A continuous sterilization process using ethylene oxide was studied in comparison with a classical method in order to evaluate gas retention as a function of time and temperature on polyethylene, PVC, and rubber materials

Chaigneau, M.

Lacomme, M.

Lemoan, G.

English

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NASA TECHNICAL MENORAMN
	
NASA TM-75022
It	 STUDY OF THE DESORPTION OF ETHYLENE OXIDE FIXEDON VARIOUS MATERIALS DURING STERILIZATION
BY A NEW PROCEDURE
M
M. Lacomme, M. Chaigneau and C. Le Moan
(NASA -TM-75022) STUDY OF THE DESORPTION OF 	 N77-27204
ETHYLENE OXIDE FIXED ON VARIOUS !MATERIALS
DURING STERILIZATION BY A NEW PROCEDURE
(Kanner (Leo) Associates) 11 p HC 
ACSCLF07D G3/25 397705A01
Translation of: Annales Pho maeeutigues Francaises,
Vol. 35. No. 3/4, 1977, pp-. 91 - 96
AUG 1977
ECEIVED
IIVP
	glt
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
	 June,197'(
. t ,Sr 	 sJ r
STANDARD TITLE. PAGE
1.	 Report NO. 2. Government Accession No. 3.	 Recipient's Catalog No.
NASA TM-75022
s.	 R#pert Dore4. Title and Subtitle	 STUDY OF THE DESORPTION OF
ETHYLENE OXIDE FIXED ON VARIOUS MATER- Jung 1977
8.	 Performing Organisation CodeIALS DURING STERILIZATION BY A NEW PRO—
QEDLIRE,_
 Author(s) 8.	 Performing Organization Report No.
M. Lacomme, M. Chaigneau and G. Le Moan
10.	 work unit No.Department of Gas Analysis of the CNRS*
Pharmacy Laborator 	 Bichat Hospital,
11.	 Contract o. Grant No..B].xd- Ae4L.,
9. Performing Organisation Name end Address
13.
	
Type of Report and Period CoveredLeo Kanner Associates
Redwood City, California 94063 Translation
12.	 Sponsoring Agency Name and Address
National Aeronautics and Space Adminis- sponsoring Agency Code
tration, Washington, D.C. 20546 I14
15.	 Supplementary Notes
Translation of:	 Annales Phaxmt►ceutiquesfrancaises, Vol. 35, No. 3/4,
1977, PP .
 
91 - 96. l
f
i
16.	 Abstract
A new continuous sterilization process using ethylene oxide
has been studied in comparison with•a classical method in
order to evaluate gas retention as a function of time and
temperature on polyethylene, PVC and rubber materials.
17. Kay Words jfdeeted by Author(s)) 18.	 Distribution Statement
Unclassified-unlimited
19.	 Security Massif. (of this report) 20.	 Security Clessif. (of this pegs) 21. No. of Pages 22.	 Price'
Unclassified Unclassified
NASA-HO
^1	 !	 C
i	 .
STUDY OF THE DESORPTION OF EHTYLENE OXIDE FIXED ON VARIOUS
MATERIALS DURING STERILIZATION BY A NEW PROCEDURE.
M. Lacomme, M. Chaigneau and G. Le Moan
Summary	 /yl *
A new continuous sterilization process using ethylene
oxide has been studied in comparison with a classical method
in order to evaluate gas retention as a function of time and
temperature on polyethylene, PVC and rubber materials.
Sterilization methods using ethylene oxide can be clas-
sified into two large categories:
The first uses ethylene oxide mixed with air generally
in a proportion of 50%. This technique has the advantage of
being economical. Its major drawback is the danger of explo-
sion. Under a pressure of one atmosphere the ethylene oxide-
air mixture is explosive for volume-to-volume concentrations
of 3-8CC. The danger of explosion is limited by using an
armored, watertight sterilization chamber under strict oper-
ating conditions. A vacuum of a few millimeters is created
in the chamber, then the gas is introduced in suitable doses,
but so as to preserve a partial vacuum in the chamber, thus
preventing any possible diffusion of the gas to the exterior.
The sterilization time is a function of the material to be
sterilized, the temperature and the ambient humidity. At the
end of sterilization the ethylene oxide is removed by pumping
followed by one or several rinsings with filtered air.
The second classic method uses ethylene oxide mixed with
different gases. The most common are carbon dioxide, nitrogen
and freons. The advantage of these mi::tures is that they
Numbers in the margin indicate the pagination in the foreign text.
5	 =
1
,.
remove the danger of explosion. The concentration of ethylene
oxide generally used is 10-20% by volume so as to obtain a
concentration greater than 400 mg of ethylene oxide per cubic
meter. The sterilization is done in armored containers.
After first putting the interior of the chamber under a
vacuum the gaseous mixture is generally introduced at a pres-
sure greater than atmospheric pressure (2-3 atmospheres) in
order to reduce the contact time which would be longer taking
into account the small concentration of ethylene oxide in the
mixture. This poses safety problems which are not insigni- J92
ficant and requires the use of large quantities of gas which
increases the cost of production. At the end of steriliza-
tion one or several rinsings are performed with sterilized
air.
These two classes of techniques have the following in
common: the sterilization process is discontinuous, it uses
large containers and requires significant safety precautions
and trained and experienced personnel.
A new original technique has been developed. It consists
of injecting a gaseous mixture consisting of 12% ethylene
oxide in a "freon" into a pocket of plastic material contain-
ing the material to be sterilized. The pocket constitutes
the sterilization chamber allows the ethylene oxide to dif-
fuse slowly. It is placed in a ventilated chamber heated to
50°C where sterilization and desorption take place simultan-
eously. This process which we will call S 1 permits continu-
ous sterilization. It does not require a large container.
The procedure is simple and quick. Therefore it seemed
interesting to us to study the desorption rate of ethylene
oxide fixed on plastic materials by this process in comparison
1. Distributed in France by the Lis group under the name of
Sterijet.
2
am
r _^
with a process M1 largely in use today.
Materials and Method
1. Materials
Three types of materials were tested:
a low pressure, high density 6050 polyethylene with 	 -_....
very few additives and in the form of irregularly shaped
"caramels" 2 mm long and 3.8-4 mm in diameter.
- two PVC's: BTS 140 A7 lucolene parallel:pipedal "cara-
mels" (4 x 3 x mm) containing 68% PVC and 2312 B PVC, also in
the form of "caramels" containing 56.4% PVC.
- a latex rubber of unknown composition used for making
Foley tubes with an i.d. of 4 mm and an o.d. of 8 mm.
All of these materials are used in the manufacture of
medicosurgical products. Their composition is gully known,
with the exception of the latex, and it will be dealt with
in future monographs of the French Pharmacopia.
2. Apparatus
We compared process S with process M. In process S
the objects to be sterilized, impregnated with ambient humidity
(40-50%), are put singly or in groups into a pocket of complex
and specially studied plastic material which takes the place
of the sterilization chamber. This pocket is made, on the
one hand, of polyamide, which is impermeable to ethylene
oxide, and, on the other hand, of low pressure polyethylene,
which is permeable to ethylene oxide. It is impermeable to
air, but allows the sterilizing gas to diffuse slowly to the
outside through the polyethylene by means of a window made
in the polyamide layer. The opening of the pocket is first of
1.
Mallet apparatus.
3
all connected to the device by means of which it can first be
emptied of air -- this is confirmed by the complete collapse
C	 of the walls -- and secondly the device injects a premeasured
dose of a gaseous mixture containing 12% ethylene oxide and
88% trichlorofluromethane. The pocket is then heat sealed
and immediately placed in a ventilated and heated chamber.
All of these operations take only a few seconds, Then, con- /93
comitant with this begins the sterilization, or more pre-
cisely the desorption. During the first hours the concentra-
tion at a temperature of 50°C is greater than the minimum
dose of bactericide. This length of time corresponds to
an effective sterilization time. Further, desorption con-
_	 tinues until the ethylene oxide has been removed.
Process M uses a mixture of ethylene oxide of air in a
proportion of about 50%. It is characterized by steriliza-
tion at 40°C at a pressure less than atmospheric pressure.
The steps involved in the sterilization process are as follows:
1. Packets containing the objects to be sterilized are
placed in the container.
2. A vacuum is created by a turbine pump in order to
remove the air from the container.
3. Sterilizing gas is introduced into the chambeo at
a pressure ranging between 600 and 650 mm of Hg.
4. Contact continues for six hours.
5. Removal of ethylene oxide by creating an initial
vacuum followed by introduction of air until atmospheric
pressure is released, followed in turn by a second (rinsing)
vacuum and a final injection of air.
The packets are then placed at the outlet of the device
in the desorption chamber used in process S.
4
Experimental Procedure
The tests were carried out identically for all the materials
according to the following procedure:
Ten g of plastic materials were placed in packets made
of paper on one side and polyethylene on the other and sealed
closed. In process S these packets are put into special
pockets described above furnished by the manufacturer. The
entire unit in this case constitutes a double wrapping which
differentiates it from process M, since in the latter process
the packets are placed as is into the chamber.
Analytic Method Used
Measure of the residual ethylene oxide in the materials
was done according to a method which we have described pre-
viously [2]. Measurements were made at 48, 72, 120 and 16b
hours after the beginning of sterilization. The time lag
between the two processes is due to the fact that in process
S the handling operations last only a few seconds, whereas
in process M they take at least six hours.
Results
The results obtained are given in 'fables I, I1, III and
IV.
Table I. Process S. Ethylene oxide concentration in ppm
in polyethylene (PE), lucolene PVC and in PVC
2312 as a function of the aeration time at 50°C.
Aeration time	 PVC
	
PVC
in hours	 PE Lucolene 2312 B
48	 S	 57	 31
78	 2	 14	 12
120	 < 1	 3,3	 2.2
168	 t2	 <2	 i2
5
a"
fTable II. Process M. Ethylene oxide concentration in ppm d4
in lucolene PVC and PVC 2312 as a function of
aeration time at 50°C
C =
Aeration time	 PVC	 PVC
in hours	 Lucolene 2312 B
4a	 361	 < so
72	 17	 2
1.40	 1.2	 1.7
!61
	
<2	 <2
Table III. Process S. Ethylene oxide concentration in
ppm in a latex rubber as a function of aera-
time at 500C
Aeration time in hours Rubber
24	 to
a	 2.2
%	 <2
Table IV. Process S. Ethylene oxide concentration in
ppm in polyethylene (PE), lucolene PVC and
in 2312 PVC as a function of aeration time
at ambient temperature.
Aeration time	 PVC	 PVC
in days	 PE	 Lucolene 2312 B
2	 4"	 7M	 62"
3	 311	 2 911	 2%3
7	 116	 2 419	 1269
14	 64	 444	 75
Discussion
	 195
The following facts emerge from these various results:
1. Polyethylene retains less ethylene oxide than PVC,
as we have stated previously [1J.
2. After 4$ hours the concentration is lower with process
S than with process M. This would be due to the difference
ir ethylene oxide concentration in the sterilizing mixture.
3. Desorption is slightly more rapid with process M.
This would be explained by the fact that in order for the
ethylene oxide to be removed it must pass through wrapping
layers in process S instead of one. The first ordinary
wrapping does not retain any ethylene oxide and the second
only allows the gas to diffuse slowly. However, the increase
in the storage time with process S is only a few hours with
respect to process M (Tables I and II).
4. The desorption chamber is essential with process S.
The figures obtained with desorption at ambient temperature
in fact very high (greater than 50 ppm after 14 days). Never-
theless, it also turns out to be desirable to use the desorp-
tion chamber in process M (Table IV). In fact, by comparing
these results to findings obtained for identical materials
under similar conditions L31 it would appear that the storage
time is reduced from 15 to 5 days with aeration at 50°C.
5. Ethylene oxide penetration was checked chemically
by means of test papers furnished by the manufacturer of
the device which were placed in the packet. However, the
gas-object contact time is difficult to determine in process
S. According to the manufacturer this time is three hours.
Bacteriological checks were done at the Institut Pasteur in
Lille. The results of these tests were negative. The bac-
teriological effectiveness of this process his also already
been studied in the United States by Anderson [4].
C
6. Even if the desorption results are similar in the
two processes, it can be said that process S permits numer-
ous continuous sterilizations (1,000 pockets per day) and
moreover at the end of desorption the absence of free gases
in each pocket is confirmed by the fact that the pocket is
collapsed completely with both sides touching one another.
This makes it possible to check that sterilizations are main-
tained and thus that the wrapping remains intact until the
pocket is used.
Conclusion
This original device appears
time is very short and it permits
As in most processes using ethyle;
oven is essential and under these
times are equivalent to those for
used.
easy to use. The handling
continuous sterilization.
ne oxide, the desorption
conditions the storage
processes currently being
Summary
	
/96
Study of the desorption of ethylene oxide fixed on various
materials during sterilization by a new procedure.
by M. Laeomme, M. Chaigneau and G. Le Moan
A new continuous sterilization process using ethylene
oxide has been studied in comparison with a classical method
in order to evaluate gas retention as a function of time
and temperature on polyehtylene.
9riv .
Bibliography
[1] Cara, M., M. Chaigneau, A. German, J. L. Kiger and G.
Le Moan, ADRAPHARM Research Contract No. 85, 110 and
112, September 1974.
[2] Lacomme, M., G. Le Moan and M. Chargneau, Ann. pharm.
franc. 1, pp. 411-419 (19'4).
C37 Lacomme, M., G. Le Moan and M. Chaigneau, Ann. pharm.
franc. 33, pp . 337- 3 44 (1975).
[4] Anderson, S. G., J. Lab. Clin. Med. 77, pp. 346-356
(1971).	 -


Study of the desorption of ethylene oxide fixed on various materials during sterilization by a new procedure

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