Dye Penetration Testing Methods For Porous Packaging Materials
*Note that dye penetration testing methods described in this article are for porous materials. ASTM has a separate dye penetration guidance for nonporous packaging materials.
What is dye penetration testing useful for?
Medical devices and products can be contaminated through packaging leaks. These leaks are often found at small pinholes in the packaging or breaks in the seals between packaging components. Defects in seal channels can be detected via the dye penetration procedures described. These dye penetration procedures are good for individual package leaks. However, multiple small leaks will not be detected using these methods.
Dye penetration testing is a qualitative pass/fail test. Packaging with any indication of a leak will be rejected. Note that these testing methods are not robust enough to verify and locate leakage sites or to determine leak size.
What types of packages can be tested?
The dye penetration testing methods described herein are limited to porous packaging materials. This is because porous packaging materials are capable of retaining the dye solution and preventing the dye solution from discoloring the seal area long enough for a technician to visually detect any seal leaks. Additionally, the dye penetration testing methods detailed below are used to detect package edge seal leaks between a transparent material and a porous material. You will not be able to use these testing methods if you do not have at least one transparent material in your packaging system.
The aforementioned requirements aside, all types of packages can be tested for seal leaks through dye penetration testing. For example, you can test fully packaged medical devices, empty packages, or seal edge samples. Most commonly, fully packaged and terminally sterilized medical devices are evaluated using dye penetration testing to ensure packaging systems meet FDA package integrity requirements.
Dye Penetration Testing Conditions
For a package to be tested, it must be free of any condensation or liquid water. If there is any condensation or liquid water found, then the package must be stored at 23 °C and 50 % relative humidity for 24 hours minimum to support the removal of any condensation or water. For this method, dye solutions must have good contrast to the opaque packaging material. Most commonly a blue dye is used so make sure that your packaging material has good contrast with the blue dye that is used for testing.
Dye Penetration Testing Methods
There are three types of dye application methods. These methods are injection, edge dip, and eyedropper techniques. Toluidine blue is recommended as the dye indicator for the dye penetrant solution in all three dye application methods.
Injection Method
The first and most common method for dye penetration testing is the injection method. In this method, the dye penetrant solution is injected via a hypodermic needle. Flexible tubing is attached to the syringe instead of a needle to prevent any accidental puncturing of the packaging material by the needle during testing. For the injection method, dye solution is injected to cover the longest package edge to a depth of 1/4 inch. Following administration of the dye, the seal area is visually examined through the transparent side of the package. Any channels in the seals will be readily detected by the technician within five seconds. This process is then repeated for the remaining sides of the package.
For all dye penetration testing, evaluation of the dye must occur within five seconds of application maximum. The visual examination must be performed within five seconds of dye application, as prolonged exposure of the dye solution on the packaging can result in wicking of the dye through the porous packaging material.
When evaluating package seals, technicians look for penetration of the dye solution across the seal. If penetration occurs, this indicates that there is a leakage in the package.
Edge Dip Method
The second method for dye penetration testing is the edge dip method. For the edge method, a container with a length long enough to accommodate the longest edge of the package seal is selected. A dye solution is then poured up to 1/4 inch in height within this container. If the package tested has excessive material beyond the seal (such as a Chevron style opening), a modification excess material will be removed from the package. Excess material will be cut such that only 1/8 inch of material is remaining from the seal. Once excess material has been removed, an edge of the package under evaluation will be dipped just long enough to completely wet the entire packaging edge. Any channels in the seals will be readily detected by the technician within five seconds. This process is repeated for the remaining sides of the package.
Eyedropper Method
The third and final method for dye penetration testing is the eyedropper method. To use the eyedropper method, a package needs to have an unsealed area beyond the outer edge of the seal. To perform this method, dye solution is poured into an open container. A finger or the end of a paperclip is used to brush back the long edge of the porous material away from the transparent edge. An eyedropper or pipette is then inserted into the dye solution. With the transparent side of the package facing the technician, a bead of dye solution is placed along the top edge of the package between the transparent and porous material. The entire edge is wetted with this dye solution and the seal is evaluated within five seconds for any leaks. This method is repeated for all sides of the package.
False-Positives
Wicking, the movement of a liquid into the body of fibrous material, can result in a false-positive result if the dye penetrant solution is left more than 5 seconds. Thus, dye penetrant testing technicians must detect seal leaks before the dye wicking into the packaging material. Bending or folding of the packaging material can also result in false-positives for flexible, porous packaging materials. Some sterilization procedures can alter the hydrostatic head of some porous materials and result in false-positive results. This is known as oxidative sterilization. Check the sensitivity of your packaging materials to modifications following sterilization.
Dye Penetration Testing Summary
Dye penetration testing is a pass/fail method of detecting defects in packaging seals. There are three methods of dye penetration testing for porous materials: injection, edge dip, and eyedropper methods. Evidence of dye penetration to the opposite side of the seal via a channel is an indication of seal leakage. However, wicking of the dye penetrant solution is not taken as an indication of seal leakage. When dye penetration tests are performed, you can expect to receive information on the packaging material being tested, conditioning of the package materials (ie. sterilization treatments), dye penetration test method performed, dye solution used, if the visual inspection was aided or unaided, and pass/fail results. If leakage is detected, a qualitative description or sketch of the leakage site is provided. Overall, dye penetration testing is an important testing parameter to prove the integrity of your medical device packaging.
MycoScience is a contract manufacturing organization specializing in sterile syringe and vial filling. MycoScience also offers Preservative Efficacy Testing, Sterilization Validations, Bioburden Testing, Cleaning Validations, Microbial Aerosol Challenge Testing, Accelerated Aging, Microbiology Testing, Cytotoxicity Testing, Bacterial Endotoxin Testing, EO Residual Testing, Package Integrity Testing & Environmental Monitoring services medical devices and allied industries. MycoScience is an ISO 13485 certified facility.
References
American Society for Testing and Materials. Standard Test Method for Detecting Seal Leaks in Porous Medical Packaging by Dye Penetration. West Conshohocken, PA, United States. (ASTM F1929-15).
