+
sterilization;
b2
b2 x C(xi - x/J2
\
C(Xi - XP)~ is the sum of squares for x (time).
where
All data obtained for release of medical devices in
is the calculated average value of the
compliance with this part of IS0 10993 shall be ob-
X0
release time corresponding to the EO
tained from experiments and data analyses carried out
limit;
following valid standard operating procedures.
is the log value of EO limit;
When sterilization process parameters listed in
Yo
annex C are changed, an audit shall be made of the
a
is the intercept of the linear re-
product residue. When this audit shows an increase
gression line;
in the level of residual EO, new residue dissipation
curves shall be obtained to ensure product accept-
b is the slope of the regression line;
ability. When this audit shows a decrease in the level
of residual EO, consideration should be given to the
generation of new dissipation curves.

IS0 10993=7:1995(E)
Annex A
(normative)
Evaluation of gas chromatograms
is the retention time for a non-retained
A.1 General
component, such as air, which is not re-
tarded in its passage through the column;
This annex discusses the minimum requirements for
the analytical procedures employed for EO and ECH
t t is is the the retention retention time time of of the the relevant relevant resi- resi-
measurements.
due due peak peak (EO (EO or or ECH). ECH).
A.4 A.4 Minimum Minimum requirements requirements
A.2 Background
A.4.1 A.4.1 For For these these procedures, procedures, it it is is recommended recommended that
that
the the following following minimum minimum requirements requirements be be met met for
These requirements are discussed in reference books for
these these parameters parameters (see (see figures figures A.1 A.1 and and A.2): A.2):
on gas chromatography (USP, 1989) and should be
reviewed by analysts before their use of any of the
Resolution, Resolution, R, R, calculated calculated as as follows, follows, shall shall be be greater greater
procedures. Also recommended is a review of the ar-
than than or or equal equal to to 1,2: 1,2:
ticles concerning detection limits (Ball, 1984; Chesler
et al., 1985, Hubaux and Gilbert, 1970).
(t ( t - - t,) t,)
2 2
R=2 R=2 (Wz+W,) (Wz+W,)
for for peak peak area area or or peak peak height height quantitation. quantitation.
A.3 Symbols
Alternatively, Alternatively, the the following following equation equation may may be be useful useful to to
calculate calculate capacity capacity factor, factor, k’, k’, which which shall shall be be greater greater
For the purposes of this annex, the following symbols
than than or or equal equal to to 1,5: 1,5:
apply (see figures A.1 and A.2).
I
=--
R is the resolution; k t 1
G
T is the tailing factor;
Tailing, T, given by the following equation, shall be
less than or equal to 1,5:
is the retention of chromatographic peaks
4' t2
1 and 2, where t, is EO (or ECH) and t2 is
wo,05
T=-------
an immediately adjacent peak;
2f
is the respective widths ext
...