Page 225 - Biomedical Engineering and Design Handbook Volume 2, Applications

204 MEDICAL DEVICE DESIGN

Since leaks may change in size with different ambient conditions, comparisons between test stations
are not conclusive. Therefore, this method is usually employed as a go, no-go test.
The dye solution will wick through any porous material over time, but usually not within the maximum
time suggested. If wicking does occur, it may be verified by observing the porous side of the subject seal
area. The dye will have discolored the surface of the material.
When puncturing the packaging to allow injection of the dye penetrant solution, care should
be taken not to puncture other package surfaces. Puncturing of the package is facilitated if it is
done adjacent to a dummy device inside the package. The device will provide a tenting effect that
will separate the two sides of the package, reducing the chance of accidental puncture of both
sides.

The basis of the test method is that when the test solution comes in contact with a channel or breach
in the package seal, it will flow through the channel by capillary action. The leak will be indicated by
a blue streak visible in the seal and/or a profuse and consistent flow of the dye through the channel.
This test method is generally considered to be more sensitive than the whole package microbial
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challenge methods discussed earlier in this chapter. It is reported in a study on Tyvek -to-plastic
pouches that seal defects down to 0.0015 in (38 μm) were readily detected with a blue dye solution.
The published test standard has verified through round-robin testing that the smallest channel which
can be reliably detected is on the order of 0.002 in (50 μm) or larger. In fact, the detection rate for
breathable pouches and trays with breathable lids was found to be 98 to 99 percent. It was discovered
during the testing that significant reductions in test performance were observed when indicator dyes
other than toluidine blue were used. Also, the round robin results are specific for the wetting agent
(Triton X-100) used for the solution.
The most effective application for the dye penetration test method is for detecting breaches in the
seals of transparent packages since seal defects must be observed easily. It is possible to use this
method for opaque packages; however, observation of the seal leak must be made at the seals out-
side edge and the exact location of the leak may be difficult to ascertain. One attribute of this test
methodology is that it is difficult to use for detecting leaks in the surfaces of package components.
That is, pinholes, gouges, or abrasions of the materials cannot be detected, since the dye cannot be
easily contacted with all of the package surfaces. So, although the dye penetration test is a sensitive
leak indicator for seals, it is not a good whole-package integrity test. Other means must be used to
detect material leaks, such as the bubble emission leak test. Other attributes of this test method must
be considered before incorporating it into a package validation protocol. First the method is difficult
to use for packages having a paper component as the dye solution can destroy the material in a very
short time—maybe even faster than the dye would travel through a channel. Other porous packages
may allow the dye solution to wick through, causing difficulty in detecting a true leak from the per-
meation or wicking of the solution through the material. Since the dye solution is injected into the
package, the method is destructive to the package and, in many instances, also to the product.
Other Package Integrity Test Methods. Several other package integrity test methods have been
developed by the ASTM F2 Committee. These include methods using trace gas sensing devices and
other mechanical means for determining when a leak exists in a package. Several methods are listed
below. These methods are developed around specific types of packages and apparatus:
• F2227-02 (2007), Standard Test Method for Nondestructive Detection of Leaks in Nonsealed and
Empty Medical Packaging Trays by CO2 Tracer Gas Method
• F2228-02 (2007), Standard Test Method for Nondestructive Detection of Leaks in Medical
Packaging which Incorporates Porous Barrier Material by CO2 Tracer Gas Method
• F2338-07 Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum
Decay Method
• F2391-05 Standard Test Method for Measuring Package and Seal Integrity Using Helium as the
Tracer Gas
All the ASTM test methods are available from ASTM International and are published in the ASTM
Book of Standards, volume 15.10.